OLGA Manual 6.2.3.pdf

Table of Contents OLGA

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1

Welcome to OLGA 6 ......................................................................................................................................................................... 1 Release Information .......................................................................................................................................................................... 2 Introduction ............................................................................................................................................................................................ 3 Introduction ..................................................................................................................................................................................... 3 Background ..................................................................................................................................................................................... 4 OLGA as a Strategic Tool ........................................................................................................................................................... 5 OLGA Model Basics ..................................................................................................................................................................... 6 How to use in general .................................................................................................................................................................. 7 Threaded Execution ................................................................................................................................................................... 11 Applications ................................................................................................................................................................................. 12 Input files ...................................................................................................................................................................................... 16 Simulation model ....................................................................................................................................................................... 22

24 Introduction .................................................................................................................................................................................. 24 New Project ................................................................................................................................................................................. 25 New case ...................................................................................................................................................................................... 26 Open existing case .................................................................................................................................................................... 27 Start page .................................................................................................................................................................................... 28 Model view ................................................................................................................................................................................... 29 File view ........................................................................................................................................................................................ 31 Component view ......................................................................................................................................................................... 32 Property editor ............................................................................................................................................................................ 33 Network view ............................................................................................................................................................................... 35 Flowpath view ............................................................................................................................................................................. 47 Connection view ......................................................................................................................................................................... 49 Output window ............................................................................................................................................................................ 50 Time series editor ...................................................................................................................................................................... 52 Plotting .......................................................................................................................................................................................... 54 Active case trend plot ............................................................................................................................................................. 55 Active case profile plot ........................................................................................................................................................... 56 Fluid properties ...................................................................................................................................................................... 58 Multi-case plotting .................................................................................................................................................................. 59 Some general features of the plotting tool .............................................................................................................................. 60 Export/import data to/from MS Excel ...................................................................................................................................... 61 Parametric Studies .................................................................................................................................................................... 63 Geometry editor .......................................................................................................................................................................... 66 Activating ................................................................................................................................................................................ 67 Enter a new profile ................................................................................................................................................................. 69 Edit geometries ...................................................................................................................................................................... 71 Edit the table ................................................................................................................................................................... 72 Edit the graph .................................................................................................................................................................. 73 Check angle distribution ................................................................................................................................................... 74 Filter the data .................................................................................................................................................................. 75 Complete the data ............................................................................................................................................................ 76 Define sectioning ............................................................................................................................................................. 77 Use the new geometry ...................................................................................................................................................... 79 Menus .................................................................................................................................................................................... 80

Graphical User Interface ..............................................................................................................................................................

81 Moving windows ......................................................................................................................................................................... 82 Hot keys ........................................................................................................................................................................................ 83 Moving view in 3D ...................................................................................................................................................................... 84 Graphic Configuration ............................................................................................................................................................... 85 Menus ........................................................................................................................................................................................... 86 Toolbars ........................................................................................................................................................................................ 88 Properties and settings ............................................................................................................................................................. 90 Simulation with bundles ........................................................................................................................................................... 92 Simulation with controllers ...................................................................................................................................................... 94 Simulation with separators ...................................................................................................................................................... 97 Model descriptions .......................................................................................................................................................................... 99 2nd Order Scheme .................................................................................................................................................................... 99 Purpose .................................................................................................................................................................................. 99 When to use ........................................................................................................................................................................ 100 Methods and assumptions .................................................................................................................................................. 101 Limitations ........................................................................................................................................................................... 104 How to use .......................................................................................................................................................................... 105 Blackoil ...................................................................................................................................................................................... 106 Purpose ............................................................................................................................................................................... 106 When to use ........................................................................................................................................................................ 107 Methods and assumptions .................................................................................................................................................. 108 Limitations ........................................................................................................................................................................... 116 How to use ........................................................................................................................................................................... 117 Complex Fluid .......................................................................................................................................................................... 118 Purpose ............................................................................................................................................................................... 118 When to use ........................................................................................................................................................................ 119 Methods and assumptions .................................................................................................................................................. 120 How to use .......................................................................................................................................................................... 121 Compositional Tracking ......................................................................................................................................................... 122 Purpose ............................................................................................................................................................................... 122 When to use ........................................................................................................................................................................ 123 Methods and assumptions .................................................................................................................................................. 124 Limitations ........................................................................................................................................................................... 125 How to use .......................................................................................................................................................................... 126 Controller .................................................................................................................................................................................. 131 Controller introduction ......................................................................................................................................................... 131 Analog Vs Digital Controllers .............................................................................................................................................. 132 Controller mode ................................................................................................................................................................... 133 Controller activation deactivation ......................................................................................................................................... 135 Constraining the controller output ....................................................................................................................................... 136 Controller details ................................................................................................................................................................. 137 Controller terminals ............................................................................................................................................................. 139 Actuator time of controlled device ....................................................................................................................................... 140 Connecting the controllers .................................................................................................................................................. 141 Controller Setpoint ............................................................................................................................................................... 142 Controller measured variable ............................................................................................................................................... 143 Algebraic controller ............................................................................................................................................................. 144 Purpose ....................................................................................................................................................................... 144 When to use ................................................................................................................................................................. 145 Methods and assumptions ............................................................................................................................................. 146 How to use ................................................................................................................................................................... 147 Limitations ..............................................................................................................................................................................

ASC controller ..................................................................................................................................................................... 148

148 149 Methods and assumptions ............................................................................................................................................. 150 How to use ................................................................................................................................................................... 151 Cascade controller .............................................................................................................................................................. 152 Purpose ....................................................................................................................................................................... 152 When to use ................................................................................................................................................................. 153 Methods and assumptions ............................................................................................................................................. 154 Limitations ................................................................................................................................................................... 156 How to use ................................................................................................................................................................... 157 ESD controller ..................................................................................................................................................................... 158 Purpose ....................................................................................................................................................................... 158 When to use ................................................................................................................................................................. 159 Methods and assumptions ............................................................................................................................................. 160 How to use ................................................................................................................................................................... 161 Manual controller ................................................................................................................................................................. 162 Purpose ....................................................................................................................................................................... 162 When to use ................................................................................................................................................................. 163 Methods and assumptions ............................................................................................................................................. 164 How to use ................................................................................................................................................................... 165 Override controller ............................................................................................................................................................... 166 Purpose ....................................................................................................................................................................... 166 When to use ................................................................................................................................................................. 167 Methods and assumptions ............................................................................................................................................. 168 How to use ................................................................................................................................................................... 170 PID controller ...................................................................................................................................................................... 171 Purpose ....................................................................................................................................................................... 171 When to use ................................................................................................................................................................. 172 Methods and assumptions ............................................................................................................................................. 173 How to use ................................................................................................................................................................... 175 PSV controller ..................................................................................................................................................................... 179 Purpose ....................................................................................................................................................................... 179 When to use ................................................................................................................................................................. 180 Methods and assumptions ............................................................................................................................................. 181 How to use ................................................................................................................................................................... 182 Scaler controller .................................................................................................................................................................. 183 Purpose ....................................................................................................................................................................... 183 When to use ................................................................................................................................................................. 184 Methods and assumptions ............................................................................................................................................. 185 How to use ................................................................................................................................................................... 186 Selector controller ............................................................................................................................................................... 187 Purpose ....................................................................................................................................................................... 187 When to use ................................................................................................................................................................. 188 Methods and assumptions ............................................................................................................................................. 189 How to use ................................................................................................................................................................... 191 STD Controller .................................................................................................................................................................... 192 Purpose ....................................................................................................................................................................... 192 When_to_use ............................................................................................................................................................... 193 Methods_and_assumptions ........................................................................................................................................... 194 Limitations ................................................................................................................................................................... 195 How_to_use ................................................................................................................................................................. 196 Purpose .......................................................................................................................................................................

When to use .................................................................................................................................................................

Switch controller .................................................................................................................................................................. 197

197 198 Methods and assumptions ............................................................................................................................................. 199 How to use ................................................................................................................................................................... 200 Table controller .................................................................................................................................................................... 201 Purpose ....................................................................................................................................................................... 201 When to use ................................................................................................................................................................. 202 Methods and assumptions ............................................................................................................................................. 203 Limitations ................................................................................................................................................................... 204 How to use ................................................................................................................................................................... 205 Transmitter .......................................................................................................................................................................... 206 Purpose ....................................................................................................................................................................... 206 When to use ................................................................................................................................................................. 207 Methods and assumptions ............................................................................................................................................. 208 Limitations ................................................................................................................................................................... 209 How to use ................................................................................................................................................................... 210 Corrosion ................................................................................................................................................................................... 211 Purpose ............................................................................................................................................................................... 211 When to use ........................................................................................................................................................................ 212 Methods and assumptions .................................................................................................................................................. 213 How to use .......................................................................................................................................................................... 215 Limitations ........................................................................................................................................................................... 218 Drilling Fluid ............................................................................................................................................................................. 219 Purpose ............................................................................................................................................................................... 219 When to use ........................................................................................................................................................................ 220 Methods and assumptions .................................................................................................................................................. 221 How to use .......................................................................................................................................................................... 222 Hydrate Check ......................................................................................................................................................................... 223 HydrateCheck - Purpose ..................................................................................................................................................... 223 HydrateCheck - When to use .............................................................................................................................................. 224 HydrateCheck - Methods and assumptions ........................................................................................................................ 225 HydrateCheck - Limitations ................................................................................................................................................. 227 HydrateCheck - How to use ................................................................................................................................................ 228 Hydrate Kinetics ...................................................................................................................................................................... 229 Purpose ............................................................................................................................................................................... 229 When to use ........................................................................................................................................................................ 230 Methods and assumptions .................................................................................................................................................. 231 Limitations ........................................................................................................................................................................... 233 How to use .......................................................................................................................................................................... 234 Inhibitor Tracking .................................................................................................................................................................... 235 Purpose ............................................................................................................................................................................... 235 When to use ........................................................................................................................................................................ 236 Methods and assumptions .................................................................................................................................................. 237 Limitations ........................................................................................................................................................................... 239 How to use .......................................................................................................................................................................... 240 Leak ............................................................................................................................................................................................ 241 Purpose ............................................................................................................................................................................... 241 When to use ........................................................................................................................................................................ 242 Methods and assumptions .................................................................................................................................................. 243 Limitations ........................................................................................................................................................................... 244 How to use .......................................................................................................................................................................... 245 Purpose .......................................................................................................................................................................

When to use .................................................................................................................................................................

Near-Wellbore .......................................................................................................................................................................... 246 Purpose ............................................................................................................................................................................... 246 When to use ........................................................................................................................................................................ 247

248 250 How to use .......................................................................................................................................................................... 251 Phase Split Node .................................................................................................................................................................... 252 Purpose ............................................................................................................................................................................... 252 When_to_use ...................................................................................................................................................................... 253 Methods_and_assumptions ................................................................................................................................................ 254 Limitations ........................................................................................................................................................................... 255 How_to_use ........................................................................................................................................................................ 256 Pig ............................................................................................................................................................................................... 257 Purpose ............................................................................................................................................................................... 257 When to use ........................................................................................................................................................................ 258 Methods and assumptions .................................................................................................................................................. 259 Limitations ........................................................................................................................................................................... 261 How to use .......................................................................................................................................................................... 262 Process Equipment ................................................................................................................................................................ 263 Check Valve ........................................................................................................................................................................ 263 Purpose ....................................................................................................................................................................... 263 When to use ................................................................................................................................................................. 264 Methods and assumptions ............................................................................................................................................. 265 Limitations ................................................................................................................................................................... 266 How to use ................................................................................................................................................................... 267 Compressor ........................................................................................................................................................................ 268 Purpose ....................................................................................................................................................................... 268 Methods and assumptions ............................................................................................................................................. 269 Limitations ................................................................................................................................................................... 274 How to use ................................................................................................................................................................... 275 Gas Lift Valve ...................................................................................................................................................................... 276 Purpose ....................................................................................................................................................................... 276 When to use ................................................................................................................................................................. 277 Methods and assumptions ............................................................................................................................................. 278 Limitations ................................................................................................................................................................... 281 How to use ................................................................................................................................................................... 282 Heat Exchanger .................................................................................................................................................................. 283 Purpose ....................................................................................................................................................................... 283 When to use ................................................................................................................................................................. 284 Methods and assumptions ............................................................................................................................................. 285 Limitations ................................................................................................................................................................... 286 How to use ................................................................................................................................................................... 287 Pump .................................................................................................................................................................................. 288 Purpose ....................................................................................................................................................................... 288 When to use ................................................................................................................................................................. 289 Methods and assumptions ............................................................................................................................................. 290 Limitations ................................................................................................................................................................... 299 How to use ................................................................................................................................................................... 300 Separator ............................................................................................................................................................................ 304 Purpose ....................................................................................................................................................................... 304 When to use ................................................................................................................................................................. 305 Methods and assumptions ............................................................................................................................................. 306 Methods and assumptions ..................................................................................................................................................

Limitations ...........................................................................................................................................................................

309 How to use ................................................................................................................................................................... 310 Valve ................................................................................................................................................................................... 312 Purpose ....................................................................................................................................................................... 312 When to use ................................................................................................................................................................. 313 Choke - Methods and assumptions ................................................................................................................................. 314 Valve - Methods and assumptions ................................................................................................................................... 317 Valve - Cv To Area ......................................................................................................................................................... 319 Limitations ................................................................................................................................................................... 320 How to use ................................................................................................................................................................... 321 Single Component .................................................................................................................................................................. 322 Purpose ............................................................................................................................................................................... 322 When to use ........................................................................................................................................................................ 323 Methods and assumptions .................................................................................................................................................. 324 How to use .......................................................................................................................................................................... 329 Slug Tracking ........................................................................................................................................................................... 330 Purpose ............................................................................................................................................................................... 330 When to use ........................................................................................................................................................................ 331 Methods and assumptions .................................................................................................................................................. 332 Limitations ........................................................................................................................................................................... 334 How to use .......................................................................................................................................................................... 335 Slug Tuning .............................................................................................................................................................................. 338 Purpose ............................................................................................................................................................................... 338 When to use ........................................................................................................................................................................ 339 Methods and assumptions .................................................................................................................................................. 340 Limitations ........................................................................................................................................................................... 341 How to use .......................................................................................................................................................................... 342 Source ........................................................................................................................................................................................ 343 Purpose ............................................................................................................................................................................... 343 When to use ........................................................................................................................................................................ 344 Methods and assumptions .................................................................................................................................................. 345 How to use .......................................................................................................................................................................... 349 Steady State Processor ......................................................................................................................................................... 350 Purpose ............................................................................................................................................................................... 350 When to use ........................................................................................................................................................................ 351 Methods and assumptions .................................................................................................................................................. 352 Limitations ........................................................................................................................................................................... 353 How to use .......................................................................................................................................................................... 354 Steam\Water-HC ..................................................................................................................................................................... 355 Purpose ............................................................................................................................................................................... 355 When to use ........................................................................................................................................................................ 356 Methods and assumptions .................................................................................................................................................. 357 How to use .......................................................................................................................................................................... 361 Thermal Components ............................................................................................................................................................ 362 Annulus ............................................................................................................................................................................... 363 Purpose ....................................................................................................................................................................... 363 When to use ................................................................................................................................................................. 364 Methods and assumptions ............................................................................................................................................. 365 Limitations ................................................................................................................................................................... 366 How to use ................................................................................................................................................................... 367 FEMTherm .......................................................................................................................................................................... 368 Purpose ....................................................................................................................................................................... 368 Limitations ...................................................................................................................................................................

369 Methods and assumptions ............................................................................................................................................. 370 Limitations ................................................................................................................................................................... 375 How to use ................................................................................................................................................................... 376 Bundle ................................................................................................................................................................................. 377 Purpose ....................................................................................................................................................................... 377 When to use ................................................................................................................................................................. 378 Methods and assumptions ............................................................................................................................................. 379 Limitations ................................................................................................................................................................... 380 How to use ................................................................................................................................................................... 381 LINE .................................................................................................................................................................................... 382 Purpose ....................................................................................................................................................................... 382 When to use ................................................................................................................................................................. 383 Limitations ................................................................................................................................................................... 384 How to use ................................................................................................................................................................... 385 Thermal Computations .......................................................................................................................................................... 386 Purpose ............................................................................................................................................................................... 386 Methods and assumptions .................................................................................................................................................. 387 Limitations ........................................................................................................................................................................... 389 How to use .......................................................................................................................................................................... 390 Tracer Tracking ........................................................................................................................................................................ 391 Purpose ............................................................................................................................................................................... 391 When_to_use ...................................................................................................................................................................... 392 Methods_and_Assumptions ................................................................................................................................................ 393 Limitations ........................................................................................................................................................................... 394 How_to_use ........................................................................................................................................................................ 395 Transmitter ............................................................................................................................................................................... 206 Purpose ............................................................................................................................................................................... 206 When to use ........................................................................................................................................................................ 207 Methods and assumptions .................................................................................................................................................. 208 Limitations ........................................................................................................................................................................... 209 How to use .......................................................................................................................................................................... 210 Tuning ........................................................................................................................................................................................ 396 Tuning - Purpose ................................................................................................................................................................ 396 Tuning - When to use ......................................................................................................................................................... 397 Tuning - Methods and assumptions .................................................................................................................................... 398 Tuning - How to use ............................................................................................................................................................ 399 Water ......................................................................................................................................................................................... 400 Purpose ............................................................................................................................................................................... 400 When to use ........................................................................................................................................................................ 401 Methods and assumptions .................................................................................................................................................. 402 Limitations ........................................................................................................................................................................... 405 How to use .......................................................................................................................................................................... 406 Wax ............................................................................................................................................................................................ 408 Purpose ............................................................................................................................................................................... 408 When to use ........................................................................................................................................................................ 409 Methods and assumptions .................................................................................................................................................. 410 Limitations ........................................................................................................................................................................... 414 How to use .......................................................................................................................................................................... 415 Well ............................................................................................................................................................................................ 416 Purpose ............................................................................................................................................................................... 416 When to use ........................................................................................................................................................................ 417 When to use .................................................................................................................................................................

418 Limitations ........................................................................................................................................................................... 425 How to use .......................................................................................................................................................................... 426 REFERENCES ........................................................................................................................................................................ 428 Keywords .......................................................................................................................................................................................... 432 CaseDefinition ......................................................................................................................................................................... 435 CASE .................................................................................................................................................................................. 435 DTCONTROL ..................................................................................................................................................................... 436 FILES .................................................................................................................................................................................. 437 INTEGRATION ................................................................................................................................................................... 438 OPTIONS ........................................................................................................................................................................... 439 RESTART ........................................................................................................................................................................... 441 Compositional .......................................................................................................................................................................... 442 BLACKOILCOMPONENT .................................................................................................................................................. 442 BLACKOILFEED ................................................................................................................................................................ 443 BLACKOILOPTIONS ......................................................................................................................................................... 444 COMPOPTIONS ................................................................................................................................................................ 445 FEED .................................................................................................................................................................................. 447 Controller .................................................................................................................................................................................. 448 Algebraic Controller ............................................................................................................................................................. 448 ASC Controller .................................................................................................................................................................... 451 Cascade Controller ............................................................................................................................................................. 454 ESD Controller .................................................................................................................................................................... 457 Manual controller ................................................................................................................................................................. 459 Override Controller .............................................................................................................................................................. 461 PID Controller ..................................................................................................................................................................... 463 PSV Controller .................................................................................................................................................................... 466 Scaler Controller ................................................................................................................................................................. 468 Selector Controller ............................................................................................................................................................... 469 STD Controller .................................................................................................................................................................... 472 Switch Controller ................................................................................................................................................................. 474 Table Controller ................................................................................................................................................................... 476 Output ................................................................................................................................................................................. 477 OUTPUTDATA ............................................................................................................................................................. 477 TRENDDATA ................................................................................................................................................................ 478 FA-models ................................................................................................................................................................................. 479 FLUID ................................................................................................................................................................................. 479 SINGLEOPTIONS .............................................................................................................................................................. 481 SLUGTRACKING ............................................................................................................................................................... 483 SLUGTUNING .................................................................................................................................................................... 485 WATEROPTIONS .............................................................................................................................................................. 486 FlowComponent ...................................................................................................................................................................... 488 NODE ................................................................................................................................................................................. 488 NODE .......................................................................................................................................................................... 488 Output ......................................................................................................................................................................... 492 NODE_OUTPUTDATA .............................................................................................................................................. 492 NODE_TRENDDATA ................................................................................................................................................ 493 FLOWPATH ........................................................................................................................................................................ 494 FLOWPATH ................................................................................................................................................................. 494 Piping .......................................................................................................................................................................... 495 BRANCH .............................................................................................................................................................. 495 GEOMETRY .......................................................................................................................................................... 496 Methods and assumptions ..................................................................................................................................................

PIPE

.................................................................................................................................................................... 497

POSITION

............................................................................................................................................................. 498

499 CHECKVALVE ....................................................................................................................................................... 499 COMPRESSOR ...................................................................................................................................................... 500 HEATEXCHANGER ................................................................................................................................................. 502 LEAK ................................................................................................................................................................... 503 LOSS .................................................................................................................................................................. 505 PUMP .................................................................................................................................................................. 507 TRANSMITTER ....................................................................................................................................................... 511 VALVE ................................................................................................................................................................. 512 Boundary&InitialConditions ............................................................................................................................................ 514 HEATTRANSFER .................................................................................................................................................... 514 INITIALCONDITIONS ................................................................................................................................................ 517 NEARWELLSOURCE .............................................................................................................................................. 520 SOURCE .............................................................................................................................................................. 522 WELL .................................................................................................................................................................. 531 Output ......................................................................................................................................................................... 544 PROFILEDATA ....................................................................................................................................................... 544 OUTPUTDATA ........................................................................................................................................................ 545 TRENDDATA .......................................................................................................................................................... 546 FA-models ................................................................................................................................................................... 548 CORROSION ......................................................................................................................................................... 548 DTCONTROL ......................................................................................................................................................... 550 HYDRATECHECK ................................................................................................................................................... 551 HYDRATEKINETICS ................................................................................................................................................ 552 PIG ..................................................................................................................................................................... 554 SLUGILLEGAL ....................................................................................................................................................... 557 SLUGTRACKING .................................................................................................................................................... 558 TUNING ................................................................................................................................................................ 560 WAXDEPOSITION ................................................................................................................................................... 562 Library ........................................................................................................................................................................................ 566 DRILLINGFLUID ................................................................................................................................................................ 566 HYDRATECURVE .............................................................................................................................................................. 568 MATERIAL .......................................................................................................................................................................... 569 SHAPE ............................................................................................................................................................................... 571 TABLE ................................................................................................................................................................................ 572 TIMESERIES ...................................................................................................................................................................... 573 TRACERFEED ................................................................................................................................................................... 575 WALL .................................................................................................................................................................................. 576 Output ........................................................................................................................................................................................ 577 OUTPUT ............................................................................................................................................................................. 578 OUTPUTDATA ................................................................................................................................................................... 579 PLOT .................................................................................................................................................................................. 580 PROFILE ............................................................................................................................................................................ 581 PROFILEDATA ................................................................................................................................................................... 582 TREND ............................................................................................................................................................................... 583 TRENDDATA ...................................................................................................................................................................... 584 ProcessEquipment ................................................................................................................................................................. 585 PHASESPLITNODE ........................................................................................................................................................... 585 SEPARATOR ...................................................................................................................................................................... 587 Output ................................................................................................................................................................................. 590 ProcessEquipment ........................................................................................................................................................

590 TRENDDATA ................................................................................................................................................................ 591 ThermalComponent ............................................................................................................................................................... 592 ANNULUS .......................................................................................................................................................................... 592 ANNULUS .................................................................................................................................................................... 592 AnnulusComponents ..................................................................................................................................................... 593 COMPONENT ........................................................................................................................................................ 593 FLUIDBUNDLE .................................................................................................................................................................. 594 FLUIDBUNDLE ............................................................................................................................................................. 594 BundleComponents ....................................................................................................................................................... 595 COMPONENT ........................................................................................................................................................ 595 FEMTherm/Solidbundle ...................................................................................................................................................... 596 SOLIDBUNDLE ............................................................................................................................................................ 596 BundleComponents ....................................................................................................................................................... 598 COMPONENT ........................................................................................................................................................ 598 Drilling ........................................................................................................................................................................................ 600 TOOLJOINT ....................................................................................................................................................................... 600 How to use ....................................................................................................................................................................................... 105 2nd Order Scheme ................................................................................................................................................................. 105 Annulus ...................................................................................................................................................................................... 367 Blackoil ....................................................................................................................................................................................... 117 Check valve .............................................................................................................................................................................. 267 Complex Fluid .......................................................................................................................................................................... 121 Compositional Tracking ......................................................................................................................................................... 126 Compressor .............................................................................................................................................................................. 275 Controller .................................................................................................................................................................................. 147 Algebraic controller ............................................................................................................................................................. 147 ASC controller ..................................................................................................................................................................... 151 Cascade controller .............................................................................................................................................................. 157 ESD controller ..................................................................................................................................................................... 161 Manual controller ................................................................................................................................................................ 165 Override controller ............................................................................................................................................................... 170 PID controller ...................................................................................................................................................................... 175 PSV controller ..................................................................................................................................................................... 182 Scaler controller .................................................................................................................................................................. 186 Selector controller ............................................................................................................................................................... 191 Switch controller .................................................................................................................................................................. 200 Table controller .................................................................................................................................................................... 205 Transmitter .......................................................................................................................................................................... 210 Corrosion .................................................................................................................................................................................. 215 Drilling Fluid ............................................................................................................................................................................. 222 FEM Therm ............................................................................................................................................................................... 376 Fluid Bundle ............................................................................................................................................................................. 381 Gas Lift Valve ........................................................................................................................................................................... 282 Heat Exchanger ....................................................................................................................................................................... 287 HydrateCheck .......................................................................................................................................................................... 228 Inhibitor Tracking .................................................................................................................................................................... 240 Leak ............................................................................................................................................................................................ 245 LINE ........................................................................................................................................................................................... 385 Near-Wellbore .......................................................................................................................................................................... 251 Pig ............................................................................................................................................................................................... 262 Pump ........................................................................................................................................................................................ 300 OUTPUTDATA .............................................................................................................................................................

Separator ................................................................................................................................................................................. 310 SingleComponent ................................................................................................................................................................... 329 Slug Tracking .......................................................................................................................................................................... 335 SlugTuning ................................................................................................................................................................................ 342 Source ........................................................................................................................................................................................ 349 Steady state processor .......................................................................................................................................................... 354 SteamWater-HC ...................................................................................................................................................................... 361 Thermal computations ........................................................................................................................................................... 390 Transmitter ............................................................................................................................................................................... 210 Tuning ........................................................................................................................................................................................ 399 Valve ........................................................................................................................................................................................... 321 Water Module ........................................................................................................................................................................... 406 Wax ........................................................................................................................................................................................... 415 Well ............................................................................................................................................................................................ 426

577 Boundary Output Variables .................................................................................................................................................. 601 Branch Output Variables ....................................................................................................................................................... 605 Bundle Output Variables ....................................................................................................................................................... 608 Check valve Output Variables .............................................................................................................................................. 609 Compositional Output Variables ......................................................................................................................................... 610 Compositional slugtracking Output Variables ................................................................................................................. 614 Compressor Output Variables ............................................................................................................................................. 616 Controller Output Variables .................................................................................................................................................. 617 Conversion Factors ................................................................................................................................................................ 618 Corrosion Output Variables .................................................................................................................................................. 626 Drilling Output Variables ....................................................................................................................................................... 627 Global Output Variables ........................................................................................................................................................ 629 Heat exchanger Output Variables ....................................................................................................................................... 630 Hydrate kinetics Output Variables ...................................................................................................................................... 631 Inhibitor Output Variables ..................................................................................................................................................... 633 Leak Output Variables ........................................................................................................................................................... 634 Node Output Variables .......................................................................................................................................................... 636 Pig Output Variables .............................................................................................................................................................. 637 Pump Output Variables ......................................................................................................................................................... 639 Separator Output Variables .................................................................................................................................................. 640 Slugtracking Output Variables ............................................................................................................................................. 643 Source Output Variables ....................................................................................................................................................... 648 SteamAndSingle Output Variables ..................................................................................................................................... 650 TracerTracking Output Variables ........................................................................................................................................ 651 Valve Output Variables .......................................................................................................................................................... 653 Volume Output Variables ...................................................................................................................................................... 654 Waxdeposition Output Variables ......................................................................................................................................... 657 Well Output Variables ............................................................................................................................................................ 659 Data Files ......................................................................................................................................................................................... 660 Compressor data file .............................................................................................................................................................. 661 Wax table file ........................................................................................................................................................................... 663 Hydrate curve definition file .................................................................................................................................................. 665 OLGA Rocx ............................................................................................................................................................................... 666 Fluid Properties File ............................................................................................................................................................... 667 Feed file for compositional tracking ..................................................................................................................................... 668 PVT properties for non-existing phase ................................................................................................................................ 669 Keyword based .................................................................................................................................................................... 670 Output Variables ...........................................................................................................................................................................

671 Table Structure ............................................................................................................................................................. 672 Keyword PVTTABLE ..................................................................................................................................................... 673 Examples ..................................................................................................................................................................... 678 Standard conditions ...................................................................................................................................................... 684 Standard format .................................................................................................................................................................. 685 Complex fluid module .................................................................................................................................................... 692 Pump Data Files ..................................................................................................................................................................... 694 Pump Data Table for Centrifugal Pumps ............................................................................................................................. 695 Pump Data Table for Displacement Pumps ........................................................................................................................ 698 Restrictions and Limitations ..................................................................................................................................................... 700 Restrictions and Limitations ................................................................................................................................................. 700 Memory consumption ............................................................................................................................................................ 701 Fluid properties ........................................................................................................................................................................ 702 Input/Output Limitations ........................................................................................................................................................ 703 Standard Conditions in OLGA ............................................................................................................................................. 704 Flow Model Limitations .......................................................................................................................................................... 705 Important Numerical Recommendations .......................................................................................................................... 706 Sample cases ................................................................................................................................................................................. 708 Sample cases .......................................................................................................................................................................... 708 2nd-order scheme ................................................................................................................................................................... 709 Advanced Well ......................................................................................................................................................................... 711 Blackoil ...................................................................................................................................................................................... 712 Centrifugal Pump .................................................................................................................................................................... 714 CO2 - Single Component ...................................................................................................................................................... 716 Compositional Tracking ......................................................................................................................................................... 717 Corrosion .................................................................................................................................................................................. 719 Displacement Pump ............................................................................................................................................................... 721 Drilling Fluid ............................................................................................................................................................................. 723 Fluid bundle .............................................................................................................................................................................. 725 H2O - Single Component ...................................................................................................................................................... 727 H2O - Steam/Water-HC ........................................................................................................................................................ 728 Hydrate Kinetics ...................................................................................................................................................................... 729 Hydrodynamic slugging ......................................................................................................................................................... 731 MEG Tracking .......................................................................................................................................................................... 733 Network ..................................................................................................................................................................................... 734 PID Controller .......................................................................................................................................................................... 736 Pigging ....................................................................................................................................................................................... 738 Process Equipment ................................................................................................................................................................ 740 Pump Battery ........................................................................................................................................................................... 742 Separator .................................................................................................................................................................................. 744 Simplified Pump ...................................................................................................................................................................... 745 Solid bundle .............................................................................................................................................................................. 747 Source, Leak and Choke ....................................................................................................................................................... 749 Start-up slug ............................................................................................................................................................................. 751 Tracer Tracking ........................................................................................................................................................................ 753 Wateroptions ............................................................................................................................................................................ 755 Waxdeposition ......................................................................................................................................................................... 756 Troubleshooting ............................................................................................................................................................................. 758 Geometry Editor problems ................................................................................................................................................... 759 GUI uses a lot of Memory ..................................................................................................................................................... 760 Inp files assosciated with GUI ............................................................................................................................................. 761 The syntax of the keyword ..............................................................................................................................................

License issues ......................................................................................................................................................................... 762 Mouse pointer changed to an unrecognize symbol ........................................................................................................ 763 Plots-no units ........................................................................................................................................................................... 764 Problems showing the graphics .......................................................................................................................................... 765 Restore layout .......................................................................................................................................................................... 766 Simualtion state runnable ..................................................................................................................................................... 767 Simulation not runnable ........................................................................................................................................................ 768 Update Graphical driver ........................................................................................................................................................ 769

OLGA 7

Welcome to OLGA 6 User Manual This is the OLGA 6 User Manual. The User Manual includes both information about the OLGA 6 engine and the graphical user interface (GUI). The complete program documentation includes - Release Document for OLGA 6.2 - OLGA 6 User Manual (this document) - OLGA 6 GUI User Manual - OLGA 6 Conversion Guide - Well GUI User Manual - Tutorial - Installation Guide All documents listed above are available from the Start Menu (Start - All Programs - SPT Group - OLGA 6.2 - Documentation). The OLGA 6 User Manual, OLGA 6 GUI User Manual, OLGA 6 Conversion Guide, Wells GUI User Manual and the Tutorial are also available from the Help menu in the GUI). User Manuals for other tools included with the OLGA 6 installation are available from the Help menus in the tools.

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OLGA 7

Release Information Please refer to the Release Document for detailed release information for OLGA 6.2. The Release Document describes changes in OLGA 6.2 relative to OLGA 5 and OLGA 6.1, and should be read by all users of the program. The complete program documentation consists of the OLGA User Manual, OLGA 6 GUI User Manual, OLGA 6 Conversion Guide, Wells GUI User Manual, Tutorial, Installation Guide, and the Release Document. The program is available on PC’s with Microsoft Windows operating systems (Windows XP, Windows Vista and Windows 7). Several versions of OLGA may be installed in parallel. Note that you may also run several versions of the engine from one version of the GUI - please refer to the Installation Guide to learn how to configure the GUI for several engines. The support center provides useful information about frequently asked questions and known issues. The support center is available from the SPT Group Support Center Please contact SPT Group if problems or missing functionality are encountered when using OLGA or any of the related tools included in the OLGA software package. E-mail: [email protected] Telephone: +47 6484 4550 Fax: +47 6484 4500 Address: SPT Group AS, P.O. Box 113, N-2027 Kjeller

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OLGA 7

Introduction OLGA is the industry standard tool for transient simulation of multiphase petroleum production. The purpose of this manual is to assist the user in the preparation of the input data for an OLGA simulation. In this manual you can find a general introduction to OLGA an overview of the required and the optional input to OLGA. It also describes in some detail different simulation options such as wax deposition, corrosion etc. a detailed description of all input data and the required fluid property tables a description of the output The sample cases presented with the installation of OLGA are intended to illustrate important program options and typical simulation output. A description of the sample cases are also included in this manual. OLGA comes in a basic version with a number of optional modules;FEMTherm, Multiphase Pumps, Corrosion, Wells, Slug Tracking, Wax Deposition, Inhibitor Tracking, Compositional Tracking, Single Component Tuning, Hydrate Kinetics and Complex Fluid. In addition there is a number of additional programs like the OLGA GUI and the FEMThermViewer for preparation of input data and visualisation of results. These optional modules and additional programs are available to the user according to the user's licensing agreement with SPT Group. See also: Background OLGA as a strategic tool OLGA Model Basics How to use in general Graphical User Interface Simulation model Input files Applications Threaded Execution

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Background OLGA 6 is the latest version in a continuous development which was started by the Institute for Energy Research (IFE) in 1980. The oil industry started using OLGA in 1984 when Statoil had supported its development for 3 years. Data from the large scale flow loop at SINTEF, and later from the medium scale loop at IFE, were essential for the development of the multiphase flow correlations and also for the validation of OLGA. Oil companies have since then supported the development and provided field data to help manage uncertainty, predominantly within the OLGA Verification and Improvement Project (OVIP). OLGA has been commercially available since the SPT Group started marketing it in 1990. OLGA is used for networks of wells, flowlines and pipelines and process equipment, covering the production system from bottom hole into the production system. OLGA comes with a steady state preprocessor included which is intended for calculating initial values to the transient simulations, but which also is useful for traditional steady state parameter variations. However, the transient capabilities of OLGA dramatically increase the range of applicability compared with steady state simulators.

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OLGA as a strategic tool

OLGA is applied for engineering throughout field life from conceptual studies to support of operations. However the application has been extended to be an integral part of operator training simulators, used for making operating procedures, training of operators and check out of control systems. Further, OLGA is frequently embedded in on-line systems for monitoring of pipeline conditions and forecasting and planning of operations. OLGA can dynamically interface with all major dynamic process simulators, such as Hysys, DynSim, UniSim, D-SPICE, INDISS and ASSETT. This allows for making integrated engineering simulators and operator training simulators studying the process from bottom hole all the way through the process facility in a single high fidelity model. Note that the OLGA flow correlation has been implemented in all major steady state simulators providing consistent results moving between different simulators.

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OLGA Model Basics OLGA 6 is a three-fluid model, i.e. separate continuity equations are applied for the gas, for the oil (or condensate) and water liquids and also for oil (or condensate) and water droplets. These may be coupled through interfacial mass transfer. Three momentum equations are used; one for each of the continuous liquid phases (oil/condensate and water) and one for the combination of gas with liquid droplets. The velocity of any liquid droplets entrained in the gas phase is given by a slip relation. One mixture energy equation is applied; assuming that all phases are at the same temperature. This yields seven conservation equations to be solved: three for mass, three for momentum, and one for energy. Two basic flow regime classes are recognised ; distributed and separated flow. The former comprises bubble and slug flow [1], the latter stratified and annular mist flow.

Figure A Flow patterns in horizontal flow Transition between the regime classes is determined by the program on the basis of a minimum slip concept combined with additional criteria. To close the system of equations, fluid properties, boundary and initial conditions are required. The equations are linearised and a sequential solution scheme is applied. The pressure and temperature calculations are de-coupled i.e. current pressure is based on previous temperature. The semi-implicit time integration implemented allows for relatively long time steps, orders of magnitudes longer than those of an explicit method (which would be limited by the Courant Friedrich Levy criterion based on the speed of sound). The numerical error is corrected for over a period of time. The error manifests as an error in local fluid volume (as compared to the relevant pipe volume). [1] In standard OLGA a slug unit model is applied which calculates average liquid hold-up and pressure, but which does not give any details about individual slugs. To follow individual slugs through the system the slug tracking module must be applied.

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How to use in general Numerics OLGA applies one global time-step for the time integration and there is an automatic time-step control based on the limitation that a fluid particle should not spend less than one time-step on passing through any numerical section length of a pipe (the Courant Friedrich Levy (CFL) criterion based on the fluid velocity). The user controls the time integration by specifying simulation period in time, time-step parameters such as initial time-step and maximum and minimum time-step values. The latter overrules the automatic control. There is also an option for using the second-derivative of pressure as a time step controlling criterion. Some functions in OLGA, e.g. slug-tracking, take control of the time-stepping in order to ensure a successful simulation. The spatial integration is performed on a user-defined grid. There are tools available to facilitate the gridding. There are no formal limitations on the numerical section lengths, but it is considered good practice to keep all neighbour section length ratios between 0.5 and 2: 0.5 ≤ Dxi/Dxi+1 ≤ 2 for all i Additionally it is recommended that each pipe should have at least two sections. Due to the numerical solution scheme, OLGA is particularly well suited for simulating rather slow mass flow transients. This is important for the simulation of long transport lines and thermal calculations, where typical simulation times in the range of hours to several days, and sometimes years, will require long time steps, to obtain efficient use of the computer. OLGA is also being used successfully for fast transients such as water hammer and pressure surges in general. Certain precautions w.r.t. spatial grid and time-stepping may be needed in order to keep the numerical error within acceptable limits. Since OLGA not accounts for pipe elasticity the calculated pressure peaks should be conservative. The de-coupling of temperature from pressure would normally give a pressure wave propagation velocity in gas which would be about 15% too low. However, in OLGA 6 a quasi implicit correction of temperature reduces this error considerably. Critical flow calculations are performed in the OLGA valve model, only. A valve with cross section equal to the pipe should then be positioned on e.g. a pipe outlet if choked flow is expected.

Temperature OLGA is particularly well suited for sophisticated thermal simulations. Since OLGA is one-dimensional (calculates along the pipe axis) any 2 and 3-dimensional effects must be modelled explicitly. The basic OLGA thermal model calculates the inner wall heat transfer coefficient. The built-in correlations are valid for natural- and forced convection and also for the transition between them. Flow pattern is accounted for. The user may specify pipe walls with material properties, including emissivity to account for radiation, and must give the ambient properties, i.e. temperature and heat transfer coefficient. Based on this the fluid temperature is calculated. Special features like Annulus, Solid- and Fluid bundles make it possible to simulate very complex structures of pipe-in-pipe and parallel pipes within structures of various solid materials. Taking into account that temperature is calculated along the pipes one obtains a combination of two-dimensional convective heat transfer within 3-dimensional heat conducting structures. Solid bundle cross section of 4 vertical tubes within rock – neighbour tubes are 2.5 m apart. The black "line" is a 7 / 769

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neighbour tubes are 2.5 m apart. The black "line" is a temperature iso-line. One clearly sees how the area between the tubes is subject to inter-tube heating.

Initial Conditions The requirement for initial conditions is a fundamental difference between a transient and a steady state model, e.g. the results of a steady state calculation may serve as the initial condition (at t=0 ) for a transient simulation. With OLGA the user decides, and later specifies in the input, whether the simulation is to start from a user defined condition (for instance a specific shut-in condition), or from a steady state multiphase flowing situation calculated by the program. The steady state pre-processor in OLGA can be used to provide good initial values for most production situation. In addition, the user may specify the initial condition in detail, for example for a shut-in system, by defining the initial values for pressures, temperatures, mass flow and gas fractions. Tools for interpolation are available, for filling in the initial values in all numerical sections of the system. Finally, the restart capability may be used to start a simulation from conditions saved during a previous simulation.

Boundary Conditions The boundary conditions define the interface between the simulated system and its surroundings and they are crucial to the relevance to any type of simulations. For a network of pipelines and wells there are several options available, but basically flow rate or pressure, in addition to temperature and gasliquid ratio must be specified at each flow path inlet and outlet boundary (at least one pressure must be given). The boundary conditions, e.g. a pressure, can be given as time series to model a certain transient situation.

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Moreover, the ambient temperature along the flow paths and ambient heat transfer coefficient (film heat transfer resistance) must be specified and OLGA provides a number of options for this, including water and air velocity profiles and seasonal variations of temperature. Inflow from reservoirs to well-bores define the most important boundary in a petroleum production network. In addition to various well-inflow correlations and options OLGA comes with an implicit coupling facility to the OLGA Rocx module which is a complete 3-D, 3-phase reservoir simulator. Separators, pumps, compressors and valves, all with controllers, can be modelled to improve the relevance of the outlet boundaries.

Fluid properties The necessary fluid properties (gas/liquid mass fraction, densities, viscosities, enthalpies etc.) are normally assumed to be functions of temperature and pressure only, and have to be supplied by the user as tables in a special input file. Thus, the total composition of the multiphase mixture is assumed to be constant both in time and space for a given part of the network. The user may specify different fluid property tables for each flow path, but has to ensure that a realistic fluid composition has been used to make a table for a flow path with a fluid mixture coming from two or more pipeline branches merging upstream.

It is also possible to perform simulations using Compositional Tracking, where the basic information on the chemical components is provided in a separate text file and then OLGA calculates the fluid properties internally with PVT routines provided by Calsep A/S. This means that the total composition may vary both in time and space, and that no special considerations are needed for the downstream system. Special models are also available for tracking hydrate inhibitors like MEG and methanol. The numerical solution of the OLGA model is generally able to handle multi component fluid systems but will normally have problems with single component systems or systems with a very narrow phase envelope.

Rheology The standard OLGA flow models assume a Newtonian rheology (viscosities are well defined fluid characteristics). Dispersions and non-Newtonian behavior are quite common in petroleum production and OLGA provides several semi-empirical models to account for more complex rheologies. In some cases the model takes care of the rheology with a minimum of user interference (e.g. for oil-water dispersions and also for waxy oils). For other systems the user needs to specify the various parameters for such fluids to describe e.g. Bingham or power law non-Newtonian behavior.

Network In OLGA the network comprises flow paths coupled with nodes which have a volume. General networks with closed loops can then be modelled, see below. The flow paths have a user defined direction but the flow is invariant to direction as such and any fluid phase may flow co-currently or counter-currently with respect to the pre-defined direction at any time and position. 9 / 769

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Pipe-bends are not accounted for as such (except for differences in static head). The user may apply pressure loss coefficients at boundaries between numerical sections. Equipment is positioned on the flow path – usually on a pipe-boundary. However, the separator in OLGA is a network component similar to a node. Controllers are specified as integral parts of the simulation model and they have their own network formalism.

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Threaded Execution Pipe sections belonging to the same branch may be updated in parallel. Suppose a branch has 100 sections, and that two threads are available to the OLGA engine: Section 1 and section 51 will be updated simultaneously, then section 2 and section 52 are updated, and so on. Depending on the computer hardware, this method can drastically reduce the time OLGA takes to advance one time-step. Normally, you do not need to change the default settings of neither OLGA nor your operating system. Parallel updating of segments is usually activated in the OLGA engine if your PC supports it.

Controlling the degree of parallelism The Windows operating system decides how many threads will be used. If your PC is equipped with a quad-core CPU, typically four threads will be simultaneously running to update four sections in parallel. Is your CPU a single-core Intel Xeon processor with "hyper-threading" (HT), probably two engine threads will be used. It is possible to overrule the choice of the operating system by setting the environment variable OMP_NUM_THREADS; use Windows' Control Panel to do this. However, the preferred way to change the degree of parallelisation is do so from the OLGA menu system. Setting the value here takes precedence over the OMP_NUM_THREADS environment variable. A situation where you might want to reduce the number of threads, arise if you execute parametric studies. Given that your license permits, it would be preferable to spend the CPU's cores on simultaneous simulations, rather than on speeding up each simulation in the study. Another situation could be when you don't want OLGA to consume all your computing power, e.g., if you want to write a report while OLGA is working. Most large cases will benefit from the parallelisation. Still, please note that some of your PC's cache memory will be used for forking and joining the threads, and doing the necessary book-keeping. As a consequence, special cases will run faster with a single engine thread.

Parallel speed-up The parallelisation encompasses heat calculations in section walls, updating fluid properties and flashing, and, most importantly, calls to the flow model which decides friction factors, liquid holdup and the flow regime. If the flow model calculations dominate the overall simulation, the utilization of the CPUs is most efficient.

Monitoring the OLGA process The Task Manager can be used to check how OLGA loads your CPU. When the number of engine threads equals the number of cores (or equals two on a single core HT-CPU) you should see the CPU usage being clearly over fifty percent when OLGA is simulating. In the Task Manager's list of processes it is possible to view the number of threads for each process. With 1 engine thread, it uses a total of 5 threads in batch mode, and 8 threads while running under control of the GUI. With 2 engine threads allowed, the task manager would display 6 threads for a batch run and 9 threads for a GUI run; with 4 engine threads the total number of threads would be 8 and 11, respectively.

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Applications When the resources become more scarce and complicated to get to careful design and optimisation of the entire production system is vital for investments and revenues. The dimensions and layout of wells and pipelines must be optimised for variable operational windows defined by changing reservoir properties and limitations given by environment and processing facilities. OLGA is being used for design and engineering, mapping of operational limits and to establish operational procedures. OLGA is also used for safety analysis to assess the consequences of equipment malfunctions and operational failures. REFERENCES contains a list of papers describing the OLGA model and its applications.

Design and Engineering OLGA is a powerful instrument for the design engineer when considering different concepts for hydrocarbon production and transport - whether it is new developments or modifications of existing installations. OLGA should be used in the various design phases i.e. Conceptual, FEED [2] and detailed design and the following issues should be addressed: • Design Sizes of tubing and pipes Insulation and coverage Inhibitors for hydrate / wax Liquid inventory management / pigging Slug mitigation Processing capacity (Integrated simulation) • Focus on maximizing the production window during field life Initial Mid-life Tail • Accuracy / Uncertainty management Input accuracy Parameter sensitivity • Risk and Safety Normally the engineering challenge becomes more severe when accounting for tail-end production with reduced pressure, increasing water-cut and gas-oil ratio. This increase the slugging potential while fluid temperature reduces which in turn increase the need for inhibitors and the operational window is generally reduced.

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Operation OLGA should be used to establish Operational procedures and limitations Emergency procedures Contingency plans OLGA is also a very useful tool for operator training Training in flow assurance in general Practicing operational procedures Initial start up preparations When systems become more complex and critical e.g. with long and deep Flow lines/risers, start-up situations need to be forecasted on a short-term basis and OLGA is regularly being used for assistance at start-up. Some typical operational events suitable for OLGA simulations are discussed below.

Pipeline shut-down If the flow in a pipeline for some reason has to be shut down, different procedures may be investigated. The dynamics during the shut-down can be studied as well as the final conditions in the pipe. The liquid content is of interest as well as the temperature evolution in the fluid at rest since the walls may cool the fluid below a critical temperature where hydrates may start to form. Pipeline blow-down One of the primary strategies for hydrate prevention in case of a pipeline shut-down is to blow down. The primary aim to reduce the pipeline pressure below the pressure where hydrates can form. Main effect that can be studied are the liquid and gas rates during the blow-down, the time required and the final pressure. Pipeline start-up The initial conditions of a pipeline to be started is either specified by the user or defined by a restart from a shut-down case. The start-up simulation can determine the evolution of any accumulated liquid slugs in the system. A start-up procedure is often sought whereby any terrain slugging is minimised or altogether avoided. The slug tracking module is very useful in this regard. In a network case a strategy for the start-up procedure of several merging flow lines could be particularly important.

Change in production Sometimes the production level or type of fluid will change during the lifetime of a reservoir. The modification of the liquid properties due to the presence of water, is one of the important effects accounted for in OLGA. A controlled change in the production rate or an injection of another fluid are important cases to be simulated. Of particular interest is the dynamics of network interactions e.g. how the transport line operation is affected by flow rate changes in one of several merging flow lines.

Process equipment Process equipment can be used to regulate or control the varying flow conditions in a multi-phase flow line. This is of special interest in cases where slugging is to be avoided. The process equipment simulated in OLGA includes critical- and sub-critical chokes with fixed or controlled openings, check-valves, compressors with speed and anti- surge controllers, separators, heat 13 / 769

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exchangers, pumps and mass sources and sinks.

Pipeline pigging OLGA can simulate the pigging of a pipeline. A user specified pig may be inserted in the pipeline in OLGA at any time and place. Any liquid slugs that are created by the pig along the pipeline can be followed in time. Of special interest is the determination of the size and velocity of a liquid slug leaving the system ahead of a pig that has been inserted into a shut-down flow line. Hydrate control Hydrate prevention and control are important for flow assurance. Passive and active control strategies can be investigated: Passive control is mainly achieved by proper insulation while there are several options for active control which can be simulated with OLGA: Bundles, electrical heating, inhibition by additives like MEG. Wax deposition In many production systems wax would tend to deposit on the pipe wall during production. The wax deposition depends on the fluid composition and temperature. OLGA can model wax deposition as function of time and location along the pipeline. Tuning Even if the OLGA models are sophisticated models made for conceptual studies and engineering will be based on input and assumptions which are not 100% relevant for operations. Therefore OLGA is equipped with a tuning module which can be used on-line and off-line to modify input parameters and also critical model parameters to match field data. Wells - Flow stability e.g. permanent or temporary slugging, rate changes - Artificial lift for production optimization - Shut-in/start-up - water cut limit for natural flow - Cross flow between layers under static conditions - WAG injection - Horizontal wells / Smart wells - Well Clean-up and Kick-off - Well Testing - Well control and Work-over Solutions

Safety Analysis Safety analysis is an important field of application of OLGA. OLGA is capable of describing propagation of pressure fronts. For such cases the time step can be limited by the velocity of sound across the shortest pipe section. OLGA may be useful for safety analysis in the design phase of a pipeline project, such as the positioning of valves, regulation equipment, measuring devices, etc. Critical ranges in pipe monitoring equipment may be estimated and emergency procedures investigated. Consequence analysis of possible accidents is another interesting application. The state of the pipeline after a specified pipe rupture or after a failure in any process equipment can be determined using OLGA. Simulations with OLGA can also be of help when defining strategies for accident management, e.g. well killing by fluid injection. Finally it should be mentioned that the OLGA model is well suited for use with simulators designed for particular pipelines and process systems. Apart from safety analysis and monitoring, such simulators are powerful instruments in the training of operators. 14 / 769

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powerful instruments in the training of operators. [2] Front End Engineering and Design

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Input files The OLGA simulator uses text files for describing the simulation model:

.opi; generated and used by the OLGA GUI .inp; input format used by OLGA 5 and earlier versions .key; input format used by OLGA The .key format has been introduced as the new input file format for the OLGA engine. The OLGA GUI will automatically generate files in this format (with the extension .genkey). The .key format reflects the network model described in the simulation model and should be the preferred format. In addition to the simulation file, OLGA handles input in several other formats as described in Data files.

Simulation description The input keywords are organised in Logical sections, with Case level at the top, followed by the various network components and then the connections at the end.

Case level Case level is defined as the global keywords specified outside of the network components and connections. Case level keywords can be found in the CaseDefinition, Library, FA-models and Output sections. The following keywords must or can be defined at Case level: CaseDefinition; CASE, FILES, INTEGRATION, OPTIONS, DTCONTROL, RESTART Library; MATERIAL, WALL, SHAPE, TABLE, DRILLINGFLUID, HYDRATECURVE Compositional; COMPOPTIONS, FEED, BLACKOILOPTIONS, BLACKOILCOMPONENT, BLACKOILFEED, SINGLEOPTIONS FA-models; CORROSION, FLUID, WATEROPTIONS, SLUGTRACKING, TUNING, SLUGTUNING Output; OUTPUT, TREND, PROFILE, PLOT, OUTPUTDATA, TRENDDATA, PROFILEDATA Drilling; TOOLJOINT CASE PROJECT="OLGA Manual", TITLE="Example case", AUTHOR="SPT Group AS" INTEGRATION STARTTIME=0, ENDTIME=7200, DTSTART=0.1, MINDT=0.1, MAXDT=5 FILES PVTFILE=fluid.tab MATERIAL LABEL=MAT-1, DENSITY=0.785E+04, CAPACITY=0.5E+03, CONDUCTIVITY=0.5E+02 WALL LABEL=WALL-1, THICKNESS=(0.9000E-02, 0.2E-01), MATERIAL=(MAT-1, MAT-1)

Network components The network components are the major building blocks in the simulation network. Each network component is enclosed within start (NETWORKCOMPONENT) and end (ENDNETWORKCOMPONENT) tags as shown below. Each data group belonging to this network component will be written within these tags. NETWORKCOMPONENT TYPE=FlowPath, TAG=FP_BRAN ... ENDNETWORKCOMPONENT

The following network component keywords can be specified (see links for further details on each component):

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component): FlowComponent;FLOWPATH, NODE ProcessEquipment;PHASESPLITNODE, SEPARATOR Controller;CONTROLLER ThermalComponent;ANNULUS, FLUIDBUNDLE, SOLIDBUNDLE FLOWPATH Piping The flowpath can be divided into several pipes, which can have an inclination varying from the other pipes in the flowpath. Each pipe can again be divided into sections as described above. All sections defined within the same pipe must have the same diameter and inclination. Each pipe in the system can also have a pipe wall consisting of layers of different materials. The following keywords are used for Piping: BRANCH; Defines geometry and fluid labels. GEOMETRY; Defines starting point for flowpath. PIPE; Specifies end point or length and elevation of a pipe. Further discretization, diameter, inner surface roughness, and wall name are specified. POSITION; Defines a named position for reference in other keywords. BRANCH LABEL=BRAN-1, GEOMETRY=GEOM-1, FLUID=1 GEOMETRY LABEL=GEOM-1 PIPE LABEL=PIPE-1, DIAMETER=0.12, ROUGHNESS=0.28E-04, NSEGMENT=4, LENGTH=0.4E+03, ELEVATION=0, WALL=WALL-1

Boundary&Initialconditions For the solution of the flow equations, all relevant boundary conditions must be specified for all points in the system where mass flow into or out of the system. Initial conditions at start up and parameters used for calculating heat transfer must also be specified. The following keywords are used for Boundary & Initial conditions: HEATTRANSFER; Definition of the heat transfer parameters. INITIALCONDITION; Defines initial values for flow, pressure, temperature and holdup. INITIALCONDITIONS is not required when a steady state calculation is performed. NEARWELLSOURCE; Defines a near-wellbore source used together with OLGA Rocx. SOURCE; Defines a mass source with name, position, and data necessary for calculating the mass flow into or out of the system. The source flow can be given by a time series or determined by a controller. WELL; Defines a well with name, position and flow characteristics. HEATTRANSFER PIPE=ALL, HAMBIENT=6.5, TAMBIENT=6, HMININNERWALL=0.5E+03 SOURCE LABEL=SOUR-1-1, PIPE=1, SECTION=1, TIME=0, TEMPERATURE=62, GASFRACTION=-1, TOTALWATERFRACTION=-1, PRESSURE=70 bara, DIAMETER=0.12, SOURCETYPE=PRESSUREDRIVEN

Process Equipment In order to obtain a realistic simulation of a pipeline system, it is normally required to include some process equipment in the simulation. OLGA supports a broad range of different types of process equipment, as shown below. It should be noted that the steady state preprocessor ignores the process equipment marked with (*) in the list below. 17 / 769

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the list below. The following keywords are used for Process equipment: CHECKVALVE (*); Defines name, position and allowed flow direction for a check valve. COMPRESSOR (*); Defines name, position and operating characteristics of a compressor. HEATEXCHANGER; Defines name, position and characteristic data for a heat exchanger. LOSS; Defines name, position and values for local pressure loss coefficients. LEAK; Defines the position of a leak in the system with leak area and back pressure. The leak can also be connected to another flowpath to simulate gas lift etc. PUMP (*); Defines name, type and characteristic data for a pump. TRANSMITTER (*); Defines a transmitter position. VALVE; Defines name, position and characteristic data for a choke or a valve. VALVE LABEL=CHOKE-1-1, PIPE=PIPE-1, SECTIONBOUNDARY=4, DIAMETER=0.12, CD=0.7, TIME=0, OPENING=1.0

Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUT(DATA); Defines variable names, position and time for printed output. PLOT; Defines variable names and time intervals for writing of data to the OLGA viewer file. PROFILE(DATA); Defines variable names and time intervals for writing of data to the profile plot file. TREND(DATA); Defines variable names and time intervals for writing of data to the trend plot file. TRENDDATA PIPE=1, SECTION=1, VARIABLE=(PT bara, TM, HOLHL, HOLWT) PROFILEDATA VARIABLE=(GT, GG, GL)

NODE Boundary&Initialconditions PARAMETERS; A collection keyword for all node keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. NETWORKCOMPONENT TYPE=Node, TAG=NODE_INLET PARAMETERS LABEL=INLET, TYPE=CLOSED ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_OUTLET PARAMETERS LABEL=OUTLET, GASFRACTION=-1, PRESSURE=50 bara, TEMPERATURE=32, TIME=0, TOTALWATERFRACTION=-1, TYPE=PRESSURE, FLUID=1 ENDNETWORKCOMPONENT

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Boundary&Initialconditions PARAMETERS; A collection keyword for all phase split node keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. SEPARATOR Boundary&Initialconditions PARAMETERS; A collection keyword for all separator keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. CONTROLLER Boundary&Initialconditions PARAMETERS; A collection keyword for all controller keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. NETWORKCOMPONENT TYPE=ManualController, TAG=SetPoint-1 PARAMETERS SETPOINT=(2:0.1,2:0.2,0.3), TIME=(0,2000,2010,4000,4010) s, STROKETIME=0.0, MAXCHANGE=1.0 ENDNETWORKCOMPONENT

ANNULUS Initialconditions PARAMETERS; A collection keyword for all annulus keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the Annulus ambient conditions. AnnulusComponents COMPONENT; A component to place within the annulus definition. 19 / 769

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Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. FLUIDBUNDLE Initialconditions PARAMETERS; A collection keyword for all fluid bundle keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the fluid bundle ambient conditions. BundleComponents COMPONENT; A component to place within the fluid bundle definition. Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. SOLIDBUNDLE Initialconditions PARAMETERS; A collection keyword for all solid bundle keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the solid bundle ambient conditions. BundleComponents COMPONENT; A component to place within the solid bundle definition. Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file.

Connections The CONNECTION keyword is used to couple network components, such as a node and a flowpath. Each flowpath has an inlet and an outlet terminal that can be connected to a node terminal. Boundary nodes (i.e. CLOSED, MASSFLOW, PRESSURE) has one terminal, while internal nodes has an arbitrary number of terminals where flowpaths can be connected to. CONNECTION TERMINALS = (FP_BRAN INLET, NODE_INLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN OUTLET, NODE_OUTLET FLOWTERM_1)

Separator and PhaseSplitNode has special handling of terminals. The CONNECTION keyword is also used for coupling signal components. CONNECTION TERMINALS = (FP_BRAN SOUR-1-1@INPSIG, SETPOINT-1 OUTSIG_1)

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Example file The keyword examples shown above can be combined to an OLGA .key file. CASE PROJECT="OLGA Manual", TITLE="Example case", AUTHOR="SPT Group AS" INTEGRATION STARTTIME=0, ENDTIME=7200, DTSTART=0.1, MINDT=0.1, MAXDT=5 FILES PVTFILE=fluid.tab MATERIAL LABEL=MAT-1, DENSITY=0.785E+04, CAPACITY=0.5E+03, CONDUCTIVITY=0.5E+02 WALL LABEL=WALL-1, THICKNESS=(0.9000E-02, 0.2E-01), MATERIAL=(MAT-1, MAT-1) NETWORKCOMPONENT TYPE=FlowPath, TAG=FP_BRAN BRANCH LABEL=BRAN-1, GEOMETRY=GEOM-1, FLUID=1 GEOMETRY LABEL=GEOM-1 PIPE LABEL=PIPE-1, DIAMETER=0.12, ROUGHNESS=0.28E-04, NSEGMENT=4, LENGTH=0.4E+03, ELEVATION=0, WALL=WALL-1 HEATTRANSFER PIPE=ALL, HAMBIENT=6.5, TAMBIENT=6, HMININNERWALL=0.5E+03 SOURCE LABEL=SOUR-1-1, PIPE=1, SECTION=1, TIME=0, TEMPERATURE=62, GASFRACTION=-1, TOTALWATERFRACTION=-1, PRESSURE=70 bara, DIAMETER=0.12, SOURCETYPE=PRESSUREDRIVEN VALVE LABEL=CHOKE-1-1, PIPE=PIPE-1, SECTIONBOUNDARY=4, DIAMETER=0.12, CD=0.7, TIME=0, OPENING=1.0 TRENDDATA PIPE=1, SECTION=1, VARIABLE=(PT bara, TM, HOLHL, HOLWT) PROFILEDATA VARIABLE=(GT, GG, GL) ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_INLET PARAMETERS LABEL=INLET, TYPE=CLOSED ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_OUTLET PARAMETERS LABEL=OUTLET, GASFRACTION=-1, PRESSURE=50 bara, TEMPERATURE=32, TIME=0, TOTALWATERFRACTION=-1, TYPE=PRESSURE, FLUID=1 ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=ManualController, TAG=SetPoint-1 PARAMETERS SETPOINT=(2:0.1,2:0.2,0.3), TIME=(0,2000,2010,4000,4010) s, STROKETIME=0.0, MAXCHANGE=1.0 ENDNETWORKCOMPONENT CONNECTION TERMINALS = (FP_BRAN INLET, NODE_INLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN OUTLET, NODE_OUTLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN SOUR-1-1@INPSIG, SETPOINT-1 OUTSIG_1) ENDCASE

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Simulation model An OLGA simulation is controlled by defining a set of data groups consisting of a keyword followed by a list of keys with appropriate values. Each data group can be seen as either a simulation object, information object, or administration object.

Logical sections The different keywords are divided into logical sections: · CaseDefinition; administration objects for simulation control · Library; information objects referenced in one or more simulation objects · Controller; controller simulation objects · FlowComponent; network simulation objects · Boundary&InitialConditions; simulation objects for flow in and out of flowpath · ProcessEquipment; simulation objects for flow manipulation · ThermalComponent; thermal simulation objects · FA-models; administration objects for flow assurance models · Compositional; administration and information objects for component tracking · Output; administration objects for output generation · Drilling; drilling simulation object · OLGA Well; OLGA Well simulation object

Network model A simulation model is then created by combining several simulation objects to form a simulation network, where information objects can be used within the simulation objects and the administration objects control various parts of the simulation. The simulation objects can again reference both information and administration objects. The network objects can be of the following types: · Flowpath; the pipeline which the fluid mix flows through · Node; a boundary condition or connection point for 2 or more flowpaths · Separator; a special node model that can separate the fluid into single phases · Controller; objects that perform supervision and automatic adjustments of other parts of the simulation network · Thermal; objects for ambient heat conditions The simulation model can handle a network of diverging and converging flowpaths. Each flow path consists of a sequence of pipes and each pipe is divided into sections (i.e. control volumes). These sections correspond to the spatial mesh discretization in the numerical model. The staggered spatial mesh applies flow variables (e.g. velocity, mass flow, flux) at section boundaries and volume variables (e.g. pressure, temperature, mass, volume fractions) as average values in the middle of the section. The figure below shows a flow path divided into 5 sections.

Each flowpath must start and end at a node, and there are currently three different kinds of nodes available: · Terminal; boundary node for specifying boundary conditions · Internal; for coupling flowpaths (e.g. split or merge) · Crossover; hybrid node for creating a closed-loop network

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OLGA 7 The figure below shows a simple simulation network consisting of three flowpaths and four nodes.

The flowpath is the main component in the simulation network, and can also contain other simulation objects (e.g. process equipment, not shown in the figure above). It is also possible to describe the simulation model with a text file. See Input files for further descriptions.

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Introduction With OLGA 5 a new graphical user interface (GUI) was introduced that replaced the OLGA 2000 GUI. OLGA 6 uses the same GUI as OLGA 5 with some additional features. The main new features in the OLGA 6 GUI are: Plot configurations (variables, colours, etc) may be saved as templates for easy recreation of plots Graphical configuration of signal network (controllers) New graphical configuration of Bundles New utility for running cases in batch (without having to start the GUI) The main new features of the OLGA 5 GUI compared with the OLGA 2000 GUI are: Graphical configuration and visualization of complex networks with Drag and drop Graphical copy paste Automatic detection and classification of internal nodes Positive flow direction can be indicated on flow path Pressure boundary nodes are distinguished Network coupling table with configuration capability Design time verification of model and listing missing items Errors are detected while the model is created Action buttons for missing items GEOMETRY Editor with spreadsheet type input Copy directly from Exce l Both XY and Length-Elevation input are displayed. Automatic Sectioning without simplification Direct access to simplification procedure with new angle distribution details Automatic inversion of pipe profiles which facilitates e.g. annular models New Plotting Functions Select variables from a complete list with descriptions Make your own standard sets of variables with units Within a graph - copy directly to and from Excel Spreadsheet type input and visualization of input series New Parametric study function New RESTART function Context sensitive help

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New Project A new project is defined by:

· Select File/New/Project · Ctrl+Shift+N · Click the New Case icon

or New Project at the base of the Start Page.

When starting a new project a new folder can optionally be created by checking the ”Create folder” box.

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New case A new case is defined in one of the following ways:

· Select File/New/Case (you will be taken into a dialog to create a new project if not already done) · Ctrl+N · Click the New Case icon Then, the window below appears:

Enter a case name (or use default), fill in location (or use default) and select template.

· OLGA Case File. This generates an empty case. · OLGA Basic Case. This generates a complete basic case. Ready for simulation. · OLGA Network case. This generates a complete basic case with an internal merge node.

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Open existing case You may open an existing Project, an existing OLGA case or an existing OLGA 2000 case (*.inp). If you open an existing case after you have opened or created a project the case will be added to the project. However, if you open an existing case without having a project, a project with the case name is created. You should save this project immediately. Open project Select either of these: · Select File/Open/Project · Ctrl+Shift+o and open a file with extension .opp. Open case Select either of these: · Select File/Open/Case · Ctrl+o · Click the Open Case icon and open a file with extension .opi, .key or .inp.

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Start page When opening the OLGA graphical user interface the Start page will appear. The central window contains a list of recent projects and the date when they were last modified. A project can be opened by double clicking on the case name. A new project can be started from the New Project button at the bottom of the screen.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Model view

The Model View is used for navigation between the objects of the system. The objects are ordered hierarchically with a Project on top comprising one or more cases. A case contains Case Definitions, Libraries, Output, Network Connections and Network Components.

· Case Definitions describe information common to the whole system simulated. · Network Components describe the properties of the flow network (currently either a node or a flow path). · Libraries contain keywords that can be accessed globally (for instance Material and Wall). · Output contains global output definitions, such as plotting intervals for trend, profile and output. · FA-models contains input to flow assurance models. · Compositional has input to the compositional model. · Advanced thermal contains input to the FEMTherm and bundle models and input to annulus calculations. When selecting an object in the project explorer, the object is made active and its properties may be edited in the ”Properties” view. The model view contains input for all cases in the project. Switching between the different cases is done by clicking on the file name in model view. See also 29 / 769

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Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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File view The ”File View” shows the input files of the project. By right clicking on a file the file can be removed or opened. If the file is a .opi-file (case-file) you get the option to open it as a text file. The text file is the OLGA 6 .key-format which resembles the OLGA 2000 inp-format. You may edit the key-file, save it and then reopen the case from the edited key fileby selecting 'reload from text file'

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Component view

Simulation objects may be fetched from the ”Components” window by Drag&Drop onto the Graphical Editor. Only objects available at the network level presented are available. This means that e.g. process equipment can be introduced this way only when the Flowpath is open. See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Property editor The ”Properties” window is a common interface to all simulation objects (keywords). Here the objects are defined setting values on the different keys. The left column gives the property name (currently the key name), the right its value. Units may be altered as shown in the figure. By default the value will update when the unit is changed. To keep the value: Press the Shift key while changing the unit. When a property is selected, a description is shown in the field at the bottom. Values may be inserted by typing or by selecting one or several values presented by the interface. The colours of the keys are the following meaning: Black : Key can be given but not required. Red : Key required. Grey : Key can not be given. Note that the colours will change as input is given. As an example: Two keys are mutually exclusive and one of them must be given. Both will then initially be red (required). When a value is given for one of the keys its colour will change to black (key is given and no more input required for that key) while the other key will turn grey (can not be given).

Some keywords have a special property page to make the process of entering data easier. These property pages can be accessed through the property editor button at the top bar of the property editor window.

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See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Network view Below you see a snapshot from the GUI with the template case Case0 loaded. All the windows are described in the following sections. The windows may be moved around (outside or inside the frame) and may be docked as described in Moving windows .

Click left button on canvas and use mouse wheel to zoom in/out

The central view in the figure above shows the Network view with its Graphical editor functions. Zooming in and out is done by the mouse wheel. Moving the mouse while the left mouse button is held down will move the layout within the window. Pressing Q adjusts the graphical view to the frames. Holding Shift and pressing Q zooms out in steps. Focus is shifted away from selected objects by pointing to the background while holding down the Shift key. Nodes and flow lines are drawn schematically. Network components (Nodes and Flowpaths) can be dragged into this view from the ”Components” window. Sources, Pressure boundaries and Process equipment are visible and their properties may be entered or modified by selecting the object (left-click) and filling in their "Properties”. In the figure the properties of the NODE OUTLET are shown to the right.

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The window above is the 2-dimensional Flowpath view which shows one Flowpath at the time. The functions for "moving" the graph are the same as for the Network view, see flowpath view for more details. You can drag equipment to the canvas from the Process Equipment Components on the left. When e.g. a valve is dropped on the canvas it "attach" to the middle of the Flowpath as illustrated below. The actual position and other data for the valve can be entered in the Properties window for the Valve which now is in focus (to the right). By entering the data e.g. the PIPE and SECTIONBOUNDARY the valve will take its specified position on the Flowpath.

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Each graphic view has its own tab and if you click on the Case0-tab (see below) you get back to the Network view.

We shall show how you make a new Flowpath: Start with dragging a Node from the Components window and drop it on the canvas, see above.

Then you make a new Flowpath by following the instructions in the drawing below:

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The new Node and Flowpath also appears in the Model View window, see below:

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An alternative method for adding a Flowpath. Select the Components window

Select a FLOWPATH and drag it to the canvas. Then drag a new node to the canvas.

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Then do as illustrated below.

Re-configure the network:

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Connecting Nodes and Flowpaths can be done as follows: · Point to the red dot at one end of a Flowpath (the red dot indicates that this end of the Flowpath is not connected). · Hold down the right mouse button, initially pointing to the blue square that has appeared at the end of the Flowpath. · Move the mouse pointer to the Node which the Flowpath should be connected to and release. · Select connect from the pop-up box that appears. The dot at the end of the Flowpath turns green, indicating that a connection is established. Alternatively: · Right-click on the view background and select Network Connections. · Select the "from-to" nodes for each Flowpath and click OK. The network should appear as specified.

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Right-click within the blue square and move pointer towards NODE_0. Select Connect to and release mouse button.

Do the same with the other end of the Flowpath.

Disconnect a Flowpath from a Node by left-clicking on the Flowpath and then point to the green dot at the end of the Flowpath. Hold down the left mouse button while moving the end of the Flowpath away from the node and release. The dot at the end of the Flowpath should now be red, indicating that it is not connected.

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Left-click on Flowpath, select green dot (left-click) and drag endpoint away from Node.

Right-click while pointing to an object in the Network view brings up various menus depending on the object: - Add : Add items to the network object. - Verify : Checks input file and reports errors and missing input in the output window. - Copy : Copy selected item. - Paste : Past the copied item onto the currently selected item. - Delete : Delete selected object. - Properties : Starts property editor for selected object. For a Flowpath this would be to Geometry Editor while for other items it would typically be a time series editor. For example: pointing to a Flowpath gives the alternatives below.

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Text labels in the Network view (which reside in their separate text boxes) can be rotated and scaled in addition to moved (except those for Flowpaths). Move is the default edit mode. You can either select the edit mode on the toolbar

or you can type one of the following letters to change the edit mode for the selected text box.

s:

Scale: (left-click in the triangle and drag while keeping the mouse button down)

r:

Rotate: (left-click in the sector and drag horizontally)

m:

Move: (left-click in the square and drag)

You can add fixed points on a Flowpath by pressing Ctrl while double-clicking anywhere on it. A fixed point, indicated by a small square, appears on the Flowpath.

The fixed points can be moved to shape the Flowpath (this does not change the actual geometry of the Flowpath).

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More points are added by repeating the Ctrl double clicking. You remove the fixed points by Ctrl double click within its blue square. Right-click in the Network view activates a menu with the following items:

Copy as picture: Network Connections:

A "Case.jpg" file with the Network view is copied to the folder where the project resides. Opens the network overview/connection window

Network plot allows for a quasi-animated plotting of profiles in the Network view. Configure:

Allows for (re)configuration of e.g. colours and line interpolation.

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3D View

Changes to 3D view as described in Moving view in 3D .

Show directions

Direction arrows are displayed on each Flowpath.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Flowpath view The actual profile of the geometry may be viewed by opening the Flow path; double click FLOWPATH in the ”Model View”. This opens a new tab in the Graphical Editor

showing the selected flow path only (including equipment). In the Flowpath view equipment may be added by drag and drop from the ”Components” window (the available components are now the ones that are located on a specific Flowpath).

Focus an object by a left mouse click to bring up the Property editor, and the properties of the object can be entered or modified.

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Focus is shifted away from selected objects by pointing to the background while holding down the Shift key. Zooming in and out is done by the mouse wheel and moving the mouse while the left mouse button is held down will move the layout within the window.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Connection view The connection view is used for showing connections for a single component or all connections in a case. The connection view can also be used to create new connections. The connection view has two modes. The above figure shows connections for a selected component. When a component is selected, all terminals for the component is shown in left column in the view. The column "Connected NC" shows the name of the network component which is connected. The column "Connected terminal" shows which terminal is used on the connected network component. In a signal connection a variable is given. This variable is shown in the column "Variable". Creating a new connection for a selected component: 1. Select a network component from the column "Connected NC". Only network components with compatible terminals are shown in the list of available network components. 2. Select a terminal on the component from the column "Connected Terminal". After selecting a terminal, the connection is made. 3. Select a variable (only for signal connections) from the column "Variable". The other mode is for showing all connections in the case. In this mode it is easier to see the direction of the signals (see figure below) Creating a new connection when showing all connections: 1. Select a network component in the column "From". 2. Select the out-signal (terminal) from this component in the column "Out". 3. Select a network component to receive the signal in the column "To". 4. Select the in-signal (terminal) in the column "In" 5. Select a variable (only for Transmitters) from the column "Variable".

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Output window The output window (not to be confused with the OUTPUT keyword/OUTPUT File) gives information about the state of the cases, modeling and simulations. The information comes out three categories:

· Error messages (and task list) - : Cannot simulate o Errors in input o Errors from initialization phase o Errors during simulation o List of incomplete keywords. o Click on the symbol to go to the incomplete keyword. · Warnings - : The simulation may still be performed [1] · Information o Simulator state changes o Progress during simulation o Any messages during simulation (info previously directed to DOS window) The windows can be cleared from the context menu (right click). Text can be copied: · Mark text · Right click and copy

Which Output categories are active are indicated by the "orange" background around the category names in the top bar of the output window. A left mouse click on the text will activate and deactivate.

By default the output from the active case is shown. Output from other cases is selected from the pulldown menu at the top of the output window.

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[1] Warnings from the OLGA interpretation of fluid files which takes place when the simulation has started are categorized as Information See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Time series editor Input keys that have time series can be edited in a time series editor. The time series editor is accessed through the properties for the relevant keyword.

If there are several independent time-varying parameters within one keyword the graph of these can be displayed by checking them in the graph legend (which shows the minimum necessary input parameters).

You can insert columns in the spreadsheet by right-clicking on a column-header, see below.

Selecting "cancel" nullifies all actions performed within the time series editor.

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A trick: to fill in the same value for several time points: enter the value in the column for the last timepoint and then enter.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Plotting Trend and profile plot output as defined by the user can be viewed during and after simulation. The plotting buttons on the top menu will show red lines when plot files are available for the active case.

TREND Plot PROFILE Plot Plot PVT file Multi-case plotting General features of the plotting tool Export/import data

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Active case trend plot Select trend plot with the buttons in the top menu. Trend plot gives you the menu below. Select the variables you want to plot. Move the selection over to the upper right hand side window where you may change units. Click OK to see the graph.

The default time unit for a Trend plot is Seconds which you change at the lower left.

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Active case profile plot You select the profile button and then select variable(s) to plot:

You may now "play-back" the profile plot, either by dragging the slide or by clicking the green triangle. You may also freeze a curve by clicking the "needle" button.

You get a frozen curve each time you click it. You "un-freeze" by disable the needle . The play-back is stopped by clicking the blue square. You may play-back several profiles simultaneously, but the speed will of course depend on your PC-capacity.

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Fluid properties You can use the plot-tool to plot fluid-properties. Select PVT file plot with the buttons in the top menu (.tab). You then select the property or properties you want to see and proceed as usual.

You may use the freeze-function as for profile plots. You click the nail and then the green triangle. You repeat clicking the nail to freeze more curves. The default x-axis is temperature. You can change this by moving the column header fields in the righthand side window to locate the "X-Axis" field (which is in the far right position by default) and select Pressure instead of Temperature.

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Multi-case plotting It is possible to plot results from several cases/projects simultaneously. For example you can plot data from all the cases in your project (use the Plot Project button in the select variables… dialog), the inactive as well as the one active. You can open several results files by the Tools -> Plot menu (select several files, either trend (.tlp) or profile (.plt) or from within the plot tool itself by adding files, see below. You plot as for single cases.

Note that for profile plots where different plotting intervals have been used in the different files the profile closest to the selected time will be used and no interpolation is currently applied.

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Some general features of the plotting tool The plotting tool is a quite sophisticated program and you have access to several functions for modifying your graph

· Add/remove data to plot: o Right click and select Dataset /Select or o Menu Options/Select Plot Variables · View values: Right click and select Track values · For profile plots: select plot time point with slider at bottom right · Collapse/expand axes: Right click and select o Axes/Collapse all or o Axes/Expand all · Display legend: Right click and select Show legend · Modify settings o Right click and select Configuration (window as below) or o Menu Options/Configuration · Zoom: o o o

Select upper left corner with left mouse button Drag to lower right corner while holding button Release

· Un-zoom: Do as for zoom, but drag to the left (any start and end point works) · Zoom in/zoom out/un-zoom buttons are also available

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Export/import data to/from MS Excel Export data: In the Select variable… dialog, mark the variables that you want to export and then press the Export button. The marked variable data are then copied to the clipboard and can easily be pasted into MS Excel. Some examples are shown below. Paste from Excel: Select data columns in and select copy. In Plot window right click and select Dataset->Paste. Trend:

All the variables marked in the selection dialog are copied to separate columns in the Excel-worksheet. Profile:

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When exporting profile variables, there are some options. First, choose the points in time that are of interest. Secondly, choose the output grouping. On time copies the variables sorted on time, while the On variable option copies the variables sorted on variables. See examples below:

Showing data sorted on time

Showing data sorted on variable

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Parametric Studies Parametric studies are defined through Tools-Studies, where new studies can be added or previously performed studies reopened.

The input screen for parametric studies is shown below.

The number of parameters is given in the field labelled "#Parameters”. At present studies can only be performed on the local machine, but the number of simultaneous simulation can be given (#Parallel simulations). This can be useful for machines with multiple processors or multithreading.

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The quick way to enter an equidistant parameter variation is given below:

Right-click in MASSFLOW below and select Set Value(s)

Set the e.g. the values below:

This results in the definition of 4 cases ready for running. You may save the study by clicking OK. The study is saved in a separate folder together with the Project/Case.

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Click Run Study and observe the progress:

For more information on XY-plot and Matrix see the Tutorial (accessed from the Help menu).

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Geometry editor Activating Enter a new profile Edit Geometries Edit the table Edit the graph Check angle distribution Filter the data Complete the data Define sectioning Use the new geometry Menus Limitations

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Activating Pipeline profiles are edited in the Geometry Editor. The tool can be started like this:

· Tools/Geometry Editor (opens with only default data) or · Select the Property page for the active geometry (opens with data for the selected geometry)

You may also select FLOWPATH (or GEOMETRY) in the Model-View and right click and then select Properties:

You will now see this graph of the default geometry for the single branch template:

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Enter a new profile You can work with an existing profile in the .xy-format by File/Import and opening the relevant xy-file with the browser (e.g. Profile-A.xy - this Geometry is given below).

You should save this new Geometry with a new label while in the Geometry Editor (e.g. GEOM-A. The saved geometry file has the extension .geo:

You must also give the new Geometry relevant sections, diameters, roughness and walls. How to do this is described below. You can also copy directly from an Excel –worksheet: Open the Geometry Editor and select Fileà New. You will get a new Geometry with one pipe and default values as given below. The geometry is now presented in a tabular format and you can toggle between this and the graphic format by clicking on the relevant tab.

Open the Excel-file with your profile-data, select the X-Y columns and copy.

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Select the Start Point 0, 0 in the Geometry Editor with the default geometry open and then Paste. You will get the question below. Answer yes and the data will be pasted directly over to your open geometry.

Please observe that if your excel geometry contains fewer pipes than the one you paste over you must delete the obsolete pipes. You can now save this Geometry (e.g. GEOM-B) and use it for one or several Flowpaths in any model. First you must of course complete it with sections, diameters etc., see below.

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Edit Geometries When opening the Geometry Editor you have seen that two views are available i.e. the graph of the profile and a table of pipes. The two windows can be viewed simultaneously by selecting the e.g. plot tab and drag it towards the bottom of the window (as has been done below).

See also Edit the table Edit the graph Check angle distribution Filter the data Complete the data Define sectioning Use the new geometry

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Edit the table New pipes are added, renamed or deleted, by right-clicking in the Pipe column and selecting the relevant action.

X and Y in the table give the data for the end point of the pipe. Changing Length-Elevation affects X-Y and vice-versa. Units are changed by right clicking in the title cell (e.g. ”r;Diameter [m]”) and selecting a unit.

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Edit the graph You can also edit the Geometry by the following actions under the Actions menu:

Normal (no change) A: Add a point M: Move a point D: Delete a point

Restrictions on the graphic editor can be imposed (Actions -> Restrictions):

X Fixed (X remains fixed, Y can be changed) X Bound (Point X-value can not be moved upstream or downstream neighbors) Y Fixed (Y remains fixed, X can be changed) Y Bound (Point Y-value can not be moved above or below neighbors) Recursive (all points downstream will follow the point that is being moved)

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Check angle distribution You can check the angle distribution of a Geometry by selecting Tools -> Check angle distribution. You can see the angle groups that are used by right clicking when in the output window from the angle distribution calculation. You can also change the angel groups. The colour of the bars and the % values in the output window indicate the difference between the average angle of the pipes within a group and the mean value of the angle group. Green (and a low % deviation) means a good relevance of the angle group. The % value is a numerically calculated standard deviation divided by half of the angle group span.

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Filter the data Select Tools/Filter. You have two options: a Box filter or a preservation of angle distribution / total flowpath length (the algorithm is identical to the one used in the OLGA 2000 Grid Generator).

Box filter: This filter is more relevant for removing relatively small disturbances from a pipeline survey. Enter the horizontal sample distance and the vertical sample height. These values define a moving rectangle (a box) within which all data points will be filtered out. The filtered data appear as a new geometry which may be further filtered/edited. Angel distribution: Enter the maximum pipe length that shall be used to filter the profile while maintaining the angle distribution and the total pipe length. When filtering has been completed it is a good idea to compare the angle distributions of the original geometry and the filtered ones. The filter with the best reproduction of the original geometry should be used – keeping in mind that the angel groups should be representative.

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Complete the data You may want to open the e.g. GEOM-A.geo file. All fields except the ”r;Length of sections” are editable directly, and copy/paste may be used for single cells. The "Length of sections" has its own input support-tools In contrast to OLGA2000 all Pipes must have a Diameter, a Roughness and a Wall (if relevant). You can use copy-paste functions to achieve this. If defined in the OLGA case, walls may be selected from the drop down menu. Within the Graph window the profile may be edited activating either of the four menu functions (found under Actions -> Graphical):

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Define sectioning The pipe sectioning can be performed in two ways: 1.

Manually enter number of sections in the ”r;# Sections” column. This gives you equally long sections for a given pipe.

2.

If you double click in the Length of Section list you enter a tool to distribute sections of various lengths over the pipe-length.

Change (the nominal) no of sections to 3 and enter 4.75 m in Section 1 and click OK.

You get 2 sections of 4.75 m and 1 0f 4.64214 m.

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The main rule is that the tool ensures that you get a sum of sections which is equal to the pipe length. Moreover, open section lengths mean that you repeat the value above. The "remaining of total" is the total pipe length minus length accumulated over the section lengths specified (including the open ones).

If you double-click in the Length of Sections field again

You get the window below and you see that the remaining now is very close to zero.

To start over again you can set # of sections to 0. 3.

Use the discretization tool (Tools/Discretize). Then all pipes are given the same selected number of sections.

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Use the new geometry A new geometry may be imported to a case as follows: Open the geometry files you want to use (you can open them from the Geometry editor or in explorer) Right click on FLOWPATH or Piping in the Model View, select ”r;Exchange Geometry” and pick the desired geometry. If you use the same Geometry file for several branches you must re-label the Geometries afterwards to secure that the labels are genuine. You can also exchange geometries between flow paths in the same case. Select the flow path and its Property Page of the Geometry you want to distribute to other flow paths. Then you select the flow paths that you want to import to and select Exchange Geometry. Select FLOWPATH and click on Properties. This opens the Geometry GEOM-1_2

Select destination FLOWPATH and click on Exchange Geometries and then on GEOM-1_2.

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Menus The Geometry Editor features the following menus: File New New geometry Import Import xy-data Open Open geometry file (*.geo) Close Close geometry Save Save geometry Save As Save geometry as new file Print Print active window Print Preview Print Setup Send Exit Edit Undo Cut Copy Paste Configure Configure graph window View Standard Restrictions Graph Status Bar Labels Actions Graphical Normal/Add/Move/Delete Restrictions X Fixed/X Bound/Y Fixed/Y Bound/Recursive Tools Angle groups Check Angle Distribution Check section lengths calculate the length ratio of adjoining sections. Discretize Automatic pipe sectioning (all equal) Filter Filter data Reset Pipe Labels Use default pipe labeling Reverse geometry Creates a geometry that is the mirror image of the original geometry (in xdirection). Window New window New window with active data (works on same data set) New window Select graph or table representation New Horizontal Tab Group New Vertical Tab Group More Windows Help Help Topics Not implemented About Geometry Version Information

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Limitations The following important limitation applies: 1. For export to Excel, dot (”r;.”) must be selected as decimal separator for Excel

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Moving windows Windows may be hidden and re-opened through the view menu. They may be detached from the frame (floating) and may be docked again by moving the window to the border of the frame. Double click on a floating window to move it back to the last docked position. In the picture below the blue area indicates where the window will end up if dropped at the current location. If the cursor is moved over one of the arrows towards the edge of the screen the window will dock on the corresponding border of the frame. If dropped on one of the four arrows in the centre of the screen the window will dock towards the corresponding side of the frame of the pipeline schematic window. Double clicking on the top bar of a docked window makes it float and double clicking on the top bar of a floating window makes it dock.

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Hot keys Ctrl+z z Leftshift+z Mouse wheel Delete

Undo Enable zoom in graphical editor; mark area with mouse Enable un-zoom in graphical editor; mark area with mouse Zoom in or out in graphical editor Deletes object

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Moving view in 3D The following illustration shows how to navigate the camera in fly mode. In Orbit Mode left mouse button + moving the mouse will make the camera orbit around the pivot point. If you release the left mouse button you can use the key combinations to move around. Camera maneuvering: · Mouse wheel · Arrows · Right shift · Left shift Left mouse button

Zoom in/out Move camera in/out/left/right Move up Move down (or: Insert move down) No selection: Rotate camera Network selected: Rotate network (see below)

Camera Movement Speed Slow to Fast Keys 1 – 9 Rotate/Move/Scale Rotate Move Scale

Select object + key R+ left mouse button + move mouse Select object + key M + left mouse button + move mouse Select object + key S + left mouse button + move mouse

Scene View Shortcuts Fly Mode Key F Orbit Mode Key O Field of View Mouse wheel, or key Z + left mouse button + mark area, or key Z + left mouse click (zoom in)’ Left Shift + key Z + left mouse click (zoom out) Space Deselect interaction mode Escape Deselect objects Q (in 2D View) Zoom to extent Delete [Del] Delete selected object.

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Graphic Configuration The graphical layout of individual flow paths can be changed through the Graphical configuration dialog. The choices made her will affect only the selected flow path.

If one want to change the layout of all the flow paths, this can be done in Tools -> Options ->Graphics.

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Menus File New > Project... New > Case... Open > Project... Open > Case... Save Case Save Case As... Duplicate Case... Save Project Close Project Print... Print Preview Print setup... Recent projects Recent cases Exit

Create new project Create new case Open project Open case Save case Save a new case Makes a copy of the selected case Save project Close (and save) project Disabled Disabled List of projects recently opened List of cases recently opened Exit

Edit Standard windows commands Undo Redo Cut Copy Paste Paste special...

Disabled Disabled

View Select what windows and toolbars to be visible.

Project Add New Item... Add Existing Item... Project Dependencies Close Project Simulation Run

Same as New Case Open an existing file e.g. an .opi file Option to specify the dependencies between the cases

Start simulation (Start simulation in batch- messages from simulation are sent to the Output window)

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Stop Pause Run Project Run Batch Run Project Batch

simulation are sent to the Output window) Stop simulation. Returns to initial state Pause simulation. Simulation may be resumed (Not implemented for OLGA). Start to run all cases in a project in a given order Start simulation in a DOS-control window. Start to run all cases in a project in a DOS-control window

Tools The tools available are listed below.

Windows Standard windows operations. Help Help topics GUI Manual Tutorial About OLGA

OLGA User Manual Opens OLGA GUI USer Manual (pdf). Starts OLGA 6 Tutorial Release information

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Toolbars Standard

New case Open case Save Save Project Copy Paste Undo Redo Model view Property editor Components File view Output view Connection view

Saves Case

Disabled

Simulate

Run Run Batch Verify

Start simulation Stop Pause Run batch in DOS window Verify case

Stop simulation. Returns to initial state. Disabled

Plot

Plot current trend plot Plot current profile plot Plot current PVT file View current Output File Layout

Fit window Move Scale Rotate Circular Grid

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Hierarchical type 1 Hierarchy Hierarchical type 2 Hierarchy Radial For systems with defined center V Layout algorithm direction is vertical. H Layout algorithm direction is horizontal. Layout of equipment Toggle between relative and sequential layout of inline equipment Snap to grid Toggle snap to grid

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Properties and settings The overall simulator settings are specified under Tools->Options; making it possible to work with different simulation engines under the same GUI (this includes OLGA 2000 versions as long as it accepts the keywords you actually use). Settings under the General tab are: My Project locations: Location where file dialogs will open. Show start page at start-up: If applied - start-page with recent projects will appear when starting the GUI. A sub-setting is "show the project list on the start-page". Use cached static data: This is set by default during installation. The GUI will then store certain data the first time the simulator is started. This speeds up file loading and is recommended to obtain the best performance from the program. The General tab can also be used to specify if the program shall execute auto-save at specified intervals. In the OLGA version tab one can specify which version to use by marking one of the displayed versions. External programs that should be available from the Tools menu can be specified under the External Tools tab. Some programs are set by default during installation and the user can specify additional programs like Excel, a text-editor etc. The Graphics tab is used to specify the pipeline layout view: Turn the background grid on and off and specify the colours of the gridlines. Set the canvas colour. Choose the interpolation method for the flowpath lines. Set flowpath colour.

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Simulation with bundles This description covers Fluid Bundles, Solid Bundles and Annuluses. In OLGA 6 these bundle types are network components. In this chapter the simulation of bundles is illustrated by a SOLIDBUNDLE example. To add a SOLIDBUNDLE right click the case level tab and choose Add > ThermalComponent > SOLIDBUNDLE (see figure below).

When the Solid Bundle is added, go to the property window and specify the required fields: DELTAT and DTPLOT. These parameters govern the frequency of updates of output from the FEMTherm computation (i.e. the computation of temperatures in the solid). The LABEL and MESHFINENESS fields may also be updated. A bundle in OLGA 6 consists of several components. The components of the bundle are flowpaths, shapes and possibly internal bundles. Note that all the components that constitute the bundle must be defined (added) elsewhere. Flowpaths and Lines must be defined as FlowComponents, Shapes must be defined under Library and bundles must be defined as ThermalComponents. Position labels to use for the specification of TO and FROM must be defined for each flowpath under "Piping". To add a component to a bundle (i.e. to specify that it is a part of the current bundle) choose Add > BundleComponents > COMPONENT in the Model View as shown in the figure below.

In the property window for the new component, specify the required fields:

· The type of the component (specify either a FLOWPATH, a LINE, a FLUIDBUNDLE, an ANNULUS or a SHAPE) · The start and stop position of the Bundle (TO and FROM) · The geometric center of the component (XOFFSET and YOFFSET) · The OUTERHVALUE of the component (optional) Note that the position of the origin of any cross-sectional coordinates is irrelevant as long as all coordinates within one and the same bundle refers to the same coordinate system. It is only the relative cross-sectional position that matters. 92 / 769

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coordinate system. It is only the relative cross-sectional position that matters.

About SHAPES A SHAPE in OLGA 6 defines the circumference of an area where a cross-sectional temperature profile may be computed by the FEMTherm module. Within this area heat is assumed to be transported by conduction in the radial direction. To add a SHAPE to a case right click the Library in the Model View and choose Add > SHAPE. In the property window for the new shape, fill out the type of the shape (CIRCLE, ELLIPSE, RECTANGLE, POLYGON) and the material. For any type of SHAPE the layout of the cross-section must also be defined. As illustrated by the property window to the right, a Circle requires the specification of a radius, an ellipse requires a width and a height, a rectangle requires the specification of coordinates of the lower left and upper right corners, and a polygon must be defined by a series of coordinates.

About LINES A LINE in OLGA 6 is a flowpath for which a simplified one-phase computation is performed. LINEs can be connected in networks, just as regular flowpaths can, but in a LINE network all the network components must have the parameter LINE set to YES. A complete case may contain several LINE-networks and several multiphase networks, but the two types of networks can not be coupled to each other. To add a line to a case in the GUI, right click the FlowComponent in the Model View and choose Add > FLOWPATH. In the property window for the new flowpath select LINE=YES. Then select FLUIDTYPE (gas, oil or water). Connect the LINE to a node in the same manner as other flowpaths are connected. Note, however, that the connected nodes must also have the parameter LINE set to YES.

About CROSSOVER nodes A CROSSOVER node in Olga 6 is a special type of single phase node which can be used in LINE networks only. The CROSSOVER node is a pressure boundary node with the following additional features: It must be connected to two LINES, and it imposes a given pressure difference (called MAXPRESSUREBOOST) between these two lines (at the connection point). A crossover node is added to a case in the same manner as any node is added: right click the FlowComponent in the Model View and choose Add > NODE. In the property window for the new node select TYPE=PRESSURE and LINE=CROSSOVER, then enter the rest of the required fields.

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Simulation with Controllers In OLGA 6 the controllers are signal components. Signal components are a special kind of network components, able to transfer signals between each other. Coupling in the signal network is possible between the following components (notice that a controller is always involved): · Pipeline section variable (via a transmitter) to controller · Inline component (ex. valve, pump, compressor etc.) to controller · Sources (source and well) to controller · Node variable to controller · Separator variable to controller · Controller to controller · Controller to inline component · Controller to separator · Controller to source This chapter describes how to connect signal components in the GUI.

Signal network terminology The following explanations of the terminology used for signal networks can make it easier to understand how controllers are connected to other components. A signal component is a component that can send and/or receive a signal. A signal component (e.g. a controller) is connected to other signal components (e.g. a flowpath) via terminals. Terminals are best explained with an example; A PID Controller has 3 terminals, 2 for receiving signals (the setpoint signal terminal and the measured signal terminal) and one for sending signals (the output signal terminal). Another signal component like a separator can send its holdup value as a signal to the PID Controller. The holdup will be sent via the measured signal terminal of the controller. The PID Controller will calculate an output signal based on the measured value and send it via the output signal terminal to e.g. a valve. A signal is just a value. There isn’t much difference between a signal in a signal network and a flow in a flow network. The flow represents a physical flow of oil, gas or water while the signal can represent anything. The meaning of the signal to the signal component depends on which terminal that is used to send the signal. In the example above the signal represented a measured value since it was sent via the measured signal terminal. A flowpath may send measured values as signals. To do this one must add a transmitter to the flowpath. The transmitter acts as an output signal terminal for the flowpath. Most inline process equipment added to the flowpath can act as a signal terminal for the flowpath in the same way as a transmitter (you may for example connect a controller directly to a valve).

Graphical configurations of controller connections Coupling of signal components is possible with two different techniques in the graphical user interface; i) Coupling with drag and drop - or ii) Coupling through the connection view

Drag and drop coupling The drag and drop coupling between two signal components is done in the same manner as between two multiphase network components: 1. Click a component and drag towards another component in the signal network (see list of legal couplings above) 94 / 769

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2.

Release on the second component. A context menu is shown with available terminals to connect from and to

3.

Choose one of the available terminals to connect from (only OUTSIG_1 is available in the figure above) and a terminal to connect to (MEASRD and SETPOINT is available in the figure above). A connection between the two components is created.

4.

Select variable to transmit. If the coupling is between a transmitter and a controller, a variable to be transmitted has to be given. Setting this variable must be done in the connection view

Coupling using the connection view The drag and drop technique for coupling components in the signal network is less practical when the case is large with many components. Dragging from one component to another may involve zooming to view both components, and thereby making the coupling difficult. It is possible to connect signal components using the connection view without seeing the other components. In the figure below the connections for a PID-controller is shown. All terminals (in-/out-signals) for controller CNTRL-1 are listed in column one (Terminal). Column two (Connected NC) and three (Connected terminal) lists which network components and terminals the controller is connected to. If a user-chosen variable is supposed to be transmitted column four (Variable) is used. 95 / 769

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The connection view has two modes. The above figure shows connections for a selected component. The other mode is for showing all connections in the case. In this mode it is easier to see the direction of the signals (see figure below)

Hiding and deleting connections If there are many controllers the case may be too complicated to get a good overview. In such cases you may hide the controllers and their connections. Do this by right clicking on a controller and select 'Hide'. To hide all controllers select 'Hide all of this type'. If you have connected a controller by mistake you may delete the connection by selecting it and pressing the 'Delete' button. NOTE: If you delete a controller the connection is not deleted automatically - you have to select the connection and press the 'Delete' button.

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Simulations with separators In OLGA 6 the separator is a network component. This means that it can not be inserted into a flowpath the same way as inline process equipment (like sources and valves). The separator has four types of terminals, INLET, GAS, OIL and WATER (only for three-phase separator). One or more flowpaths leads into the separator and are connected to the separator INLET terminals. It is required to connect at least one flowpath to each terminal type. All terminals allow both in and out flow from the separator. A separator is connected to flowpaths much the same way as nodes. Chapter 8.1 shows how a separator is coupled to flowpaths and nodes.

Graphical configuration and multiphase coupling of separator The multiphase coupling of a separator is made in the same manner as a multiphase coupling between a node and a flow path. Add a node and a separator to your case from the component view. Connect a flowpath from the node to the separator as follows: 1. Click the node and drag. 2. Release on separator. 3. A context menu will display which out-terminals on the node it is possible to connect from and which in-terminals on the separator it is possible to connect to. In the figure below the flow path is connected to the inlet terminal of the separator

Add another node to your case. Connect a flowpath from one of the separator outlets to the node as follows: 1. Click the separator and drag. 2. Release on the node. 3. A context menu will display which out-terminals on separator it is possible to connect from and which in-terminals on the node it is possible to connect to. In the figure below the flow path is connected from the gas outlet terminal of the separator to node 1. The oil outlet terminal of the separator is connected via another flowpath to node 2. 97 / 769

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2nd order scheme Mass equations can be solved with two different schemes in OLGA. The default is a 1st order scheme (upwind implicit) and the alternative is a 2nd order TVD scheme. The 1st order scheme is more robust and should be the preferred choice in most situations. The 2nd order scheme has less numerical diffusion and therefore keeps holdup fronts better. See also: When to use Methods and assumptions Limitations How to use

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When to use The 2nd order scheme for mass equations is to be used when it is important to track relatively sharp holdup fronts. Examples are: 1. Oil-Water fronts 2. Inhibitor fronts 3. Gas-Oil fronts

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Methods and assumptions The 2nd order method used for the mass equations is a combination of different numerical schemes in order to get a stable method which satisfies the TVD (Total Variation Diminishing) condition. For smooth gradients the method is 2nd order while for non-smooth flow (shocks) the method reduces to 1st order upstream. The smoothness of the data is measured on the control volume boundary like this

Where m is the mass and θ is the measure of smoothness. If θ < 0 the method reduces to first order upstream and if θ > 0 the method uses 2nd order methods. In the 2nd order region the numerical scheme is determined based on a 2nd order limiter. In OLGA the limiter known as the van Leer limiter is chosen.

Simulation differences between the 1st order and 2nd order schemes

Figure 2 Profile plot of an oil–water front showing the differences between the two schemes. The number of sections in the pipeline are 50, 100 and 500, respectively.

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Figure 3 Profile plots of a gas–oil front. The number of sections in the pipeline are 50, 100, 200, 500 and 1000, respectively.

Figure 4 Trend plot showing the hold-up at the top of a riser. The number of sections in the riser are 15, 30 and 60, respectively.

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Figure 5 The above figures show profile plots of an oil–water front. Inside the area filled with water, there are three areas containing MEG.

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Limitations The 1st order scheme diffusive behavior reduces unphysical numerical instabilities in the simulation if they occur. For simulations where instabilities are observed it is not recommended to use the 2nd order scheme. For such problems the 2nd order will only make matters worse because it enhances the numerical oscillations. Since the 2nd order method is only implemented for the mass transport equations the final result from the equation set will not converge to 2nd order accuracy. The improvement in the result will also differ depending on which physical phenomena which are of interest. For example simulations where pressure waves or temperature waves are of interest the improvement from the 2nd order method will be small. For simulations where propagation of holdup fronts is of interest the improvement can be significant. The 2nd order method only works if the CFL criterion is fulfilled. This means that it is not possible to violate CFL criterion by increasing MINDT when the 2nd order options is set.

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How to use The 2nd order scheme for the mass equations is activated by setting MASSEQSCHEME=2NDORDER in the OPTIONS keyword.

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Blackoil Blackoil modelling allows one to make a compositional model with a minimum of input. Compared to compositional tracking, the blackoil module is faster in terms of CPU cycles, and it treats shut-in cases more accurately than does the standard PVT table option. The module makes it possible to perform calculations with a minimum of information about the production fluids. Details about the fluid composition are not required for a blackoil simulation; specific gravity of gas and oil and the gas–oil ratio (GOR) at standard conditions are the only necessary data. If water is present, also the specific gravity of water must be input. Note that no fluid table is needed. A blackoil feed can consist of one gas, one oil and one water component. The gas component consists of hydrocarbon gas, and optionally H2S, CO2 and N2 components. It is possible to specify more than one blackoil feed, and for such a mixture each component of each feed is tracked, cf. the example network in Figure A below. Inside the OLGA engine, the blackoil module uses the framework of the compositional tracking module to track the components through the pipelines. Water properties are calculated by the standard OLGA routines. The physical properties of gas and oil are calculated from correlations belonging to a specific blackoil model – the user has a choice between four different blackoil correlations. To find the properties at a position in a pipe, the correlations use the pressure and the temperature, as well as the specific gravities of gas, oil and water, and the GOR, at that position. In the case of multiple feeds, the specific gravities and the GOR are mixture values. The mixture is the average taken over the constituting blackoils weighted by volume at standard conditions.

Figure A: Network case with several blackoil fluids (feeds) specified. Each component is tracked through the network. The fluid properties are calculated based on the fluid mixture. See also: When to use Methods and assumptions Limitations How to use

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When to use Due to the limited amount of input, the blackoil module can be a good choice when little is know about the production fluids. For instance, during planning or design one may use specific gravities and a GOR typical of the geographical area. Later when production is established, one may insert the actual values, and possibly make use of the module’s tuning mechanism to further improve the match between observations and the predictions made by OLGA. As mentioned above, the blackoil module is related to the compositional tracking module, and may be preferred as the computationally faster alternative. This is due to the fact that blackoil models are intrinsically crude, and cannot provide the detailed analyses of compositional tracking. It is however possible to include the effects of MEG in the density calculations by specifying a larger specific gravity for water. This method should also be used if salts are present.

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Methods and assumptions The following three assumptions are made for the blackoil module: 1. An oil component cannot exist as gas in the gas phase. As a consequence, the module is not suited for studying gas condensate systems. However, this assumption does not exclude the dispersion of oil and water, the existence of water/oil droplets in the gas or gas bubbles in the liquids. 2. Gas can dissolve in oil. 3. Gas cannot dissolve in the water phase, and water cannot exist as steam in the gas phase. (This assumption may change in a future version of OLGA.)

Blackoil Correlations To calculate the solution gas-oil ratio RSGO and the bubble point pressure Pb, four different correlations are available in OLGA. They are based on fluids from different areas, and have recommendation for use as mentioned in Table 1. The default correlation is Lasater. Table 1: Blackoil correlations and their recommended usage. Standing /28/ API < 15 Based on fluids from California Lasater /27/ API > 15 Based on fluids from Canada, U.S. and South America Vazquez & Beggs API > 15 Similar as Lasater /29/ Glasø /30/ API > 15 Based on fluids from the North Sea These correlations can be used to calculate the bubble-point pressure, Pb, for a given GOR or an equilibrium value of RSGO (< GOR) at any pressure below Pb. If measured values for GOR and the bubble point Pb(Tb) are available, it is recommended to tune the correlations for RSGO(P,T) and Pb(T). In the following, the four sets of correlations are presented with their tuning coefficients.

Lasater Correlation The basis for the Lasater correlation is the following relationships: (a) with , and

(b)

.

(c)

For the purpose of calculating the RSGO, the above equations are inverted with GOR replaced by RSGO, and Pb replaced with the actual pressure P. That is, find yg from Equation (c) with P instead of Pb, and invert Equation (c) to get RSGO, viz.: .

(d)

Please note that if P > Pb, then RSGO = GOR. In these equations we have that API = 141.5 / γo - 131.5 yg = mole fraction of gas γg = specific gravity of gas 108 / 769

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= specific gravity of oil Mo = effective molecular weight of tank oil GOR = gas-oil ratio f1(yg) = tabulated function of yg f2(API) = tabulated function of API CPb = tuning coefficient (default = 1) CRSGO = tuning coefficient (default = 1) γo

Pressure must be given with a unit of psia, temperature in 0R (degrees Rankine), and GOR and RSGO in scf/STBO.

Standing Correlation The bubble-point pressure at a given GOR is given by (e) where (f) Symbols have the same meanings as for the Lasater correlation. To calculate RSGO, replace Pb with the actual pressure P, and replace GOR with RSGO, and invert Equation (f) to obtain .

(g)

If the pressure is above the bubble-point pressure, then RSGO = GOR. With the Standing correlation, pressure is measured in psia, and temperature is measured in 0F.

Vazques & Beggs Correlation For API < 30: , and .

(h) (i)

, and .

(j) (k)

For API > 30:

If P > Pb, then RSGO = GOR. Symbols have the same meanings as for the Lasater correlation. Units for pressure and temperature are psia and 0R, respectively.

Glasø Correlations For known GOR, the bubble-point pressure is given implicitly by 109 / 769

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, and

(l)

.

(m)

Substitute RSGO for GOR and P for Pb to obtain .

(n)

If P > Pb, then RSGO = GOR. Symbols have the same meanings as for the Lasater correlation. Units for pressure and temperature are psia and 0F, respectively.

Treatment of Water Water is treated as inert in the current version, hence no water vapour enters the gas phase, and natural gas does not dissolve in the free water phase. With regard to the water density and viscosity, the blackoil module uses the same built-in routines for pure water property calculations as for the standard PVT table option.

Oil and Gas Density The oil density depends on pressure, temperature and the amount of gas dissolved in oil. At pressures below the bubble-point the procedure is as follows. First, the oil volume formation factor BO is calculated, see /28/, ,

(o)

where .

(p)

Now, the oil density is calculated as .

(q)

The density at the bubble-point, ρob, is given by the above equations with RSGO = GOR. At pressures above the bubble-point, the compressibility is taken into account, and the density is calculated by .

(r)

co is the isothermal compressibility of undersaturated oil. .

(s)

Units for Equations (o) to (s): Temperature is given in 0F, pressures in psia. BO is given in bbl/STB. The basis for calculating the gas density is the compressibility equation of state, viz.:

pV = znRT.

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When other variables have units of psia, ft3, lbm, moles and 0R, the gas constant R has the value 10.72. Now, the gas volume formation factor, BG, can be expressed as .

(u)

The gas density is obtained from (v) where ρgsc = 0.0764 γg. (The value 0.0764 is the density of air at standard conditions expressed as lbm/ft3). γg denotes specific gravity of gas at standard conditions. The gas compressibility z expresses the deviation of the real gas volume from the ideal gas behaviour. The assumption that real gas mixtures will have the same z-factor for the same values of pseudoreduced pressure Ppr and temperature Tpr, is used to determine the value of z. An algebraic relationship, cf. /28/, has been developed, and this relates z to Ppr and Tpr. The implicit set of equations that emerges, requires an iterative solution procedure. In order for OLGA to save CPU CYCLES, THE Z-VALUES HAVE BEEN PRE-COMPUTED, AND TABULATED AS A FUNCTION OF PPR AND TPR. Values for Tpr and Ppr are found from the pseudocritical temperature Tpc and the pseudocritical pressure Ppc:

Ppr = P/Ppc and Tpr = T/Tpc.

(w)

Empirical equations exist for Ppc and Tpc, /28/, and we use them: , and

(x)

.

(y)

As already mentioned, the units are psia and 0R. The presence of CO2 and H2S is accounted for by correcting the pseudocritical values Ppc and Tpc. Nitrogen, N2, is assumed to have no significant effect on the z-factor. The corrected values become

Tpc’ = Tpc - ε, and Ppc’ = Ppc Tpc’ / (T pc + B(1-B) ε),

(z) (aa)

where

A = yCO2 + yH2S, B = yH2S (yCO2 and yH2S are mole-fractions), ε = 120 (A0.9 - A1.6) + 15 (B0.5 - B4.0).

(ab) (ac)

Oil and Gas Viscosity Dead oil viscosity is calculated using the following equation: 111 / 769

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(ad) Now, the live oil viscosity μo is found by modifying the dead oil viscosity according to the gas dissolved in the oil, i.e., ,

(ae)

where , and

.

(af)

Note that Covisc is a tuning coefficient; its default value is 1. If the pressure is above the bubble pressure Pb, the above expression corresponds to the viscosity at the bubble point μob, where RSGO = GOR. For these pressures the viscosity is modified, viz.: , with

.

(ag)

Units: Pressures are measured in psia, temperatures in 0F, viscosities in cp and RSGO in scf/STB. The gas viscosity is calculated, according to /27/, from the correlation ,

(ah)

with

A = (9.379 + 0.016Ma)T1.5 / (209.2 + 19.26Ma + T ) B = 3.448 + 986.4 / T + 0.01009Ma C = 2.447 - 0.2224B Ma = 29γg (Ma is the apparent molecular weight)

(ai) (aj) (ak) (al)

Units: ρg given in g/cm3; T in 0R; μg in cp. Liquid viscosity is calculated as for the standard pvt table option with oil viscosity as above. Surface Tension The expression for the gas-oil surface tension needs to be simple without the information about the fluid composition. Given values of API, T (0R) and P (psia), we can use (am) for dead oil, and then correct the value for saturated oil at saturation pressure: .

(an)

For undersaturated oil, the corresponding saturation pressure for P(T,RS) is used. The unit of a surface tension σ is dynes/cm (1 dyne/cm = 0.001 N/m). The expression used for the gas-water surface tension is .

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For oil-water surface tension empirical data are scarce, and a preliminary relation is used: ,

(ap)

with default coefficients A1 = 30.0, A2 = 0.0 and A3 = 0.0. The above correlations are based on data from /31/ and /33/.

Thermodynamic Properties of Blackoil SPECIFIC HEAT OF GAS The specific heat or heat capacity of gas cpg will be tabulated as a function of temperature and specific gravity of gas. The data are taken from /31/, Figure 4-49. It is assumed that the specific heat of a gas mixture corresponds to the specific heat of a pure gas with the same specific gravity. SPECIFIC HEAT OF OIL The specific heat of oil, cpl, can be calculated using the following equation, cf. /32/: , (aq) where γo = specific gravity of oil

T = temperature in 0C The unit of cpl is kJ/kg0C. ENTHALPY OF GAS The enthalpy of gas, Hg is calculated from the equation (ar) The term (dH/dP)T can be expressed as -(RT2/P)*(dz/dT)P . From tabulated values for cpg and z, a table for Hg can be generated; 00C and 1 bara is used as the zero point. The compressibility factor z is tabulated as a function of Tpr and Ppr. Thus the term (dH/dP)TdP in Equation (ar) can be expressed in terms of Tpr and Ppr: .

(as)

ENTHALPY OF OIL The enthalpy of oil Ho is calculated directly by integrating cpo from zero to the actual temperature. Modifications of Ho at elevated pressures are ignored. ENTHALPY OF GAS DISSOLVED IN OIL The latent heat for gas dissolved in oil ΔHgo will be used to calculate the enthalpy of liquefied gas Hgo. We have 113 / 769

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We have

Hgo = Hg - ΔHgo

(at)

The term ΔHgo can be approximated by a simple correlation from /32/. First, the latent heat is estimated at 1 bara.

ΔHgosc = 4.19 Tabp (8.75 + 4.57 log(Tabp)) / M,

(au)

where Tabp is the atmospheric boiling point measured in K. The unit of the latent heat thus becomes kJ/kg. Second, the latent heat is extrapolated for pressures above 1 bara, according to

ΔHgo = ΔHgosc - 1.7 (P - 1)

(av)

Tabp is tabulated as a function of oil specific gravity and molecular weight, cf. /32/, see Table 2 below. Table 2: Tabp as a function of specific gravity of oil and molecular weight. Atmospheric boiling point, Tabp (0C) M 70 80 90 100 120 140 160 180 200 220 Spec grav. Tabp 0.6 27 42 60 79 104 128 146 165 190 205 0.9 66 93 116 132 165 202 222 252 274 294

Thermal conductivity Data for the thermal conductivity of gas as a function of M and T is plotted in /31/. A function has been developed that gives a reasonable approximation to these data, and this function is used by OLGA. Little data are available for oil, and so a simple linear function is used, viz.: ,

(aw)

The default values for the coefficients are:

, and

.

(ax)

Blackoil Tuning It is possible to tune the correlations for gas dissolved in oil RSGO, bubble pressure Pb and oil viscosity to measured data. Tuning of the correlations use data for a single fluid or a mixture. If there are several blackoil feeds (e.g., a network case), one must either tune to one of the fluids or to a mixture of the fluids. If the measurements are from a separator, the data available will typically be for the mixture. Please note that the tuned correlations are used for the whole network. See the description of the correlations for how the tuned parameters enter the calculations.

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the tuned parameters enter the calculations. Tuning is specified through the BLACKOILOPTIONS keyword.

Converting to mass flow rate When converting the volume flow rate at the standard conditions to the mass flow rate, the densities of gas, oil, and water that are used are taken from the corresponding blackoil components as given in BLACKOILCOMPONENT. When converting the in-situ mass flow rates to the volumetric flow rate at the standard conditions, the densities at the standard conditions are calculated from the blackoil correlations. The density from the blackoil correlations does not give the same density as the input. Therefore, the standard volumetric flow rates that are calculated by flashing the in-situ mass flow rate to the standard conditions differ from the standard volumetric flow rates given in the input. The difference is however within the uncertainty of the blackoil correlations.

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Limitations The blackoil module has the same limitations to its usability that the compositional tracking module.

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How to use Set the following keywords to use the blackoil module: OPTIONS to set COMPOSITIONAL = BLACKOIL BLACKOILOPTIONS to set GORMODEL (optional) BLACKOILCOMPONENT to set the properties of the gas, oil and/or water components BLACKOILFEED to combine the gas/oil/water blackoil components into feeds, and specify GOR and WATERCUT. NODE/SOURCE/WELL to set flow rates or volume fractions of the feeds to enter the pipeline system The steady state pre-processor may be used with the blackoil module. If one chooses to start from INITIALCONDITIONS, the initial volume fractions for the feeds must be given. See also: Sample case for Blackoil

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Complex Fluid Complex fluids are liquids with high viscosity, yield stress, or liquids exhibiting shear thinning. Such properties might arise in waxy oil or emulsions which often exhibit shear thinning and high viscosity, whereas a slurry of hydrate crystals in oil may have a yield stress depending on the particle concentration. Hydrate is a snow like substance formed by water and natural gas that might occur in hydrocarbon transport lines at ambient temperatures well above the normal freezing point of water at elevated pressure. Fluids that demonstrate both shear thinning and a yield stress, e.g., gelled waxy crude, can only be approximated using complex fluid models. The presence of yield stress or shear thinning in the liquid might result in a decreasing pressure drop with increasing production rates up to a certain point where the pressure drop is at a minimum, even for horizontal pipes. For production rates below this minimum, unstable operation might occur depending on the boundary conditions of the transport line. These instabilities can interact with other, more well known, multiphase flow phenomena such as terrain slugging and give rise to a wider range of unstable operational conditions. The purpose of the complex fluid model is to predict such behavior. See also: When to use Methods and assumptions How to use

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When to use The complex fluid module should be used whenever a fluid exhibits significant deviation from Newtonian behavior, either by shear thinning (e.g., heavy oils) or influence of yield stress (e.g., waxy oils). For Newtonian liquids, the module should be used when modeling fluids with viscosity above 50 cP and it has been tested up to 1000 cP.

License requirements The Complex Fluid Module requires a separate license.

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Methods and assumptions The complex fluid model utilizes the Bingham model for fluids exhibiting yield stress, while the Power law is used for shear thinning fluids. As opposed to the complex viscosity model, the complex fluid model includes numerous modifications to the physical models for both separated and distributed flow taking into account the non-Newtonian behavior of the fluids. Non-Newtonian behavior can be modeled for the liquid hydrocarbon phase, the water phase or both. The Newtonian option is included to capture the peculiarities of higher viscosity liquids. Bingham plastic model (a) where

Power law model (b) where K = consistency factor Newtonian fluid (c) where μ = viscosity When running standard OLGA, i.e., without slug tracking activated, the use of complex fluid yields an important improvement since the slug flow model includes the effects of the above rheologies and at the same time as it covers the range of Reynolds numbers from laminar to turbulent flow. This affects the bubble front velocity, and, consequently, the liquid accumulation. Furthermore, it yields a better model of the liquid flowing below the slug bubble as well as a better prediction of the slug fraction. Using this as basis for pressure drop predictions is a major difference from the complex viscosity model, which is very important for more viscous liquids. For stratified flow, the wall friction calculations should yield better results than when using an equivalent viscosity.

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How to use The Complex Fluid module is activated in the FLUID keyword by setting the key TYPE=COMPLEXFLUID. The fluid viscosity model to be used is determined by the keys CFLUML and CFLUMW for the liquid hydrocarbon phase and water phase, respectively. Except for the default Newtonian modeling, fluid viscosity can be modeled using either the Bingham model or the power law model. The parameters of the viscosity models can be given in two ways. If the key FULL=YES, the fluid viscosity parameters (yield stresses/power exponents) are read from the fluid property file as functions of pressure and temperature. If, on the other hand, FULL=NO, the yield stresses YIELDSRL and YIELDSTW or power exponents POWEXPL and POWEXPW have to be given if the liquid hydrocarbon or water viscosity model is set to BINGHAM or POWERLAW respectively. For both options, the viscosity given in the fluid file is interpreted as the plastic viscosity for Bingham fluids and as the consistency factor for Power law fluids.

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Compositional Tracking The compositional tracking model combines the powerful multiphase capabilities in OLGA with customised calculations for fluid properties and mass transfer. Part of this module is a software package developed by Calsep. With the compositional tracking model, every single fluid component is accounted for throughout the calculation, enabling simulation of scenarios such as start-up and blowdown with a high level of detail and accuracy. See also: When to use Methods and assumptions Limitations How to use

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When to use It is important to acknowledge that the extra level of detail given by compositional tracking compared to table-based approach is CPU-intensive and will increase the simulation time. Note that a higher number of components will also increase the simulation time. Standard OLGA will in many cases, such as for single pipeline flow and networks where the fluids in the pipelines are similar, give satisfactorily accurate results. Typical cases where compositional effects may have influence are: Networks with different fluids Changes in composition at boundaries Blowdown Gas injection / gas lift Start-up Shut-in and restart

License requirements The Compositional Tracking Module requires a separate license.

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Methods and assumptions The standard OLGA model uses a fluid table with material properties calculated for a predefined composition, and this composition is assumed to be constant throughout the whole simulation. Different compositions can be used for each branch in a system, but with compositions that are constant with time. In reality the composition may vary along the pipeline due to slip effects (velocity differences between phases), interphasial mass transfer, merging network with different fluids, elevated geometry, and changes in fluid composition at the inlet. In the Compositional Tracking model the mass equations are solved for each component (e.g. H2O, C1, C14-C22) in each phase (e.g. gas, liquid droplets, bulk hydrocarbon liquid and bulk water). Thus, the model will keep track of the changes in composition in both time and space, and will ensure a more accurate fluid description compared to using the standard OLGA model. Instead of using a fluid file with pre-calculated material properties, a so-called feed file must be generated (by PVTsim) and given as input to OLGA. The feed file contains information about the feeds (fluid composition used in a source or well and as boundary or initial conditions) that the user wants to use in the simulation, and about the components comprising the feeds. In addition, the user may define additional feeds through the FEED keyword. These feeds may only contain a set of the components defined in the feed file. It is not possible to define additional components outside the feed file.

PVT package The material properties of the fluid along the pipeline will be calculated continuously during the simulation, based upon the current conditions (i.e. local pressure, temperature and composition). These calculations are part of a PVT package delivered by Calsep. This PVT package uses functions that are similar to the ones used by PVTsim, although they are optimised for increased computational speed. PVTsim must also be used to characterize the fluid and generate the feed file to be used as input to the model. Moreover, the molar fractions and their derivatives with respect to the current conditions at phase equilibrium are also delivered by the package. Based on these results, the mass transfer between the phases needed for the mixture to be at equilibrium is calculated. Physical limits for the temperature and pressure used in the PVT calculations are introduced and can not be changed by the user (as it can with fluid tables). The temperature range is from -200 to 500 C and the pressure range is from 0.05 to 1000 bara. If the temperature or pressure goes out of range, they are reset to the upper or lower limits. These reset values are used in the PVT calculations only and are not fed back to the overall calculations of temperature and pressure. The phase equilibrium calculations in PVTsim are based on either the Soave-Redlich-Kwong (SRK) or the Peng-Robinson (PR) equation of state (EOS) [Soave (1972) and Peng and Robinson (1976)]. The fluid data in the feed file are based on one of these equations, with or without the Peneloux volume correction [Peneloux et al. (1982)], and the same EOS will be adopted in the OLGA simulation.

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Limitations Maximum number of components allowed in a feed file is 30. Except for this, there are no special limitations associated with the Compositional Tracking model. However, as described, be aware of the additional CPU-intensive calculations that are performed.

Other considerations Steady state pre-processor A compositional steady state pre-processor is implemented in OLGA. Process equipment The system can include process equipment such as critical and sub-critical chokes, compressors with controllers, check valves, valves, separators, heat exchangers, pumps, and controlled mass sources and sinks. Combination with other models The compositional tracking model can not be combined with other compositional models such as slug tracking, inhibitor tracking, blackoil or wax. Flow model The descriptions of the flow regimes, friction factors and wetted perimeters etc in the compositional tracking model are as in the standard OLGA model. Restart The Compositional Tracking model is available with full restart functionality. However, it is not possible to switch from or to the compositional model in a restart case.

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How to use Input In order to use the Compositional Tracking model, follow the steps below;

Step 1: Use PVTsim to characterize the fluids to the same pseudo components and generate the feed file with all the necessary compositional data for the fluid. The ”Plus” and ”No-plus” fluid types only require mole or weight fractions, mole weights and liquid densities. For the ”Plus” fluid, PVTsim will generate pseudo-components based on the last (plus) component. The ”Characterized” fluid type is used when the fluid characterization has been performed in another PVT tool, and requires all fluid properties such as critical temperature, accentric factor, etc. Choose ”Interfaces” from the Main Menu in PVTsim, and then choose ”Compositional Tracking”. In this window the feed file that is an input to the Compositional Tracking module is generated. The feeds defined in the feed file will then be available as feeds in OLGA, with the name specified in the Well column in the Fluid box in PVTsim as feed name.

Step 2: Prepare the OLGA input using the following keywords; OPTIONS; COMPOSITIONAL set to ON. FILE; FEEDFILE to specify the feed file name. FEED; to define additional feeds and their composition (use components from the feed file) COMPOPTIONS; to define calculation options to be used by the PVT routines. INITIALCONDITIONS; to specify initial feeds. SOURCE; to specify feeds and feed flows in the mass source. WELL; to specify feeds in the well stream. NODE; to specify feeds and feed flows in mass flow and pressure nodes.

Step 3: Specify output variables for detailed plotting of simulation information. OUTPUTDATA to print compositional information to output file (*.out). TRENDDATA to print compositional variables to trend file (*.tpl). PROFILEDATA to print compositional variables to profile file (*.ppl). PLOTDATA to print compositional variables to OLGA Viewer file (*.plt). Plot data for individual components can be specified with the addition of the COMPONENTS=() key to each plotting keyword. If COMPONENTS is not specified, it will be plotted for all components for the specified variable. Note: Output variables for rates at standard conditions (e.g. QGST) are CPU demanding since a flash must be performed, and should be used with care for Compositional Tracking simulations.

Special considerations In the keyword COMPOPTIONS the user should evaluate what flash algorithm to use, what kind of viscosity correlation to use, if any of the fluid components should be assigned delay constants, and if needed specify the density limit for the dense phase region. The user can also choose to use the default values, in which case none of these parameters have to be specified. 126 / 769

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Flash algorithms (key FLASHTYPE) The FLASHTYPE key specifies the flash algorithm to be used. FLASHTYPE = TWOPHASEFLASH treats water as an inert component. Hydrate inhibitors such as MeOH and glycols in the water phase will also be inert. A two-phase flash is carried out for the hydrocarbon components. There will not be any aqueous components in the hydrocarbon phases and no hydrocarbon components in the water phase. Classical mixing rule is used for all component pairs for the two-phase flash calculation. This is the only option allowed when performing simulations with fluids consisting purely of nonaqueous components. It may also be used with fluids containing aqueous components when high simulation speed is wanted, provided the amount of free water is believed to have little impact on the conclusions. It should not be used if: Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. FLASHTYPE = SIMPLETHREEPHASE means that the water components are treated as an inert phase initially. A two-phase flash is performed for the hydrocarbon components. Then aqueous components are added to the hydrocarbon phases, and hydrocarbon components and inorganic gasses are added to the aqueous phase until the fugacity is the same for all the phases. Classical mixing rule is used for all component pairs throughout the calculation. This approach involves two simplifications relative to full three phase flash The change in phase equilibrium due to dissolution of components in a phase is not taken into account, i.e. the result is not rigorous equilibrium but approximated equilibrium. A simplified model for the solubility of hydrocarbon components and inorganic gasses in the aqueous phase and vice versa is used. This is the default option when at least one aqueous component is defined in the feed file, and is expected to provide accurate results for most simulations involving fluids consisting of both hydrocarbons and aqueous components. Full three phase flash is recommended for rigorous simulations if Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. Note that simplified three phase is the recommend option for performing screening/approximate simulations where high accuracy may not be required even in the aforementioned cases. This is due to the full three phase option being significantly slower than the simplified three phase option. FLASHTYPE = FULLTHREEPHASE means that a full three-phase flash is performed for the total composition. The fugacity of all the components in all the phases is the same. All the phases are in rigorous equilibrium, i.e. any component can dissolve in any phase. Classical mixing rule is used for component pairs not involving aqueous components while the Huron-Vidal mixing rule is used for all component pairs involving aqueous components. 127 / 769

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This option is significantly slower than the simplified three phase flash option. It is recommended as an option to make a final check of whether the accuracy obtained using the simplified three phase flash is adequate for the given case. Full three phase flash is also recommended if Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. Note that simplified three phase is the recommend option for performing screening/approximate simulations where high accuracy may not be required even in the aforementioned cases. This is due to the full three phase option being significantly slower than the simplified three phase option. This is the only option allowed when performing simulations with fluids containing salts.

Viscosity correlations (key VISCOSITYCORR) The VISCOSITYCORR key can be used to specify the viscosity calculations. The viscosity calculations can be based on the corresponding states principle (CSP) or the LohrenzBray-Clark (LBC) correlation (1964). If the fluid has been tuned to one of the correlations in PVTsim, it is not possible to choose a different correlation in OLGA Compositional tracking module (an error will be given if the other correlation is chosen). The default viscosity correlation is CSP. When using CSP the PVT code executes 2-3 times slower than when LBC is used. Since 10-90% of the calculation time in an OLGA simulation is spent in the PVT code, the cost of using CSP instead of LBC may vary a lot. However, the LBC model is not reliable as a predictive model. The following steps should therefore be taken when using LBC: Tune LBC to experimental or simulated CSP viscosity data in PVTSim. Check if tuned oil viscosity data match reasonably well with the experimental data. If a good match cannot be obtained, use the CSP viscosity model in OLGA Compositional Tracking module (a mismatch is more likely for heavy oils). Substantial tuning of the a-coefficients in the LBC-model can affect the gas viscosity. Evaluate gas viscosity before and after tuning if the a-coefficients are changed considerably. In case the CSP viscosity model is chosen, it is still recommended to tune to experimental viscosity data if available. The predictive capability of the CSP model is within 10% up to viscosities of approximately 1 cP. For higher viscosities the capability is more uncertain. It is further recommended to consider if oil viscosities at temperatures below approximately 20-40 C are influenced by precipitated wax. The CSP and LBC viscosity models cannot account for the influence of precipitated wax, nor the non-Newtonian effects associated with the precipitation. The CSP and LBC models may still be forced to follow the apparent oil viscosities. Since the Compositional Tracking module does not account for wax precipitation/ deposition, viscosities will follow the apparent oil viscosity.

Dense phase specification (key DENSITYLIMIT) The DENSITYLIMIT key specifies the limit for the dense phase region density. 128 / 769

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In the dense phase region (see Figure A below), there are no good criteria to distinguish gas from oil, and the "chosen" phase does not affect the fluid properties for simulations with Compositional Tracking. This can be a problem especially for INITIALCONDITIONS where a user specifies e.g. voidfraction=0 for an entire branch, but gets an error saying that this is not valid input since there is no liquid for parts of the branch. The user then has to specify voidfraction pipe-wise, which can be a lot of work. Also, PVTsim might predict another phase than Compositional Tracking since a different and more time demanding approach is used, which adds to the confusion.

Figure A. Dense phase region. In the dense phase region, a fluid with higher density than the given DENSITYLIMIT value is defined as liquid and a fluid with lower density is defined as gas. If the user gets an error saying there is no gas for this branch the DENSITYLIMIT should be increased. The DENSITYLIMIT should preferably be set equal to the density found in PVTsim when performing a flash at the critical point. If not specified, internal routines will be used to decide phase (which may cause instabilities when crossing bubble/dew point). Note: The use of DENSITYLIMIT can also reduce oscillations, such as for cases with decreasing pressure where different sections cross from the dense phase region to the two phase region on each side of the critical temperature.

Delay constants (keys TCONDENSATE/TVAPORIZATION) The keys TCONDENSATE and TVAPORIZATION are non-equilibrium delay constants for the mass transfer from liquid phase to gas phase and vice versa. The keys can be introduced for each component, and the equilibrium state reached in the flash calculations will be delayed. The default is no delay. In the non-equilibrium model the convective mass transfer terms are calculated according to: (a) where u is the superficial velocity of the mixture flowing into the section calculated for the equilibrium conditions at the section and DZ is the section length. is the convective mass transfer term calculated by the equilibrium model for component fc. TDELAY,fc is the non-equilibrium delay factor for component fc, which has the dimension seconds. The user must specify the value of this factor, and separate values can be given for vaporization (TVAPORIZATION) and condensation 129 / 769 (TCONDENSATION).

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(TCONDENSATION). The local non-equilibrium mass transfer term is derived from the following equation:

(b)

where is the local mass transfer term calculated by the equilibrium model and is the delay factor for component fc for condensation or vaporization dependent on the sign of the equilibrium mass transfer term. This yields:

(c)

Output The keywords OUTPUTDATA, TRENDDATA, PROFILEDATA and PLOTDATA in the input file specify the data collection from the simulation. The output file (*.out), trend file (*.tpl), profile file (*.ppl) and plot file (*.plt) can be used to show detailed compositional information: Mass flow rate for each component in each phase (oil droplets, oil film, total oil phase, water droplets, water film, total water phase, and gas) Mass rate of flashing for each component to gas phase, oil phase and water phase Specific mass for each component in each phase Mole fraction for each component in gas phase, oil phase and water phase Equilibrium mole fraction for each component in gas phase, oil phase and water phase Mass fraction for each component in gas phase, oil phase and water phase Equilibrium mass fraction for each component in gas phase, oil phase and water phase Total mole fraction (all phases) for each component Total mass in branch for each component The output file shows information textually and is structured for easy reading. The trend file and profile file are ASCII files that can be plotted graphically in the OLGA GUI. The plot file is a binary file that is viewed in a separate plotting tool called the OLGA Viewer. Due to the binary format, which reduces the file size, this form of data collection can use a shorter plotting interval and is useful for detailed analysis.

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Controller introduction: Controllers is in OLGA terms a network component labeled “signal component” which mean that they can communicate with other network components by sending and receiving signals. Other network components may be other signal components or flow components (i.e. a branch). Controllers are typical signal components but also other types of network components may be signal components. All controllers have one common key; LABEL, which are used to identify the controller. There are 13 different types of controllers: Algebraic Controller ASC Controller Cascade Controller ESD Controller Manual Controller Override Controller PID Controller PSV Controller Scaler Controller Selector Controller STD Controller Switch Controller Table Controller

Both analog and digital controllers can be simulated in OLGA (see Analog vs. digital controllers for further details). A controller can be set to one of five different modes operation either by using time series in the MODE sub-key or hooking a defined controller up to the MODE terminal (see Controller modes for further details). In addition to implementing the possibility to switch the controller mode, the current version of OLGA also implements the possibility to “activate” and “deactivate” the controllers by hooking an external controller up to the ACTIVATE terminal (see controller activation/deactivation for further details). The controller output is constrained; see constraining the controller output for further details. In the most advanced usage of the OLGA controllers utilizes the possibilities of interconnecting controllers by the use of terminals. A description to the different terminals is given in controller details.

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Analog vs. digital controllers For all the controller types, the digital controller option can be selected by using the key SAMPLETIME. The difference between analogue and digital sampling in an OLGA simulation is as follows: The analogue controller collects input and gives a corresponding output at each simulation time step. The MAXCHANGE sub-key specifies the maximum allowed change in controller output from one time step to the next. The default value is 0.2. The automatic integration time step mechanism ensures that the relative change in the output signal of the controller from one time step to the next will never exceed MAXCHANGE. The digital controller collects input and generates a corresponding output at time points separated by time intervals given in sub-key SAMPLETIME. There may be one or more OLGA integration time steps in between each sample time point. The automatic time step control assures that a simulation time point always agree with a sample time point (to the accuracy specified in the MAXCHANGE sub-key). The output signal from the controller is kept constant during the sample time interval.

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Controller mode A controller in OLGA can be set in one of the five different modes:

Automatic In MODE = AUTOMATIC, the controller behaves according to the controller function as specified for the different controller types. For those controllers that make use of setpoint the value in MODE = AUTOMATIC is taken from the SETPOINT key.

Manual In MODE = MANUAL, the controller function is bypassed and the controller output is set according to the time series definition of key MANUALOUTPUT.

External signal In MODE = EXTERNALSIGNAL, the controller function is bypassed and the controller output is set according to the external controller connected to the SIGNAL terminal.

External setpoint The controller MODE = EXTERNALSETPOINT is similar to MODE = AUTOMATIC except that the setpoint is taken the controller connected to the SETPOINT terminal.

Freeze In MODE = FREEZE, the controller function is bypassed and the controller output is kept constant (equal to the previous output value). The controller MODE can be manipulated either by time series or by another controller. To manipulate the mode of a controller by time series, specify the sequence in the MODE sub-key. The predefined literals: AUTOMATIC

value 1

MANUAL

value 2

EXTERNALSIGNAL

value 3

EXTERNALSETPOINT value 4 FREEZE

value 5

are used when specifying the MODE through MODE sub-key in the GUI and input file. The MODE subkey is interpreted together with the TIME sub-key. When using the terminal to change the mode of a controller one need to connect an external controller to the MODE terminal. E.g. to manipulate the mode of controller A by a controller labeled A.MODE connect controller A.MODE to the MODE terminal of controller A. The mode of controller A id the dependent on the output value of A.MODE A.MODE

<

1.5

gives AUTOMATIC

1.5

Pc) there is no flow as there is a check valve that stops the flow going from the tubing to the casing. In the input to OLGA the terms “injection pressure” and “production pressure” is used instead of “casing pressure” and “tubing pressure”, respectively, since the injection gas may be injected in the tubing instead of the casing, and the well fluid flows up the casing. The intention of the GLV is to allow flow from the injection to the production side, so using the terms injection/production makes the input more general.

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Figure B:

Sketch of typical casing (injection) pressure operated GLV (with gas charge)

The GLV in Figure B is characterized as an Injection or Casing Pressure Operated GLV since the injection/casing pressure works on the large part of the bellows (AINJ) while the tubing pressure works on the small part (APROD). The force balance for the point where the GLV starts to open is then: (a) where R = ASEAT / ABELLOW. PINJ and PPROD switch places in the equation for a Production or Tubing Pressure Operated GLV. Calculation of flow from curves The standard volume gas rate through the GLV is found by linear interpolation in the user-given response curves (defined in LEAK/GASLIFTTABLES) using the calculated injection pressure (upstream the GLV) and production pressure (downstream). First, the code finds the two response curves with injection pressures that are closest (higher and lower) the current injection pressure. One gas rate is found for each curve by interpolating using the current production pressure, and then the resulting gas rate is found by interpolating between these two rates using the current injection pressure. If the current injection pressure is below the lowest given injection pressure, the curve for the lowest injection pressure is used directly and vice versa for injection pressure above the highest given injection pressure. That is, no extrapolation for injection pressures. Extrapolation is performed in the direction of decreasing production pressure to find the opening production pressure, if not given (allowed with a negative extrapolated value, as would be the case for the injection pressure of 790 psig in Figure A). It is required that the last point in a response curve (the point with highest production pressure) has a gas rate of 0. It is possible to create a curve with only one point for which this is not a requirement (a way to specify constant standard volume flow for all production pressures below the injection pressure). Associated liquid (in case of liquid on the injection side) through the GLV is calculated by setting the total mass flux WTOT [kg/(m2s)] as:

(b) where WG is the gas mass flux derived from the response curves, rG is the gas density and rmix the volume averaged density. For each phase, P, (gas, oil, water, etc.) the mass flux through the GLV is: 279 / 769

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(c) where xP is the mass fraction of the phase upstream the GLV (in the section where the GLV is placed). Temperature effect In the case of a gas charged dome (a GLV might have a spring instead) the pressure in the dome will increase with increasing temperature as the gas is contained in the dome. This means that the required force from the production and injection side to open the GLV also increases with increasing temperature. According to Winkler and Eads /20/ the increased pressure in a nitrogen charged dome/bellows (based on reference temperature TREF of 60 F) is expressed like:

(d) where TB is the bellows temperature, and the pressures and temperature are given in psia and F. These equations have been implemented in OLGA, but with a user given reference temperature. That is, it has been assumed that the equations give reasonable results also for other reference temperatures than 60 F. The bellows temperature will depend on the production temperature, injection temperature, flow conditions, geometry of GLV, placement of GLV, etc. The user must give a parameter a where the bellows temperature is a linear interpolation between the injection and production temperature: (e) From the force balance equation (a) we get the following expressions for the increase in required production pressure to open the GLV (assuming constant injection pressure): (f) where DPB is calculated in equations (d). This effect can be very significant. For a sufficiently high temperature above the given reference temperature the GLV might never open: PPROD, open + DPPROD > PINJ. In OLGA this effect is included with a right-shift of all the response curves associated with the GLV. The point with maximum gas rate (for each of the curves) is identified, and the points to the left of this maximum point are shifted with the calculated DPPROD. The new response curve will then consist of the adjusted left side of the curve, the original right side of the curve, and a new maximum point where they cross each other. This procedure is a simplification of how the response curves are affected in the dynamic region; only the opening point is correctly calculated (except for the uncertainty in using equations (d) for a reference temperature different from 60 F). E.g., the curve for a casing/injection pressure of 850 psig in Figure A will not be affected by temperature with this procedure. This is not physically correct.

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Limitations The temperature effects on the opening/closing of a GLV are mainly uncertainties in using the GLV characteristics. The average of the temperatures on the production and injection side is used as temperature inside the valve body. In reality, the temperature distribution within the valve is more complex because of interaction between the production string and the injection string, the expansion of lift gas through the valve, and axial heat transfer along the pipes. It is also assumed that the maximum flow rate point of the GLV performance curve corresponds to the flow rate of a fully opened valve. For the curves which do not have the maximum point, the effects of temperature on the closing of the valve are not considered.

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How to use Use the keyword TABLE to specify the curves of gas flow rate as a function of production pressure for different injection pressures. Use the keyword LEAK to specify the gas injection position and the name of the table the GLV performance curves are given. Use ANNULUS keyword to configure the injection and production strings.

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Heat Exchanger A heat exchanger is included to raise or lower the temperature in the fluid. There are two different types of heat exchangers in OLGA;’Setpoint Heat Exchanger’ and ’Controlled Heat Exchanger’. Both can be configured to give practically the same results, but each is configured differently and this allows for different usages. See also: When to use Methods and assumptions Limitations How to use

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When to use When a heat exchanger is used in the anti-surge recirculation loop of a compressor, it is specified through the keys of the COMPRESSOR keyword (keys COOLER and COOLCAPACITY). Otherwise, use this HEATEXCHANGER keyword to create a heat exchanger.

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Methods and assumptions The setpoint heat exchanger is an idealised heat source/sink, and no description of the real heat transfer process is included. It simply provides a way of specifying a temperature at the heat exchanger outlet, consistent with the energy equation in OLGA. In the setpoint heat exchanger, a heat source/sink is estimated that will give the specified fluid temperature for a particular section. More specifically, the heat exchanged is equal to the enthalpy difference corresponding to the difference between the inlet temperature and the specified outlet temperature of the heat exchanger. The controlled heat exchanger has a simpler model. In the controlled heat exchanger, the effect of the heat exchanger is determined by the controller system. The heat source/sink is not estimated as the heat exchanger has no knowledge of any target temperature. The CONTROLLER for the heat exchanger knows the current temperature and the target temperature and adjusts the effect of the heat exchanger to obtain the target temperature.

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Limitations A heat exchanger can not be positioned at the first or last section boundary of a pipeline.

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How to use To select between a setpoint heat exchanger and a controlled exchanger, simply set the TYPE. To use a setpoint heat exchanger, specify the position, an outlet temperature and an upper limit of the heat source, the capacity. To use a controlled heat exchanger, specify the position and the capacity, but instead of setting the outlet temperature, connect the heat exchanger to a controller. The controller will typically measure the temperature at a specified position along the pipeline and compare the measured temperature to a setpoint. Based on the difference between the setpoint and the measured temperature, the controller will deliver a signal to the heat exchanger which determines how large a fraction of the heat exchanger’s capacity will be applied. Different types of controllers can be used, making the input of a controlled heat exchanger more flexible than that of the setpoint heat exchanger. For example, one can measure the average temperature over several sections by using a Linear Combination Controller.

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Pump The PUMP keyword is used to model specific pump types of common commercial interest. Real commercial pumps may be classified into the following categories; 1. Rotodynamic pumps 2. Positive displacement (volume) pumps 3. Other types (jet pump, water hammer pump, etc). OLGA currently offers four different pump models; the centrifugal pump and the simplified centrifugal pump which belong to category 1 above, as well as the displacement pump and the pump battery which belong to category 2 above. No explicit OLGA models are yet implemented for the less-common types of specialized pumps listed in category 3 above. See also: When to use Methods and assumptions Limitations How to use

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When to use If the inlet pressure of a pipeline is too low to drive the fluid to the outlet of the pipeline, or if we want to increase the oil production, a pump can be installed to increase the flow rate in the pipeline.

License requirements The centrifugal and displacement pumps are part of the Multiphase Pump Module that requires a separate license. The pump battery model is used for drilling applications, and is only available with the Wells Module. The simplified centrifugal pump requires no additional license.

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Methods and assumptions Centrifugal pump Theory and multiphase dynamics For a generalized multiphase centrifugal pump, the pressure increase over the pump, DP, is dependent on the flow rate Q, pump speed N, inlet gas volume fraction aI, and the pump inlet pressure PI: (a)

For the liquid (assuming incompressible), the specific work delivered from the pump into the fluid is: (b) where PO is the pump outlet pressure, PI the pump inlet pressure and rl the liquid density. For a compressible gas, and assuming a polytropic process, the work done by the pump is:

(c) Where n is the polytropic constant and rg, I the gas density at pump inlet. The work input to the gas is equal to the increase in the gas enthalpy. When the gas is assumed to be ideal Win can be written as:

(d) The polytropic efficiency is defined as the ratio of the work done by the pump divided by the work input to the gas. If the adiabatic constant k for the gas and the compressor efficiency hp are given, the polytropic constant n can be calculated. For a two-phase mixture, the pump power to the fluid is weighted by mass fractions (αm = gas mass fraction) as follows:

(e) With W calculated from the pump characteristics, Equation (e) can be solved for PO/PI. The relationship between head H and specific work W is W = gH = ghHR, where HR is rated head and h is the head ratio. For a two-phase mixture (except for very high gas fractions) an isothermal compression of the gas may be assumed (i.e. n=1.0) to account for rapid vapor-phase heat loss to all of the associated liquid, the pump impeller / case, and the surroundings. Assuming n = 1.0, equation (e) can then be rewritten by a series expansion to:

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(f)

Modeling in OLGA OLGA's transient calculations for centrifugal pump performance utilize multi-dimensional interpolation across four separate (default, or user-specified) quadrants of performance curves. Each quadrant is defined in a specific normalized / homologous format (see Pump Data Table for Centrifugal Pumps for an exact definition of all quadrant formats). Together, these four quadrant curve sets give OLGA advanced capability to model all possible transient combinations of Positive and Negative Normalized Speed Ratios and Flow Ratios (including transient backflows that often occur during pump startup and shutdown, in combination with either weak forward impeller rotation or actual reverse impeller rotation). However, most pump manufacturers do not publish performance curves directly in this normalized / homologous format required by OLGA. Nor do they typically offer any curves at all for the operating quadrant representing Positive Speed with Negative Flow (where the pump is transiently unable to overcome external backpressure, typically during Startup/Speedup) or the operating quadrant representing Negative Speed with Negative Flow (where the centrifugal impeller is physically rotating backwards, either due to reverse power input or overwhelming external backpressure). Instead, most manufacturers publish one Head versus Flowrate Curve (with Power or Torque overlaid) for the case of Gas Volume Fraction (GVF) = ZERO, plus additional curves for increasing GVF's, up to a "Degraded Performance Limit" (often GVF=60-70%, but variable by manufacturer and model).

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In order to incorporate such manufacturer curves into an OLGA pump model, the user must first convert the manufacturer curves into homologous curves where the head and torque ratios (actual value to rated value) are functions of the pump speed and flow rate ratios, as defined in Equations (g) below. OLGA's special homologous centrifugal pump curves utilize the following non-dimensional variables: - head ratio

- speed ratio

- flow ratio

- torque ratio

(g)

where subscript R means rated value. OLGA interpolates over four quadrants of homologous curve sets, all defined in terms of the above nondimensional variables. Each quadrant curve set includes: Single phase head HS Two phase head HT Single phase torque THS Two phase torque THT The two-phase head HT and two-phase torque THT curves should be based on fully-degraded twophase conditions. The transfer from single-phase conditions to fully-degraded two-phase conditions is described by a two-phase multiplier. The pump head H and hydraulic torque TH under two-phase conditions are determined as:

(h) where HM(a) is the two-phase head multiplier, TM(a) is the two-phase torque multiplier and a the gas volume fraction at the pump inlet. Each set of homologous curves consists of four curves. These are defined in Table 1 and Table 2. 292 / 769

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A complete default set of homologous curves is tabulated in the code (and also documented in an external file that is linked to the example centrifugal pump in the pump.opi sample case installed with OLGA) . These built-in default centrifugal pump curves are based on experimental data, and are representative for typical centrifugal pumps. However, users can change these data easily by specifying their own experimental data through the pump data table. An example of a graphical presentation of the tabulated pump characteristics is shown in Figure A. This figure shows the single phase homologous head curves. Because the homologous curves are dimensionless, one set of curves can be used to describe a variety of different pumps (i.e., within a single OLGA model) by specifying the desired rated density, head, torque, flow rate and speed for each pump. In calculating the hydraulic torque, TH, the difference between actual fluid density and rated density must be corrected as: (i)

Table 1: Dependence of Pump Head on Pump Speed and Flow Rate

Curves

Range

Independent variables

Dependent variables

1

w > 0,

q/w

h/w 2

2

q > 0,

w /q

h/q2

3

q < 0,

w /q

h/q2

4

w < 0,

q/w

h/w 2

Table 2: Dependence of Pump Torque on Pump Speed and Flow Rate

Curves

Range

Independent variables

Dependent variables

1

w > 0,

q/w

b/w 2

2

q > 0,

w /q

b/q2

3

q < 0,

w /q

b/q2

4

w < 0,

q/w

b/w 2

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Figure A: Single Phase Homologous head curves The OLGA centrifugal pump model also includes embedded numerical models for typical recycle and bypass lines, including user-specified orifices that may be linked to OLGA controllers. For more detail, see the heading Recycle and bypass flow below. For details of the energy balance across the OLGA Displacement Pump, see the heading Energy balance below.

Displacement pump Theory and multiphase dynamics For the displacement pump, the pump flow rate is the theoretical flow rate minus the backflow through the pump. The theoretical flow rate is a function of the pump speed and the characteristics of the pump, expressed through the specific flow rate. The backflow rate is a function of several parameters and is tabulated in a backflow table. This can be summarized as follows:

(j)

where Q0 Qb Qspc N DP aI nl PI

- theoretical flow rate - back flow rate - pump specific flow rate - pump speed - pressure increase across the pump - void fraction at the pump inlet - liquid kinetic viscosity - pressure at the pump inlet

Modeling in OLGA For a given displacement pump, the specific flow rate Qspc is a constant. Qb is tabulated in the backflow table as a function of N, DP, aI, nl and PI. A default implementation of the backflow table is implemented in the displacement pump (and also documented in an external file that is linked to the example displacement pump in the pump.opi sample 294 / 769

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documented in an external file that is linked to the example displacement pump in the pump.opi sample case installed with OLGA). Other backflow tables may be given by using the TABLE keyword.(See Pump Data Table for Displacement Pumps.) The OLGA displacement pump model also includes embedded numerical models for typical recycle and bypass lines, including user-specified orifices that may be linked to OLGA controllers. For more detail, see the heading Recycle and bypass flow below. For details of the energy balance across the OLGA Centrifugal Pump, see the heading Energy balance below.

Pump Battery Accurate simulation of the pumps used for a standard drilling operation is important for the overall estimation of the pump power needed as well as the volume of mud/water required during the operation. Defining the total flow rates proportional to the rate of pump strokes simulates the battery of positive displacement pumps. We define the pump battery through a proportionality factor for the volume delivered at a certain pump rate: (k) where QP = PFAC = SPES =

Volume delivered by the pump battery Pumping factor Strokes per time unit

The pump rate is normally controlled by the following set of controllers: Controller on the maximum hydraulic horsepower allowed Controller on the maximum pump rate Controller on the minimum pump rate Controller on the maximum pump pressure allowed If any one of these controllers is set into action the pump rate is adjusted automatically. The number of controllers can be extended above the number shown above and different variables (e.g. fluid rate, inflow rate) can be used to control the pumps. The total hydraulic horsepower, HHP, is calculated from the following definition:

(l) where Qinj = Pump injection rate of mud or water (bbl/min) WHP = Pump injection pressure (bara)

Recycle and bypass flow Recycle and bypass flows are only defined for centrifugal (not simplified) and displacement pumps. The recycle flow, GR, is considered as the flow through a controlled choke. The flow is calculated with a 295 / 769

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recycle flow, GR, is considered as the flow through a controlled choke. The flow is calculated with a given pressure difference between the two sides of the choke, DPch, and the choke upstream conditions. The choke upstream condition is taken from the pump downstream section (pump pressure side). The choke flow can be regulated by a controller. If the recycle flow is in subcritical condition, GR is calculated by: (m) where Cd is the choke discharge coefficient and Ach the choke opening area. If the mass flow through the choke exceeds the critical flow rate, critical flow conditions will be used. The flow rate through a critical choke is governed by the choke upstream conditions and the choke opening. No forward flow is allowed in the recycle loop. The bypass flow, Gb, is controlled by a choke and calculated in the same way as for the recycle flow. If the bypass flow line is opened, the fluid flows from the pump inlet to the pump outlet in the normal pumping flow direction without going through the pump. Back flow is not allowed through the bypass line.

Simplified centrifugal pump Theory and multiphase dynamics The simplified centrifugal pump in OLGA is intended for quick, approximate modeling. It models a linearized approximation to the local behaviour of a real centrifugal pump, and is therefore only accurate for use across small excursions from its specified local operational point (where the tangent to the real nonlinear operating curve does not change significantly). These simple algebraic expressions are used to calculate the pressure increase over this simplified pump, as well as its pump efficiency:

DPo = DPr ( 1 + D1 ( N - Nr ) + D2 ( Q - Qr ) ) ( 1 - D3 a ) =

r ( 1 + E1 ( N - Nr ) + E2 ( Q - Qr ) ) ( 1 - E3 a )

DP = DPo

r

(n) (o) (p)

where:

DPo DP N Q a

= Pump pressure increase at rated density ( bar ) = Pump pressure increase ( bar ) = Pump speed ( rpm ) = Flow rate ( m3/s ) = Gas volume fraction = Pump efficiency ( adiabatic ) = Specific density ( kg/m3 ) D1,2,3 = Input coefficients for pressure increase E1,2,3 = Input coefficients for efficiency Subscripts:

r = rated

The power to the fluid is calculated in the following manner: a. Inlet enthalpy (Hs) (J/kg) and entropy (Ss) are found from the fluid file. The enthalpy at discharge 296 / 769

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pressure is found assuming isentropic conditions (Hiso). The actual enthalpy change is then calculated by following formula: (q) b. Outlet enthalpy is calculated from: Hd = Hs + ΔH

(r)

c. The power input to the fluid is calculated from: Wfluid = GT×ΔH

(s)

where Wfluid is in W, and GT is the total mass flow in kg/s. Total shaft power: Wtot = Wfluid / η M

(t)

Pump torque: = Wtot /

(u)

Pump hydraulic torque: TH = Г η M

(v)

where = 2 N / 60, and M the pump mechanical efficiency. Modeling in OLGA Note that by setting the coefficients D1,2,3 and E1,2,3 = 0.0, a pump with a constant pressure increase will be simulated. If the user wants to obtain a certain flow rate in a simple way, one can either iterate on the input value for Pr or assume some value for D1 and let a controller determine the necessary speed.

Energy balance Centrifugal and Simplified Centrifugal pumps The total power input to the fluid from any pump (including the OLGA centrifugal, displacement, and simplified pumps described above) is: (w) where TH is the pump hydraulic torque, w the pump speed and M the pump mechanical efficiency. Displacement pump For the displacement pump, the hydraulic torque, TH, may not be available, and it is therefore difficult to calculate the term QPt. In this case, the total power input to the fluid is calculated by summing the mechanical work on the fluid and the different losses as following: 297 / 769

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The power used for mechanical work on the fluid, QPM, is calculated as: (x) where, Wl Ql rl Wg Qg rg

- specific work delivered from pump into liquid - liquid flow rate - liquid density - specific work delivered from pump into gas - gas flow rate - gas density

Mechanical friction loss: (y) Viscous friction loss: (z) where, a - experiment coefficient for mechanical friction loss b - experiment coefficient for viscous friction loss Nref - pump reference speed QPmf,ref - mechanical friction loss at the pump reference speed QPvis,ref - viscous loss at the pump reference speed Then, the total power input to the fluid is calculated as: (aa)

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Limitations The recycle flow and bypass flows around the OLGA centrifugal and displacement pumps are considered as flows through controlled chokes. Each flow is calculated with the given pressure difference between the two sides of the choke and the choke upstream conditions. The pipeline effect of the recycle flowline and bypass flowline is not considered. The recycle flow can only flow from the pump downstream section to the upstream section, and the bypass flow can only flow from the pump upstream section to the downstream section. It is impossible to insert any component in the recycle flowline or bypass flowline, because no pipeline is considered. Pumps can not be positioned at the first or last section boundary of a flow path.

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How to use General setup (all pump types) 1 Add the PUMP keyword to the desired flowpath 2 Specify pump location by one of ABSPOSITION (length), PIPE & SECTIONBOUNDARY, or POSITION (an alias) 3 Choose a desired PUMPTYPE from the list below: A Simplified Centrifugal to roughly simulate multiphase transient dP and efficiency with only three algebraic coefficients, as either constant or linearly sensitive to transient fluctuations in speed, flowrate, and void fraction. B Centrifugal to more rigorously model the real nonlinear transient operation of a particular multiphase centrifugal pump (including recycle and bypass). OLGA calculations are based on either built-in nonlinear curves for a "typical" pump, or user input of special dimensionless OLGA curves for a particular pump that must usually be derived from given dimensional curves before OLGA entry. C Displacement to rigorously model the real nonlinear transient operation of a particular multiphase positive displacement pump (including recycle and bypass). OLGA calculations are based on either built-in nonlinear curves for a "typical" pump, or detailed manufacturer's curves expressing that multiphase displacement pump's internal backflow rate as a 5-dimensional tabular function of speed, dP, multiphase void fraction, inlet pressure, and liquid-phase viscosity. D Pump Battery to simulate the special case of a battery of positive displacement liquid-phase drilling mud pumps. by specifying a proportionality constant relating operating speed to total volumetric flowrate, subject to specified control limits for minimum and maximum flowrate, as well as maximum hydraulic horsepower and outlet pressure. NOTE: The related topic Pump - When to use documents the differing OLGA module license requirements for each PUMPTYPE described above. 4 Choose any applicable means of controlling the pump speed, as described in detail at the bottom of this section.

Simplified Centrifugal setup 1 In addition to the General Setup above, you must specify DPRATED, FLOWRATED, SPEEDR, and MAXSPEED. Allso override the (900 kg/m3) default of the required DENSITYR with your actual rated liquid density, if significantly different. 2 You may also specify related sensitivity of pump DP to varying speed, flowrate, and void fraction via the linear departure coefficients DCOEFF1 - DCOEFF3. NOTE: Without these optional user inputs, the OLGA simplified centrifugal pump defaults to a constant DP = DPRATED regardless of any transients. 3 You may also override the default (0.5) adiabatic efficiency by entering EFFRATED, then make that efficiency sensitive to speed, flowrate, and void fraction if desired by also entering ECOEFF1 ECOEFF3. NOTE:Adiabatic efficiency of the Simplified Centrifugal Pump affects OLGA calculations for fluid heating, hydraulic horsepower, total shaft horsepower and torque, through the relations documented in Pump - Methods and assumptions. 4 If more accurate estimation of Total Shaft Power is also required, you may also override the default (0.7) EFFIMECH.

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1 Like the Simplified Centrifugal Pump discussed above, the OLGA Centrifugal Pump also requires DENSITYR (same 900 kg/m3 default, or specified), plus FLOWRATED, and SPEEDR. 2 However, OLGA's full Centrifugal Pump model also requires you to specify HEADRATED and TORQR as a minimum, in order to scale the general transient response surface of either the built-in default or user-specified Homologous Centrifugal Pump Curves to your actual pump. 3 You may optionally enter custom transient centrifugal pump performance curves to precisely represent the exact transient response surface for your actual pump. However, note that most manufacturers do not publish pump curves directly in this format, and it may also be difficult to obtain degraded multiphase performance curves up to the maximum degraded Gas Volume Fraction (GVF) for your particular hardware and application (often somewhere in the range of 30 - 70% vapor volume).For more specific information about the theoretical basis of these special OLGA input requirements, consult Table 1, Table 2, and Figure A of the Pump - Methods and Assumptions topic. 4 The OLGA Centrifugal Pump will run without any further inputs, already representing a much more realistic transient modeling upgrade to the Simplified Centrifugal Pump model at only slightly greater modeling cost in setup time and runtime. 5 This PUMPTYPE also includes additional provisions for simple "branch-less" Bypass and Recycle modeling to further increase the realism of OLGA's transient responses for typical pump packages. The setup procedures and modeling assumptions for these Built-in Bypass and Recycle features are described in detail below.

Displacement setup 1 The OLGA Displacement Pump requires significantly different types of inputs than the Centrifugal or Simplified Pumps. For example, none of DENSITYR, FLOWRATED, HEADRATED, SPEEDR, or TORQR are used. 2 You must enter SPECAPACITY (the total specific volume displaced per revolution or displacement cycle). as well as MAXSPEED. OLGA will then multiply these two inputs to determine the (gross) theoretical volumetric flowrate displaced (before subtracting internal bypass). 3 The OLGA Displacement Pump will run without any further inputs, although equipment manufacturers or others with detailed knowledge may wish to override the defaults for one or more of ACOEFFICIENT, BCOEFFICIENT, MDISSIPATION, VDISSIPATION, etc in order to tune the model very precisely. 4 You may optionally enter custom transient displacement pump backflow (performance) curves to precisely represent the exact transient response surface for your actual pump. However, note that the required input format is a complex 5-dimensional matrix of internal backflow rates as a function of pump speed, head, void fraction, inlet pressure, and liquid viscosity - information normally only available from the manufacturer's experts, perhaps even requiring new eperimental work on a prototype pump for your particular fluid and operating conditions..For more specific information about the theoretical basis of these special OLGA input requirements, consult the Displacement Pump Theory topic in the Pump - Methods and Assumptions section. 5 Like the Centrifugal pump, this PUMPTYPE also supports additional provisions for simple "branch-less" Bypass and Recycle modeling to further increase the realism of OLGA's transient responses for typical pump packages. The setup procedures and modeling assumptions for these Builtin Bypass and Recycle features are described in detail below.

Pump Battery setup 1 Setup of and use of the special Pump Battery model (for a battery of dtilling mud pumps) is primarily described within the Pump Battery topic of the Pump - Methods and Assumptions section. 2 Required inputs include MAXSPEED, MINCAPACITY, MAXCAPACITY, MAXPRESSURE, and HPMAX. MINSPEED is optional. 3 These inputs are used to simulate simple limit controls on horsepower, flowrate, and pressure.

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To activate OLGA's simplified Bypass feature for any Centrifugal or Displacement Pump, specify BYDIAMETER and connect a bypass controller of your choice. No other bypass inputs are offered or required. To activate OLGA's simplified Recycle feature for any Centrifugal or Displacement Pump, specify at least RECDIAMETER and MAXRECYCLE, plus any non-default values for RECPHASE, MINRECYCLE, and ACCECOEFF. Then connect a recycle controller of your choice. Further details about the internal workings of these simplified Bypass and Recycle features are provided in the following text, equations, and block flow diagrams. A common multiphase transportation system with pump is shown in Figure B.

Figure B: Multiphase Transportation System with Pump Within OLGA, this system will be simplified as shown in Figure C. Note that in this implementation the pump is abstracted into a volume-less element on the section boundary J between section J-1 and section J. The recycle flow is out of section J and into Section J-1, and the bypass flow out of section J1 and into section J. No-slip flow is assumed for all of gas, liquid, and droplets moving through section boundary J, as: Ug = Ud = Ul = U OLGA also permits the user to add a separate VALVE keyword at the same section boundary where a centrifugal pump is located. The user may then close that optional OLGA Valve to block any possible backflow transients (that may otherwise occur due to higher downstream pressure at any moment when the centrifugal pump is shut down).

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Figure C: Multiphase Transportation System modelled in OLGA The centrifugal pump model requires a pump table with the characteristics of the pump. The displacement pump model requires a backflow table. The pump manufacturers generally characterize their pumps by pump operating characteristics. There is a default implementation of such tables in OLGA. If other tables are needed they should be given with the TABLE keyword. Each of the characteristics is assigned a label, which is referred to in the PUMP keyword. The user can choose the recycle flow as gas only, liquid mixture, water only, or fluid mixture.

Controlling the pump speed The following options are available for controlling the pump speed: 1. Pump speed regulated by controller (All pump models): a. Controlled manually by specifying time and speed series in the controller definition. b. Regulated by a physical parameter. The speed is calculated by: (ab) where Nmax is the maximum pump speed (defined by user), Nmin is the minimum pump speed (defined by user) and u the signal from the controller.

2. Controlled by an override controller (Only for centrifugal and displacement pumps): To adapt the pump to the production change (because the recycle flow is at upper or lower limits), the pump speed will be changed automatically according to the required speed variation (speed acceleration). The speed variation may be given in form of:

where A is a constant pump speed variation rate (acceleration). The speed variation will stop once the recycle flow is within a defined range below MAXRECYCLE and above MINRECYCLE.

3. If the maximum pump torque has been given by users (Only for centrifugal and displacement pumps): The effective pump torque is calculated from the total power input to the fluid, QPt : (ac) where QPt is the total power input to the fluid. If the pump shaft torque is over the limit the pump speed is reduced, and a warning message will be given in the output file.

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Separator The network separator is not intended to accurately model separation phenomena, but is meant to include the influence of a separator on transient pipeline dynamics. The behaviour of the separator is mainly based upon user given input for the separation efficiency (gas/liquid, oil/water), and set critical levels for oil and water drainage. See also: When to use Methods and assumptions Limitations How to use

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When to use It is recommended to use the separator model whenever a ”real” separator is present in the flow network and the effect of the downstream flow pattern is of interest. If it is only interesting to look at the upstream flow pattern, it sometimes is appropriate to replace the separator with an ordinary pipe with large diameter to stabilize the boundary conditions and in that way avoid the needs for more complex specification of outgoing pipes, valves and controllers linked up to the separator. It can also be useful to employ a separator as a downstream boundary condition for controlling the boundary pressure. This may reduce unwanted flow oscillations in the network compared to using a constant pressure boundary condition.

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Methods and assumptions Separator type The separator may be two-phase or three-phase and the geometry orientation is horizontal, vertical or table specified. Connections to external pipelines The separator has an arbitrary number of inlets/outlets. Two phase separators must have connected at least one inlet, one gas-outlet and one oil-outlet to pipes. Three phase separators must in addition also have one water-outlet connected. Valves/controllers The separator has no internal valves and controllers, so they have to be specified on the outgoing pipes. Level control The separator levels are controlled by the valves and controllers in the outlet pipes. For a three-phase separator, the water level limit for when the water will be drained together with the oil can be specified in the separator keys: HHWATHOLDUP or HHWATLEVEL

Separation efficiencies a)

Liquid carryover in gas outlet. The gas-liquid separation efficiency is defined as one minus the volume fraction of the liquid droplets in the gas outlet stream. By default, the gas-liquid separation efficiency is equal to one, that is, no liquid carryover in the gas outlet. The user can, however, specify a constant gas-liquid separation efficiency, effg by the key EFFICIENCY in the keyword SEPARATOR. The liquid droplet volume fraction in the gas stream is then equal to one minus the value assigned to EFFICIENCY. For three phase flow the liquid droplet volume fraction is distributed to water and oil droplet volume fractions according to the water and oil volume fractions in the settled liquid in the separator. To prevent instabilities in the separator when the liquid holdup becomes very large, it is possible to specify two input keys, EFFLOW and EFFHIGH, to assure a continuous transition from effg = EFFICIENCY to effg = 0.0. EFFLOW is the liquid volume fraction when efficiency is being reduced and EFFHIGH is the liquid volume fraction when efficiency becomes zero and the gas outlet is treated as a normal flow path. The gas-liquid separation efficiency, effg is modified by the following set of rules: The liquid volume fraction, αl ≤ EFFLOW:

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αl > EFFLOW and αl < EFFHIGH:

(b)

αl ≥ EFFLOW: (c)

b)

Oil in water drain. The oil volume fraction in the water drain is determined by the following relation for separation efficiency:

(d) where Kso is the time constant, OILTCONST, for separating oil from water and Trsp is the residence time which is defined as the separator liquid volume / liquid volume flow into the separator. The oil volume fraction in the water drain is then 1 eff0. c)

Water in oil drains. The water volume fraction in the oil drains is determined by an equation similar to the one above:

(e) where Ksw is the time constant, WATTCONST, for separating water from oil. If the water level is above a certain limit, HHWATHOLDUP or HHWATLEVEL, the water above this limit is assumed to be drained together with the oil and the separation efficiency for separating water from oil is modified as follows:

(f) where Hof is the ratio of the water layer height above the limit to the liquid height above the same limit. The water volume fraction in the oil stream is then 1effw.

Heat transfer The heat transfer, qtr into the separator or out from the separator is given by: 307 / 769

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(g) where U is the overall heat transfer coefficient, A is the surface area, T sep is the separator temperature and Tamb is the ambient temperature. If adiabatic temperature option is given for the total flow network, U is set to zero for all separators in the network.

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Limitations The network separator is not intended for design purposes. It only simulates a predefined behaviour of a ”real” separator. The separator is only treated as a simple volume tank with no internal separation equipment The separator efficiencies is user given No wall temperatures is calculated There are no time restrictions for calculation of the flash contributions. The total mass internally is taken into account and treated as at equilibrium. Due to the internal geometry of the separator, this might give incorrect results if the separator pressure or temperature suddenly changes.

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How to use

Figure A An illustration of a three-phase separator

Input Connections to external flow paths For a two phase separator, the following connections are defined: INLET_1, …INLET_N inlets GAS_1, … GAS_N outlets (Use GAS_2 to model flare outlet) OIL_1, …OIL_N outlets(Use OIL_2 to model emergency outlet) For a three phase separator, the following connections are defined: INLET_1, …INLET_N inlets GAS_1, … GAS_N outlets (Use GAS_2 to model flare outlet) OIL_1, …OIL_N outlets(Use OIL_2 to model emergency outlet) WATER_1, …WATER_N outlets(Use WATER_2 to model emergency outlet) Initial conditions Key INITTEMPERATURE gives initial value for the separator temperature Key INITPRESSURE gives initial value for the separator pressure Key INITWATLEVEL gives initial value for the water level Key INITOILLEVEL gives initial value for the oil level Geometry There are two ways to specify the geometry of the separator. One method is to specify the separator length, LENGTH and the separator diameter, DIAMETER. The surface area and volume is then calculated by using the knowledge of the cylindrical form. The other method is to define a specific level table LEVELTABLE, a set of user defined values giving the volume as a function of the level (height). Using this method the surface area, SURFACEAREA also has to be given. Separator valves/controllers The separator has no internal valves and controllers. All valves must be defined on the outgoing pipes and might be positioned at the first section boundary of the pipes. The controllers are connected to the valves and must also be defined outside the separator. It is recommended that the water valve opening is controlled by a water level controller, the oil valve opening is controlled by a oil level controller and the gas valve opening is controlled by a separator pressure controller. 310 / 769

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Output Many of the plot variables specified under volume variable are available for the separator. In addition a number of separator specific plot variables also are available: Mass flow rates for each mass field for each pipe connection Separator levels (oil, water) Separator efficiency

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Valve The valve models the pressure drop for flow through chokes and valves. See also: When to use Choke — Methods and assumptions Valve — Methods and assumptions Limitations How to use

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When to use Use to model orifices, chokes and different types of valves. For high velocities in the pipeline, a fully open valve can be used to limit the flow to critical flow. Use a choke with choke diameter equal to the pipeline diameter. Position the Valve at the last section boundary of the pipe where the flow rate should be limited.

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Methods and assumptions The choke model uses mixture balance equations for mass, momentum and energy. Compression of gas into the narrow throat is accounted for in the model. A circular-symmetric flow geometry and steady-state over the choke is assumed. See Selmer-Olsen et al. for the full model description [34]. The choke model describes the effects of both subcritical and critical chokes. The choke opening may be controlled by the control system, by a predefined time series, or be fixed. The choke has finite opening and closing time (stroke time) specified by the user. A subcritical choke is represented through its pressure drop as a function of flow rates and choke openings. The flow rate through a critical choke is governed by the upstream conditions and the choke opening (choke flow area). The choke flow rate is limited to critical flow.

Figure A: An illustration of a choke. Fluid is flowing from position 1 to position 2.

Choke model The flow through the choke is assumed frictionless, homogeneous and adiabatic. The flowing phase fractions are frozen at inlet conditions. Phase change occur after the throat, and the fluid reaches equilibrium in position 2. The choke model in OLGA describe the pressure drop from upstream (position 1 in Figure A) to downstream (position 2 in Figure A) an orifice or other constriction in the pipeline. The model include pressure drop from position 1 to throat (position t in Figure A) and pressure recovery when the fluid expands from the throat to position 2. The pressure drop to throat — Bernoulli and continuity equation Bernoulli Equation:

(a) where um ρm P

mixture velocity (m/s) momentum density (kg/m3) pressure (Pa)

Momentum density: (b) Flowing gas mass fraction: 314 / 769

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(c) where M is the overall mass flow through the choke and Mg is the gas flow through the choke. Continuity equation: (d) where A is the cross sectional area. Recovery after throat — Momentum and continuity equation Momentum equation: (e) The overall pressure drop over the choke is found by combining equations (a) through (e). Critical flow The critical flow through the choke is found at the maximum of equation (a). Differentiating equation (a) w.r.t. pressure and combining with equation (d) yields the following relation for the critical flow, MC,

(f) The throat area, At, is corrected with the choke discharge coefficient, Cd, to find the minimum flow area. Simplified fluid property calculations The liquid properties are calculated in position 1 and treated as constant, while the gas is compressed/expanded isentropically. Gas density:

(g) where γ is the isentropic gas expansion coefficient,

(h) The reported throat temperature (TVALVE) is the gas temperature

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Critical flow options Two options are available when calculating the critical flow through a choke: 1. Frozen: No mass transfer, isentropic expansion of gas. (Homogeneous frozen critical flow model) 2. Henry–Fauske: The Homogeneous frozen critical flow model corrected for mass transfer in the throat [3]. If the Henry–Fauske model is used and entropy values are given in the fluid property tables file (with the word ENTROPY in the heading of the fluid file), the entropy values in the fluid file will be used. Otherwise, the entropy changes will be calculated from enthalpy, mass fraction and density by integrating the following equation from the upstream conditions (position 1) to the throat conditions (position 2): (j) The integration is performed in two steps, from P1 to P2 at T1 and from T1 to T2 at P2.

Controlled choke In the case of a controlled choke, the choke area, Ao, is varied according to the controller signal us : (k) where (l) Do is the choke diameter and Amax is the maximum choke area. In the case of an uncontrolled choke, the choke flow area is varied according to the time tables of the relative choke area, orel, (m) In the case of a fixed choke, the choke flow area is constant; (n) Note that it is possible to simulate a choke without a controller; the choke area is then given by a time series.

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Methods and assumptions In the valve model the pressure drop and critical flow are calculated according to a valve sizing equation. The valve model uses a table (keyword TABLE) that contains the valve sizing coefficients, Cv or Cg, versus valve opening. It is possible to give a table representing the valve sizing coefficients either for gas flow or for liquid flow. It is not possible to give a table for two/three-phase flow. The sizing coefficients are tabulated as functions of the relative valve opening. The liquid valve sizing coefficient can also be given as a function of both relative valve opening and pressure drop over the valve. Note: The input data for the valve sizing coefficients must be consistent with the units specified together with the valve sizing equations below. A valve can be located anywhere in a pipeline. Liquid Valve sizing equation If a liquid sizing table is given, the valve flow rate (even three-phase flow) will be calculated using the choke model in OLGA. The liquid sizing table should be used for liquid flow, near incompressible gas flow and two/three-phase flow. The pressure drop through a valve is calculated as follows: Liquid sizing equation:

(o) where

Q Cv G DP

Flow rate (gallons/min.) Valve sizing coefficient (gal/min / psi 1/2) Specific gravity (-). Water = 1. Pressure difference across the valve (psi)

OLGA converts Cv for liquid to the choke flow area, Ao, used in eq. (p). Equations (p) and (o) will produce a relation between Cv and Ao. Setting CD=1.0, the choke area can be calculated. The pressure drop and the critical flow rate are calculated using the choke model, regardless if the flow is gas, liquid, or multiphase flow. The mixture density is used in the calculation. Orifice equation:

(p) where Cd A

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Ao Wtot Ui αi ΔPorf

Choke (orifice) flow area Total mass flux Velocity of flow field i, (film velocity, droplet velocity etc.) The volume fractions of flow field i Pressure drop over the orifice

See Cv to area conversion for the details of the conversion from Cv to orifice area. Gas valve sizing equation If the MODEL key is set to HYDROVALVE, the gas sizing equation is used in the same manner as the liquid valve sizing. Combining equations (p) and (q), a choke area can be calculated. The critical flow will then be determined by the choke model. If instead the model option GASSIZING (keyword MODEL) is used, the gas sizing equation will be used for both subcritical and critical flow. The choke model will not be used. Gas sizing equation: (q) where Qm rg p1 Cg DP Cf

Mass flow rate (lb/hr.) Gas density (lb/ft3) Upstream pressure (psi) Gas sizing coefficient (lb/hr / (psi × lb/ft3)1/2) Pressure drop (psi) Coefficient ratio, Cg/Cv (-)

The critical flow rate is obtained by setting the sine-term equal to one. The upstream density is used in the calculation.

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Conversion between liquid valve sizing coefficient (Cv) and orifice area The orifice equation for an incompressible fluid:

(a)

rFluid Q αi Ui A AOrifice Cd ΔPOrifice

Is the fluid density Is the volumetric flow rate Volumetric fraction of mass field i Velocity of mass field i Pipeline area Orifice area Orifice discharge coefficient Orifice pressure drop

The valve sizing equation:

(b)

Cv Q ΔPSizing G ρRef ρFluid

Valve sizing coefficient (gal/min/psi1/2) Is the volumetric flow rate (gal) Sizing pressure drop (psi) Specific gravity (-) Water density at 39ºF/4ºC and 1 atmosphere (998.840 kg/m3) Fluid density at reference conditions

Setting ΔPOrifice = ΔPSizing and solving for Cv or orifice area (AOrifice):

(c) Above we have assumed that the orifice equation is given with the same units as the sizing equation. Converting to SI units:

CvSI = Cv · (d)

(m3/s/Pa1/2)

Using SI units for the area, m, and inserting the reference water density we get the following equation:

(e)

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Limitations Friction and gravity forces are neglected in the choke model. See Selmer-Olsen et al. for limitations in the choke model /34/. When using the Henry-Fauske critical flow model (CRITFLOWMODEL = HENRYFAUSKE) make sure the entropy is given in the thermo tables. Otherwise the entropy must be integrated from the enthalpy and density data in the thermo tables. In some cases, this will slow down the simulation. Further, it is not allowed to position a valve at the first section boundary in a flowpath next to a closed node in OLGA 6. OLGA 5 does not have this restriction.

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How to use Position the valve. Valves can be inserted anywhere in the pipeline. Choose which valve model to use from available information in data sheet etc. If no Cv/Gg is given, use the choke model. The choke is used when the model option HYDROVALVE (keyword MODEL) is set. A discharge coefficient, CD and maximum choke diameter must be defined for the choke. If the discharge coefficient is unavailable, use the default value. Consider using the CRITFLOWMODEL option HENRYFAUSKE for two/three-phase simulations with flashing fluids. Otherwise use CRITFLOWMODEL = FROZEN. If Cv data are available, use the model option HYDROVALVE, and specify the Cv vs. valve opening in a table. The valve Cv can also be described as a function of valve pressure drop (DELTAP) and valve opening. If Cg data are available, use the model option GASSIZING (key MODEL). Specify the Cg vs. valve opening in a table. It is also possible to use the HYDROVALVE (MODEL key) to simulate a gas valve. To control the valve flow in the choke, or the pressure drop over it, connect a controller to the input signal terminal INPSIG. When connected, INPSIG will be used as the valve opening. Otherwise, the key OPENING will set the valve opening. The given OPENING can be constant, or a function of time. To limit the rate of change in valve position, set the valve stroke time. Set CLOSINGTIME/ OPENINGTIME or STROKETIME. Setting STROKETIME will give CLOSINGTIME = OPENINGTIME = STROKETIME. It is possible to tune both the choke and valve model. The input signal CVTUNINGSIG will scale the choke CD, or the valve Cv/Cg.

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Single component The single component module allows for tracking of a single component, e.g., H2O or CO2, that crosses the saturation line in time or space in a pipeline. Standard OLGA cannot deal with single component systems if the saturation line is crossed due to the explicit coupling between volume balance and energy balance equations and the lack of a two phase region (two phase envelope) for single component systems. In order to circumvent this limitation, time constants, or delays, are introduced in the evaporation/condensation process. The difference between the saturation temperature and the fluid temperature serves as a potential for phase mass transfer. Multiplying this temperature difference with a certain heat or energy transfer coefficient yields an energy transfer rate that can be used to estimate the mass transfer rate. An asymptotic approach to equilibrium occurs where the speed at which equilibrium is reached is determined by the size of the energy transfer coefficient. See also: When to use Methods and assumptions How to use

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When to use The single component module should be used for all single component fluids. Special options exist for H2O and CO2, for which the fluid property calculations have been hard coded into OLGA. For other single component fluids, it is necessary to specify input parameters to the fluid property calculations. The numerics in standard OLGA have been designed for multi component hydrocarbon fluids. A consequence of the chosen approach is that standard OLGA become unstable when simulating single component fluids that cross the saturation line in time or space. The same can happen for multi component fluids with very narrow phase envelopes, for example a fluid composed predominantly of one component, but with a small amount of impurities. Since the behavior is very case dependent, it is hard to give general guidelines on the exact amount of impurities required before standard OLGA can be expected to yield reasonable results. One should, however, be careful when using standard OLGA to simulate fluids consisting of 90% or more of one component. Besides the numerical issues, it is important to make sure that the fluid property calculations are accurate for the particular fluid composition to be simulated. As implied by the name, the single component module can only be applied to pure single component fluids. At present, OLGA is thus not able to simulate single component fluids with small amounts of impurities.

License requirements The Single Component Module requires a separate license.

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Methods and assumptions The following assumptions are made in the single component model: the gas and liquid phases have the same temperature. the pressure of the gas and liquid phases is the same. if the fluid temperature is higher than the saturation temperature, flashing or boiling of liquid will take place. if the fluid temperature is lower than the saturation temperature, condensation of vapor takes place. The inner pipe wall surface can be superheated or subcooled as compared to the saturation temperature. Such situations might lead to surface boiling or surface condensation in cases where the liquid or gas is in direct contact with the pipe wall. The resulting, additional, mass transfer term is not explicitly included, but it can be accounted for by an enhanced heat transfer due to surface boiling/condensation.

Generation of gas and liquid properties The equations used to calculate the H2O properties are taken from ref. 1. For CO2, the thermodynamic equations are taken from ref. 4. The transport properties are calculated through the equations given in ref. 2. For other components, the Soave–Redlich–Kwong (SRK) cubic equation of state (Appendix 1) is used to calculate the saturation line and the physical properties of the vapor and liquid phases. Temperature dependent volume translation is applied to improve the accuracy of phase density. The transport properties are determined by the corresponding state method by Pedersen (ref. 2). The evaluation of the fluid property equations is time consuming, and, therefore, they are only evaluated at the start of the simulation. The properties are evaluated at a grid of pressure/temperature values that is limited by the minimum and maximum values of pressure and temperature given in the input. An equidistant grid is used with a minimum of 50 and maximum of 100 grid points for both pressure and temperature. During the simulation, linear interpolation is used to evaluate the properties in between grid points.

Saturation line for a single component The saturation line is determined by solving the equal fugacity of gas and liquid from the equation of state (EOS). Below the critical point, determined by the critical pressure, PC and the critical temperature, TC, the saturation pressure, Psat(T), and saturation temperature, Tsat(P), at a given grid point (P,T) are determined from the saturation line. Above the critical point, the saturation line is extrapolated with the slope of the saturation line at the critical point.

Liquid properties for a single component For pressures below the critical pressure liquid properties are determined by the EOS in the liquid region. In the gas region, the liquid properties are extrapolated from the saturation point — the enthalpy equals the gas enthalpy minus the latent heat at the saturation temperature and the density is integrated from the vapor saturation pressure to actual pressure using the compressibility at the saturation temperature. All the other properties are from the saturation temperature. For pressures above the critical pressure, liquid properties are calculated from the EOS.

Gas properties for a single component For pressures below the critical pressure, the gas properties in the gas region are acquired from the EOS. In the liquid region and a pressure below the critical pressure, the gas properties are extrapolated from the saturation line — the enthalpy equals the liquid enthalpy plus the latent heat at the saturation temperature corresponding to the pressure and the density is acquired by linear interpolation between the value at critical pressure and the saturation pressure. All other properties are taken at the saturation temperature corresponding to the pressure. For pressures above the critical pressure, gas properties 324 / 769

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temperature corresponding to the pressure. For pressures above the critical pressure, gas properties are calculated based on the EOS. Using this procedure, the gas and liquid properties are continuous across the fictitious gas-liquid (V–L) division line when the pressure is above the critical one. At the critical point and its vicinity, the thermal capacity and density derivatives show extreme sensitivity to temperature and pressure changes, even to the extent where discontinuities occur. Therefore, a buffer zone is introduced near the critical temperature as shown below. Within this zone, the liquid density derivative and thermal capacity are given the values calculated at a temperature, Tlow, less than the saturation point. Similarly, for the vapor phase, the gas density derivative and the thermal capacity are given the values calculated at a temperature, Thigh, above the saturation point.

The buffer zone is bounded by the coordinates [Tlow, Psat(Tlow)], [Tlow, Pc], [Thigh, Pc], [Thigh, Psat(Thigh)].

Saturation line for H2O Below the critical point, (PC,TC), the saturation pressure, Psat(T), and saturation temperature, Tsat(P), at a given grid point (P,T), are determined from the saturation line. Above the critical point, PC=221.2 bar and TC=647.3 K, and up to T=676 K and P=250 bar, a straight line is used to divide the single-phase or dense-phase region into gas and liquid. Above 676 K and 250 bar, the boundary line between region 2 and region 3 is used as the division between gas and liquid. The definition of the regions is found in ref. 1.

Liquid properties for H2O For pressures below 225 bar in region 1, the water properties equations found in ref. 1 are used for water in the water region. 325 / 769

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In the gas region, the properties for water are extrapolated from the saturation point — the enthalpy is based on thermal capacity at the saturation temperature corresponding to a given pressure. The density, on the other hand, is calculated using the density derivative w.r.t. pressure at the saturation pressure corresponding to the given temperature. All the other properties are evaluated at the saturation temperature. For pressures above 225 bar, water properties are calculated based on equations for the different regions specified in ref. 1. The thermal capacity and enthalpy for water are singular near the critical point. To avoid numerical problems in region 3, the water properties from region 1 are used instead of those for region 3 when the pressure is below 225 bar. The same procedure is used for steam (gas).

Gas properties for H2O For pressures below 225 bar, steam property equations for region 2 are used for gas in the gas region. In the water region, the gas properties are extrapolated from the saturation point. Enthalpy is based on thermal capacity at the saturation temperature corresponding to the given vapor pressure and the density according to the density derivative w.r.t. pressure at the saturation pressure corresponding to the given temperature. All other properties are evaluated at the saturation temperature corresponding to the vapor pressure. For pressures above 225 bar, vapor properties are calculated based on equations for the different regions. Using this procedure, the vapor and water properties are continuous across the vapor-liquid (V–L) division line when the pressure is above 225 bar.

Flashing/Condensation The driving force for flashing of liquid or condensation of gas is the difference between the saturation temperatures and the fluid temperature. The effect of local boiling on a hot wall surface or condensation on a cold one are not explicitly included in the mass balance of liquid and gas, but can be accounted for through an enhanced heat transfer at the pipe wall. The total energy available for generating gas or condensing it to obtain saturated conditions is (a) where mg = specific mass of gas [kg/m3] ml = specific mass of liquid [kg/m3] cpg = specific heat of gas [kJ/kgC] cpl = specific heat of liquid [kJ/kgC] h S V

= heat transfer coefficient at inner wall surface [kJ/m2sC] = inner surface area per unit volume of pipe [1/m] = section volume [m3]

The total mass transfer to obtain saturated conditions is: 326 / 769

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(b) where hsat,g = enthalpy of saturated gas [kJ/kg] hsat,l = enthalpy of saturated liquid [kJ/kg] In order to reduce numerical problems, it is assumed that this mass transfer occurs over a time Tψ. This yields the mass transfer rate (c) The mass transfer per time step must not be larger than the available component mass of the diminishing phase.

References 1.

Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, The International Association for the Properties of Water and Steam, Lucerne, Switzerland, August 2007 2. K. S. Pedersen et al. Properties of Oils and Natural gases. Gulf Publishing Company, 1989, Houston, Texas. 3. B.E.Poling, J.M.Prausnitz, J.P.O’Connell: The properties of gases and liquids. 5th Edition. McGRAW-HILL 2000. 4. R. Span and W. Wagner: A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures up to 800 MPa. J. Phys. Chem. Ref. Data, Vol. 25, No. 6, 1996

Appendix 1 The Soave–Redlich–Kwong (SRK) equation of state: (A.1) where

The SRK equation of state can be written on the form: 327 / 769

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(A.2) where

The solution, Z, to the above equation is found by iteration. As initial guess, the pressure is given by the Antoine equation except for CO2 where the Wagner equation is used. Coefficients for these equations can be found in ref. 3. The solution for Z can be adjusted by a volume tuning factor (A.3) according to (A.4) where XV1 and XV2 are given through the keys VOLX(1) and VOLX(2), respectively, and Pr = P/Pc. The specific heat, CP, is calculated through the equation (A.5) where the coefficients, CPi, are given through the input by CPIC(i+1).

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How to use The single component model is activated by setting the key COMPOSITIONAL=SINGLE under the OPTIONS keyword. The time constants for condensation and boiling are specified by the keys TCONDENSATION and TBOILING, respectively, under the keyword SINGLEOPTIONS. These keys are available as time series if desired. Large values of the time constants will slow down the mass transfer leading to a fairly large non-equilibrium. Small values will speed up the mass transfer and thereby reduce the thermal nonequilibrium. Too small values might however cause instabilities which in turn can result in nonphysical results. The keyword SINGLEOPTIONS specifies options for COMPOSITIONAL=SINGLE. COMPONENT can have the values H2O, CO2, or OTHER. H2O is set by default. N.B., if COMPONENT=OTHER, it is required to specify additional fluid properties such as viscosity tuning factor, VISX critical temperature, TC [C] critical pressure, PC [bara] acentric factor, OMEGA molecular weight, MW volume tuning factors, VOLX(2) coefficients in equation for specific heat, CPIC(5) For many different components values of these coefficients can found in ref. 3. The keys MINPRESSURE, MAXPRESSURE, MINTEMPERATURE and MAXTEMPERATURE in SINGLEOPTIONS are used to generate a PVT tables for the single component properties, i.e., no external PVT file is needed. 51 to 52 pressure and temperature points are used when generating the tables and the griding is adjusted so that a grid point is close to the critical point. During the simulation, linear interpolation between the grid points (P,T) is applied. For boundaries, sources and wells, the gas fraction will be either gas or liquid, all depending on the specified temperature as compared to the saturation temperature at the specified pressure. For sources without any given pressure, the pressure of the source receiving position is used. The output variables TSAT, TSV, PSAT, PVAP (see output variables description) are used to retrieve the vapor data. TSV equals TM and PVAP equals PT for single component simulations (no partial pressure since only a single component is considered). Other data can be obtained by specifying compositional variables. Under OPTIONS, the key WRITEPVTFILES=[NO]/YES controls whether the program will write the single component properties that are being used to file or not. For YES, a tab file _pvt.tab (fixed format) will be generated. Furthermore, the saturation line will be written to a file _pvt.env. Both these files can be visualized in the GUI.

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Slug Tracking In the standard OLGA model, physically sharp fronts in liquid hold-up are smeared out by the numerical scheme, a phenomenon that is more pronounced in horizontal or near horizontal high velocity transient flow cases. In situations where slug flow is identified by the flow model, hydrodynamic slugs are accounted for only in an average manner that does not give any information about slugs, their properties, or how they affect the flow. However, many flow parameters are highly dependent on the slug pattern, e.g., the pressure drop in a flow-path. Thus, it is necessary to be able to explicitly account for the occurrence of slugs. The slug tracking model is designed to initiate, maintain, and track physically sharp fronts such as those constituted by start-up slugs and hydrodynamic slugs. Among other things, the model gives information about position, velocity, length, and other characteristic quantities of each individual slug. In turn, this information is used to give better estimates of the actual properties of the overall flow. See also: When to use Methods and assumptions Limitations How to use

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When to use The slug tracking model have two different options initiating slugs (keyword SLUGTRACKING). These options are: 1. Level slug initiation, which initiate slugs when changes in liquid hold-up are detected from one section to another. The change in hold-up might be caused by a start-up situation, liquid sources, or boundary conditions changing with time just as well as geometry effects. This option is activated through the LEVEL key and is mainly to be used for well-defined start-up slugs. 2. Hydrodynamic slug initiation, which is the recommended slug initiation method for hydrodynamic and terrain slugging. Hydrodynamic slugs can be initiated when OLGA predicts transitions from either stratified or annular flow to slug flow. This option is activated by the key HYDRODYNAMIC. In addition to these two options, there is manual hydrodynamic slug initiation. This option is activated through the HYDRODYNAMIC key and requires that all slugs initiated are given as user input. Thus, in order to use this option, detailed knowledge about the slugging is required since the user has to specify the number of slugs to set up, at which positions to set them up, and at which times.

License requirements Slug tracking is part of the Slugtracking Module that requires a separate license.

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Methods and assumptions Initiation of level slugs

Figure A Schematic visualization of a pipeline shut-in situation where liquid has been accumulated at low points. The pipeline consists of a well, a transport line, and a riser. Level slug initiation may be carried out at any time in the user specified time interval given by STARTTIME and ENDTIME. The detection of level slugs is based on differences in the gas fraction. SLUGVOID is used to specify the maximum void allowed in a slug whereas BUBBLEVOID determines the minimum void in a bubble. When a section is found with void less than SLUGVOID, a level slug might be initiated, all depending on the void in the neighboring sections. If the void increases and exceeds BUBBLEVOID within two upstream sections, a tail is initiated. If, on the other hand, the void increases and exceeds BUBBLEVOID within two downstream sections, a front is initiated.

Initiation of hydrodynamic slugs

Figure B Schematic visualization of the initiation of a hydrodynamic slug. If OLGA predicts slug flow (ID=3) at boundary J, a hydrodynamic slug may be initiated in section J, J-1, or over both sections, see Figure B. Initiating a new slug implies redistribution of masses which might lead to discontinuities in pressure in inclined or vertical pipes. To avoid such discontinuities, the new slug is set up with an as short slug length as possible. These short hydrodynamic slugs will then grow into larger slugs as they propagate through the pipe if the conditions are favorable. When OLGA predicts slug flow, two criteria must be met before a hydrodynamic slug is initiated in a section: The distance to the closest slug must exceed a minimum distance. The time elapsed since a slug was either generated in or passed through the section must be larger than a specified minimum time. The minimum distance between slugs is specified through the INITFREQUENCY key (slug initiation frequency, Fi). Using the slug initiation frequency, the minimum distance is calculated as UB/Fi, where 332 / 769

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frequency, Fi). Using the slug initiation frequency, the minimum distance is calculated as UB/Fi, where UB is the bubble nose velocity of the new slug. Per default, the minimum distance is 10 pipe diameters. The idle time required before generating a new slug at any section boundary is specified through the DELAYCONSTANT key. The delay constant,DC, is given as the minimum number of pipe diameters between the new slug and the slug that last occupied the same section. The idle time is calculated according to (a) where D = pipe diameter [m] Ul = average liquid velocity [m/s] The default value for the delay constant is 150.

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Limitations Model limitations The model currently used for hydrodynamic slug initiation uses a slug frequency and a delay constant to determine when to set up new slugs. The slug frequency determines how close to an existing slug a new slug can be initiated whereas the delay constant determines the shortest time allowed between setting up two consecutive slugs at the same boundary or setting up a new slug after a slug has passed.

Compatibility limitations At present, it is not possible to run slug tracking in combination with Pig. The combination is not allowed. Complex fluid. The simulation will run, but as far as slugging goes, the results will be the same as if complex fluid had not been used.

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How to use General 1. Add the SLUGTRACKING keyword and choose a slug initiation method. 2. Add trend and profile plot variables to see differences between running the simulation with and without slug-tracking, e.g., PROFILEDATA VARIABLE=(PT, TM, ID, HOL, HOLHL, HOLWT, UL, UG) TRENDDATA PIPE=PIPE5, SECTION=3, VARIABLE=(QLT, QLTHL, QLTWT, ACCLIQ, ACCOIQ, ACCWAQ) The accumulated flow rates (ACCLIQ) can be used to estimate slug sizes. 3. Add global trend to get overview of the simulation. TRENDDATA VARIABLE=(LIQC, OILC, WATC) TRENDDATA VARIABLE=(RMERR, VOLGBL, HT, NSLUG)

Slug identification number When initiated, each slug is assigned a unique identification number. The first slug initiated gets identification number, and then 1 is added for each new slug initiated. This unique number enables the possibility to follow the development of individual slugs as they move through the pipeline. It is possible to plot, e.g., slug length, front and tail velocities, etc. Plotting individual slug data is useful mainly when there are few slugs is the system. When hydrodynamic slugging generates lots of slugs, it is difficult to identify which slug to consider.

Illegal slug section An illegal section is a section where no slugs are initialized and through which no slugs are allowed to pass (keyword SLUGILLEGAL). A slug front may enter into the illegal section, but it will be trapped inside it until the slug tail reaches the section and the slug is removed. The first section in a flow-path is by default an illegal section and so is the last one. This implies that slugs cannot propagate through networks. If stability problems are encountered when using in-line process equipment together with slug-tracking, it is recommended that illegal sections are introduced around the process equipment. Furthermore, if there are large changes in pipe diameter, e.g., when modeling a separator at the end of a pipeline as a pipe with big diameter, instabilities can be avoided by setting illegal sections on each side of such boundaries. With long pipelines mainly operating in the slug flow regime, the number of slugs can become very large which in turn results in long simulation times. In such situations, it is recommended to only allow for slugs close to the pipeline outlet, say the last 5-10 km. Yet again, this can be accomplished by using the keyword SLUGILLEGAL. In cases where terrain effects are predominant and large slugs develop far away from the outlet, illegal sections should not be used to prevent such slugs from developing.

Flow regime When slug tracking is activated, the flow regime indicator (ID) should be used with caution since the flow regime is forced to bubbly inside liquid slugs whereas it is forced to stratified in slug bubbles. Thus, the flow regime indicator will never indicate slug flow when slug tracking is activated.

Vertical riser at the end of a pipeline Problems might be encountered when slug tracking is activated and the pipeline has a vertical riser at the end. The problems are usually caused by back-flow in the riser. If such problems are encountered, the following actions might reduce them: Set the gas fraction on the outlet node equal to one. Now, if back-flow occurs at the outlet, only gas will enter the pipeline. Unless the flow in the riser is expected to influence slug patterns significantly, set the riser pipeline sections to illegal (SLUGILLEGAL). 335 / 769

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If possible, add a couple of horizontal sections at the top of the riser.

Startup slugs not detected If all start-up slugs are not detected, it is possible to specify the void limits used for initializing start-up slugs. This is done by modifying the void limits given by the keys BUBBLEVOID and SLUGVOID.

Hydrodynamic slug initiation The slug model might initiate slugs too often or too seldom as compared to the expected slug pattern. In order to tune the model to mimic the expected pattern, it is recommended that only the DELAYCONSTANT key is varied first. If it is not possible to achieve the slug pattern sought by varying DELAYCONSTANT alone, INITFREQUENCY can be modified as well. Hydrodynamic slug initiation: the delay constant The delay constant, DC, is the number of pipe diameters a slug must travel before the slug model tries to initiate a new slug at the same boundary. Thus, the time between two consecutive slug initiations on any given boundary or the time between a slug passes a boundary and a new slug can be set up is given by (a) where D = pipe diameter [m] Ul = average liquid velocity [m/s] Using the Shea correlation for the slug frequency (b) where D = pipe diameter [m] L = pipeline length [m] Usl = superficial liquid velocity [m/s] it is possible to get an estimate of the delay constant. Tuning on the delay constant should be performed such that the resulting slug frequency is in the same order of magnitude as Fsl. It should be noted that this correlation is based on experimental data and field data for systems dominated by hydrodynamic slugging. Thus, if terrain effects are predominant, one should not use the Shea correlation. The default value of 150 has been found to yield good results for a number of cases.

Profile plots, trend plots, and slug statistics When specifying, e.g., the hold-up (HOL) in TRENDDATA or PROFILEDATA, it is important to note that the hold-up plotted is the section average. It is not possible to resolve the hold-up of individual slug and bubble regions inside sections, but these are used to calculate the section average. In order to visualize the hold-up of individual slugs/bubbles, specify HOLEXP under TRENDDATA. This will show the instantaneous hold-up at the boundary specified. It is possible to plot properties of individual slugs using their identification number. This feature is mainly of use when there are few slugs in the system and the slugs of interest are easily identified. In cases with severe slugging, the large number of slugs will make it virtually impossible to single out a particular slug. However, it might be of interest to look at a statistical sample of slugs in order to get an idea of the general slug properties. The syntax for addressing individual slugs is TRENDDATA SLUGID=1, VARIABLE=(LSL, LSB, JSLT, JSLF, USF, UST, ZFSL, ZTSL, PTJF, PTJT) 336 / 769

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Slug statistics The trend plot variables LSLEXP and LSBEXP show the length of a liquid slug or slug bubble currently residing at a given section boundary. TRENDDATA PIPE=PIPE-1, SECTION=10, VARIABLE=LSLEXP Using the OLGA GUI, these variables can be used to plot slug statistics. The slug statistics is generated by post-processing of the .tpl-file and is accessed by selecting the variables LSLEXP_STAT and LSBEXP_STAT in the trend plot dialog. These two plot variables represent the statistical distribution of slug and slug bubble lengths at the boundary considered. The properties of these plots can be set through 'Slug Statistics...' under the Edit menu.

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Slug tuning The SLUGTUNING keyword makes it possible to tune parameters in the slug model. See also: When to use Methods and assumptions Limitations How to use

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When to use The SLUGTUNING keyword is used for tuning the OLGA slug tracking model to specific sets of measurement data or sensitivity studies. SLUGTUNING should be applied with great care, as it might cause the validation and verification of the OLGA model to no longer be valid.

License requirements Slug tuning is part of the Tuning Module that requires a separate license.

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Methods and assumptions The slug tuning coefficients are multiplied by the related values calculated by OLGA. The exception is slug length which is interpreted directly as slug length in number of diameters. The Taylor bubble velocity is calculated as (a) where CUB1 = CUB2 = C0 = Umix = U0 =

tuning coefficient 1 given by the key UBCOEFF1 tuning coefficient 2 given by the key UBCOEFF2 distribution coefficient mixture velocity, i.e., sum of the superficial velocities drift velocity

The slug front pressure drop is given by

(b) where CDP = CDP0 = Lslug = f(α,ρl) = Ucrit =

tuning coefficient for slug front pressure drop given by key DPFACT tuning coefficient for onset of slug front pressure drop given by key DPONSET slug length additional pressure drop cutoff velocity at which the slug front pressure drop is switched on

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Limitations The slug tuning coefficients are given globally, i.e., it is not possible to specify different sets of tuning parameters for different flow-paths.

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How to use Specify the desired slug tuning coefficients and where they should be applied. N.B., the slug tuning coefficients are global.

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Source A source can be used to model pipeline inflow and outflow of gas and liquid. OLGA use mass flow rate for internal calculations, but input flow rate may also be given as volumetric flow at standard conditions. Wells and nearwells are more specialized types of modelling pipeline inflow and outflow. See also: When to use Methods and assumptions How to use

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When to use The SOURCE key can be used when a flow needs to be inserted into the pipeline. For more advanced flow simulations the WELL or NEARWELL keys can be used.

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Methods and assumptions Two types of sources can be specified; the mass source and the pressure driven source, which is also known as a controlled mass source or source controlled by valve (SOVA). Each type of source can be either positive (flow into the pipeline) or negative (flow out of the pipeline). The upstream (for positive source) or downstream (for negative source) pressure and temperature can be specified. When the upstream/downstream pressure is given, the expansion from the given pressure to the pressure inside the pipe section will be taken into account for the temperature calculations. A mass source need not specify the upstream/downstream pressure, and this will then be set to the pressure inside the pipe section where the source is introduced. A SOVA must always specify the upstream/downstream pressure. The external pressure and temperature can be constant or given as a time series. Phase fractions can be specified in the input for a positive source. For a negative source, the phase fractions in the connected section will be used.

Mass source The mass source is the simplest model and has a given mass flow rate specified by the user. Phase fractions for gas and water can be specified, from which the oil phase fraction will be calculated. The default value for gas is -1, which means it will be read from the PVT file. The default value for water is 0. If a controller is used, the actual mass flow rate into the section (positive source) or out of the section (negative source) is a fraction of the mass flow rate given as input, with the fraction regulated by the controller. Note that the mass flow node covers the functionality of a mass source in the first section after a closed node.

Pressure driven source (SOVA) The flow for a SOVA will be calculated from a flow equation for mass flow through an orifice, where the orifice area can be governed by a controller. The figure below illustrates this.

Figure A. Illustration of a pressure driven source

Controlling the flow The flow area of the SOVA is governed by the control system, where the valve has finite opening and closing time (stroke time) specified by the user. Both sub-critical and critical flow is described. For sub-critical flow the flow rate is governed by the 345 / 769

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Both sub-critical and critical flow is described. For sub-critical flow the flow rate is governed by the difference between the internal and external pressures, the upstream conditions and the flow area. For critical flow the flow rate is governed by the upstream conditions and the flow area only. The pressure difference determines the direction of flow in or out of the pipe. The orifice area is calculated from: (a) where us = controller signal

Valve functionality The valve-specific functionality is further described in the Valve section.

Calculating mass flow at standard conditions The following equations show how the total mass flow is calculated from volumetric flow given at standard conditions. Symbols used in the equations are given in the list below:

wc

r

Water cut, volume of water divided by volume of liquid at standard condition Gas oil ratio, volume of gas divided by volume of oil at standard condition Gas liquid ratio, volume of gas divided by volume of liquid at standard condition Volume flow Mass flow Density

Indexes: tot ST g o liq w *

Total At standard condition Gas phase Oil phase Liquid phase (water + oil) Water phase Equivalent phase

GOR GLR Q

The density in the equations below is taken from the PVT table. It is necessary that the properties at standard condition are included in the PVT table. If WATERCUT, GOR and volume flow of gas at standard condition ( PHASE = GAS and STDFLOWRATE =

) are known, use:

(b)

If WATERCUT, GOR and volume flow of liquid at standard condition ( PHASE = LIQUID and STDFLOWRATE =

) are known, use:

(c)

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If WATERCUT, GOR and volume flow of oil at standard condition ( PHASE = OIL and STDFLOWRATE =

) are known, use:

(d) If WATERCUT, GOR and volume flow of water at standard condition ( PHASE = WATER and STDFLOWRATE =

) are known, use:

(e) If WATERCUT, GLR and volume flow of gas at standard condition ( PHASE = GAS and STDFLOWRATE =

) are known, use:

(f) If WATERCUT, GLR and volume flow of liquid at standard condition ( PHASE = LIQUID and STDFLOWRATE =

) are known, use:

(g)

If WATERCUT, GLR and volume flow of oil at standard condition ( PHASE = OIL and STDFLOWRATE =

) are known, use:

(h)

If WATERCUT, GLR and volume flow of water at standard condition ( PHASE = WATER and STDFLOWRATE =

) are known, use:

(i) Specified GOR or GLR will shift the values of gas mass fraction in the PVT table with use of the following equation (2 phase) (j) where Gas mass flow at given pressure and temperature Gas mass flow at standard condition - calculated from given GOR or GLR Oil mass flow at standard condition - calculated from given GOR or GLR Gas mass fraction at given pressure and temperature - value from the PVT table Gas mass fraction at standard condition - value from the PVT table 347 / 769

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(k) If the equivalent gas volumetric flow rate at standard condition ( ) and the mol weight of the total flow, , are known, use: PHASE = GAS, STDFLOWRATE = and MOLWEIGHT = The density of the equivalent gas at standard conditions will then be calculated from ideal gas law, and the total mass flow will be given from the following equation on condition that GOR or GLR is greater then 1010 (infinitely in OLGA) (l) If GOR or GLR is less than 1010 the total mass flow will be calculated from the equations described earlier for PHASE = GAS with = and = . Note: There are limitations on how much the value of GOR/GLR can be changed when using a PVT table. One can check the source input by plotting the volume flow rates through the source at standard conditions (e.g. QGSTSOUR). E.g. if a source using default GOR/GLR has no gas at the in-situ conditions, one cannot give a lower GOR/GLR for this source. Removal of gas that is not present is impossible.

Steady state pre-processor Both source types can be used with the steady state pre-processor. However, there are certain limitations: With a closed node, the sum of all flows into the adjacent section (including contributions from all sources, wells, and nearwells) can not be 0

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How to use To define a SOURCE, follow the steps described below. Each SOURCE must have a unique LABEL. The position along the branch must be given; either by use of the POSITION key, ABSPOSITION key, or a combination of the PIPE and SECTION keys. Phase fractions can be given either directly with the GASFRACTION and WATERFRACTION/TOTALWATERFRACTION keys or at standard conditions with the GLR/GOR/WATERCUT keys. The upstream/downstream PRESSURE and TEMPERATURE can be specified. See Capabilities for further description. Each source type is also available for use with the compositional models (i.e. Compositional Tracking, Blackoil, MEG, Wax). All input variables can be defined as time series with the TIME key. See keyword SOURCE for more details.

Mass source There are several keys available to define the mass source. When the mass flow rate is to be specified at the source temperature and pressure without compositional tracking use the key MASSFLOW. With compositional models the keys FEEDMASSFLOW, FEEDMOLEFLOW or FEEDSTDFLOW may be used. When the volumetric flow rate at the standard conditions is given, the key STDFLOWRATE should be used. See keyword SOURCE for more details.

Pressure driven source (SOVA) The SOVA massflow is defined by the valve specific input data. For further descriptions, see the Valve section. See keyword SOURCE for more details.

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Steady State Processor The steady state pre-processor in OLGA computes a steady state solution for a pipeline or an entire flow network. Steady state pressures, temperatures, mass flows, liquid hold-ups and flow regimes are calculated along the pipelines. The steady state pre-processor is primarily intended for generation of initial values for dynamic computations, but may also be used as a standalone steady state tool. See also: When to use Methods and assumptions Limitations How to use

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When to use The steady state pre-processor may be used in order to 1. eliminate the need for user given initial conditions 2. get a consistent initial state as a basis for dynamic simulations 3. perform screening studies The steady state pre-processor can be used for flow networks with any combination of boundary conditions at inlets and outlets. Both merging and diverging networks can be calculated. Except for displacement pumps and pump battery, the steady state pre-processor incorporates the effect of process equipment. For PID controllers the bias settings are used as the controller outputs.

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Methods and assumptions The steady state pre-processor finds a consistent solution for flow networks by iteration. Networks where all inlet flows and outlet pressures are known are solved by the following sequence of computations: 1. Phase transitions are computed using old values of pressures and temperatures. The combination of phase transition and inlet flows gives consistent flow rates along all the pipelines in the entire network. 2. Using the newly computed flows, old temperatures, and the pressure boundary conditions at the outlet, new pressures are computed along all the pipelines in the network. The point model OLGAS THREE-PHASE is used in this step. 3. The temperatures along all the network components are computed. Iteration on the sequence 1) to 3) is performed until the change between two iterates is smaller than a tolerance. If the inlet flows and/or outlet pressures are not known, an outer iteration is needed in addition to the one shown above. In this iteration the initial guesses for inlet flows/outlet pressures are refined until the residuals are smaller than a given tolerance.

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Limitations The solution computed by the steady state pre-processor and the solution obtained when simulation with the dynamic solver until a steady state is achieved may not be equal. This is mainly due to the two following reasons: 1. For unstable systems (for instance slugging cases) the steady state pre-processor may find a solution that differs from the average value in the transient solution as there is no truly steady-state condition. 2. The steady state pre-processor has some small residual errors that are removed by the transient simulation. In some sensitive cases this can cause a difference in pressure, temperature and holdup profiles. Therefore, if the slug flow regime is detected in the simulation, it is recommended to perform a dynamic simulation with the slug tracking model (not available in OLGA 6.1). The steady state pre-processor is not as robust as the dynamic OLGA. This is particularly the case for simulations with pressure or well (productivity index) as inlet boundary conditions, or negative sources. In such cases, if the pre-processor does not converge to a reliable solution, the pre-processor must be turned OFF (STEADYSTATE=OFF under OPTIONS), and INITIALCONDITIONS must be applied to all the FLOWPATHS instead. The steady state pre-processor cannot handle counter-current flow (such as for instance positive gas flow and negative liquid flow). The steady state pre-processor cannot handle zero flow in the pipeline, therefore it should not be used with closed valves in the flow path or with mass sources that sum up to zero flow rate at start time. For flow networks with one or more separators the steady state pre-processor uses a simplified approach. The separator is treated as a simple node with mixture properties and the phase flow fractions of any phase are assumed to be equal for any of the outlets of a separator. This approach may lead to discontinuities between the steady state and dynamic solution. The steady state pre-processor may be run with wax deposition or hydrate kinetics activated, but the pre-processor does not consider the wax phase or hydrate formation.

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How to use To activate the steady state pre-processor from the OLGA GUI do the following: In the property window for OPTIONS. Choose STEADYSTATE=ON to get a full steady state computation including calculations of temperatures. Choose STEADYSTATE=NOTEMP to avoid the temperature calculation. In this case initial temperature profiles must be given for all the flow components in the network. The latter option can be useful if the pre-processor has problems finding a solution. This implies that the simulation must be run dynamically for some time in order to achieve a true thermal steady state solution. The steady state pre-processor can sometimes fail to find a solution if flows are negative, i.e. if the flow goes from the outlet to the inlet of a pipeline. For such pipelines it is therefore recommended to set INIFLOWDIR=NEGATIVE in the BRANCH input group. In order to do some fast studies (screening studies), one can use the steady state pre-processor results. In this case use STEADYSTATE = ON under OPTIONS and STARTTIME equal ENDTIME under INTEGRATION. If input parameters (boundary conditions, valve openings, etc.) are given as time series, the steady state pre-processor uses the values at the start time.

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SteamWater-HC The availability of the steam module depends on the User's licensing agreement with SPT Group. The SteamWater-HC module is an improved way of tracking when there is a considerable amount of H2O in the fluid. There are some basic limitations when not using this module: 1. The standard table based version of the code assumes that the gas phase is always saturated with

steam (no mass balance for steam). Does not apply for MEG/MeOH/EtOH Tracking and Compositional Tracking as they have a steam mass balance. 2. There must be a gas phase otherwise water can not be evaporated. 3. OLGA can not deal with a single component system if the saturation line is crossed. This is due to the explicit coupling of volume balance and energy balance equations and the lack of a two phase region (two phase envelope) for a single component system. The second limitation is not a real limitation as there will usually be some HC gas in situations where water is evaporating. The only situation where this limitation is real is if only water is present in the fluid and temperature and pressure conditions are such that the saturation line is crossed. The third limitation is related to the way the conservation equations are solved with an explicit coupling between volume (pressure) balance and energy (temperature) balance. This is solved by introducing time constants or delays in the evaporation/condensation process. The difference between the saturation temperature and the fluid temperature serves as a potential for phase mass transfer. Multiplying this temperature difference with a certain heat or energy transfer coefficient gives a certain energy transfer rate that can be used to estimate the mass transfer rate. In that case an asymptotic approach to equilibrium occurs. How fast this approach is depends on the size of the energy transfer coefficient. Also, this module gives more correct water/steam properties around the critical point and also in the supercritical region. See also: When to use Methods and assumptions How to use

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When to use The SteamWater–HC module should be used when there is a considerable amount of water in the fluid, or when it is important to limit the rate of boiling/evaporation/condensation, e.g., when simulating drying of a pipeline with hot gas.

License requirements SteamWater–HC is part of the Single Component Module that requires a separate license.

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Methods and assumptions The following assumptions are mode in the model: Oil, gas, water and vapor (steam) will all have the same temperature, TM. The pressure of the water phase will be equal to the total pressure. The pressure of vapor will be equal to the partial pressure of vapor in the gas phase and will be calculated assuming an ideal mix of vapor and hydrocarbon gas. Water saturation temperature, TSATW, will be calculated from the total pressure. Vapor saturation temperature, TSATV, will be calculated from the partial pressure of vapor. If the fluid temperature, TM, is higher than TSATW, flashing or boiling of water will take place. If TM is higher than TSATV but lower than TSATW, evaporation of water will take place. If TM is lower than TSATV, condensation of vapor will take place. Note that TSATV will always be less or equal to TSATW. The inner pipe wall surface may be superheated or subcooled compared to TSATW or TSATV. Such a situation may lead to surface boiling or surface condensation in cases where water or vapor is in direct contact with the pipe wall. This additional mass transfer term will not be directly included but can be accounted for by an enhanced heat transfer due to surface boiling/condensation.

Generation of steam and water properties. The equations used to calculate the steam and water properties are taken from ref. 1. These equations are time consuming to solve and will therefore be used only at the start of a simulation. The properties will be calculated at pressure/temperature values corresponding to the pressure/temperature grid points specified in the PVT table prepared for the simulation. After the saturation points and the physical properties are calculated for all the P/T grid points that correspond to the PVT table for the HC mixture, linear interpolation between the grid points is applied during the simulations. For simulation cases where the pressure may cross the critical pressure, it is important that the HC PVT table contains a grid point that is close to the critical point in order to obtain accurate crossing of the saturation line. For all the cases, a pressure interval less than10 bar and a temperature interval less than 10 K are recommended in order to maintain acceptable accuracy of the linear interpolation.

Saturation line Below the critical point, PC and TC, (pressure and temperature), the saturation pressure, Psat (T), and saturation temperature, Tsat (P), at a given grid point, P,T, is determined from the saturation line. Above the critical point, PC = 221.2 bar and TC = 647.3 K, and to 676 K and 250 bar, a straight line is used to divide the single-phase or dense-phase region into vapor and liquid. Above 676 K and 250 bar, the boundary line between region 2 and region 3 is used as the division between vapor and liquid. The definition of the regions is described in ref. 1.

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Physical properties. Water properties: For pressures below 225 bar, water property equations for region 1 (see ref. 1) are used for water in the water region. In the vapor region, the properties for water are extrapolated from the saturation point: Enthalpy is based on thermal capacity at saturation temperature corresponding to a given pressure and the density according to the density derivative to pressure at the saturation pressure corresponding to a given temperature. All the other properties are from the saturation temperature. For pressures above 225 bar, water properties are calculated based on equations for the different regions specified in ref. 1. Thermal capacity and enthalpy for water is singular near the critical point. To avoid numerical problems in region 3 the water properties from region 1 instead of those for region 3 when the pressure is below 225 bar (the equations are very similar except when you are closer than N > MINSPEED) (2). Regulated by a physical parameter. The speed is calculated by N = MINSPEED + u (MAXSPEED - MINSPEED) Here MAXSPEED is the maximum pump speed (defined by user), MINSPEED is the minimum pump speed (defined by user) and u the signal from the controller. Simplified centrifugal pump A simplified description of a centrifugal pump is used for modeling the behavior of a centrifugal pump around an operational point. Simple algebraic expressions are used to calculate pressure increase over the pump and pump efficiency. Pump battery The pump battery is used for pumping drilling fluid, e.g. muds in a drilling operation. The purpose is to get an overall estimate of pump power needed as well as the volume of mud pumped. The volume delivered iby the pump is proportional to the rate of pump strokes. (k) where QP

=

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PFAC SPES

= =

Pumping factor Strokes per time unit

The pump rate is normally controlled by the following set of controllers: Controller on the maximum hydraulic horsepower allowed Controller on the maximum pump rate Controller on the minimum pump rate Controller on the maximum pump pressure allowed If either one of these controllers is set into action the pump rate is reduced automatically. The number of controllers can be extended above the number shown above and different variables (e.g. fluid rate, inflow rate) can be used to control the pumps. Note that a pump cannot be defined at the first or last section boundary of a pipeline. See also: Pump - Purpose

PUMP (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

ACCECOEFF

Real [0.0] (rad/s2)

ACOEFFICIENT

Real

[1.6]

BCOEFFICIENT

Real

[1.6]

BYDIAMETER

Real (m) [0.0]

DCOEFF1 DCOEFF2 DCOEFF3

Real [0.0] (1/rpm) Real [0.0] (1/m3/s) Real Real

[0.0]

Description Absolute position. Distance from branch inlet. Pump speed acceleration. When recycle flow is over or below the limits, this value will be used to increase or decrease the pump speed. For centrifugal and displacement pumps. Experimentally determined exponent for calculating the mechanical friction loss for a displacement pump. Experimentally determined exponent for calculating the viscous friction loss for a displacement pump. Diameter of the valve in the bypass flow line. For centrifugal and displacement pumps. Has to be 0.0 if PUMPTYPE=SIMPLIFIED. Relative change in pump pressure increase with pump speed for simplified pump. Relative change in pump pressure increase with flow rate for simplified pump. Relative reduction in pump pressure increase with gas volume fraction. Rated pump density. Used for centrifugal 508 / 769

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DENSITYR DPRATED ECOEFF1 ECOEFF2

Real [900] (kg/m3) Real (bar) Real [0.0] (1/rpm) Real [0.0] (1/m3/s)

ECOEFF3

Real

[0.0]

EFFIMECH

Real

[0.7]

EFFRATED

Real

[0.5]

FLOWRATED

Real (m3/s)

HEADRATED

Real (m)

HPMAX LABEL MAXCAPACITY MAXPRESSURE MAXRECYCLE MAXSPEED MDISSIPATION MINCAPACITY MINRECYCLE MINSPEED PIPE POSITION PREFSPEED

PUMPTYPE

RECDIAMETER

RECPHASE

Real (W) String Real (m3/s) Real (Pa) Real (kg/s) Real (rpm) Real (W) Real (m3/s) Real (kg/s) Real (rpm) Symbol Symbol Real (rpm)

[PUMP-1]

Rated pump density. Used for centrifugal and simplified pumps. Pump pressure increase at rated conditions for simplified pump. Relative change in pump efficiency with pump speed for simplified pump. Relative change in pump efficiency with pump speed for simplified pump. Relative reduction in pump efficiency with gas volume fraction. Mechanical efficiency of centrifugal and simplified pump. Adiabatic efficiency of simplified pump at rated conditions. Rated pump flow. Used for centrifugal and simplified pumps. Rated pump head. Used for centrifugal pumps. Maximum hydraulic horsepower for each single pump in the pump battery. Label of the pump. Maximum flow capacity for pump battery. Maximum downstream pressure for pump battery. Maximum recycle mass flow rate. Maximum pump speed.

[0.0]

Mechanical dissipation at nominal speed for a displacement pump. Minimum flow capacity for pump battery.

[0.0]

Minimum recycle mass flow rate.

[0.0]

Minimum pump speed.

[3000]

Pipe label for pump location. Position where pump is located. Pump reference speed. Used for displacement pumps.

DISPLACEMENT | SIMPLIFIED | Symbol PUMPBATTERY Pump model. | [CENTRIFUGAL] Choke diameter for recycle flow. For Real (m) centrifugal and displacement pumps. Has to be 0.0 if PUMPTYPE=SIMPLIFIED. | GAS | Phase of recycle flow. For centrifugal and Symbol LIQUID | WATER displacement pumps.

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RECPHASE

Symbol

SECTIONBOUNDARY Integer SPECAPACITY SPEEDR TABLE TORQMAX TORQR VDISSIPATION

LIQUID | WATER | [MIXTURE] 0

Real (m3/R) Real (rpm) Symbol Real (Nm) Real (Nm) Real (W)

[0.0]

displacement pumps. Section boundary number where the pump is located. Pump specific volumetric capacity, Qspc. Used for displacement pumps. Rated pump speed. Used for centrifugal and simplified pumps. Name of the tables of pump back flow data or pump characteristic data. For centrifugal and displacement pumps. Maximum motor torque allowed. Can only be used for centrifugal pumps. Rated pump hydraulic torque. Used for centrifugal pumps. Viscous dissipation at nominal speed for a displacement pump.

Link to: PUMP (on FLOWPATH) Description Keys

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TRANSMITTER (on FLOWPATH) Description ( See also: Keys) This keyword defines output-signals sent from the branch. The signals can be received by a signalcomponent (typicallly a controller). The signals can be measured values in the branch, e.g. pressure, massflow etc. Controllers that receive these measured values use them to calculate new signal which in turn is used to regulate e.g. a valve opening (see Controllers).

TRANSMITTER (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

LABEL PIPE

String Symbol

[TM-1]

SECTION

Integer

0

SECTIONBOUNDARY Integer

1

Description Absolute position. Distance from branch inlet. Transmitter Terminal label. Pipe number for the transmitter. Section number where the transmitter is located. Section boundary number where the transmitter is located.

Link to: TRANSMITTER (on FLOWPATH) Description Keys

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OLGA 7

VALVE (on FLOWPATH) Description ( See also: Keys) Here data for valves and chokes are defined. The position of the valve can be specified in 3 ways: 1. 2. 3.

by referring to a pipe and a section boundary number by referring to a pre-define position by specifying the distance from the left end of the branch (absolute position)

The valve performance is either obtained from a discharge coefficient and the maximum choke diameter, or from a table with valve characteristics. The relative opening of the valve can be prescribed as a function of time, or it can be driven by a controller. There are two valve models (GASSIZING and HYDROVALVE). Model selection is done with the MODEL key. GASSIZING is a implementation of the gas sizing equation given in Valve - Methods and assumptions Valve - Methods and assumptions. The GASSIZING option requires gas valve characteristics given by the TABLE key. HYDROVALVE can be used to simulate chokes, liquid valves and gas valves.

VALVE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CD

Real

CF

Real

CRITFLOWMODEL

Symbol

DIAMETER LABEL

Real (m) String

MODEL

Symbol

OPENING

RealList

PHASE

Symbol

PIPE

Symbol

POSITION

Symbol

Description

Absolute position. Distance from branch inlet. [0.84] Discharge coefficient. Ratio between gas and liquid sizing coefficient. Choice of critical flow model to be used. HENRYFAUSKE Homogenous frozen critical flow model or | [FROZEN] Henry-Fauske model. In addition, a forced subcritical option is available. Maximum valve diameter. [VALVE-1] Valve label. Default is valve number. Valve model. HYDROMODEL is used for chokes and valves with liquid/gas GASSIZING | characteristics. GASSIZING can only be [HYDROVALVE] used to simulate valves with gas characteristics.' Relative openings in the valve opening [1.0] timetable. | GAS | The type of flow through the valve. For two LIQUID or three phase flow, use LIQUID. Pipe label where the valve is located. Position where the valve is located. If this value is defined PIPE and SECTIONBOUNDARY should not be used. 512 / 769

OLGA 7

SECTIONBOUNDARY Integer STROKETIME TABLE TIME

1

Real (s) [0.0] SymbolList RealList [0.0] (s)

Section boundary number where the valve is located. Stroke time of the valve. Label of table for valve characteristics. Time series for valve opening table.

Link to: VALVE (on FLOWPATH) Description Keys

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OLGA 7

HEATTRANSFER (on FLOWPATH) Description ( See also: Keys) This statement specifies the heat transfer data for the pipe walls. The temperature of the surroundings must be given. In addition to this one of the following three options must be used: 1. Specify overall heat transfer coefficient: UVALUE (requires TEMPERATURE=UGIVEN in OPTIONS) 2. Specify ambient heat transfer coefficient: HAMBIENT (HOUTEROPTION=HGIVEN, requires TEMPERATURE=WALL in OPTIONS) 3. Specify properties of the ambient fluid (HOUTEROPTION=OTHER / WATER / AIR, requires TEMPERATURE=WALL in OPTIONS) For options 2 and 3, the overall heat transfer coefficient is calculated and the keyword WALL have to be specified. If option 3 is used, the ambient heat transfer coefficient is a function of the pipe diameter, the fluid velocity, and fluid properties such as density and viscosity. Velocity and fluid properties have to be given only if a user specified fluid is used (HOUTEROPTION=OTHER). The VELOCITY can be specified for HOUTEROPTION=AIR or WATER, otherwise the default values 4 m/s and 1 m/s, respectively, will be used. Default values are applied for all other properties when HOUTEROPTION=AIR or WATER. In order to simplify the input of the ambient temperature distribution along a predefined pipeline section, the user can specify start and end ambient temperature and OLGA will perform an interpolation along the pipeline. Four different interpolation options are available. For the default option, SECTIONWISE, the ambient temperature is given by the user for the midpoint of the first and last section. The interpolation is performed between these points using the distance between section midpoints to achieve a linear temperature profile with respect to the distance along the pipeline. For the options HORIZONTAL, LENGTH, and VERTICAL, the ambient temperature is specified at the inlet and outlet boundaries (INTAMBIENT and OUTTAMBIENT). The interpolation is then based on either horizontal length, actual length, or vertical depth.

HEATTRANSFER (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

CAPACITY

RealList (J/kg-C)

CONDUCTIVITY

RealList (W/m-C)

Description Heat capacity of ambient fluid. If HOUTEROPTION is AIR, 1000 J/KG-K is used. If HOUTEROPTION is WATER, 4186 J/KG-K is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Thermal conductivity of ambient fluid. If HOUTEROPTION is AIR, 0.023 W/mK is used. If HOUTEROPTION is WATER, 0.56 W/mK is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Density of ambient fluid. If HOUTEROPTION is AIR, 1.29 kg/m3 is

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DENSITY

RealList (kg/m3)

EXPANSION

RealList (1/C)

HAMBIENT

RealList (W/m2-C)

HMININNERWALL

RealList (W/m2-C)

[0.0]

HOUTEROPTION

Symbol

AIR | WATER | OTHER | [HGIVEN]

INHAMBIENT

Real (W/m2-C)

INTAMBIENT

INTERPOLATION

OUTHAMBIENT

OUTTAMBIENT

PIPE SECTION TAMBIENT

HOUTEROPTION is AIR, 1.29 kg/m3 is used. If HOUTEROPTION is WATER, 1000 kg/m3 is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Thermal expansion coefficient of ambient fluid. If HOUTEROPTION is AIR, 34E-4 1/C is used. If HOUTEROPTION is WATER, 21E-5 1/C is used. Input can either be a single value (constant along range of sections), two values (lengthinterpolated) or given explicitly for each section. Mean heat transfer coefficient on outer wall surface. Input can either be a single value (constant along range of sections) or given explicitly for each section. Minimum inner heat transfer coefficient on inner wall surface. Option for ambient heat transfer coefficient.

Overall heat transfer coefficient at the inlet of the first pipe in a pipeline section where interpolation is used for overall heat transfer coefficient. Ambient temperature at the inlet of the Real (C) first pipe in a branch where interpolation is used for ambient temperature. Type of interpolation used to calculate the | ambient temperature and outer heat LENGTH | transfer coefficient. Note that the outer Symbol HORIZONTAL | heat transfer coefficient is only affected by VERTICAL | the INTERPOLATION key when [SECTIONWISE] HOUTEROPTION = HGIVEN. Overall heat transfer coefficient at the Real outlet of the last pipe in a pipeline section (W/m2-C) where interpolation is used for overall heat transfer coefficient. Ambient temperature at the outlet of the last pipe in a pipeline section where Real (C) interpolation is used for ambient temperature. Pipe label or pipe number (single or SymbolList [ALL] continuous range in the form x-y). IntegerList 0 Section number. Ambient temperature. Input can either be RealList a single value (constant along range of (C) sections) or given explicitly for each section. List of reference to TIMESERIES keywords. The value of each time series 515 / 769

OLGA 7

TAMBIENTSERIES

SymbolList

TAMBSERIESFACTOR RealList

UVALUE

RealList (W/m2-C)

VELOCITY

RealList (m/s)

VISCOSITY

RealList (N-s/m2)

[1]

is scaled with a corresponding factor in TAMBSERIESFACTOR and added as an increment to the temperature defined in TAMBIENT or INTAMBIENT and OUTTAMBIENT. List of factors to be used to scale ambient temperature time series in TAMBIENTSERIES. Note that this key also introduces the unit of the function. Overall heat transfer coefficient given by user based on the inner pipe diameter. Speed of ambient fluid. If HOUTEROPTION is AIR, default is 4 m/s. If HOUTEROPTION is WATER, default is 1 m/s. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Viscosity of ambient fluid. If HOUTEROPTION is AIR, 1.8E-5 N-s/m2 is used. If HOUTEROPTION is WATER, 1E-3 N-s/m2 is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section.

Link to: HEATTRANSFER (on FLOWPATH) Description Keys

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OLGA 7

INITIALCONDITIONS (on FLOWPATH) Description ( See also: Keys) This statement defines initial conditions for the dynamic calculation. The initial conditions are given flow path-, pipe- or section-wise. The total mass flow is defined at section boundaries while the remaining parameters are given for section volumes. There are several ways to define initial data, depending on the key STEADYSTATE in the OPTIONS statement: 1. STEADYSTATE=OFF (initial conditions not calculated by steady state pre-processor): User defines the pressure, temperature, gas volume fraction, mass flow, and water volume fraction in the liquid phase for all sections in each flow path. 2. STEADYSTATE=NOTEMP (initial temperature not calculated by steady state pre-processor): User defines the temperature for all sections in each flow path. The latter option can be useful if the pre-processor has problems finding a solution. This implies that the simulation must be run for some time in order to achieve a steady state solution. Compositional tracking input such as FEEDMOLEFRACTION can be given for all settings of STEADYSTATE (in OPTIONS). For STEADYSTATE=ON or NOTEMP, the given FEEDMOLEFRACTION will be an initial input to the steady state pre-processor. In order to simplify the input for certain initial condition variables, OLGA can perform interpolation along pre-defined flow path segments. Three different interpolation options are available; HORIZONTAL, LENGTH and VERTICAL. The variable is specified at the inlet and outlet of the pipeline segment, and the interpolation is performed based on horizontal length, actual length or vertical depth along the pipeline. LENGTH is the default option.

INITIALCONDITIONS (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

Parameter set Default:[ ]

FEEDMASSFRACTION RealList FEEDMOLEFRACTION RealList

FEEDNAME

SymbolList

FEEDVOLFRACTION

RealList

INHIBFRACTION

RealList

Description

FEED-1 | BOFEED-1

[0.0]

Mass fraction of each feed given in FEEDNAME. Mole fraction of each feed given in FEEDNAME. Can not be used with Drilling. Label(s) of initial feed(s) to be used for calculating the local fluid compositions in the pipe(s)/section(s). A list means mixing of feeds. Requires COMPOSITIONAL=ON/BLACKOIL or DRILLING=ON under the OPTIONS keyword. Volume fraction of each feed given in FEEDNAME (only for blackoil model). Mass fraction of inhibitor in water phase in each section. 517 / 769

OLGA 7

ININHIBFRACTION

Real

INPRESSURE

Real (Pa)

INSTEAMFRACTION

Real

INTEMPERATURE

Real (C)

[0.0]

[-1.0]

| HORIZONTAL Type of interpolation used to calculate the | VERTICAL | initial conditions. [LENGTH] Void fraction at the inlet to the first pipe in a branch where interpolation is used. Watercut at the inlet to the first pipe in a branch where interpolation is used.

INTERPOLATION

Symbol

INVOIDFRACTION

Real

INWATERCUT

Real

MASSFLOW

RealList (kg/s)

[0.0]

OUTINHIBFRACTION

Real

[0.0]

OUTPRESSURE

Real (Pa)

OUTSTEAMFRACTION Real

OUTTEMPERATURE

Real (C)

OUTVOIDFRACTION

Real

OUTWATERCUT

Real

Mass fraction of inhibitor in water phase at the inlet to the first pipe in a pipeline section where interpolation is used. Pressure at the inlet to the first pipe in a branch where interpolation is used. Fraction of total mass of h2o component in the gas phase inlet to the first pipe in a pipeline section where interpolation is used. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Temperature at the inlet to the first pipe in a branch where interpolation is used.

[-1.0]

Total mass flow at each section boundaries. Mass fraction of inhibitor in water phase at the outlet of the last pipe in a pipeline section where interpolation is used. Pressure at the outlet of the last pipe in a branch where interpolation is used Fraction of total mass of h2o component in the gas phase outlet to the last pipe in a pipeline section where interpolation is used. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Temperature at the outlet of the last pipe in a branch where interpolation is used. Void fraction at the outlet of the last pipe in a branch section where interpolation is used. Watercut at the outlet of the last pipe in a branch section where interpolation is used. 518 / 769

OLGA 7

PIPE

SymbolList [ALL]

REFPIPE

RealList (Pa) Symbol

REFPRESSURE

Real (Pa)

REFSECTION SECTION

Integer IntegerList 0

STEAMFRACTION

RealList

PRESSURE

TEMPERATURE VOIDFRACTION WATERCUT

RealList (C) RealList RealList

Pipe label or pipe number (single or continuous range in the form x-y). Initial pressure in each section.

[-1.0]

Pipe label for REFPRESSURE. Reference pressure used if no pressure boundary condition is used. To be given for one section only. Section number for REFPRESSURE. Section number. Fraction of total mass of h2o component in the gas phase. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Initial temperature in each section.

[0.0]

Initial void fraction in each section. Initial watercut in each section.

Link to: INITIALCONDITIONS (on FLOWPATH) Description Keys

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OLGA 7

NEARWELLSOURCE (on FLOWPATH) Description ( See also: Keys) This input definition specifies the data for a ”r;NEARWELLSOURCE” which links OLGA TO the near-wellbore reservoir simulator Rocx developed by IFE. OLGA delivers boundary conditions to Rocx, and the production from (or injection into) the reservoir is received by OLGA from Rocx as mass rate for each phase. Areas for use The link provides coupled transient simulation of near-wellbore reservoir flow and well flow. Dynamic phenomena not accurately predicted or even not seen with the steady-state inflow performance relationship model (WELL) may therefore be simulated in a more realistic way. Typical examples are well shut-in and start-up, dynamic gas and water coning, cross flow between layers, etc. Input The position of the NEARWELLSOURCE is given by referring to the distance from the inlet of the branch (ABSPOSITION), a pipe and a section number, or by reference to a defined POSITION. RESBOUNDNAME must refer to a boundary label defined in the Rocx input file. Each Rocx boundary label can only be refereed once, which means it is not allowed to split the flow from one Rocx boundary into two or more OLGA sections. But for one OLGA section, there can be several NEARWELLSOUCES. Rocx reads a separate input file describing the reservoir properties, boundary conditions and initial conditions. The file name should be given under the key ROCX under FILES. This input file is edited with the ROCX GUI. Rocx writes both formatted and binary industry standard Eclipse output files for post processing (3D visualization). Please refer to the ”r;Rocx User Manual” for how to define a proper input file for the Rocx simulator. There is no automatic check of the correspondence in positioning and size between numerical sections in OLGA and boundary grid blocks in Rocx. The user must therefore discretize both grids in such a way that this is satisfied. The flow area at the wellbore and near-wellbore interface is calculated based on the Rocx grid block rather than the corresponding OLGA numerical section. Rocx may be run with the RESTART option. Definition of the file with restart data for Rocx should be given in the Rocx input file. Rocx may be set up to read the same PVT data file as OLGA. Rocx can be run as a standalone tool. This is a useful way to obtain a suitable condition for the reservoir before initiating a coupled (and more time consuming) simulation. Limitations OLGA Rocx is not compatible with these fluid property models o Compositional option o Black oil module Other limitations on the Rocx reservoir simulator are given in the ”r;Rocx User Manual”.

NEARWELLSOURCE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Description 520 / 769

OLGA 7

Key

Unit:( )

ABSPOSITION

Real (m)

LABEL PIPE POSITION RESBOUNDNAME

String Symbol Symbol String

ROCX

String

SECTION

Integer

Default:[ ]

[NWSOUR-1]

0

Description Absolute position. Distance from branch inlet. NearWellSOURCE label. Pipe number for well. Position label for where the well is located. Name of boundary in OLGA Rocx. Name of input filename for boundary in OLGA Rocx. Section number for well.

Link to: NEARWELLSOURCE (on FLOWPATH) Description Keys

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OLGA 7

SOURCE (on FLOWPATH) Description ( See also: Keys) This statement specifies the input data needed for the simulation of sources. OLGA uses mass flow rate for internal calculations, but input flow rate may also be given as volumetric flow at standard conditions. Also, this statement may be used to specify the fraction of wax forming components in the inflow hydrocarbon mixture. A drilling fluid used with the Wells Module can be defined. There are two options to specify a mass source: 1.

The mass flow rate is given. For a positive mass source (flowing into the pipe), users can specify the upstream pressure as well as the upstream temperature. If the upstream pressure is given in the input, the expansion from the upstream pressure to the pressure inside the pipe section will be taken into account for the temperature calculations. If the upstream pressure is not given, the upstream pressure is set to the pressure inside the pipe section where the source is introduced. If a controller is used, the actual mass rate into/out of the section is a fraction of the mass rate given in the time series with the fraction regulated by the controller.

2.

The mass flow rate is to be calculated based on the opening of the choke through which a mass source is introduced into or taken out of the pipe section. The choke opening is regulated by a controller. Both critical and sub-critical flow through the choke are modelled.

When the mass flow rate is to be specified at the source temperature and pressure without compositional tracking, do the following:

Use key: MASSFLOW

Specify: Total mass flow rate (if option 1)

GASFRACTION

Gas mass fraction in gas and oil mixture at the source temperature and pressure. Free water is excluded. As default, the gas mass fraction is determined from the PVT table.

WATERFRACTION

Mass fraction of free water in the gas-oil-water mixture at the source temperature and pressure. Default value is zero, i.e. no free water.

TOTALWATERFRACTION

Mass fraction of total water in the gas-oil-water mixture at the source temperature and pressure. Default value is zero. Only one of WATERFRACTION or TOTALWATERFRACTION could be defined.

INHIBFRACTION

Mass fraction of inihibitor in water phase at source temperature and pressure. Only used 522 / 769

OLGA 7

source temperature and pressure. Only used together with inhibitor tracking, default value is zero for inhibitor tracking. TOTALINHIBFRACTION

Mass fraction of inhibitor in total water at source temperature and pressure. Only used together with inhibitor tracking, default value is zero for inhibitor tracking.

When the mass flow rate is to be specified at the source temperature and pressure with compositional tracking, do the following: Use key: Specify: FEEDMASSFLOW Total mass flow rate (if option 1) GASFRACEQ

OILFRACEQ

WATERFRACEQ

Fraction of gas mass flow relative to equilibrium flow at the source temperature and pressure. As default, the gas mass flow is equal to the equilibrium flow determined from the feed file (equilibrium gas mass fraction) and FEEDMASSFLOW: (GG = FEEDMASSFLOW * RSEQ * GASFRACEQ). Fraction of oil mass flow relative to equilibrium flow at the source temperature and pressure. Fraction of water mass flow relative to equilibrium flow at the source temperature and pressure.

Note: If GASFRACEQ, OILFRACEQ or WATERFRACEQ is lower than 1 (default value), the total flow will not add up to the specified FEEDMASSFLOW. When the volumetric flow rate at the standard conditions is given, do the following: Use key: STDFLOWRATE

Specify: Volumetric flow rate at standard conditions for the specified phase (if option 1)

PHASE

The phase for which the volumetric flow rate is specified. The allowed options are GAS, OIL, WATER, LIQUID. The total source flow is determined so that the specified flow is obtained, for the phase in question, at standard conditions. If the total volumetric flow is meant to represent equivalent gas flow instead of the single gas phase flow, the molweight of the total flow must be given.

GOR

Gas/oil ratio. By default, the GOR from PVT table is used.

GLR

Gas/liquid ratio. Note that GOR and GLR can not be used at the same time.

WATERCUT

Water cut, i.e. water volume fraction in water and oil mixture.

MOLWEIGHT

If the equivalent gas volumetric flow rate is specified, the molecular weight of the total flow should be given in order

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molecular weight of the total flow should be given in order to account for the density of the equivalent gas. By default, the gas density at the standard condition from the PVT table is used. Available units for standard volumetric flow rate, STDFLOWRATE, are listed in Conversion Factors. Default is (Sm3/s). When volumetric flow rate at standard conditions is used, the table for PVT-data must cover the standard conditions for pressure and temperature. Internal dependencies of keys: either BRANCH = 1 PIPE = 1 SECTION = [1] or POSITION = SOURCE-1 end TIME = (0, 100 ) If the mass flow rate is given, then CONTROLLER = C-101 ! Controls fraction of given mass flow either MASSFLOW = (0.0, 10.0) [kg/s] GASFRACTION = [(-1,-1)] PRESSURE = [Section pressure] either WATERFRACTION = [(0.0, 0.0)] INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALWATERFRACTION = [(0.0, 0.0)] either INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALINHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking end end if WAXDEPOSITION=ON in OPTIONS WAXFRACTION = [2:1.0] end if or STDFLOWRATE = (0.0, 1000) STB/D WATERCUT = (0.1, 0.1) PRESSURE = [Section pressure] PHASE = LIQUID If PHASE = GAS MOLWEIGHT = (20.5) ! If equivalent gas stdflowrate (gas+liquid) end if either GLR = (100, 100) or GOR = (120, 120) 524 / 769

OLGA 7

end if WAXDEPOSITION=ON in OPTIONS WAXFRACTION = [2:1.0] end if or if COMPOSITIONAL=ON in OPTIONS, then FEEDNAME = (FEED-1, FEED-3) either FEEDMASSFLOW = (20, 35.3, 20, 35.3) [kg/s] or FEEDMOLEFLOW = (50, 30.5, 50, 30.5) [kmol/s] end PRESSURE = [section pressure] GASFRACEQ = (0.5,0.5) ! override equilibrium phase fractions OILFRACEQ = (0,0) ! override equilibrium phase fractions WATERFRACEQ = (0,0) ! override equilibrium phase fractions or if the COMPOSITIONAL = BLACKOIL, then FEEDNAME = (BO-1, BO-3) STDFLOWRATE = (0.0, 0.0, 1000, 1000) STB/D PHASE = GAS || OIL or if DRILLING = ON, then MASSFLOW = (0.0, 10.0) [kg/s] PRESSURE = [Section pressure] DRILLINGFLUID = DRILLINGFLUID-1 if drillingfluid properties are NOT given in a separate file, then DENSITY = (1000, 1000) VISCOSITY = (1, 1) cP end end end if If the mass flow is to be calculated based on the opening of the choke, then (standard conditions not allowed) CD = [0.84] DIAMETER = 0.45 CONTROLLER = C-101 PRESSURE = 2:40 bara either GASFRACTION = 2:-1 either WATERFRACTION = 2:0 INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALWATERFRACTION = 2:0 TOTALINHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking end or if COMPOSITIONAL = ON, (multiple time and feeds, see note below) FEEDNAME = (FEED-1, FEED-3) either FEEDMASSFRACTION = (0.7, 0.3, 0.7, 0.3) or FEEDMOLEFRACTION = (0.6, 0.4, 0.5, 0.5) 525 / 769

OLGA 7

end WATERFRACEQ = (0,0) ! override equilibrium phase fractions or if COMPOSITIONAL = BLACKOIL then FEEDNAME = (BO-1, BO-3) FEEDVOLFRACTION = ( 0.7, 0.3, 0.7, 0.3 ) or if DRILLING = ON then DRILLINGFLUID = DRILLINGFLUID-1 DENSITY = 2:1000 VISCOSITY = 2:1 cP end end if Note: For the subkeys FEEDMASSFLOW, FEEDMOLEFLOW, FEEDMASSFRACTION and FEEDMOLEFRACTION, the array is a function of both feed and time as shown below. FEEDMASSFRACTION = FEED-1 (T1), FEED-2(T1), FEED1(T2), FEED-2(T2))

SOURCE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CD

Real

CF

Real

CGR

RealList (Sm3/Sm3)

COMPONENT

Symbol

PRODUCTION | DRILLINGFLUID | [ALL]

CRITFLOWMODEL

Symbol

HENRYFAUSKE | [FROZEN]

DENSITY

RealList (kg/m3)

[0.84]

Description Absolute position. Distance from branch inlet. Discharge coefficient. Used for pressure driven source. Ratio between gas and liquid sizing coefficient. Condensate-gas ratio. By default, CGR from the PVT table is used. Component specify the fluid that is going to be exstracted by a negative source. ALL defines that both types shall be exstracted, production fluid and drillingfluids. If only one of more drilling fluids are to be extracted, DRILLINGFLUID = must be specified instead. Choice of critical flow model to be used. Homogenous frozen critical flow model or Henry-Fauske model. The density of the drilling fluid injected at a given time point. The density must be at standard conditions and within the min and max density as specified in the keyword DRILLINGFLUID 526 / 769

OLGA 7

DIAMETER

DRILLINGFLUID

FEEDMASSFLOW

FEEDMASSFRACTION

FEEDMOLEFLOW

FEEDMOLEFRACTION

FEEDNAME

FEEDSTDFLOW

FEEDVOLFRACTION

GASFRACEQ

GASFRACTION

Maximum orifice diameter in pressure driven source. Refer to the drilling fluid defined by the keyword DRILLINGFLUID. Symbol Requires access to the Wells module. Mass rate for each feed (used RealList when mass source is defined). (kg/s) One item per time and feed. Mass fraction of each feed (used when pressure driven source is RealList defined). One item per time and feed. Mole rate for each feed (used RealList when mass source is defined). (kmol/s) One item per time and feed. Mole fraction of each feed (used when pressure driven source is RealList defined). One item per time and feed. Labels of feeds in the mass source defining the fluid FEED-1 | BOFEED- composition. Requires SymbolList 1 COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword. Volumetric flow rate at standard condition of phase PHASE for RealList each feed specified by (Sm3/s) FEEDNAME (only for Blackoil model). Volume fraction of each feed RealList given in FEEDNAME for choke model (only for Blackoil model). By default, the equilibrium gas fraction of the total flow is used for the gas flow in the compositional or the Black oil RealList [1.0] model (GASFRACEQ=1), however the user may specify a fraction of the gas equilibrium flow to be sent into the pipeline. Gas mass fraction in gas and oil mixture. By default, the gas mass fraction from the PVT table is used for inflow (GASFRACTION Options menu. PS. This option requires GUI to close to take action. 2. If it is just a floating window, e.g. the property dialog, double click on the top of floating window, and the window will dock itself were it last was docked. 3. If a window is missing from the layout. It can be reopened from the View menu.

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Simulation state is runnable, but the simulation will not run 1. Check that a simulation engine is defined. Click Tools -> Options and select the OLGA Version tab. Verify that a version number is listed and selected. If not, click the Advanced button and add an 'OLGA engine/rules'. You can also add an OLGA 5 engine (refer to the installation guide for a description on how to set up OLGA 5 engines in the OLGA 6 GUI). 2. Try to run the case in batch (F4). If the case runs in batch then inspect the genkey file. The genkey file can be viewed by right clicking the case name in the file view window and selecting Open as text file. If the .genkey file shows keys that you didn't think you had specified, check that the write default values are not turned on. To check this go to Tools -> Options and see if Write default values to OLGA is turned on. If so, uncheck the option and try to start the simulation again. 4. If you still cannot find out what is wrong please send the case and the associated files to [email protected].

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OLGA 7

Simulation state is not runnable Normally, when the simulation state is "not runnable", there is something wrong with the input. Press F7 or the Verify button to verify the case. The output window will display a list of errors and warnings related to the given input. 1. Fix the errors that are displayed in the Output window. 2. If an error message states that something is wrong even though it appear to be correct (e.g. An error claims that the list of specified keys are not of the same length even though they are) try to define one of the keys over again. If this doesn't help you can try to define the keyword over again starting from an empty keyword. 3. If no error message appear, check that the Error button on the upper left corner of the output window is turned on. This is a filter button that removes all error messages reported to the output window if it is turned off. 4. If you still have a problem, send the opi file and the associated files (like the .tab file) to [email protected]. 5. Generate a genkey file by selecting the File view, right click on the filename and select -> Open as text file. A genkey file is now saved on the same location as the opi file. Rename the *.genkey file to *.key. Close the opi file that you are having trouble with and open the newly created *.key file. If you still get a simulation state that is not runnable, wait for the reply from olgasupport.

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OLGA 7

Update Graphical driver This is a short guide to how you can check and/or update your graphics driver. OLGA has some requirements with regard to the PC's graphics driver. In order to make OLGA work properly, you have to make sure your graphics card comply with these requirements. 1. Identify your graphics driver. a. Open the Display properties (i.e. right-click on the desktop and select ”Properties”). b. Select the ”settings” tab. c. Click on the ”Advanced” button. The page that appears here is created by the graphics card vendor, and may very a lot from one pc to the other. It is difficult to say what to look for in general, but if you have an ”Adapter” tab here, that’s a start. What you need is the properties of the adapter, which in turn should list what driver the pc currently uses. d. The graphics driver should be provided by the graphics cards manufacturer. On some older pc’s it is likely that Microsoft has provided the driver, if so it must be updated. 2. Update the graphics driver. a. Open the graphics cards manufacturers’ homepage. b. Try to find ”Download” or ”Driver” or something. If you find a newer driver for your specific graphics card, download it and install. c. If you can't find the correct driver, try the pc manufacturers homepage, and try to locate a new graphics driver there. 3. Reboot the pc (if necessary).

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