Description
Presmo d_ U S E R M A N UA L
be dynamic ®
V E R S ION 5
Drillbench Presmod User Guide
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TABLE OF CONTENTS Page 1.
GENERAL 1.1 Overview
1 1
2.
MAIN ENVIRONMENT 2.1 Overview
3 3
3.
CREATING A CASE FILE 3.1 Overview 3.2 The data model - DEML 3.3 New session (.dml) file 3.4 Editing an existing session (.dml) file 3.5 Converting legacy session files 3.6 Library 3.6.1 Library editor
5 5 5 6 7 7 9 11
4.
INPUT PARAMETERS 4.1 Description 4.2 Formation 4.2.1 Surface temperature 4.2.2 Lithology 4.3 Survey 4.4 Pore pressure and fracture pressure 4.5 Wellbore geometry 4.6 String 4.7 Mud 4.8 Temperature
12 12 13 13 13 15 17 18 23 25 34
5.
EXPERT INPUT PARAMETERS 5.1 Model parameters 5.2 Eccentricity 5.3 Surface pipeline 5.4 RCH and Choke
36 36 37 39 39
6.
MENUS AND TOOLBARS 6.1 File 6.1.1 New 6.1.2 Open 6.1.3 Reopen 6.1.4 Save 6.1.5 Save as 6.1.6 Save as template 6.1.7 Save library 6.1.8 Import 6.1.9 Export 6.1.10 Exit 6.2 Edit 6.2.1 Cut 6.2.2 Copy 6.2.3 Paste
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6.4
6.5
6.6
6.7
6.2.4 Undo View 6.3.1 Well schematic 6.3.2 Survey plot 6.3.3 Log view 6.3.4 Navigation bar 6.3.5 Input 6.3.6 Expert input 6.3.7 Simulation Simulation 6.4.1 Start/Pause 6.4.2 Step 6.4.3 Reset 6.4.4 Load state from file 6.4.5 Save state… Results 6.5.1 Keep previous results 6.5.2 Export results 6.5.3 Import results 6.5.4 Add page 6.5.5 Rename page 6.5.6 Remove page 6.5.7 Load/save layouts Tools 6.6.1 Take snapshot 6.6.2 Report 6.6.3 Validate parameters 6.6.4 Edit unit settings 6.6.5 Options Help 6.7.1 About
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43 43 44 44 46 46 46 46 46 46 47 47 47 47 48 48 48 49 49 49 50 50 50 50 50 51 52 52 53 56 56
7.
RUNNING A SIMULATION 7.1 Overview 7.2 Controlling a simulation 7.3 Simulation window 7.3.1 Graphical output 7.3.2 Plot properties 7.3.3 Print and export 7.3.4 Import data 7.3.5 Zooming 7.4 Interactive simulation mode 7.5 Batch simulation mode 7.6 Dynamic surge and swab simulations
58 58 58 58 59 61 61 64 64 64 65 67
8.
WORKING WITH PRESMOD 8.1 Multiple runs – keep results 8.2 Improved results view 8.2.1 Trend plots 8.2.2 Profile plots 8.3 Well schematic 8.4 Add external data 8.5 Create presentation graphics
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9.
SELECTING THERMAL PROPERTIES 9.1 Introduction 9.2 Drilling fluids 9.2.1 Specific heat 9.2.2 Thermal conductivity 9.3 Other materials
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10.
RHEOLOGY MODELS 10.1 Models 10.1.1 Bingham plastic model 10.1.2 Power law model 10.1.3 Robertson-Stiff model 10.1.4 Shear rate dependent fluid parameters
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11.
KEYBOARD SHORTCUTS
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12.
ACKNOWLEDGEMENTS
84
13.
REFERENCES
85
Drillbench Presmod User Guide
1.
GENERAL
1.1
Overview
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Drillbench is an advanced software suite for design and evaluation of all drilling operations. It is a result of more than 15 years of drilling research and has unique features in dynamic simulation of the wellbore flow process. As a software suite Drillbench is a compilation of several individual applications focusing on different challenges encountered in a drilling operation. All the applications are based on the same design basis and they have a lot of tools and features in common, but each application has a user interface that is tailored to the tasks the application is designed for. The combination of a common look and feel and tailored interfaces ensures that it is very easy to move from application to application for analyzing various phases of the drilling operation. Presmod is one of the applications in Drillbench. It focuses on drilling hydraulics and modeling of wellbore pressures and temperatures during all phases of the drilling operation. Presmod couples dynamic modeling of wellbore temperatures with dynamic flow modeling. Presmod also includes a dynamic surge and swab model. Presmod includes important parameters like pressure and temperature dependent fluid properties, thermophysical properties, detailed geometry description and operational effects. It has been proved to accurately model both pressure (ECD & ESD) and temperature in deepwater and HPHT wells, where it is crucial to include effects of temperature. The accuracy of Presmod makes it a very valuable tool in drilling operations with narrow margins between pore and fracture pressures. Typical examples of wells with narrow margins are:
HPHT and ultra-HPHT wells
Deep water wells
ERD wells with long horizontal sections
Wells in depleted reservoirs
Presmod has a wide range of applications. It can be used for:
Selecting fluid systems o
Decide maximum and minimum circulation rates
o
Decide maximum trip velocities
o
Evaluate temperature effects
Developing operational procedures that ensures the well objectives without exceeding the pressure limits
Filling the gaps in the information stream from the PWD, and providing information in static periods when the transmission from downhole sensors are unavailable
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Providing temperature information in wells that are outside the operating conditions for downhole electronics.
Presmod has several visualization features that can be used for analyzing the wellbore flow process. With the unique batch feature and the ability to run several runs on top of each other it is also very easy to perform sensitivity analysis.
Drillbench Presmod User Guide
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MAIN ENVIRONMENT
2.1
Overview
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The Presmod installation by default creates a Presmod entry under Programs SPT Group in the Start menu. Presmod is started either by selecting this shortcut, by clicking a desktop icon or by selecting from the Windows Explorer. Regardless of the start-up method, the program will look similar to Figure 2-1 when starting up. The contents of the parameter display may be different depending on parameter group and selected window.
Figure 2-1: This is a typical view when starting Presmod. A summary page shows the most important parameters to give the user an overview of the case. The environment consists of 4 main areas; the menu line and the toolbar at the top of the window, and in the main Presmod window there is a navigation bar to the left and a data entry window to the right. The menu line A standard menu line with File, Edit, View, Simulation, Results, Tools and Help entries. File operations, selecting views and simulation control may be done from here.
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The toolbar Standard commands like File New, File Open, Save, Copy, Cut, Paste and Undo, are placed in a toolbar for easy access. These commands can also be accessed by standard Windows keyboard shortcuts (ref. Chapter 11) . A toolbar for controlling the simulation with start, pause, one-step and reset buttons is placed next to the normal toolbar. The user can also select the desired type of simulation, interactive, batch or surge/swab.
Navigation bar The navigation bar contains: -
Input for specification of the most frequently used input parameters
-
Expert input for specification of optional or expert features
-
Simulation for calculation and output of results
Data entry window Displays either input parameters or calculated output parameters depending on the current selection in the navigation bar
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CREATING A CASE FILE
3.1
Overview
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This section briefly describes the data model in Drillbench and how a new case can be created. All Drillbench applications share the same data model, therefore this section is similar for all applications. A new case can be created either by building a new file or by editing an old file. The data needed for a simulation may be selected from the library or specified on the input parameter sheets. The input parameter sheets and the library are presented in more detail in section 3.6 and chapter 4. If you have used older versions of Drillbench, you can open your input files as normal and you will be notified that your input has been upgraded. Note that this upgrade is irreversible – files saved from this version cannot be loaded in older versions of Drillbench.
3.2
The data model - DEML The data model illustrated in Figure 3-1 handles all internal data transfer between the user interface and the numerical models and store all the information in XML files. The data model is the same for all Drillbench applications, but most applications only use a subset of the full model. When switching from one application to another, all available data will be used and the user must add only the data specific to the application in use.
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Figure 3-1: Data model in Drillbench. Data can be collected from several sources. In many cases, companies have some standards, guidelines or common practices that will remain unchanged from case to case. Also vendors of tools and fluids may be the same in many cases. The total amount of data needed to run a Presmod session may therefore be divided into case specific data and more standard data that will remain unchanged or only slightly modified from case to case. The standard data can, as before, be defined in the Library to simplify the case definition phase. Among the case specific data are well trajectory, geometry, operational conditions and temperature. Typical library entries are fluids, pipes and tools.
3.3
New session (.dml) file To create a new session file, select File New from the menu line. The new file dialog offers choices of starting with a blank file or with predefined templates. Templates can be defined either for specific well types (i.e. HPHT, deep-water, extended reach) or for specific fields. The idea behind the templates is that the input process should be simplified. All the predefined data is available from the user interface so it is easy to review the data and verify that it fits the case you want to simulate.
Figure 3-2: New file dialog.
The path to the templates is configured in the Tools Options dialog.
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Editing an existing session (.dml) file Existing input files are opened by choosing File Open and selecting the file. A recent used file can also be opened from the File Reopen list. The edit process is very similar to what you do when you open a template file. After editing the input file, choose File Save as…from the menu line and give the input file a new name. The input file can be saved in any directory.
3.5
Converting legacy session files Drillbench has since version 4 used a new data file format and files created with older versions of Drillbench (3.X) needs to be converted for use in Drillbench applications. There are two tools for converting old files: Convert file
- converts a single file or database
Convert folder
- converts all files in a folder and (optional) subfolders
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To convert a file: Open the convert file application (Start [Program location] Tools Legacy Convert file) The application shown in Figure 3-3 is opened. By clicking the folder symbol, an explorer window is opened for selection of files to convert. The corresponding new file (.dml) will be located in the same folder as the original file.
Figure 3-3: Tool for converting session and database files from Drillbench 3.X.
To convert a folder: Open the convert folder application (Start [Program location] Tools Legacy Convert folder) Figure 3-4 shows the convert folder tool. Just select the folder you want to convert and all old session files including those in subfolders will be scanned and converted. This can be performed at the root (C:\ or any other location where you have Drillbench files), but note that if you have many files, this command can take some time to complete.
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Figure 3-4: Tool for conversion of all session files in a folder (including subfolders).
A log file is created for each file that is converted to the Drillbench format (.dml). The log file is automatically stored together with the file and contains any messages and warnings that may have been generated during the conversion to the new format.
3.6
Library All data is entered in the parameter input section. For some data that is typically entered based on data sheets or from handbooks, an optional library function is included. The default installation of Drillbench contains a library with values for pipes & tubulars, tools, fluids etc. The user can easily add information to the library to define new items. The entries from the library are selected in the parameter input sections for Wellbore geometry, String and Mud. The library can be accessed by clicking on the Name field for the item/component. The items/components that can be found and stored in the library are:
Riser
Casing/Liner
String components
Bit
Mud (Drilling fluid)
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Figure 3-5: Library browser and filter dialog for casings.
To find a specific item or component in the library, there is a filter option to help you search for the item or component you need. You can set up several different filters to make your library search more detailed. Click the Add button to add a line in the filter dialog or press remove if you want to remove a line. Remember to click Apply filter – no filtering is performed before this button is clicked. To select an item from the list of matching components you can double click on the element. You will then return to the input screen and can continue to specify other data. If you do not find a suitable item or component in the library, you can specify all the properties of the item or component manually in the input parameter window. The item or component can then be added to the library by right-clicking on the line in the table and choosing add item to Library.
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Library editor There is also a standalone library editor that can be opened from the Start menu (Start [Program location] Tools Library editor).
Figure 3-6: Library editor.
In the Library editor all the information that is stored in the library can be reviewed. It is possible to add new items or edit the specification of existing items.
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INPUT PARAMETERS The input parameters have been divided into nine main groups. Summary
A brief summary of the most important input data
Description
Information about the present study/case
Formation
Defines the formations and geothermal properties
Pore pressure & Fracture pressure
4.1
Defines pore and fracture pressures with depth
Survey
Describes the well trajectory
Wellbore geometry
Defines the casing program for the well
String
Configures and defines the drill string and bit
Mud
Defines the drilling fluid
Temperature
Defines temperatures and temperature model
Description Use the Description window to describe the main purpose and key parameters of the current case. The input is self-explanatory and consists of the most important parameters needed to identify the case. Use the Description field to distinguish several computations performed for the same case.
Figure 4-1: Description window.
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Formation The formation section is only required if the dynamic temperature model (see chapter 4.8) is used. If a measured temperature profile is selected the Formation section can be disregarded. The formation input contains all information about the environment where the well is going to be drilled. Different horizontal layers (lithologies) are defined together with the properties for each layer.
4.2.1
Surface temperature The Surface temperature specifies the starting point for calculating the geothermal temperature. In offshore wells this is the sea water temperature at the surface. Note that it may differ significantly from the flowline temperature.
4.2.2
Lithology Figure 4-2 shows a typical formation window, containing four layers; two different sea water layers and two formation layers. Changing depths or geothermal gradient will give an immediate update of the preview plot. This is very useful in order to check that the entered data is correct. Also note that the plot of the geothermal gradient, like all Drillbench plots, can be modified by right-clicking on the plot area. Lithology is used as a term for formation materials in vertical direction from sea level. Even if seawater is not a formation, it is treated similarly and is included among the lithologies. The same information has to be given for seawater as for the other lithologies. For offshore wells at least two lithologies are required: seawater and formation. If more detailed knowledge about the geology and thermophysical properties of the different geological layers is available, several formation layers with different properties can be defined (see also chapter 9 Selecting thermal properties). To append lines to the table just use the down arrow key. To add or remove lines within the table, use either Ctrl+Ins or Ctrl+Del. Note that depths entered in the table are true vertical depth with reference to RKB. Seawater specification can also be differentiated. Especially for deep-water wells this can be of importance. It is possible to select different temperature (geothermal) gradients at different water depths. Default values are given for seawater and formation. However, it can be necessary to change the defaults, since the geothermal gradient is defined as a material property. It is important to note that if the geothermal gradient changes, a new lithology should be defined, even if other properties are the same. The last column in the lithology table contains an option to edit the thermophysical properties for the different layers. Clicking the right hand side of the last column activates the cell for edit and a button appears in the cell. Clicking this button opens the window shown in Figure 4-3. The default data are displayed in the window.
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These data can be modified by clicking the radio button that activates the Customized fields, where new values can be entered.
Figure 4-2: Formation input window.
Figure 4-3: Thermophysical properties.
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Survey The input data for the survey are Measured depth, Inclination and Azimuth. The simulator calculates the true vertical depth (TVD) by using the minimum curvature algorithm. The angle is given as deviation from the vertical, which means that an angle of 90 indicates the horizontal. The angle between two points is the average angle between the points. The simulator handles horizontal wells, but angles higher than 100 are not recommended. This window is optional and the well is assumed vertical if no data is entered. The survey data can be entered manually, copied from a spreadsheet or imported from an existing survey file. Figure 4-4 shows the survey data table and a 2D sketch of the well trajectory.
Figure 4-4: Specification of survey data. Inclination data can also be imported from file (Ref. Figure 4-5) by choosing File Import Survey data or RMSwellplan data.
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Figure 4-5: Menu option for survey data import.
The RMSwellplan option opens a File open dialog and a *.dwf file can be selected. The Survey data import is different as this option opens a file import tool, shown in Figure 4-6. The import tool is very general and can handle different units, different column order or delimiters. It can also handle any number of header or footer lines.
Figure 4-6: Survey Import window.
The survey profile can be previewed in 3D, by selecting View Survey plot.
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Figure 4-7: 3D survey plot.
4.4
Pore pressure and fracture pressure Pore pressure and the corresponding Fracture pressure can be specified for various depths. This is an optional window and can be left empty. However, the given data will be used as reference values in plots of ECD and pressure. It is therefore very useful to enter the expected profiles. The window is shown in Figure 4-8. As soon as depths or gradients are entered or modified in the tables, the plot on the right hand side will be updated. Measured depth and the corresponding pore pressure data are defined in the upper table. Either the Pore pressure gradient or the Pore pressure is specified. If the gradient is specified, the corresponding pore pressure at the given depth is automatically calculated, and vice versa. Measured depth and the corresponding fracture pressure data are defined in the lower table. Either the Fracture pressure gradient or the Fracture pressure is specified. If the gradient is specified, the corresponding fracture pressure at the given depth is automatically calculated, and vice versa. The corresponding TVD values are automatically displayed for information purposes. To append lines to the table, just use the down arrow key. To add or remove lines within the table use either Ctrl+Ins or Ctrl+Del.
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Figure 4-8: Specification of pore pressure and fracture pressure.
4.5
Wellbore geometry The wellbore geometry section contains the specification of the actual hole. A typical window appearance is shown in Figure 4-9. The wellbore is divided in three parts: Riser (if applicable) Casing/Liner Open hole
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Figure 4-9: Specification of Riser, casing and liner data.
Riser
Figure 4-10: Riser. The riser is specified by the length (water depth) and the dimensions. The ellipsis button in the Name column can be used to refer to entries in the library. The library functionality is described further in Chapter 3.6.
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Figure 4-11: Library browser for Casings and Risers (database).
Casing/Liner Due to the fact that the temperature model is two-dimensional, it is normal to include all the casings and the materials surrounding them in the specification of the well. If the dynamic temperature model is not going to be used, it is enough to specify the innermost layer of casings and liners, and data in the columns Hole diameter, Top of cement, and Material above cement will not be used.
Figure 4-12: Casing/Liner.
Each row in the casing and liner window is used for specifying the information necessary for one casing string.
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The first column contains the casing/liner name. The Name fields contain an ellipsis button that can be used to reference the casing and liner library. All the information about dimensions and properties can be taken from the library. The library functionality is described in Chapter 3.6. Note that you don’t have to pick the information from the library. If the dimensions are more readily available from other applications or reports, the information can easily be pasted into the table. Right clicking on a line in the table will allow you to store new elements to the library. The second column is the liner hanger depth. It specifies the starting point of the casing. The liner hanger depth will often be equal to the water depth. If there are deeper liners the hanger depths for these should be specified as well. The third column is used to specify the setting depth for the casing or depth for cross-over to another casing dimension. In the fourth and fifth columns the inner and outer diameters of the casing are specified (these values will be taken from the library, but can be manually updated as well). In the sixth column the hole diameter outside the casing is specified. This is the bit diameter that was used when drilling the section In the seventh column the depth for top of cement is specified. The eighth column is specifying the material above the cement. Note that even if it is cemented to the seabed, there will be a seawater column on top of the cement. All depths are metered depths with reference to RKB. The last column has an option to manually update some properties of the casing, including thermophysical properties.
Figure 4-13: Thermophysical properties of casing.
If you do a copy and paste of an item where you have altered the thermophysical properties, you will have to specify this information again for the new item.
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To append lines to the table, just use the down arrow key. To add or remove lines within the table use either Ctrl+Ins or Ctrl+Del. A schematic of the casing diagram can be viewed from the menu View Well schematic. A visual inspection of the well can reveal errors in the input data.
Open hole
Figure 4-14: Open hole. You specify the open hole section by the length from the last casing shoe to the bottom of the well and the open hole diameter.
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String You may choose to use tool joints in the calculations. In that case, you must specify an average stand length in order to let the program calculate the numbers of tool joints.
Figure 4-15: Average stand length and tool joints.
Figure 4-16: String configuration.
String Select components from the library browser to configure the drill string. The selection is performed using the filter dialog, launched using the ellipsis button in the first column of the table. The library functionality is described in Chapter 3.6. The first row in the table is the component next to the bit, i.e. all components, including the bottom hole assembly (BHA), are defined from the bit and upward in this table. It is possible to create items with custom dimensions by modifying diameters of an already defined item or by entering the information manually. To add new items to the library, right click on the component. It is also possible to edit/view the properties of the different components by clicking in the last column of the chosen component. The thermophysical properties are modified as in Figure 4-13. Figure 4-17 shows the Properties window for the motor. The dimensions and flow rate interval with corresponding pressure loss can be
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specified. In the table of flow rates the minimum and maximum rate is taken as lower and upper motor limitation.
Figure 4-17: Specification of motor properties.
To append lines to the table, just use the down arrow key. To add or remove lines within the table use either Ctrl+Ins or Ctrl+Del.
Bit The bit is defined separately. Select the bit from the library browser by clicking the ellipsis button. It is possible to edit the bit dimensions and properties by adjusting the values in the window. The flow area through the nozzles is defined either by entering the Total flow area (TFA) or by entering the diameter of each nozzle. To add a newly created bit to the library, click on the Add to library button.
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Figure 4-18: Bit configuration.
If nozzle diameter is selected and it is necessary to specify more than four nozzles, the extra nozzles can easily be added by pressing the down arrow key at the last line in the table, or alternatively by pressing Ctrl+Ins
4.7
Mud In Figure 4-19 the specification of mud properties are illustrated. Fluids can either be selected from the library or a new fluid can be defined by entering relevant data in the window. A fluid can be selected from the available library fluids by clicking on the button in the Fluid name field. This will open the select fluid dialog shown in Figure 4-20. If a fluid similar to the actual fluid is not found, it can be created. This is done by entering data in the relevant input fields for Component densities, PVT, Thermophysical properties and Rheology. The newly created drilling fluid can be added to the library by using the Add to library button in the upper right corner. The mud window can contain several pre-configured muds. The list on the left side shows the list of current contained fluids. All pre-configured muds are available for selection in the simulation window to easily switch mud system, or they can be used in the batch table to simulate circulation of a sequence of different muds. When specifying a new fluid, either by selecting from the library or creating a new, press the Add button to add it to the list. Muds can be deleted from the list with the Delete button.
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Figure 4-19: Mud window.
Figure 4-20: Library browser for fluids.
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Component densities Below the drilling fluid entry, the fluid component densities are displayed. Unless the fluid density is calculated based on data from a field mud, see Measured PVT model below, a component density model is used. In this case, the p, T dependency of each phase will be treated separately, and a resulting density will be calculated based on the weight fractions of each phase and the density of the mud at standard conditions. Base oil density and water density are specified at standard conditions (1 bar,15°C / 14.7 psia and 60 °F). Solid density is the density of the weight material. A solid density of 4.2 sg is suggested by default, which corresponds to the density of barite. In these calculations, the compressibility of solids is assumed to be negligible, an assumption that in most cases is fairly correct. Density refers to the density of the whole mud phase and must be specified at the corresponding reference temperature and atmospheric pressure. The last parameter to be specified is the mud Oil/water ratio. The ratio is specified as 'oil volume%/water volume%' (e.g. '80/20').
Figure 4-21: Component densities.
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PVT model Two different PVT models are available, Measured PVT model or a Density correlations PVT model. The model is selected from the PVT model dropdown list.
Figure 4-22: PVT model.
Measured The measured PVT model is based on measured fluid and oil density data for different pressure and temperatures. The measured values can be specified by clicking on the PVT properties button in the PVT section. Clicking the properties button opens a sub-window with two tab sheets; one for density of the whole fluid and one for density of the base oil. Both tab sheets contain spreadsheet tables that support copy and paste between other programs and Drillbench.
Mud density The table for mud density consists of a spreadsheet component with temperature data in the first row and pressure in the first column. The densities are filled in for each pair of pressure and temperature. This table is not needed unless Measured PVT is chosen as PVT model.
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Figure 4-23: Measured mud density data.
Base oil density The table for base oil density consists of a spreadsheet component with temperature data in the first row and pressure in the first column. The densities are filled in for each pair of pressure and temperature. This table is not needed unless Measured PVT is chosen as PVT model.
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Density correlations
Figure 4-24: Density correlations PVT model.
Oil density submodel Three models (Sorelle(oil), Glassø, Standing) are available, these are based on experimental work on different oil samples. There is also a possibility to enter measurements on the actual fluid. Standing : The Standing model was originally presented in 1947. The correlations were formulated based on experimental work on Californian oils, and were since reformulated in 1974. Glassø (recommended): The Glassø model is similar to the Standing model, but it is formulated for North Sea oils. Both the Standing and Glassø models are valid only for the low to moderate pressure range. Above this, in the high pressure and temperature range, the Vazques and Beggs model (Reference III) is used. Sorelle (oil): The Sorelle model is based on laboratory measurements of diesel oil. The model is formulated for HPHT conditions. Table: The table approach uses the PVT properties spreadsheet component, as described in the section above under Measured PVT model, for entering experimental data for base oil densities.
Water density submodel There are three options available: Dodson & Standing, Kemp & Thomas and Sorelle. Dodson & Standing (recommended): Dodson and Standing have published a correlation for compressibility and thermal expansion of pure water.
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Kemp & Thomas: The Kemp and Thomas model is formulated for brines. The model compensates the change of compressibility and thermal expansion of brine due to variations in the ionic interaction with elevated pressures and temperatures. The brine content in the mud must be known if this model is selected. A sub-window appears when clicking the Brine button and the weight fractions of each salt can be specified. The weight fractions are relative to the whole fluid.
Figure 4-25: Brine data. Brine data is only relevant if the Kemp & Thomas model is selected as water density model. Sorelle (water): Sorelle et. al. also formulated a correlation for the water phase. The correlation is based on literature data.
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Thermophysical properties The thermophysical properties of the drilling fluid can be edited/viewed by clicking the Thermophysical properties button. The data in this sheet is used in the dynamic temperature model. All the parameters, Specific heat capacity, Thermal conductivity, Density and Static viscosity, can be given either as a constant value or as a temperature dependent value. Default values are displayed to the left. These values are automatically calculated by Presmod, see Chapter 9 Selecting thermal properties. Values can be customized by enabling the checkbox next to a field.
Figure 4-26: Thermophysical properties of drilling fluid.
Rheology The Rheology model dropdown list is used to specify which correlation should be used for calculation of rheology data at elevated pressure and temperature. Three models are available; Power law, Bingham and Robertson-Stiff model. RobertsonStiff is the recommended model for most situations.
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Figure 4-27: Rheology input. It is possible to enter pressure and temperature dependent rheology data, or the rheology curve can be given for only one pressure and temperature value. The data are entered in the shear rate vs. shear stress (Fann reading) table for selected combinations of pressure and temperature, as illustrated in Figure 4-28. The rheology table is a spreadsheet table and supports copy and paste between other programs and Drillbench. If Robertson -Stiff is chosen as rheology model, the table should, if applicable, contain at least three Fann readings. Alternatively, the rheology data can be given in terms of plastic viscosity (PV), yield point (YP).
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Figure 4-28: Fann tables.
4.8
Temperature
Figure 4-29: Temperature input window.
Platform
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The first item to be selected in the temperature window is the model for the injection temperature. Platform temperature data is used only when the Dynamic temperature model is selected. The data specifies how to calculate the surface temperature of the drilling fluid just before being pumped into the drill string. If Constant mud injection temperature is selected, the temperature of the mud pumped into the well will be the same throughout the simulation. If Constant temperature difference is selected, the mud injection temperature will always be the given number of degrees below the mud outlet temperature, which is continuously being calculated, and will thus vary with time. The third option is Surface temperature model. The user has to specify initial pit tank temperature and a heat loss constant from the pit tanks that the mud passes through from the outlet back to the pumps. The heat loss constant should be in the range 40 – 100.
Dynamic temperature model/Measured data The next item to be selected in the temperature window is whether the dynamic temperature model should be used or not. The simplest case will be to use Measured data. In this case a temperature profile is specified for the mud inside drill pipe and annulus. Pairs of measured depth and temperatures are entered both in the drill string and in the annulus. The number of pairs may be different for annulus and drill string. The program will interpolate between the entered points to get the information needed for the calculations. The first data points in the tables are the mud temperature at surface. If Dynamic temperature model is selected, the heat transfer and temperature will be computed dynamically with grid cells generated both in the radial direction and along the flow line. The dynamic temperature model needs to know if the mud inlet temperature should be constant, at a constant difference from the mud outlet or if a surface temperature model should be used to calculate the inlet temperature. This is specified in the upper part of this window.
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EXPERT INPUT PARAMETERS The expert input parameters have been divided into four main groups.
5.1
Model parameters
Numerical parameters, observation points and gel model
Eccentricity
Eccentricity of the drill string
Surface pipeline
Pressure loss in surface equipment
RCH & Choke
Specifications for RCH and choke
Model parameters
Figure 5-1: Model parameters window.
Number of Grid cells The number of grid cells is a numerical parameter. The user specifies the number of grid cells used to create the underlying mathematical model. More specifically, it defines the level of detail at which the drillstring and annulus is discretized. Increasing the number of grid cells will increase the accuracy of the simulation, but at the cost of the computation time. The computation time will at best increase
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linearly with respect to the grid cells. To avoid the simulation becoming too timeconsuming, the recommended value for this parameter is around 90. Maximum number of cells is 2000.
Observation Points Five positions can be specified in the well where pressure, ecd and temperature can be observed. The measured depth of the observation point is specified together with a specification of point type. The points can either be moving or fixed. A moving point is a point that is “attached” to the drillstring and moves together with the string. A fixed point refers to a fixed depth, independent of string movement or bit position. Depths greater than bit depth are allowed. For fixed observation points this is interpreted as being below bit, while for observation points moving with drillstring it is taken to be inside drillstring, with distance measured down the annulus, through the bit, and up the drillstring.
Gel model If the model is activated, all muds at rest in the annulus will start gelling, with gel strength properties calculated from the two given gel readings in the input. The most common way to describe the gelling properties of drilling fluids is the 10s and 600s (10minute) gel strength, which is why we require the input of two gel strength readings.
5.2
Eccentricity Presmod can account for an eccentric drillstring. This is specified in the Eccentricity window (Figure 5-2)
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Figure 5-2: Eccentricity window. There are three different options for eccentricity.
Figure 5-3: Eccentricity type options. The eccentricity can be turned completely off (Not used). This means that the drillstring is concentric within the annulus. The second option is Maximum eccentricity in deviated sections. Presmod will use maximum eccentricity above a given deviation, concentric drill string in vertical sections, and smooth transitions in between. Tool joints are taken into account if used (see the “String” window). If a stand-off calculation is performed this can also be entered in the table. Using the third option, Table, eccentricity of the drill string versus depth can be entered. Each line gives eccentricity from the specified depth and downwards. Eccentricity is zero above the first depth. By definition, the sum of standoff and eccentricity is always 100 %.
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Surface pipeline
Figure 5-4: Surface pipeline window.
If there is a considerable loss of pressure in the surface piping between the pump and the wellhead, the surface pressure loss should be entered in this window. A linear interpolation will be used between the points, and a graphical verification of the surface pressure loss is plotted. The simulator assumes a linear increase from no pressure loss at zero flow rate up to the lowest flow rate entry, and a constant pressure loss at all rates above the maximum flow rate entry. Note: The flow rates must be given in increasing order.
5.4
RCH and Choke Choke If you are using a rotating control head (RCH), enable it in this window and specify information for the choke. The inner diameter must be given together with the minimum time required to close the choke fully. The simulator automatically adds a surface pipe length to the system.
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Figure 5-5: RCH and Choke window.
The user may control the well pressure in a dynamic simulation by modifying the well head pressure. In the choke input window the user specifies how to operate the choke by selecting either Pressure, Opening or Automatic from the Choke control drop down list. If Automatic choke control is selected, some automatic choke control parameters have to be set: Constant bottomhole ECD Proportional gain Feed forward gain Integral gain Derivative gain
Separator A separator working pressure has to be set if “Use RCH” is enabled.
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MENUS AND TOOLBARS Menus and toolbar icons have standard Windows functionality. We assume that Presmod users are familiar with Windows operations, and will only describe the menu and toolbar functions specially designed for Presmod.
6.1
File
6.1.1
New Use File New to create an input file from scratch. This dialog offers choices of starting with a blank file or with predefined templates. The template path is configured in the option dialog.
Figure 6-1: New file dialog.
6.1.2
Open Open a file using a standard file selection dialog.
6.1.3
Reopen Reopen one of the last used files.
6.1.4
Save Save a file using a standard file selection dialog.
6.1.5
Save as
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Save a file under a new name using a standard file selection dialog.
6.1.6
Save as template Save the file as a template-file.
6.1.7
Save library Save all data in the library.
6.1.8
Import Use File Import to import either a survey file in some ASCII format or survey data from the RMSwellplan application. When the survey data file has been selected, the survey data import dialog appears. Select the appropriate column delimiter, the units used in the survey file and the number of header/footer lines to be skipped.
Figure 6-2: Survey import.
The survey file must be in ASCII format with columns for measured depth, inclination and azimuth. By default, the program assumes that the first column is used for Measured depth , the second column is for Inclination and the third for Azimuth. If this is not the case, the column headers can be rearranged by drag and drop: Click and hold the left mouse button on the column header, drag to the correct position and release the mouse button.
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Export Use File Export to save the survey data in the RMSwellplan (*.dwf) file format.
6.1.10 Exit Exits the application.
6.2
Edit Standard windows functionality.
6.2.1
Cut Standard windows functionality. In complex input tables the Edit option is not available. A field must be active for edit before this option is active. To select and cut a range of spreadsheet cells – highlight the cells and press Ctrl+X.
6.2.2
Copy Standard windows functionality. In complex input tables the Edit option is not available. A field must be active for edit before this option is active. To select and copy a range of spreadsheet cells – highlight the cells and press Ctrl+C.
6.2.3
Paste Standard windows functionality. In complex input tables the Edit option is not available. A field must be active for edit before this option is active. To select and paste a range of spreadsheet cells – highlight the cells, or alternatively the starting cell for the area to paste, and press Ctrl+V.
6.2.4
Undo Standard windows functionality.
6.3
View Used to switch between Input, Expert Input and Simulation on the Navigation bar. The Navigation bar and Log view can be displayed or hidden by checking or unchecking their tag in the menu.
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Well schematic A schematic plot that includes the riser, seabed, casing/liner program, open hole and the drill string is shown by selecting View Well schematic or using the well schematic button in the tool bar. A visual inspection of the well can reveal errors in the input data. The well schematic has a view properties window to toggle items and labels to be drawn, which can be opened from the popup menu item Properties… The well schematic will provide live feedback on changes done in the well specification by highlighting the well component currently selected for modification, and by updating geometry changes as they happen.
Figure 6-3: Well schematic view.
6.3.2
Survey plot To view a three-dimensional representation of the survey, select View Survey plot. The default view is in front of the XY-plane. To rotate the view around the well, move the mouse in the direction of desired rotation while pressing the left mouse button. To zoom in, move the mouse up while pressing the right mouse button. To zoom out, move the mouse down while pressing the right mouse button. To move the figure, move the mouse while pressing the left mouse button and the shift key.
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There is a menu line in the survey plot with a File and a View menu. To reset the view, select View Reset camera from the plot’s menu line. The plot can be saved in a variety of formats by selecting File Save As… from the plot’s menu line.
Figure 6-4: 3D-survey plot view.
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Log view By default, the log view is located in the lower part of the main window. It displays errors, warnings and information messages concerning input data and calculations. Use the check box on the View Log View menu to display or hide the log window. Double-clicking an error or warning leads the user to the input page that caused the problem. Clicking the right mouse button over the log displays a popup menu offering the following commands: Clear messages This command empties the log. Save messages This command lets you save the log contents to a text file for later review. Show timestamp This check box toggles the use of timestamps for the lines in the log. This feature can be used to distinguish messages from various runs and can be helpful when the content of the log is saved to a file.
6.3.4
Navigation bar Toggle the navigation bar on/off. Hiding the navigation bar can be useful to make more room for the main input or simulation window. The state of this selection is saved between sessions.
6.3.5
Input Switch to an Input window.
6.3.6
Expert input Switch to an Expert input window.
6.3.7
Simulation Switch to a Simulation window.
6.4
Simulation The simulation control panel can be found both in the menu bar and as a separate toolbar.
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Figure 6-5: The simulation control panel toolbar. The toolbar has buttons for start/pause, single step and reset of a simulation. You can also choose from a drop down menu which type of simulation you are going to run: Interactive simulation, Batch simulation or Dynamic surge and swab simulation. The simulation is started by clicking Start, and it will continue to run until it is stopped by the user. When starting the simulation, this button changes to Pause (Figure 6-6). The simulation can be stopped temporarily by clicking Pause and continued after a pause by clicking Start. By clicking One step, one time step is performed and the simulator pauses until Continue or One step is chosen again. To start the simulation from the very beginning, the Reset button has to be clicked.
Figure 6-6: The simulation control while running a simulation. By using Pause, changes in the operational conditions can be made at any time during the simulation.
6.4.1
Start/Pause Start a simulation and pause a simulation. Continue a simulation after a pause.
6.4.2
Step Run the simulation one step forward. The step length can be specified to a max length in the simulation window.
6.4.3
Reset Reset the simulation. All previous simulation results will be blanked out on the plots and the simulation will start from the beginning the next time Start is clicked.
6.4.4
Load state from file Load a previous run simulation that was saved as a state file. . If keep previous results enabled the simulation resumes as new simulation run, i.e., all plot results will populate new curves; otherwise the plot curves are truncated to the time stamp the state was saved.
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Figure 6-7: Resuming simulation as a new simulation run.
6.4.5
Save state… The current simulation state may be saved at any time during a simulation. This way, the simulation can be continued at a later occasion. To save the state, choose Simulation Save state. A save dialog appears asking for a file name. By default, the state file is given the extension .pr. Later, the simulation can be continued by first opening the same input file, then choosing Simulation Load state file. Load the previously saved restart file and continue the simulation by pressing Start or Run one time step.
6.5
Results
6.5.1
Keep previous results You can choose to keep the results from previous simulations and run a new simulation(s). The new simulation will be plotted together with the previous simulation. This makes it easier to compare different scenarios or procedures. Starting a new simulation run with disabled keep previous results will clear out all previous simulation results.
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Figure 6-8: Results of running two simulations with keep results option “on”.
6.5.2
Export results The simulation results may be saved at any time during a simulation. To save the results, choose Results Export results. A save dialog appears asking for a file name. By default, the result file is given the extension .dbr. Later, the results can be imported independently of the input file and among all Drillbench application supporting export and import of results; by choosing Results Import results. The loaded results will be added as the oldest runs in the simulation result stack.
6.5.3
Import results Imports simulation results that were saved by export results. The loaded results will be added as the oldest runs in the simulation result stack. The simulation results can be imported across other Drillbench application and do not depend on the input file, i.e., to compare the bottom hole pressure run with Kick and Presmod.
Figure 6-9: Import of results across Presmod and Kick.
6.5.4
Add page
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If you want to add more result pages for custom plots or special plot setups, you can add a page in which you can add new plots. Pages can also be added by typing Ctrl-T.
6.5.5
Rename page You can rename the custom plots pages to organize your plots. Pages can also be renamed by double-clicking on the page tab.
6.5.6
Remove page You can remove a plots page by selecting from the menu or by typing Ctrl-F4.
6.5.7
Load/save layouts Custom chart layout and properties are stored in the DML file. All open plots and customizations to plots are automatically restored when DML file is opened. Plot and layout customizations can also be stored and loaded separately to override the defaults or customizations in a DML. This function can also be used to create templates for typical plot configurations used in different types of simulations.
6.6
Tools Tools for functionality like reporting, data validation, screen capture of the graphics window, changing unit settings and program options can be found in the Tools menu. Some of these tools are used frequently. These have been given a separate Toolbar icon for easy access.
Figure 6-10: Toolbar.
6.6.1
Take snapshot The snapshot feature places a snapshot of the active plot window on the Clipboard, which can then be pasted into reports or presentations. Combined with customized plot layouts this is a very useful tool for presentation of simulation results.
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Report The reports are opened by selecting Tools Report from the menu bar. All reports use the HTML format. The Input report is a summary report showing the most important input data. The Current results report includes some input information and all the result plots that are selected for viewing in the results plot pages in the simulation window. The tabular results report shows most of the result data as columns in one big table. Another report, tabular results (printable), shows the same information, but with the table divided into multiple tables and the table formats specifically adjusted for printing. Use your web browser’s commands to save or print the report.
Figure 6-11: The Tools menu – Report. The reports use standard HTML style sheets (CSS) to define the visual layout. This makes it easy to customize the format (fonts, colors etc.). Presmod provides a default style sheet (ircss.css) which can be edited or replaced to match the user’s preferred report style. Figure 6-12 shows the layout of an excerpt from the input report using the default style sheet. The other reports behave similarly and use the same layout.
Figure 6-12: Layout of the Input report. The format of the reports makes it easy to export data to other applications like Microsoft Excel. The reports can be opened by Excel directly, or the tables can be
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copied from the reports to an Excel worksheet by standard copy and paste. However, if you are using Internet Explorer to view the report, an even simpler way is available. Data can be exported directly to an Excel sheet by right-clicking on a table and selecting Export to Microsoft Excel. An Excel sheet will be opened, containing the data from the selected report table.
Figure 6-13: Export of Survey data from a report to Excel.
6.6.3
Validate parameters Validation and documentation of input parameters are important to work efficiently. Drillbench has a parameter validation tool. It can be started either by pressing on the toolbar or by selecting Tools Validate parameters from the menu bar.
6.6.4
Edit unit settings To edit the unit setting, you can select Tools Edit unit setting from the menu bar, or click on the unit name in the status bar to pop up the unit menu.
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Figure 6-14: Unit menu. The unit menu is allows quick change of unit sets and access to the unit edit page.
6.6.5
Options To open the options tab window, you can select it from Tools Options from the menu bar or by clicking on
on the toolbar.
This is a dialog that controls the Drillbench program settings. This window is divided in 3 sheets: General, Appearance and Unit definitions, which are described below.
Figure 6-15: The Drillbench option dialog.
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6.6.5.1 General Library path Fluids, casings and string components are selected from a library. The location of the library file is entered in this field. The library selected here is shared among all Drillbench applications. Use the arrow in the right corner of the field to select from a list of previous paths.
Template path Path to Drillbench default template files.
At program startup Reload last used file resumes the session you were working on when exiting Presmod the last time.
Remember last selected page Start at the page you were on when exiting Presmod.the last time. Reports Option to indicate if you want to include the default results in all results reports. Default is to include.
View Option to control if log window should open automatically when new messages are produced by Drillbench. Default is to automatically open log.
Input file Show input read diagnostics This is an option to enable diagnostic messages when loading an input file. This should normally not be used. It is only to be used when having trouble loading an input file. You may be asked by Drillbench support to turn this option on. Load plot layout(s) Custom chart layout and properties are now stored in the DML file. All open plots and customizations to plots are automatically restored when DML file is opened. Plot customizations are also preserved when using separate layout files. This option controls if Drillbench will load and use the last saved custom result plot layout and restore all open plots. Load plot style
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Drillbench will automatically save to the input file all custom changes to the plots styles, e.g. line thickness, background colors etc. This option controls whether the last saved changes are restored.
6.6.5.2 Appearance Allow the user to modify color theme, icon style and tab layout in Presmod according to personal preference.
Figure 6-16: The Presmod summary window with different color settings.
6.6.5.3 Unit definitions The unit settings can be changed by selecting the Unit definitions tab found under Tools Options in the menu bar, see Figure 6.11. Each unit is defined separately and saved in a specified unit file. However, predefined sets of units can be selected from the drop down menu. By default, SI units, metric (European) units and field units are available. You can create your own set of units by selecting the preferred units and save to file with a new name.
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Figure 6-17: Unit definitions.
6.7
Help To open the Help window in Presmod you can select it from Help Help topics or you can open it by pressing F1. The Help window will give you a short description and explanation of all the different windows in Presmod. When pressing F1 from an input window, the help page for the current window will be displayed.
6.7.1
About The Help About option gives you information about Presmod’s version number and the expiry date of the current license.
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Figure 6-18: The About window in Presmod.
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7.
RUNNING A SIMULATION
7.1
Overview
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Three different types of simulations can be performed. The interactive simulation mode allows the user to modify the operational parameters manually. In batch simulation mode, a full simulation is performed, but the changes in operational conditions are specified before starting the simulator. In the interactive and batch mode the simulations can be performed with dynamic temperature. It is also possible to evaluate surge and swab pressures by use of the Surge & Swab mode. In this case a fixed temperature profile is used.
7.2
Controlling a simulation Three buttons for controlling the simulator run are found on the toolbar.
The simulation is started by clicking Start, and it will continue to run until it is stopped by the user. Immediately after the simulation is started this button changes to Pause. Clicking Reset resets all operational parameters so the simulation can be started from the very beginning. The simulation is stopped temporarily by clicking Pause and continued after a pause by clicking Start. By clicking Run one time step, one time step is performed and the simulator pauses until Start or Run one time step is chosen again. The simulator proceeds one step at a time with variable time-step length. The step number and simulated time is updated after the computation in a particular step is finished. The length of each time step is normally decided by the simulator. The default is approximately 90 seconds, but can vary depending on the calculations. The simulation type is selected from the dropdown list on the toolbar
7.3
Simulation window The Simulation window is opened by selecting Simulation in the navigator bar.
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Figure 7-1: Simulation window. The Simulation window is divided into two sections: Simulation control: The upper part is a panel for information and control of operational parameters. This panel will change according to which type of simulation is selected. Simulation results: The lower part is a section with several views for display of results as graphical plots or numerical values.
7.3.1
Graphical output The different plot windows can be used for displaying the results as the simulation runs. The results can be viewed both graphically and numerically. The graphical section in the Simulation window is divided into different sections or views, which are easily configurable. Presmod provides a set of commonly used default plots in the first window. It is possible to customize the plots view according to personal preference and also to add new custom plots windows. To view a plot, click on the right mouse button in one of the views. A menu will then appear with selections for adding plots, removing one or all plots, as well as some options for printing, saving, renaming and customizing the plots. There are several ways to add new plots. If there are currently no plots visible, select the Set in the menu. A new submenu will then appear with all the available plots listed. If you want to add new plots, select add in the menu (when rightclicking). A new submenu will appear with several options for placement and
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with available plots listed. Above the first separator line the plots against simulation time are listed, below the first separator line the parameters versus depth are listed.
Figure 7-2: Menu showing all plots available during simulation.
You can add as many plots as you want. You can also use the vertical splitter in a window that has already been split horizontally. The split windows can be resized by dragging the splitters to the desired position. You can save the set of simulations in the active plot page by selecting Save layout to file from the right-click menu. The plot page layout can then later be used in other simulations by adding a new plot page and select load layout from file from the right-click menu. In order to save all custom simulation plot pages select Save all layout(s) to file; select Load all layout(s) from file to load or restore all custom plot layout pages.
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Plot properties Some plot properties can be modified by clicking the right mouse button on the plot and selecting the Properties option. The following window appears:
Figure 7-3: The plot properties windows.
It is possible to modify plot title, axis settings, horizontal and vertical grid lines, line style and point style. In case of a plot with multiple curves, these modifications can be made for all curves.
7.3.3
Print and export Using a plot’s right click menu, it can be printed directly from the plotting part of the program, it can be copied to the clipboard or it can be saved as a file for inclusion in reports or further manipulation in other programs. Saving to file is accomplished by selecting Export, which opens the dialog shown in Figure 7-4.
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Figure 7-4: Exporting results as picture.
There are several different file formats used for saving the plots:
Windows bitmap
Windows metafile
VML
PNG
PDF
PCX
JPEG
These file formats are widely recognized by Windows programs, and the exported plot picture can be included in word processors, web pages and desktop publishing programs. There is also an option to save the contents of the simulation plots as numerical data. The formats available are:
Text
XML
HTML table
Excel
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Figure 7-5: Exporting results as data.
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Import data There is an option to import data into the plots. This selection is available by choosing Import from the plot’s right-click menu. An open file dialog box opens up and you can import the data from a text file into your plot.
7.3.5
Zooming There is an option to zoom in and out on plots to investigate the results in further detail. To do this, left-click, hold and drag the cursor to the right to zoom in, and leftclick, hold and drag to the left to zoom out.
7.4
Interactive simulation mode Figure 7-6 shows the simulation window when running an interactive simulation. Changes in the operational conditions can be made prior to simulation start or whenever the simulation is paused.
Figure 7-6: Interactive simulation. By default, a simulation starts using the mud defined in the Mud window in the input parameter section, and the current mud density is shown disabled (in a grey font). It is possible to override the mud density by ticking the checkbox in front of the mud density field, both prior to simulation start and during a simulation. The circulation rate, rotation velocity, torque and rate of penetration (ROP) can be modified during a simulation. The torque is used in calculation of temperature effects due to rotation and is only used if the dynamic temperature model is active. The drilling mode is activated whenever the ROP is larger than 0.0.
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If Use fast mode is selected, the simulator will increase time steps up to 10 minutes and the simulation will normally run much faster. This is useful for the simulation of very long time periods when finer details are not important. To use a shorter time step than the default, activate Max timestep length and enter the maximum time step length. The choke section is enabled for user control if RCH is defined in the expert input parameters, see Chapter 5.4 RCH and Choke.
7.5
Batch simulation mode On the Simulation navigator bar there is an icon for Batch configuration. Selecting this option will open a large version of the batch configuration window. Figure 7-7 shows an example of the batch specification window. The user specifies a sequence of time periods where a set of operational conditions are kept constant, before being changed in the next time period. The parameters are the same as the ones that can be altered in an interactive simulation. To make it easier to specify the batch simulation, some parameters - like accumulated time and bit depth at end of period - are calculated and included in the table. This is very useful as reference when setting up long and complicated batch jobs. The specification of the operational parameters are stored as part of the case file when using the File Save option from the menu bar. The batch specification is a spreadsheet table and can easily be copied to another file or application using Ctrl+C for copy and Ctrl+V for paste. Changing the entries in the table is done by placing the cursor on the table cell and type the desired value. If Use fast mode is selected, the simulator will increase time steps up to 10 minutes and the simulation will normally run much faster. This is useful for the simulation of very long time periods where finer details are not important.
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Figure 7-7: A typical batch simulation setup.
The batch simulation can be started and controlled by selecting Batch simulation and using the control buttons in the toolbar. The results are viewed in the Simulation window. Figure 7-8 shows the Simulation window when a batch simulation is running. This is a typical way of running a batch job in Presmod. The Simulation window shows a snap-out of the batch configuration table in the upper part. This snap-out has full edit features and it is not necessary to go to the batch configuration window to modify the batch job. The lower part of the window shows the standard graphics display. The plot functionality is described in detail in section 7.3.1 The time period presently being simulated is highlighted in the Batch table to give the user a certain overview over the time elapsed. The user may, at all stages in the Batch simulation, change to an interactive simulation. This is done by pressing Pause, choosing the Interactive simulation mode, doing some changes in the parameters and choosing Start in this window.
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Figure 7-8: Running a batch job in Presmod.
7.6
Dynamic surge and swab simulations Presmod can calculate the dynamic effects of pipe movements. Dynamic surge and swab simulation is selected from the toolbar. Figure 7-9 shows the setup and output from a dynamic surge and swab simulation. The following parameters can be specified to control the surge and swab: Mode: Surge – for pipe movement downwards Swab – for pipe movement upwards Top status: Open top
pump not connected
Connected
Pump rate field is activated and pump rate can be specified for pumping out of hole
Acceleration: Specify the acceleration. The recommended range is from 0 to 1 m/s2 (0-3 ft/ s2) Use float valve
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A one-way valve may or may not be present in the BHA. The valve prevents backwards flow from the well into the running string, and may cause significantly higher surge pressures when the annulus is narrow, for example when tripping a casing string. The float valve is activated by selecting the Use float valve checkbox. Tripping speed velocity specified as: Velocity (average pipe velocity) Time per stand Min drillstring velocity This is the minimum pipe speed used Max drillstring velocity This is the maximum pipe speed used Number of steps This is the number of runs that will be performed
The dynamic surge and swab calculations require that measured temperature profile is selected.
Figure 7-9: Running dynamic surge and swab.
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Dynamic surge and swab has the same graphics options that are available for interactive and batch mode. These features are described in more detail in section 7.3.1. Note that the well geometry plot in Figure 7-9 indicates the initial bit position. When running a surge calculation it is important that the initial bit position is at least one stand length above the bottom of the well. If this is not the case a message will appear when starting the simulation, warning the user that the bit will reach the bottom before the simulation can be completed. (The well depth is specified as the sum of the bit depth and the open hole section).
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8.
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WORKING WITH PRESMOD Presmod includes tools and features that are very valuable for day to day engineering as well as operation decision support.
8.1
Multiple runs – keep results A very useful feature in Presmod is the ability to use the interface directly to compare results from different runs and slide back and forward in time (important for depth plots). This is extremely useful for sensitivity analysis. It can be multiple runs with the same case file only with minor differences (e.g. see the effect of changing mud system) or it can be different case files or it can be imported results from other Drillbench applications.
To perform multiple runs: Go to Simulation Keep previous results. When the Reset button is pressed the time is set back to zero, all the parameters in the plots are still showing. When a new run is started (either from the same or from another case) the new data is running on top of the previous run. The effect of changed parameters is therefore easy to see in the graphics. Furthermore, plots have a menu property to toggle the visibility of all curves of previous runs.
Figure 8-1: ECD as function of mud system.
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Figure 8-1 shows the ecd plot as function of ROP, RPM and circulation rate. The operational parameters are included below the ecd plot to study the connection between input system and the actual results.
8.2
Improved results view During a simulation the current results of each time step are stored historically on a result stack and the results can at any time be exported and imported, also across other Drillbench applications. Previous time snap shots of plots can be access by a time slider. For time plots an optional time line is drawn according to the position of the time slider. In case of depth plots the according profiles are shown in respect to the time sliders position. By default the check box to follow the simulation is checked to plot the results at the current time step.
Figure 8-2: Time slider, showing previous time snap shot.
8.2.1
Trend plots Time plots have an optional time line showing the time in respect to the position of the time slider. Beside the time axis, time plot curves can presented in respect to pumped volume or bit depth. The time and value axes can flipped, e.g., useful in conjunction with time axis as bit depth to present the plot familiar from profile plots.
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Figure 8-3: Left: Pit gain in respect to pumped volume, right: x and y axis flipped.
8.2.2
Profile plots While running a simulation the previous profile curves of the current simulation can be shown as faded curves. The faded curves will only be visible if the checkbox follow simulation is checked. Depths plots can also calculate and draw the minimum / maximum curve(s) of the whole current simulation run. There is an option to show the casing shoe depth, which is represented by a horizontal thin line
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Figure 8-4: Left: fading out curves of previous time steps; right: minimum and maximum of free gas during the whole simulation.
8.3
Well schematic The flow areas of the well schematic can be colored with respect to the values of a profile plot by selecting Results ; select None to switch off the coloring. The values to be colored depend on the actual position of the time slider such that one can slide backward and forward in time or animate the values during a simulation.
Figure 8-5: Selection of the profile to be visualized.
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The colors for minimum and maximum and the value range to be colored can be customized in the data properties window.
Figure 8-6: Well schematic showing actual free gas.
8.4
Add external data It is possible to import external data sets and add these in the Presmod plots. This way it is very easy to compare simulation results with measured data or with results from other simulations.
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Figure 8-7: Example of result from exporting and importing data.
Figure 8-8: Export dialog – select Excel format.
Figure 8-7 shows an example of what we can achieve when using the advanced options in Presmod. The temperature curve – the red line - has been exported to an Excel file. The Export dialog is shown in Figure 8-8. Note that to export the data to Excel the Data-tab has to be selected. In Excel the data has been manipulated by adding “synthetic” noise by using a random number. This is just one example of another data set – it could just as well have been from a logging tool or another data source. To import the data to Presmod again, the file has been converted to a text file (copy and paste to Notepad). By selecting Import from the plot menu a standard Windows file selection box is opened, and an Import dialog as in Figure 8-9 is opened. The Import tool shows the data-columns, the units as well as headers and footers. Dragging the column header Temperature (Celsius) to column number 3 switch the data column from number 2 to 3. Pressing OK will import the curve into the plot as shown in Figure 8-7.
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Figure 8-9: Data file import.
8.5
Create presentation graphics Plots such as the one created in Figure 8-7 can easily be manipulated and modified, by including legend, adding text and comments, changing background or other colors, fonts etc. There is a large number of options. In the following we have illustrated a few examples.
Figure 8-10: Reconfigured temperature plot.
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In Figure 8-10 we have altered the plot in Figure 8-7. Legend has been added, the line color of the modified temperature data has been changed from green to blue and the line thickness has been increased. Also the font size has been modified.
Figure 8-11: Plot properties menu.
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9.
SELECTING THERMAL PROPERTIES
9.1
Introduction
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Presmod provides a default selection of thermophysical properties based on fluid composition and component densities. The suggested properties are based on default mixing rules. The default should be used as guidance when more accurate data is not available and also to give a reasonable range for the thermophysical properties. Reliable calculation of wellbore temperature is only possible if good values of the thermophysical properties of the circulating fluid in the well are given as input to the calculations. Thermal properties of surrounding materials like steel, cement, formation and sea water are also important in many cases, especially when simulating operations that last many hours. In this note we indicate how thermophysical properties of composed fluids can be calculated when the properties of each component are known. These methods have not, however, been verified for drilling fluids at HPHT conditions, and direct measurements of thermophysical properties would be preferable. We also list some values of thermophysical properties of other materials. It should be noted, however, that values may vary much from case to case, for example due to different cement compositions or different content of fluids in the formation.
9.2
Drilling fluids
9.2.1
Specific heat If heat capacity has not been measured, it is recommended to use the following formula: N
C xi C p ,i ,
(1)
i
where x i and C p ,i are weight fraction and specific heat (e.g. kcal/kg/ºC) of component number i , and N is number of components. With this formula we neglect mixing effects. Example: The main components of a 2.0 s.g. WBM are water and a solid material with the following properties:
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(kg/m3)
C p (J/kg/ºC)
Water
1000
4190
Solid material
4500
460
First we calculate mass fractions of water and solids by solving the two equations
1
xw
xs
m w s xw xs 1
(2)
where is density and indices m , w and s denote mud, water and solids respectively. With more than two components, extra terms must be added on the right hand side of the first equation and the left-hand side of the second equation. An extra equation is needed for each extra component, like for example specification of oil water ratio if the third component is oil. The solution of the equations (2) is
1 1 xw m s
1 1 w s
1 1 1 1 0.3571 2000 4500 1000 4500 xs 1 xw
(3)
1 0.3571 = 0.6429, and the specific heat of the mud is approximated by
C p , m x w Cp , w x s Cp , s 0.3571 4190 0.6429 460 = 1790 J / kg/º C. The above formalism has not been compared with data for relevant drilling fluids at HPHT conditions since we do not have any such data.
9.2.2
Thermal conductivity Calculation of thermal conductivity for a mixture is more complicated than the above calculation of specific heat for a mixture. Some formulas for mixtures of several liquids, and a liquid and a solid, exist in the literature Thermal conductivity of a fluid with solid material dispersed in it may be calculated by the Eucken model (10), (8) which determines the thermal conductivity of a liquid with small solid spheres in it:
m w
21 X w 1 2 X s 2 X w 1 X s
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where is thermal conductivity and X is volume fraction of solid materials. A formula for a mixture of different liquids may be found in Perry’s Handbook (9). Once again we note that the above formalism has not been compared with data for relevant drilling fluids at HPHT conditions.
9.3
Other materials We have too little realistic data to give general recommendations, but we list some data that we have gathered from literature. This may be a good approximation in many cases, though better data could improve the calculations significantly. If possible one should collect better data for temperature simulations. Corre, Eymard and Guenot (8) have used the following values in their paper on the Belzeb simulator:
(kg/m3)
C p (J/kg/ºC)
Steel
7800
400
40
Cement
2700
2000
0.7
Formation
2700
800
3
(W/m/ºC)
These can be realistic values, but large variations must be expected. As an example, the thermal conductivity of low alloy steels range from 38 to 66 W/m/ºC, while specific heat ranges from 420 to 500 J/kg/ºC (9). General handbooks (9), (11) give other values for cement than the ones listed above. Heat capacity for cement is approx. 800 J/kg/ºC (and 650-920 J/kg/ºC for different kinds of concrete), while thermal conductivity ranges from 0.3 to 1.3 for different kinds of concrete, and density ranges from 1.5 to 2.3 s.g. The numbers of Corre, Eymard and Guenot can be realistic if the content of water and heavy particles is larger. Thermophysical properties of formations vary much between different species of rock. It is also dependent on content of fluids, and with large water content the heat capacity in the table above seems to be too small. Ranges of values for physical properties from 20 to 100 ºC for water and barite are listed in the table below (9), (11).
(kg/m3)
C p (J/kg/ºC)
Water
1000
4180-4220
0.59-0.68
Barite (BaSO4)
4500
457-477
(W/m/ºC)
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10.
RHEOLOGY MODELS
10.1
Models There are many rheological models describing the non-linear proportionality between shear stress and shear rate. Most of the drilling fluids behave like yieldpseudo plastics, which means that a minimum force must be applied to impart motion to them. This force is known as yield stress. In the following the three most actual models will be described.
10.1.1 Bingham plastic model This is a two-constant model with direct proportionality between shear stress and shear rate , in addition to a yield stress y. The equation is
y p, y y 0,
(4)
where p = plastic viscosity. p is the slope of the curve relating and . The weakness of this model is that it does not contain the non-linear relationship between and .
10.1.2 Power law model This model is the most used for different oil based muds. It describes fluids without yield stress by a non-linear flow curve
K n
(5)
where K = consistency index n = flow behaviour index; n 1. If n = 1, the equation becomes identical to the equation of flow of a Newtonian fluid having the viscosity K.
10.1.3 Robertson-Stiff model This is a three-constant model that includes Bingham and Power law as special cases. The fluid is defined by
A ( C ) B
(6)
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where A, B and C are constants. The Robertson-Stiff model may be regarded as a power law model where the shear rate is replaced by an effective shear rate C . This introduces a yield stress equal to
0 AC B
(7)
The model simplifies to the Bingham model if B 1, or to the power law model if C 0.
10.1.4 Shear rate dependent fluid parameters We have to fit the constants of the model that we have selected (power law, Bingham or Robertson-Stiff) to measured rheology data (Fann readings). A straightforward way to do this is to fit the constants of the model to all data points, with the same weight for all points. If the data deviates from the model that we have selected, this may not give a good result. It is possible to obtain a better result after making the following considerations: The shear rate at a given position along the flow line is largest close to the pipe wall(s), and decreases down to zero when moving away from the wall(s). Hence frictional pressure loss only depends on the part of the rheology curve (shear rate versus shear stress) with shear rates below the shear rate at the wall (for annulus: below the largest shear rate at any of the walls). Furthermore, it turns out that the part of the rheology curve with shear rate close to the shear rate at the wall is much more important than the lower shear rate part. Presmod takes these considerations into account as follows:
Fit model parameters to all rheology data points. If the fit is good, go directly to point 5
Calculate approximately wall shear rate using Newtonian formalism.
Fit model parameters to rheology data points up to first point with shear rate above the wall shear rate. Give larger weight to points with larger shear rate when fitting.
Update the wall shear rate since it depends on rheology parameters, and return to point 3 some times to improve accuracy.
Calculate frictional pressure loss
Shear stress at the wall and frictional pressure loss is calculated using the formalism given by Reed and Pilehvari (14). With the above procedure, the calculation of frictional pressure loss becomes more independent of model choice than it would be if the model constants had been independent of shear rate. Thus, the results with Bingham, Power law and Robertson-Stiff fluids will normally be relatively close.
Presmod User Guide
11.
KEYBOARD SHORTCUTS
Alt+F Alt+E Alt+V Alt+S Alt+T Alt+H
open File menu open Edit menu open View menu open Simulation menu open Tools menu open Help menu
Ctrl+N Ctrl+O Ctrl+S Ctrl+C Ctrl+X Ctrl+V Alt+BkSp
New file Open Save Copy Cut Paste Undo
Ctrl+Ins Ctrl+Del
Insert rows in a table Delete rows in a table
F9 F8 Ctrl+F2 Ctrl+F12 Ctrl+U
Start Step Reset Take snapshot Edit unit settings
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12.
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ACKNOWLEDGEMENTS
Drillbench uses the following third-party tools:
JEDI Visual Component Library (JVCL) JVCL portions are licensed from Project JEDI, and the source code can be obtained from http://jvcl.sourceforge.net/ JEDI CODE LIBRARY (JCL) JCL portions are licensed from Project JEDI, and the source code can be obtained from http://homepages.borland.com/jedi/jcl/ The Visualization ToolKit (VTK) VTK is copyright © 1993-2004 Ken Martin, Will Schroeder, Bill Lorensen All rights reserved. VTK is available from http://www.vtk.org/ Nullsoft Scriptable Install System (NSIS) NSIS is copyright (C) 1999-2006 Nullsoft, Inc. and is available from http://nsis.sourceforge.net/ TeeChart TeeChart is copyright © David Berneda 1995-2006. All Rights Reserved. http://www.steema.com/ LiquidXML LiquidXML is copyright ©2006 Liquid Technologies Limited. All rights reserved. http://www.liquid-technologies.com/ FLEXlm FLEXlm is copyright ©2002-2006 Macrovision Corporation. All rights reserved. http://www.macrovision.com/ TMS Component Pack TMS Component Pack is copyright © 2001-2009 by tmssoftware.com. All rights reserved
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13.
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REFERENCES 1.
Standing, M.B.: A Pressure-Volume-Temperature Correlation for Mixtures of Californinan Oils and Gases. Drill. & Prod. Pract. API p 247.
2.
Glasø, Ø.: Generalized Pressure-Volume-Temperature Correlations. Journal of Petroleum Technology, p. 785, May 1980.
3.
Vazquez, M. and Beggs, H.D.: Correlations for Fluid Physical Property Prediction. SPE 6719. 1977.
4.
Sorelle, R.R., Jardiolin, R.A., Buckley, P and Hauser, J.M.: Effects of Temperature and Pressure on the Density of Drilling Fluids. SPE 11114, 1982.
5.
Dodson, C.R. and Standing, M.B.: Pressure-Volume-Temperature and Solubility Relations for Natural Gas Water Mixtures. Drill. And Prod. Prac., API, 1944.
6.
Kemp, N.P. and Thomas, D.C.: Density Modelling for Pure and Mixed-Salt Brines as a Function of Composition, Temperature and Pressure. SPE/IADC 16079, 1987.
7.
Isambourg, P. , Anfinsen, B-T. and Marken, C.: Volumetric behaviour of Drilling Muds at High Pressure and High Temperature. SPE 36830, 1996.
8.
Corre, B., Eymard, R. and Guenot, A.; "Numerical Computation of Temperature Distribution in a Wellbore While Drilling", SPE 13208, 1984
9.
Green, D. W.: “Perry’s Chemical Engineers’ Handbook, sixth edition” McGraw Hill 1984
10.
Euken, A.: “Die Wärmeleitfähigkeit Keramisher Feuerfeste Stoffe”, VDI Forsch. H. no 353 (1932).
11.
Weast, R. C..; "CRC Handbook of Chemistry and Physics"
12.
Elf Report no. 99/85, SNEA(P), Pau, 1985.
13.
Drilling Data Handbook.
14.
Reed, T. D. and Pilehvari, A. A.: “A New Model for Laminar, Transitional, And Turbulent Flow of Drilling Muds”, SPE 25456, 1993.
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