Drill bench-Kick Module User Guide

Drillbench Kick User Guide

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TABLE OF CONTENTS Page 1

GENERAL 1.1 Overview

1 1

2

MAIN ENVIRONMENT 2.1 Overview

2 2

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 Library 3.5.1 Library editor

4 4 4 5 5 6 7

4

INPUT PARAMETERS 4.1 Summary 4.2 Description 4.3 Survey 4.4 Wellbore geometry 4.5 String 4.6 Surface equipment 4.7 Fracture pressure 4.8 Mud 4.8.1 Component densities 4.8.2 PVT model 4.8.3 Rheology 4.9 Reservoir 4.10 Temperature 4.10.1 Measured 4.10.2 Holmes and Swift

8 8 9 9 12 15 17 19 21 23 24 27 29 34 34 35

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EXPERT INPUT PARAMETERS 5.1 Model parameters 5.2 Sub-models

36 36 39

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RUN CONFIGURATION 6.1 Batch configuration 6.1.1 Drillers method 6.1.2 Wait and weight 6.2 Sensitivity configuration

40 40 41 41 42

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MENUS AND TOOLBARS 7.1 File 7.1.1 New 7.1.2 Open 7.1.3 Reopen 7.1.4 Save 7.1.5 Save as 7.1.6 Save as template 7.1.7 Save library

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7.2

7.3

7.4

7.5

7.6

7.7

7.1.8 Import 7.1.9 Export 7.1.10 Exit Edit 7.2.1 Cut 7.2.2 Copy 7.2.3 Paste 7.2.4 Undo View 7.3.1 Well schematic 7.3.2 Survey plot 7.3.3 Log view 7.3.4 Navigation bar 7.3.5 Input 7.3.6 Expert input 7.3.7 Run configuration 7.3.8 Simulation Simulation 7.4.1 Start/Pause 7.4.2 Step 7.4.3 Reset 7.4.4 Load state from file 7.4.5 Save state… Results 7.5.1 Keep previous results 7.5.2 Import results 7.5.3 Export results 7.5.4 Manage results 7.5.5 Add page 7.5.6 Current page 7.5.7 Load/save layouts Tools 7.6.1 Take snapshot 7.6.2 Report 7.6.3 Validate parameters 7.6.4 Edit unit settings 7.6.5 Options Help 7.7.1 Help topics 7.7.2 About

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45 46 46 46 46 46 46 46 46 46 48 49 50 50 50 50 50 50 51 51 51 51 51 52 52 52 52 53 53 53 54 54 54 55 56 56 57 60 60 60

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RUNNING A SIMULATION 8.1 Overview 8.2 Controlling a simulation 8.3 Simulation window 8.4 Interactive simulation mode 8.5 Batch simulation mode 8.6 Sensitivity simulation

61 61 61 61 63 65 66

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WORKING WITH KICK RESULTS 9.1 Plot page operations 9.2 Plot management 9.2.1 Set and plot selection 9.2.2 Add 9.2.3 Reset plot

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9.3

9.4

9.5

9.6

9.7

9.8 9.9

9.10 9.11 9.12 9.13

9.2.4 Remove plot Plot operations 9.3.1 Maximize plot 9.3.2 Normalize 9.3.3 Swap with selected plot 9.3.4 Track values 9.3.5 Print 9.3.6 Import 9.3.7 Export 9.3.8 Copy image to clipboard 9.3.9 Plot properties Profile plot operations 9.4.1 Take snapshot 9.4.2 Create trends at observation points Curve operations 9.5.1 Copy curves 9.5.2 Paste as custom curves 9.5.3 Clear custom curves Trend plot switches 9.6.1 Show timeline 9.6.2 Show previous results 9.6.3 Flip axes 9.6.4 X axis Profile plot switches 9.7.1 Show pore/fracture pressure 9.7.2 Show casing shoe 9.7.3 Fade recent results 9.7.4 Show minimum/maximum 9.7.5 Show previous results 9.7.6 Slider Zooming 3D wellbore plots 9.9.1 General functionality 9.9.2 Select run 9.9.3 Select curve 9.9.4 Holdup fraction view 9.9.5 Scale palette for entire run Multiple runs – keep results Improved results view Well schematic Create presentation graphics

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70 70 70 71 71 71 72 72 73 75 75 76 76 76 77 77 77 77 78 78 78 78 78 78 78 79 79 79 79 79 80 80 80 80 81 81 81 82 83 84 85

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RHEOLOGY MODELS 10.1.1 Generalised Newtonian models 10.1.2 Frictional pressure loss model

87 87 89

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COMPOSITIONAL PVT MODEL 11.1 Overview 11.1.1 Under-saturated liquid compressibility 11.1.2 Two-liquid formulation 11.1.3 Influx characterisation 11.1.4 Mud characterisation

91 91 91 92 92 94

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LOST CIRCULATION 12.1 Overview

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12.2 Fracturing 12.2.1 Fracturing the formation 12.2.2 The Fracture Volume 12.2.3 Fracture Closing 12.2.4 Mud mixing

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KEYBOARD SHORTCUTS

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14

ACKNOWLEDGEMENTS

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Drillbench Kick User Guide

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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. Kick is one of the applications in Drillbench. It is a unique software program for well control engineering, training and decision making support. The program includes the results of activities like flow modelling, laboratory and full-scale experiments and simulator development. The simulator uses advanced mathematical models in order to produce realistic simulations. A great number of special and complex well conditions can be handled. Kick is a result of extensive R&D within well control performed at Scandpower Petroleum Technology and Rogaland Research during the last decades. The prevention and control of kicks are of great concern to the petroleum industry. Most kicks are brought under control, but the occasional blow-out may result in danger for rig crew and great losses of economic and environmental character. The tool can be used for: 

Pre-evaluation of potential well control problems



Post-evaluation of kick incidents



Evaluation of well control procedures



Evaluation of the effect of base oil type and mud composition on kick development



Evaluation of the effect of well geometry, pump rate, reservoir properties, mud density, etc.



Evaluation of pressure conditions in the well during the control phase



Evaluating the effect of horizontal wells



Evaluating the effect of deep water well; long choke/kill lines, narrow operating window with fracture pressure gradient near formation pressure gradient



Evaluating handling of an underground flow situation



Evaluation of degasser (poorboy) capacity when circulating out a kick

The simulator can assist in the design of an optimum well program for a given geology, wellbore configuration and surface equipment. It can help to determine optimum wellcontrol procedures, and serve as a remedy for post-analyses of kick cases. The simulator is also a tool for training rig crew by simulating “what if" scenarios before drilling into new sections.

Drillbench Kick User Guide

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2

MAIN ENVIRONMENT

2.1

Overview The Kick installation creates by default a Kick entry under Programs  SPT Group in the Start menu. Kick 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. Typical view when starting Kick. A summary page shows the most important parameters to give the user an overview of the case The environment consists of four main areas; the menu line and the toolbar at the top of the window, and in the main Kick window there is a navigation bar to the left and a data entry window to the right.

Main environment

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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.

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 13). A toolbar for controlling the simulation with start, pause, single step and reset buttons is placed next to the normal toolbar. The user can also select the desired type of simulation, interactive, batch or kick tolerance.

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



Run configuration for specification of simulation specific parameters



Simulation for simulation and output of results

Data entry window Displays either input parameters or calculated output parameters depending on the current selection in the navigation bar

Main environment

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3

CREATING A CASE FILE

3.1

Overview 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 therefore 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 in the input parameter sheets. Details about the input parameter sheets and the library are presented in more details in section 3.5 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.

Figure 3-1

Data model in Drillbench

Data can be collected from several sources. In many cases the 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.

Creating a case file

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The total amount of data needed to run a Kick 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.

3.4

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.

Creating a case file

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3.5

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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 also very 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)

Figure 3-3. 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 if preferred. 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. Creating a case file

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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.

3.5.1

Library editor There is also a standalone library editor that can be opened from the Start menu (Start  [Program location]  Tools  Library editor).

Figure 3-4

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.

Creating a case file

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INPUT PARAMETERS The input parameters are divided into ten main groups.

4.1

Summary

A brief summary of the most important input data

Description

Information about the present study/case

Survey

Describes the well trajectory

Wellbore geometry

Defines the wellbore completion

String

Configures and defines the drill string and bit

Surface equipment

Defines the rig environment

Fracture pressure

Defines fracture pressures with depth

Mud

Defines the drilling fluid

Reservoir

Defines the reservoir and influx fluid

Temperature

Defines temperatures and temperature model

Summary The summary window is an overview of the most important information entered for the case.

Figure 4-1 Summary window

Input Parameters

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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 4-2

4.3

Description window

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.

Input Parameters

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Figure 4-3 Specification of survey data The survey data can be entered manually, copied from a spreadsheet or imported from an existing survey file. Figure 4-3 show the survey data table and a 2D sketch of the well trajectory. Selecting one or more rows in the survey table will highlight the corresponding part in the trajectory plot as shown in Figure 4-4.

Figure 4-4 Highlight sections in well trajectory plot Input Parameters

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Inclination data can also be imported from file (Ref. Figure 4-5) by choosing File  Import  Survey data or RMSwellplan data.

Figure 4-5

Menu option for survey data import

The RMSwellplan option opens an open file dialog where 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

Input Parameters

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The survey profile can be previewed in 3D, by selecting View  Survey plot.

Figure 4-7

4.4

3D survey plot

Wellbore geometry The wellbore geometry section contains the specification of the actual hole. A typical window appearance is shown in Figure 4-8. The wellbore is divided in two parts; Riser (if applicable), and Casing/Liner.

Figure 4-8

Specification of riser, casing and liner data Input Parameters

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Riser

Figure 4-9

Riser

The Riser is specified by the length (sea floor depth) and dimensions. Name and dimensions can either be typed directly in the table or a predefined item can be loaded from the library. The library is accessed from an ellipsis button in the Name column. The library functionality is described further in Chapter 3.5.

Figure 4-10. Library browser for Casings and Risers (database) Kick is able to simulate flow in the riser after the BOP is closed. This is important especially for deep-water wells, in case gas has entered the riser before the BOP is fully closed. Calculation of flow in riser after the BOP is closed is activated from an ellipsis button that appears when clicking in the Properties column. Enable the checkbox for Riser calculation as shown in Figure 4-11. One needs to specify the length and inner diameter of the diverter.

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Figure 4-11 Activation of riser calculation; simulation of flow in the riser when the BOP is closed

Casing / Liner

Figure 4-12 Casing and liner specification Each row in the casing and liner window is used for specifying the information necessary for one casing string. In the computations, only the annulus open for mud flow need to be known. Thus only dimensions for the innermost casing layers need to be defined and casings outside can be left out. 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 3.5. 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. Hanger depth is the starting depth for the casing string. For the uppermost casing/liner, the hanger depth will often equal the depth of the BOP, i.e. rig floor (hang-off from rotary table is usually ignored) or sea floor depth. Setting depth is the casing shoe depth or depth for cross-over to another casing dimension. In the fourth and fifth column the inner and outer diameter of the casing are specified (these values will be taken from the library, but can be manually updated as well). All depths are metered depths with reference to RKB.

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. Input Parameters

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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. Clicking on a row in the riser or casing table will highlight the corresponding item in the well schematic as shown in Figure 4-8.

4.5

String

Figure 4-13 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 3.5. 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 all the information manually. To add new items to the library, right click on the component. To append lines to the table, use the Arrow down key. To add or remove lines within the table use either Ctrl+Ins or Ctrl+Del. Clicking on a row in the string table will highlight the corresponding item in the well schematic as shown in Figure 4-13.

Input Parameters

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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.

Figure 4-14 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.

Input Parameters

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Surface equipment The surface equipment window, Figure 4-15, defines the rig equipment and some operational parameters influencing a shut-in and kill operation.

Figure 4-15 Configuration of rig equipment and operational parameters Choke line The input data required for the Choke line is shown in Figure 4-16.

Figure 4-16. Input data for chokeline

Input Parameters

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Specify the length and inner diameter of the choke line. The Duration of choke closure is the time required to close the choke from fully open to fully closed. Pressure after choke is the backpressure of the choke and is used as the boundary condition for the choke line outlet. Unless a poor boy degasser (see Chapter 5.1 Model parameters) is included in the model, Pressure after choke is typically representing the operating pressure of the separator. Number of kill and choke lines refers to the number of lines used for circulating out a kick. In case of more than one choke/kill line, the lines are assumed to have the same length and inner diameter, and they are assumed to be operated at the same choke pressure. The flow is split equally between the lines. The pressure drop across the choke is calculated based on the total flow rate.

Pump

Figure 4-17. Pump parameter input The Liquid pump rate change defines how fast the pump can be shut down, and how fast a new rate is achieved when the circulation rate is altered. Example: a Liquid pump rate change of 2000 l/min² means that when circulating at 1000 l/min it takes 0.5 min from the pump is starting to shut down until it stops flowing. Delay until pump shut down defines how long it takes from a kick is detected and until the pump is starting to shut down. It represents a human factor in the process of shutting in the well. When running a simulation in the Interactive simulation mode, the user will be given a message when it is time to shut down the pump. This message will appear when the delay period after kick detection has elapsed. During a batch or sensitivity simulation, the pump shut in is initiated automatically after the same predefined time. The Volumetric output is the pump capacity. This is used to compute the number of strokes during a wait & weight (kill sheet) well control simulation mode.

BOP Figure 4-18 shows the input data for the BOP (blowout preventer).

Input Parameters

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Figure 4-18. Input data for BOP

The Duration of closure is the time required to close the BOP from fully open to fully closed. The Delay until BOP closure represents the time from the pump has stopped flowing until the BOP starts to close. It represents a human factor in the process of shutting in the well. In the Interactive simulation mode the user will be given a message when it is time to close the BOP. This message will appear when the delay period after the pump shutin has elapsed. During a batch and sensitivity simulation, the BOP closure is initiated automatically after the same predefined time. The Duration of choke closure, Liquid pump rate change, Delay until pump shutdown and Delay until BOP closure defines the rig operational parameters. Together these parameters define the time to shut in the wellbore after a kick is detected. They are important when investigating the impact of operational parameters on the development of a kick incident and provide a basis for preparing operational procedure. A hard shut in of a kick is modeled by minimizing these parameters in the input data.

Surface

Figure 4-19 Annulus surface pressure Annulus surface pressure defines the pressure at annulus outlet and is used as the boundary condition for the simulation until the well is closed. Default value is 1 atm.

4.7

Fracture pressure Fracture pressure can be specified for various depths. The fracture pressure refers to formation strength (point of elastic deformation). This is an optional window and can be left empty. However, the given data will be used as reference values in pressure plots for evaluation of shoe strength, and it is therefore very useful to enter the expected profile. The window is shown in Figure 4-20. As soon as depths or gradients are entered or modified in the tables, the plot on the right hand side will be updated.

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Figure 4-20. Fracture pressure input window Measured depth and the corresponding fracture pressure data are defined in the 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. Selecting one or more rows in the survey table will highlight the corresponding part in the plot as shown in Figure 4-21.

Input Parameters

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Figure 4-21 Highlight sections in fracture pressure plot The columns Initiation pressure and Closing pressure are optional and refers to modeling of a lost circulation scenario. The columns are only important if losses to the formation are to be modeled, if not the values can be disregarded. At fracture initiation pressure, fluids are actually lost into the formation. Moreover, when the fluids have returned to the well, the fracture closes at the fracture closing pressure. The simulator automatically suggests an initiation pressure of 1.2 times the fracture pressure, and a closing pressure 17 bar below the fracture pressure. The values should be updated if more accurate information is available. See also Chapter 5.1 Model parameters for further description of input parameters connected to modeling of lost circulation. The simulator gives a message when the pressure in the well exceeds the fracture pressure. Note that lost circulation will only be activated if the simulator is run in interactive mode with manual choke control. In this case, mud will be lost to the formation if the fracture initiation pressure is exceeded anywhere in the open hole section during the simulation. The lost circulation model is described in more detail in Chapter 12.

4.8

Mud In Figure 4-22 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 4-23. 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 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.

Input Parameters

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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. 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.

Figure 4-22 Mud window

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Figure 4-23 Library browser for fluids

4.8.1

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, ref. Measured PVT model below, a component density model is used. The p, T dependency of each phase will then 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 is 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 correct 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').

Input Parameters

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Figure 4-24 Component densities

4.8.2

PVT model The PVT section defines the variation in mud properties with elevated pressure and temperature. There are three alternative ways of estimating these properties: Measured, Black oil and Compositional. The method is selected in the expert input section Sub-models. The currently selected model is listed here as a hyper-link which can be clicked to quickly jump to the model selection page. Each method have different input properties which are specified here.

4.8.2.1 Measured The Measured PVT model is recommended if experimental PVT data are available for different pressures and temperatures. The measured values can be specified by clicking the Properties button in the PVT section. Clicking the properties button open a sub-window with three tab-sheets; one for density of the whole fluid, one for density of saturated base oil and one for specification of gas solubility in the base oil. All tab sheets contain spreadsheet tables that support copy and paste between other programs and Drillbench. The Measured PVT model is suitable only for dry gas influx.

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Figure 4-25 Entries for experimental values for Measured PVT model

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 the density of the whole mud for a saturated base oil phase, and are filled in for each pair of pressure and temperature. This table is not needed unless Measured PVT is chosen as PVT model

Saturated oil density The table for Saturated 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. The densities entered are the density of base oil saturated with gas. This table is not needed unless Measured PVT is chosen as PVT model

The Density slope is used to compute the density of undersaturated oil. That is, the compressibility of saturated base oil beyond the pressure where all the gas is dissolved.

This is done by first calculating the density of saturated oil at the bubble point pressure that corresponds to the actual amount of gas dissolved in the oil. Furthermore, it is assumed that the oil is compressed with the given density slope to the actual pressure. Since the density slope is not constant with pressure, the entered density slope must be specified at the actual well pressure where the oil is Input Parameters

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undersaturated. An example is the density slope of a 0.750 sg oil. Measurements performed at Rogaland Research has shown that the density slope is 9.5 kg/m3*bar from 1 to 500 bar, while it is 75.8 kg/m3*bar from 500 to 1000 bar.

Oil solubility The Oil Solubility table is used for entering measurements of the solubility of gas in the oil phase of the mud. Temperature data are entered in the first row and pressure points in the first column. The solubility for each pair of pressure and temperature is entered. The table should cover the whole range of pressure and temperature relevant for the simulation. If the temperature and pressure during simulation goes beyond those covered in the table, the solubility values will be extrapolated from the table. This can cause large inaccuracies. The first row in the table should always contain data at 1 bar. This is used as a reference point in the computations. This table is not needed unless Measured PVT is chosen as PVT model 4.8.2.2 Black oil For the Black oil PVT model, the mud properties for elevated pressure and temperature are based on empirical correlations. There is no requirement to base oil chemical composition. This option is suitable mainly for dry gas influx.

Figure 4-26 Selection of Black oil PVT model The black oil model is not suitable in cases with excessive amount of dissolved gas, which typically occurs around 5-600 bar for dry gas influx. However, this limit is case dependent and not absolute. 4.8.2.3 Compositional For the Compositional model, the mud properties as function of pressure and temperature are calculated based on Equation of State (EoS). The compositional PVT model is recommended when experimental data are not available. The compositional model is suitable for influx types ranging from dry gases and condensing gases to oils, and is reliable also for extreme (HPHT) conditions.

Figure 4-27 Selection of Compositional PVT model

The Properties button activates a window for selection of base oil composition. Input Parameters

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Figure 4-28 Selection of base oil composition Compositions for common base oils are predefined; Diesel, Paraffinic, and Low Toxicity. The user can either select one of the predefined compositions, or if more specific data for the base oil composition is available, it can be entered by choosing Custom. The density of the base oil is now calculated by the compositional model, and the Base oil density, ref. Figure 4-24, is no longer required input. Once the simulation is started, the calculated base oil density is written to the log window. The EOS used is Soave-Redlich-Kwong with Peneloux volume correction term.

4.8.3

Rheology Three rheology models can be selected; Robertson-Stiff, Power Law and Bingham. Robertson-Stiff is the recommended model for most situations.

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Figure 4-29 Rheology input The rheology curve can be specified as a table of shear rate vs. shear stress (Fann reading). The rheology table is a spreadsheet table and it is possible to use copy and paste between other programs and Drillbench. If Robertson-Stiff is chosen as rheology model, where applicable, the table should contain at least three Fann readings. Rheology data can also be given in terms of plastic viscosity (PV) and yield point (YP). It is assumed that the rheology data entered is valid at atmospheric pressure and 50 °C (122 F).

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Reservoir The reservoir and type of influx fluid are defined in the Reservoir input window, as shown in Figure 4-30.

Figure 4-30 Reservoir window Reservoir zone The name of the reservoir zone is entered in the column Lithology name. Lithology is used as a term for the material in the surroundings of the well. The columns Top and Bottom define the upper and lower boundary of the reservoir zone and are given in metered depth from RKB. Reservoir top must be between last shoe depth and the bottom of the well. In case a drilled kick is to be simulated, it can be a good approach to set the reservoir top at the bit depth. Then the bit penetrates into the reservoir at simulation start-up (remember to choose a rate of penetration (ROP) above zero). Top pressure and Top temperature is the pressure and temperature in the reservoir at the top depth. The Influx column defines the rate of influx into the well. Clicking in the Influx column activates the cell for edit and a button appears in the right end of the cell. Pushing this button opens a window as the one shown in Figure 4-33.

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Figure 4-31 Specification of influx rate Two models are available, Reservoir model or Constant.  Reservoir model: influx rate depends on Permeability, Porosity, the length of the reservoir exposed to the well and the drawdown (i.e. the difference between bottomhole and formation pressure). The Reservoir model is typically used for simulation of drilled kick  Constant: influx is injected into the borehole at a constant rate specified by the user, regardless if there is underbalance or not. The rate is determined by a Volume injected over a certain Duration of time. The Volume refers to gas influx at reservoir conditions. If the reservoir fluid is heavier, the kick size may differ from the specified volume due to volume conversion. The influx stops when the borehole is shut in. If the bore hole is not shut-in when the Duration period is exceeded, the influx model automatically switches to Reservoir model and a further influx rate is calculated based on the conditions in the wellbore. Constant model is typically used for simulation of swabbed kick. It is possible to specify two reservoir zones at different depths and with different influx models.

Reservoir fluid Type of influx fluid is selected from the dropdown list in the reservoir fluid section.

Figure 4-32 Selection of influx fluid If more than one influx zone is defined, the influx fluid is the same for both zones. What type of input information is required for the reservoir fluid depends on which PVT model is selected in the Sub-model window. The available PVT models are Measured, Black oil or Compositional. The label showing the currently selected model is a hyper-link which can be clicked to quickly jump to the model selection page.

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Measured or black oil PVT model The type of fluid is selected from the dropdown list. The user can choose between predefined fluids for common fluid types; Methane, Dry gas, Volatile oil or Black oil. The fluid properties are listed in the table below. If more specific data for the reservoir fluid is available, the user can choose Custom from the dropdown list. By pressing the properties button, a window is opened where the user can specify data for the fluid, as shown in Figure 4-33.

Figure 4-33 Customized reservoir fluid properties for Measured or Black oil PVT model The user must select whether the influx fluid is to be regarded as gas only. This is done by enable the Is gas checkbox. Only very lean gases should be regarded as gas only, i.e. gases like dry gas or leaner. All other fluids should be treated with possibility for oily components as well. With condensing influx (i.e. not dry gas), the reservoir oil will mix with the mud and can significantly alter the mud properties. This is an irreversible change, in contrast to dissolved reservoir gas, which is released from the mud when approaching surface conditions. Generally, all fluids with the exception of very lean gases should be treated as “oil” to capture this effect. The density of the influx gas is specified at standard conditions. If any contamination is present, the amount of contamination is specified as well (on molar basis). The available impurity gases are: Nitrogen N2, Carbon Dioxide CO2 and DiHydrogen Sulphide H2S. The gas density should include the contaminations. For fluids heavier than very lean gases, both properties for the influx gas and influx oil must be specified. Oil density, compressibility and Gas oil ratio (GOR) are given at standard conditions, while oil formation volume factor and oil viscosity are given at reservoir conditions. The properties for the predefined fluids are listed in the tables below.

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Table 1

Properties for predefined fluids

Oil density [kg/m³]

Gas density [kg/m³]

Black oil Volatile Oil Dry Gas Methane

839 830 -

1.235 1.041 0.680 0.659

Reservoir fluid

Oil density [lbm/ft³]

Gas density [lbm/ft³]

Black oil Volatile Oil Dry Gas Methane

52.38 51.82 -

0.0771 0.0650 0.0425 0.0412

Reservoir fluid

GOR [Sm³/Sm³]

Oil Compressibility [1/bar]

Oil volume factor [-]

Viscosity [cp]

1.623E-04 3.165E-04 -

1.341 1.787 -

0.536 0.245 -

Oil Compressibility [1/psia]

Oil volume factor [-]

Viscosity [cp]

1.119E-05 2.182E-05 -

1.341 1.787 -

0.536 0.245 -

106 486

GOR [scf/stb] 595 2729

Note: Reservoir conditions for the predefined fluids are assumed 180 bar (2611 psi) and 70 °C (158 F). The oil formation volume factor and oil viscosity should be updated according to the current reservoir conditions.

Compositional PVT model If Compositional model is chosen in the Mud input window, ref. section 4.8.2, the reservoir fluid composition needs to be specified. Predefined influx compositions are available from the dropdown list. The predefined influx compositions cover the range of typical North Sea fluids, such as Methane, Dry gas, Lean condensate, Rich condensate, Volatile oil and Black oil. See Chapter 11.1.3 for further information about the predefined fluids. If detailed information about the reservoir fluid is available (e.g. from gas logs, PVTreports for wells in the vicinity, etc.), the compositional data can be entered by choosing Custom in the dropdown list. The input window is then available from the Properties button, as shown in Figure 4-34. The reservoir fluid is characterized by mole fractions of hydrocarbons grouped into single carbon number groups C1 to C19. All heavier compounds are to be lumped into the C20+ fraction (molar basis). These are the data commonly available from gas chromatography (GC) and fractional distillation. If any contamination is present, the amount can be specified for: Nitrogen N2, Carbon Dioxide CO2 and DiHydrogen Sulphide H2S.

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Figure 4-34 User defined reservoir fluid composition Properties for the reservoir fluid are calculated based on the Soave-Redlich-Kwong EoS with Peneloux volume correction term. Once the simulation is started, the density and GOR calculated for the reservoir fluid is written to the log window. The Compositional PVT model is closer described in Chapter 11.

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Temperature

Figure 4-35 Temperature input window There are two temperature options available, Measured or Holmes and Swift. The option to use is selected from the drop down list.

4.10.1 Measured If measured data for the mud temperature along the borehole is available, the data are entered in the two tables. There is one table for mud temperature inside the drill string and another table for mud temperature in the annulus. Measured depth is entered together with the corresponding temperature. The number of pairs may be different for annulus and drill string. The first data points in the tables are the mud temperature at surface. The program interpolates linearly between the given temperature points when computing the temperature profile. Thus, in deep water wells, the annulus temperature at the BOP depth should always be given.

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Note: If measured data is not available, it is recommended to calculate the mud temperature profile by using the dynamic temperature model in Drillbench® Presmod and copy the result into the tables in Kick. A Kick input file can be opened and run in Presmod. It only needs to be updated with data connected to the temperature calculations.

4.10.2 Holmes and Swift The Holmes and Swift model is a fairly basic temperature calculation based on geothermal gradient and heat transfer to the surroundings. The ambient temperature at surface, geothermal gradient and outlet temperature from the choke line must be specified. In offshore wells, the surface temperature is the sea water temperature. HTC across drillpipe is the heat transfer coefficient between the drill string and annulus, HTC across wellbore is the heat transfer coefficient between the annulus and the formation. Suggestions if thermodynamic parameters are not known: 

Heat transfer coefficient across drillpipe: 170 W/m2.K



Heat transfer coefficient across wellbore face: 5.6 W/m2.K

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5

EXPERT INPUT PARAMETERS

5.1

Model parameters The model parameters window defines mathematical correlations and numerical parameters for the simulation.

Figure 5-1

Model parameters window

Number of grid cells The number 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 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 linearly with respect to the grid cells. To avoid the simulation becoming too time-consuming, the recommended value for this parameter is around 90. Maximum number of cells is 2000.

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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 moves together with the string. A fixed point refers to a fixed depth, independent of string movement or bit position.

Lost circulation The lost circulation input data group refers to modeling of mud losses to the formation and a possibly lost circulation situation. Formation initiation and closing pressures are defined in the Fracture pressure window, see Chapter 4.7.

Figure 5-2 Specification of lost circulation parameters The Amount of fluid returned is the fractional amount of fluids lost in the fracture that will return into the annulus when the fracture closes. A value of 1 means everything will re-enter annulus. The default is set to a value of 0.5. The Secondary fracture initiation factor (SFIF), sets the fracture initiation pressures for a second time fracture. If the well should fracture a second time during a simulation, the difference between the fracture pressure and the fracture initiation pressure is reduced by a factor of SFIF. So a value of 1 means that the initiation fracture pressure is unchanged, a value of 0.5 means that the initiation pressure will be reduced by half the difference between the fracture pressure and the old initiation pressure. The formula is:

Second frac.init.pr. =Frac.init.pr. + (Frac.init.pr. - frac.pr.) * SFIF

If the amount of fluid returned is set to zero, the closing pressure should be set equal to the fracture pressure. Note: Lost circulation is only active when running interactive simulation in manual choke mode.

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Separator A poorboy degasser can be included in the simulation by enable the Separator checkbox.

Figure 5-3. Input for poorboy degasser The geometrical parameters, such as Height and Diameter must be given. It is assumed that the separator is cylindrical. If the horizontal cross section is not circular, specify diameter such that the cross sectional area is correct. Level is the vertical level of the separator inlet relative to drill floor. Flare and Pit line dimensions are also defined in the Separator section. The entry fields are only needed when a poorboy degasser is modeled. Pit line liquid seal is the highest vertical level of the mud line between separator and pit tanks. This is measured relative to the mud outlet of the separator. The gas separator calculations use very small time steps in order to calculate dynamic effects. They therefore slow the calculation somewhat as soon as gas enters the choke line. Once the mud level exceeds the top of the separator or empties, a warning message is given and the simulation continues with no gas separator calculations. Results from the separator module are provided interactively, and not saved to files. It is therefore automatically disabled in batch and kick tolerance calculation mode.

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Degasser capacity is the maximum flow rate that the separator can handle. It is used by the sensitivity simulation to calculate the maximum circulation rate that can be handled without exceeding the degasser capacity.

5.2

Sub-models Two-phase pressure loss model Two options are available for calculation of Two-phase pressure loss; Beggs and Brill and Semi-Empirical. The Semi-Empirical is the recommended choice in most cases.

PVT model The PVT section defines the variation in mud properties with elevated pressure and temperature. There are three alternative ways of estimating these properties: Measured, Black oil and Compositional. The method is selected from the PVT model drop-down list.

Figure 5-4 Selection of PVT model When using the Compositional model you can optionally specify the PVT range. Default range is 10ºC to reservoir top temperature, and 1 bar to reservoir top pressure + 100 bar. The user can override these values by clicking the check box and entering a different value.

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6

RUN CONFIGURATION

6.1

Batch configuration The Batch simulation mode gives the user an opportunity to run one or several simulations without any interaction from the user. The operational conditions are defined prior to simulation start and the well control procedures are performed automatically. Several operational scenarios can be predefined. On the Run configuration navigator bar there is an icon for Batch configuration, as shown in Figure 6-1. Each simulation has its own set of operational data, and more simulation scenarios are added by using the Add button at the bottom of the window. A simulation scenario can be deleted by using the Delete button. A set of batch simulations are stored as part of the case file when using the File  Save option from the menu bar. All the simulations defined in one batch are based on the same input file.

Figure 6-1 Set of batch simulations

Pre-kick circulation period defines the circulation rate before a kick is taken. Up to two circulation periods can be defined, with different pump rates and duration. After the pre-kick circulation periods, the kick is taken at the circulation rate specified in the Interactive simulation control panel. If no pump rate is specified in the Interactive simulation control panel the kick is taken without circulation.

The Kick intensity defines the degree of underbalance and thereby also defines the rate in which the kick is taken; see Figure 6-2 below. The corresponding formation Run configuration

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pressure is determined by the specified kick intensity and the reservoir pressure defined in the Reservoir input parameter window is not used.

Pressure gradient

Formation pressure

underbalance

kick intensity

Flowing bottomhole pressure

Hydrostatic head

Time

Figure 6-2 Definition of kick intensity

The pit alarm level indicates when the kick is detected at surface. When the alarm is triggered, the simulator will start the shut in procedure. The shut in procedure is performed according to the operational times given in the Surface equipment group in the Input Parameter section. It is possible to perform a flow check after the pumps are stopped. The flow check may continue a certain time, or until a certain volume increase in the pit is achieved. The selection is made from the drop down list. After the well is shut in, the wellbore pressure can be allowed to stabilize. The shut in time is either set by the user, or the well can be kept shut in until the bottomhole pressure equals the pore pressure and the influx has stopped. This is selected from the Shut in period drop down list. Circulation rate is defining the pump rate when circulating the kick. The circulation of the kick can be performed in three different modes; Drillers method, Wait and weight and Reference depth.

6.1.1

Drillers method The bottomhole pressure during circulation of the kick is controlled according to the shutin pressure plus a pressure margin to pore pressure defined by the user in Dynamic safety margin and the kick circulation rate. After the kick is circulated out, a kill mud is circulated at a given Kill mud circulation rate. The kill mud weight is calculated based on the Static safety margin.

6.1.2

Wait and weight Circulation is performed according to a kill sheet computed by the simulator, with pre-determined pump pressure versus time. The static safety margin is taken into account in the computation of the kill mud weight. Run configuration

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6.1.2.1 Reference depth In this mode, the choke pressure while circulating the kick is controlled in order to keep the pressure at a certain well position constant. The depth and the corresponding pressure at this depth is specified by the user. Clicking the Calculate preview button will calculate and show the corresponding reservoir pressure for the entered kick intensity, and the corresponding ECD for the entered circulation rate. After the button is pressed, these values will update live when changing the kick intensity or circulation rate. The preview is dependent on the selected mud. Changing the mud type or mud density will require clicking the Calculate preview again.

6.2

Sensitivity configuration The Sensitivity simulation mode is a tool for running a number of sensitivity simulations. The well control procedure is defined up front and the sensitivities are run automatically without any user interaction. Combining different sensitivity parameters the user can simulate many different sensitivity scenarios, e.g.: 

Maximum kick size vs. kick intensity



Casing shoe position vs. kick intensity



Degasser capacity vs. kick intensity

This input page enables configuration of the initial parameters, detection and well control procedures as well as the two sensitivity parameters. See Figure 6-3.

Figure 6-3 Sensitivity configuration The sensitivity parameters are divided in groups of similar or equivalent parameters: Run configuration

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1. Rate 

Circulation rate

2. Reservoir (equivalent, based on mud type, density and pump rate) 

Kick intensity



Reservoir pressure

3. Kick detection (similar) 

Kick Size (after pump off, reservoir)



Pit alarm level (after or when pump off, at surface)

The input expects that the two parameters are of different parameter groups and will not pass validation if they belong to the same group. The selected parameters will disable the input which is already covered by the parameters and enable the missing input fields belonging to the parameter group not covered by the parameter selections. Flow check, initial without reservoir and circulation mode without circulation rate are always mandatory input. Clicking the Calculate preview button will calculate and show the corresponding reservoir pressure for the entered kick intensity (or vice versa), and the corresponding ECD for the entered circulation rate. After the button is pressed, these values will update live when changing the kick intensity, reservoir pressure or circulation rate. The preview is dependent on the selected mud. Changing the mud type or mud density will require clicking the Calculate preview again.

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MENUS AND TOOLBARS Menus and toolbar icons have standard Windows functionality. We assume that Kick users are familiar with Windows operations, and will only describe the menu and toolbar functions specially designed for Kick.

7.1

File

7.1.1

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 7-1. New file dialog

7.1.2

Open Open a file using a standard file selection dialog.

7.1.3

Reopen Reopen one of the last used files.

7.1.4

Save Save a file using a standard file selection dialog.

7.1.5

Save as Save a file under a new name using a standard file selection dialog. Menus and toolbars

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Save as template Save the file as a template-file.

7.1.7

Save library Save all data in the library.

7.1.8

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 7-2. 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.

7.1.10 Exit Exits the application.

7.2

Edit Standard windows functionality.

7.2.1

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.

7.2.2

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.

7.2.3

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.

7.2.4

Undo Standard windows functionality.

7.3

View Used to switch between Input, Optional Input and Calculation on the Navigation bar. The Navigation bar and Log view can be displayed and hidden by checking or unchecking their tag in the menu.

7.3.1

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. 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… .

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Figure 7-3. Well schematic view 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. Hovering the mouse cursor above elements in the well schematic will highlight the element under the cursor and show the element name. See Figure 7-4.

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Figure 7-4 Highlight and hint in well schematic

7.3.2

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. 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.

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Figure 7-5. 3D-survey plot view

7.3.3

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 checkbox 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. Menus and toolbars

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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.

7.3.4

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.

7.3.5

Input Switch to an Input window.

7.3.6

Expert input Switch to an Optional input window.

7.3.7

Run configuration Switch to Run configuration window.

7.3.8

Simulation Switch to a Calculation window.

7.4

Simulation The simulation control panel can be found both in the menu bar and as a separate toolbar.

Figure 7-6. 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 Kick tolerance simulation. The simulation is started by clicking Start, and it will continue to run until it is stopped by the user. When the simulation is started, this button changes to Pause (Figure 7-7). 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 7-7

The simulation control while running a simulation

By using Pause, changes in the operational conditions can be made at any time during the whole simulation. Menus and toolbars

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Start/Pause Start a simulation and to pause a simulation. Continue a simulation after a pause.

7.4.2

Step Run the simulation one step forward. The step length can be specified to a max length in the simulation window.

7.4.3

Reset Reset the simulation. All previous simulation results will be blanked out on the plots and the simulation will start from the beginning.

7.4.4

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.

Figure 7-8, Resuming simulation as a new simulation run

7.4.5

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.

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7.5

Results

7.5.1

Keep previous results You can choose to keep the results from previous simulations and run a new simulation. The new simulation will be plotted together with the previous simulation(s). This makes it easier to compare different scenarios or procedures. Starting a new simulation run with Keep previous results disabled will clear out all previous simulation results.

Figure 7-9 Results of running two simulations with keep results option “on”.

7.5.2

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.

Figure 7-10, Import of result across Presmod and Kick

7.5.3

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 Menus and toolbars

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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.

7.5.4

Manage results Manage results opens a result manager that allows definition of a label for each run which will show as a prefix in the plot legend. There is also a global option to disable simulation runs in all result plots, and an option to delete all results of a simulation run.

Figure 7-11: Result manager

7.5.5

Add page If you want to add more result pages for custom plots or special plot setups, you can add a page where you can add new plots.

7.5.6

Current page This submenu contains page operations; actions that act upon the currently active plot page in the simulation view. Some of these operations are only relevant for custom plot pages, and will be disabled for the default page, which has a fixed layout. The submenu is unavailable altogether if the simulation view is not active. The page submenu can also be accessed as a context sensitive popup menu by right-clicking on a plot page tab.

7.5.6.1 Rename You can rename the custom plots pages to organize your plots. Pages can also be renamed by double-clicking on the page tab. 7.5.6.2 Normalize layout This will restore the layout of a page with multiple plots to its default state. The page will be split successively into halves, so all splits will be centered vertically or horizontally within their region. This corresponds to how plot splits (Add operations) will be done before the user applies any manual adjustments.

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7.5.6.3 Load and save page layout Save page layout will save the layout of the current page, along with the page title and any customizations and axis settings, to a file that can later be imported into another page or another session using Load page layout. 7.5.6.4 Copy as image to clipboard An image of the entire plots page will be copied to the system clipboard. This can be copied into other applications for purposes such as information sharing and presentations. 7.5.6.5 Clear This operation removes all plots on the current page, leaving you with an empty plot page. The page title is retained. 7.5.6.6 Close Closes and discards the active custom plots page. You can also remove the current page by hitting Ctrl-F4.

7.5.7

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. The difference between these menu items and the ones in the Current page menu is that these operations save and load layout and customizations for all plot pages in the application, which is useful for creating comprehensive templates for typical plot configurations, while the Current page operations save and load a single page layout for reuse.

7.6

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 7-12. Toolbar.

7.6.1

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 7-13: 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.). Kick provides a default style sheet (ircss.css) which can be edited or replaced to match the user‟s preferred report style. Figure 7-14 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 7-14: Layout of the Input report Menus and toolbars

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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 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 7-15: Export of Survey data from a report to Excel

7.6.3

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 clicking its icon on the toolbar or by selecting Tools  Validate parameters from the menu bar.

7.6.4

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 7-16: Unit menu The unit menu allows quick change of unit sets and access to the unit edit page.

7.6.5

Options To open the options tab window, you can select Tools  Options from the menu bar or 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 7-17. The Drillbench option dialog.

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7.6.5.1 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 Kick the last time.

Remember last selected page Start at the page you were on when exiting Kick.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.

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Load plot style 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. 7.6.5.2 Appearance Allow the user to modify color theme, icon style and tab layout in Kick according to personal preference.

Figure 7-18 The Kick summary window with different color settings 7.6.5.3 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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7-19 Unit definitions

7.7

Help

7.7.1

Help topics To open the Help window in Kick 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 Kick. By pressing F1 from an input window, the help page for the current window will be displayed.

7.7.2

About The About option gives you information about Kick‟s version number and the expiry date of the current license.

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8

RUNNING A SIMULATION

8.1

Overview Three different types of simulation can be performed:  Interactive simulation: This runs a single simulation and allows the user to modify the operational parameters manually. During the simulation, messages from the simulator are given to inform about events. The user may change the control parameters during the simulation  Batch simulation: The changes in operational conditions are specified before starting the simulator. The whole simulation is performed without any interaction from the user  Sensitivity simulation: This mode is used to run sensitivity analyses for a predefined set of operational parameters. Combining different sensitivity parameters, a sensitivity simulation can be run to investigate many different scenarios including the maximum kick size, the casing shoe position or the degasser capacity.

8.2

Controlling a simulation Three buttons for controlling the simulator run is 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

8.3

Simulation window The simulation window is selected by clicking the Simulation tab in the navigator bar.

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Figure 8-1 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 is only shown when running in interactive simulation mode. It can be minimized by clicking the black triangle in the upper left corner of the panel.



Simulation results: The lower part contains a collection of page views for display of graphical result plots. Functionality pertaining to plot pages and result data is described in detail in chapter 9.

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Interactive simulation mode Figure 8-2 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 8-2

Interactive simulation

By default, a simulation starts using the mud defined in the Mud window in the input parameter section, the current mud density is shown in grey font. If a heavier or lighter mud is to be circulated, it is possible to alter the mud density by enable the checkbox in front of the mud density field, both prior to simulation start and during a simulation. Reservoir pressure is the pressure in the formation at TD. The value specified in the Reservoir input parameter group is automatically suggested as initial value. The user may for instance want to temporarily change the reservoir pressure in order to impose influx into the borehole when simulating a swabbed kick. The Rate of penetration indicates how fast one is drilling into the reservoir and determines the length of the reservoir that is exposed to the well in case of a drilled kick. The penetration stops when the pump is shut down. The Pump can be turned on or shut down by using the radio buttons. The circulation rate can be modified during a simulation by entering the new rate. The BOP and Choke status can be set to Open or Closed. The choke opening can be manually controlled by the user if the simulation mode is set to Manual (see below). The Pit alarm level is indicating when the kick is detected at surface. The simulation is automatically stopped when a kick is detected and a message is given in the log window, leaving the user free to do the appropriate action, i.e. a shut in procedure. Running a simulation

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Other kick detection criteria may be used, but the simulator stops automatically only on pit gain level. After the kick has been taken, the well can be shut in and the kick circulated out at a rate specified by the user. The Circulation mode is related to the pressure control during circulation of the kick. The circulation mode field is a drop down list, which offers the user four choices; Manual, Constant bottomhole pressure, Reference depth and Kill sheet.

Manual In this mode, the user has full control of the process. During circulation, the user can manually change the choke opening, the BOP status, the pump rate, the mud density etc. Thus, the user can control the kick by manipulating the same control as in real life well control. This mode enables simulation of lost circulation. (See Chapter 12 - Lost circulation.)

Constant bottomhole pressure In this mode, the choke pressure while circulating the kick is computed automatically by the simulator in order to keep the bottom hole pressure constant. The bottom hole pressure during circulation will equal the bottom hole pressure immediately before starting the circulation of the kick, plus an additional safety factor defined by the user in the field Dynamic safety margin. In this mode, the user does not have to worry about the choke opening during kill at all.

Reference depth In this mode, the choke pressure while circulating the kick is computed automatically by the simulator in order to keep the pressure at a certain well position constant. The depth and the corresponding pressure at this depth are given by the user.

Kill sheet Circulation is performed according to a kill sheet computed by the simulator. The kill sheet can be opened by View  Kill sheet from the menu bar after the simulation is started, a kick is detected and the well is shut in. The circulation is performed automatically according to this curve.

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Figure 8-3

Kill sheet

The low circulating pressure is the Shutin casing pressure and Shutin drill pipe pressure is the choke and stand pipe pressure at shut in. The kick circulation rate is specified by the user in the Low circulation rate field. The static safety margin is representing how large safety factor to the pore pressure is required. The kill mud weight is then calculated automatically to meet this requirement. Alternatively, the user can specify the kill mud weight directly. The curve is illustrating the development of the stand pipe pressure that will be observed during circulation of the kick when following the outlined procedure. The time and number of strokes required to circulate the kick is calculated and displayed above the plot.

8.5

Batch simulation mode The Batch simulation mode gives the user an opportunity to run one or several simulations without any interaction from the user. The operational conditions are defined prior to simulation start and the well control procedures are performed automatically. See section 6.1 for a description of the input configuration. The Batch simulation can be started and controlled by selecting Batch simulation and using the control buttons in the toolbar. The simulator runs through all the predefined scenarios, one by one. The results are viewed in the Simulation window. Figure 8-4 shows the Simulation window when a batch simulation is running. A progress bar in the bottom right corner shows how far the simulation has come in the batch job. The progress bar color indicates the state of the simulation: It is green while running and yellow when simulation is paused. The lower part of the window shows the standard graphics display. The plot functionality is described in detail in chapter 9. Running a simulation

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Figure 8-4

8.6

Running a batch simulation

Sensitivity simulation The Sensitivity simulation is a tool for running a number of sensitivity simulations. The well control procedure is defined up front and the sensitivities are run automatically without any interaction from the user. Combining different sensitivity parameters the user can simulate many different sensitivity scenarios, e.g.: 

Maximum kick size vs. kick intensity



Casing shoe position vs. kick intensity



Degasser capacity vs. kick intensity

See section 6.2 for a description of the input configuration. When pressing Start, the simulator runs through the well control scenario for each of the sensitivity simulations, i.e. taking a kick, shut in the borehole, stabilize and circulate out the kick according to the defined well control procedure. The shut in procedure is performed according to the operational times specified in the Surface equipment group in the Input section. Graphical output can be viewed during the simulation course. Trend and profile plots are viewed the same way as for interactive and batch simulations. The sensitivity summary plot consists of a set of isobar curves and user selected x- and y-axis. When first opened the plot will by default show sensitivity parameter 1 on the x-axis and casing shoe position on the y-axis. The x-axis parameter and y-axis value can be changed by right-clicking on the plot and selecting from the menu. Possible parameters Running a simulation

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 Circulation rate  Kick intensity (equivalent reservoir pressure based on mud type, density and pump rate)  Kick Size (after pump off, reservoir)  Kick volume (effective kick size, after BOP closed, reservoir)  Pit alarm level (after or when pump off, at surface)  Pit gain (effective, after BOP closed, at surface)  Reservoir pressure (equivalent intensity based on mud type, density and pump rate) Parameters are only available for selection if they are selected as sensitivity parameters or belong to the same parameter group (see section 6.2). Y-axis value can be one of the following:  Casing shoe position (maximum during out circulation)  Degasser capacity (maximum during out circulation)  Kick volume (effective kick size, after BOP closed, reservoir)  Pit gain (effective, after BOP closed, at surface)  Pressure difference at casing shoe (maximum during out circulation) Degasser capacity is only available if a separator has been specified. The isobar curves use the remaining parameter of the 2 parameter groups which is not already covered by the parameter choice. I.e. if sensitivity parameter 1 has been chosen as x-axis parameter, the plot will contain one curve per step of parameter 2 with the parameter value printed in the legend. See Figure 8-5.

Figure 8-5 Sensitivity: Different summary plots. Running a simulation

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WORKING WITH KICK RESULTS Kick includes tools and features that are very valuable for day to day engineering as well as operation decision support. This chapter describes the functionality of the plots and plot pages in detail, and provides some usage examples.

9.1

Plot page operations Operations that deal with page organization and management are available from the Results  Current page menu on the main menu bar (see section 7.5.6 on page 53 for a description of these menu items). Right-clicking on one of the page tabs produces a context-sensitive popup menu (see Figure 9-1) that offers the same selections as the main menu item.

Figure 9-1: The tab context menu showing page operations.

9.2

Plot management The different plot windows can be used for displaying the results as the simulation runs. The graphical section in the Simulation window is divided into different views or pages, which are easily configurable. Kick 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 pages. To view a plot, click on the right mouse button in one of the pages. A context menu (see Figure 9-2) will appear with a set of operations, including layout, plot customizations and options, plot selection and more, based on the state of the page.

9.2.1

Set and plot selection In an empty page, Set is the only available option. Set has a submenu listing all available plots, organized into categories. Trend plots are time series. Profile plots show current conditions throughout the well, which will change as the simulation runs. 3D Wellbore is a graphical representation of conditions on the well shown on a three-dimensional well geometry. Summary plots are used for sensitivity simulations. To add a plot to an empty page, navigate the Set submenus and select a plot. Using Set on an existing plot will replace the plot with the new selection. Working with Kick results

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Figure 9-2: Plot selection in the plot context menu

9.2.2

Add To add more plots to a page, use Add. Placement of added plots is determined by the location of the mouse pointer when you right-click to open the plot context menu. Drillbench uses diagonal quadrants to determine where the new plot will be placed. The direction zones are illustrated in Figure 9-3, below. Right-clicking anywhere within a zone will produce a context menu where the Add item indicates the direction that corresponds to that zone. Right-clicking in the Above zone will produce a menu with an Add above item, and so on. An Add will split the current plot in half, and add the new plot on the appropriate side of the split. Add operations offer the same organization and selection of plots as the Set menu shown above.

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. Figure 9-3: Direction zones for Add operation

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. Plots can be resized freely by dragging the splitters to the desired position. The configuration of all pages will automatically be saved to the input file. You can manually export the layout, including plot selections and configurations, in the active plot page by selecting Save page layout from the Results  Current page menu, or from the page context menu accessed by right-clicking the page tab. The plot page layout can then later be reused in other simulations by adding a new plot page and selecting Load page layout. To export the configuration of all custom plot pages to a single file, select Save layouts in the Results menu (on the main menu bar); select Load layouts to load or restore all custom plot page configurations.

9.2.3

Reset plot This menu operation returns the plot to its default configuration. This will delete any imported curves, undo any customizations (to axes, colors, fonts etc.) and zoom out to the default full view.

9.2.4

Remove plot Remove plot will erase the plot and remove its associated splitter frame, and accordingly reorganize the layout of the plots page.

9.3

Plot operations The rest of the plot context menu contains operations that mostly act upon a single plot. Some of these operations are common for all plots.

9.3.1

Maximize plot The first of the sizing and placement operations in the Layout submenu will resize the current plot to the maximum possible size within the constraint of the plot page. Working with Kick results

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The other plots and splitter walls will still be there, but squashed as much as possible. This can be useful if you need to focus on details in a particular plot.

9.3.2

Normalize Normalize, in the Layout submenu, is really a page-wide operation, but is also available from the plot popup menu because it can be seen as a complement of the Maximize operation (but not the opposite or reverse). It does the same thing as the Normalize layout items in the tab popup menu and the Results menu; which is to restore the layout of a page with multiple plots to its default layout. This involves adjusting the splitter positions, and thereby the plot size ratios, so that all splits divides their target pane in half. This is illustrated in Figure 9-4. Note that the Normalize only returns layout to its default state – it does not undo the specific effects of the Maximize.

Figure 9-4: Normalized layout in a plot page with three splits; a vertical, followed by a horizontal split in the right pane, then another horizontal split in the top right pane.

9.3.3

Swap with selected plot The final item in the Layout submenu allows you to reorder plots within a page by swapping them. If you click a plot on the page, it will get a red border. This signifies that the plot is now selected. Right-click the other plot you want to switch around and select Swap with selected plot. The plots will switch place on the page without otherwise affecting the page setup and plot sizing. Like other operations that affect plot organization, this operation is only available for custom plot pages, not for the default plot page. The menu item will also be unavailable if you have not first clicked another plot to select it.

9.3.4

Track values Track values allows you to inspect actual numerical values from a plot. The indicator line in the plot can be dragged to the desired position. Color coded data values from all curves in the plot will be continuously updated based on the indicator position.

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Figure 9-5: „Track values‟ in action in a pressure plot.

9.3.5

Print Selecting Print from the plot popup menu will open a print preview dialog, which allows you to select a device for printing and adjust print options. Some manipulation of chart characteristics is also possible at this level; the detail level for axes and the grid can be adjusted, and the plot can be printed as a bitmap (Smooth) or natively using the device resolution.

9.3.6

Import Import lets you import curve data for a single curve at a time from a column based text file. The file could contain data exported from a Drillbench plot from the Data tab of the Export dialog (described in section 9.3.7), or data from an external plot. This makes it easy to compare Drillbench results to measured data or results from other simulations. Selecting Import will open a file dialog which lets you browse to and select a data file. After this, a file import tool will open up (Figure 9-6). This tool allows you to select columns for import, assign measurement units used in the file, and set header and footer lines to be skipped. Dragging the column header Temperature (Celsius) to column number 3 will make Drillbench interpret column 3 as temperature, in degrees Celsius. An example of a Drillbench plot (from Presmod) with an imported curve is shown in Figure 9-7.

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Figure 9-6: Data file import.

Figure 9-7: Temperature plot with imported data (green curve).

9.3.7

Export The plot Export tool includes facilities for exporting a plot picture, under the Picture tab (Figure 9-8) or plot data, under the Data tab (Figure 9-9). Plot pictures may be copied to the clipboard or saved in any of a number of file formats:  Windows bitmap  Windows metafile Working with Kick results

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 VML  PNG  PDF  PCX  JPEG

Figure 9-8: Exporting a plot image. These file formats are widely recognized by Windows programs, and the exported plot picture can easily be included in reports, web pages and presentations.

The full data contents of the plot can similarly be copied to the clipboard or exported to file in a number of formats:  Text  XML  HTML table  Excel

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Figure 9-9: Exporting result data. Exported data can later be imported into external applications such as Excel for processing or presentation purposes, or they can be imported back into other Drillbench plots using the plot Import feature.

9.3.8

Copy image to clipboard This menu item will let you copy an image of the current plot to the clipboard directly without going via the Export dialog.

9.3.9

Plot properties A wide array of plot properties can be modified using the Properties dialog, available from the plot popup menu.

Figure 9-10: The plot properties dialog.

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Options available for modification include plot title, axis style and settings, horizontal and vertical grid lines, line style, point style, and more. In a plot with multiple curves, modifications can be made individually for each curve.

9.4

Profile plot operations For profile plots, the plot popup menu contains a set of operations specific to this type of plot.

9.4.1

Take snapshot Take snapshot will store the currently shown profile curves as a “ghost image” in the plot. By using the slider to navigate through the simulated sequence of events and storing one or several snapshots along the way, the progression of a physical property throughout the depth of the well over time can be visualized in a single plot. This can be useful for inspection and analysis, as well as for presentation purposes. By selectively storing snapshots at key points in time, before/after effects related to simulated events may be emphasized.

9.4.2

Create trends at observation points Opens a popup window with a chart showing trends for the current result parameter at custom reference points. Reference points are defined in the table on the right side of the plot. Rows are added to the table by pressing Tab or arrow down.

Figure 9-11: Trends at two depths, opened from the pressure profile plot. Printing, import/export and configuration is available from the right-click menu in the popup window. Trends can be generated from the Current run, the Previous run, or from All runs in sessions with multiple runs and Keep previous results active. Pressing the Copy curves button will copy trend curves to memory for inclusion in an existing trend plot using Paste as custom curves, see below. Working with Kick results

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Curve operations For regular plots (trends and profiles), the popup menu contains a set of functions that allows you to directly copy curves between plots without having to go via file export and import.

9.5.1

Copy curves Copy curves will grab a selection of curves from the current plot for later inclusion in other plots. The submenu specifies which curves to grab:

9.5.2



Current run is the current result set native to the plot, i.e. the most recent choke pressure result curve in the choke pressure plot.



Previous run is the native result curve from the previous run. This is only applicable in a session with multiple runs and Keep previous results active (see section 7.5.1 on page 52 for details).



Custom will grab all non-native curves from a plot. This includes curves that have been added using Paste as custom curves as well as curves that have been added from file using Import.



All grabs all curves, native as well as custom, from all runs.

Paste as custom curves Adds the current curves in the curve buffer (added by Copy curves or Copy trends at observation points) into the current plot as custom curves. If the new curve data are not in the same unit group as the native curves in the current plot, a secondary axis will be added (see Figure 9-12).

Figure 9-12: Choke pressure trend plot with gas flow rate out added as a custom curve with dedicated secondary axis.

9.5.3

Clear custom curves Removes all custom curves, including curves that have been added from file using Import. Similar to Reset plot in that it restores the contents of the plot to only the default “native” curves, but does not revert zoom levels and custom configuration settings. Working with Kick results

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Trend plot switches The lowermost section of the plot popup menu contains a collection of switches, or toggle options, specific for the current plot type. For trend plots, these are:

9.6.1

Show timeline When on, displays a thin vertical line that indicates the current slider position. Helpful in correlating profile plots with trend results.

9.6.2

Show previous results When on, shows curves for previous runs in a session with multiple runs and Keep previous results active.

9.6.3

Flip axes When on, flips the axes around so the X (time) axis becomes vertical and the Y (value) axis becomes horizontal. This can be useful when using bit depth instead of time in trend plots, as this will produce a vertical depth-based plot similar to profile plots.

9.6.4

X axis Using this submenu, a trend plot can be presented based on a variety of reference parameters by setting the X axis to represent time, bit depth, or pumped volume.

Figure 9-13, Left: Pit gain in respect to pumped volume, right: x and y axes flipped

9.7

Profile plot switches

9.7.1

Show pore/fracture pressure When on, displays pressure/ECD pore and fracture margins as reference lines. This option is only applicable for pressure-related profile plots. Working with Kick results

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Show casing shoe When on, shows the position of the casing shoe as a horizontal reference line in the depth plot.

9.7.3

Fade recent results When on, displays profile curves from the last few steps of the current simulation run as increasingly faded curves (see figure).

9.7.4

Show minimum/maximum When on, displays running minimum/maximum curves for the simulation so far (see figure).

Figure 9-14: Left: Running minimum and maximum so far during the simulation. Right: Fading curves showing recent results. Both: reference lines for pressure margins and casing shoe position.

9.7.5

Show previous results When on, result curves from previous runs will be shown in the plot. This is only applicable in a session with multiple runs and Keep previous results active.

9.7.6

Slider The slider – which allows panning back and forth in results throughout the simulator run (or runs) – is coupled to time by default. Using this submenu, the slider can be set to pan along the bit depth or pumped volume axes. This corresponds to the way these parameters can be applied as the reference for the X axis in a trend plot. Working with Kick results

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Zooming For all regular plots, it is possible to zoom in and out to investigate the results in further detail. To do this, left-click, hold and drag the cursor to the right to zoom in. Left-click, hold and drag to the left to zoom out. If you have progressively zoomed in on a detail in several steps, each time you zoom out you will return the plot to the previous zoom level.

9.9

3D wellbore plots

Figure 9-15: 3D wellbore plot showing free gas in annulus (corresponds to the red curve in the conventional profile plot on the right hand side) The wellbore plots show depth-based results mapped onto a three-dimensional representation of the well trajectory. This can be an informative supplement to profile plots, and will effectively highlight any correlations with position and geometry. Wellbore plots are available for the same selection of result data as the profile plots. This section outlines the interaction features that are available for wellbore plots.

9.9.1

General functionality Wellbore plots behave much like profile plots. They show depth-based data, and the results they display are coupled to the current slider position. Well bore plots have a fixed view, and show a single result “curve” at a time. If you wish to see several properties in a wellbore plot, either switch back and forth between curves in a result set (e.g. tubing and annulus mud density profiles) by using Select curve, or open several wellbore plots side by side to show all profiles at the same time.

9.9.2

Select run In a session with multiple runs and Keep previous results active, select which run will be displayed on the wellbore here.

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Select curve For result data with multiple curves (e.g. tubing and annulus), select which of the profile curves to show on the wellbore here.

9.9.4

Holdup fraction view Fractional data (0-1, percent) can be displayed either in the normal mode (a color relative to minimum and maximum values, mapped on the surface of the wellbore “pipe”) or as a “holdup view”, which shows the absolute fraction as a wave amplitude along the wall of the pipe.

Figure 9-16: Wellbore plot showing free gas as holdup. Note that the radial extent of the holdup corresponds to the fraction shown in the profile plot (peaks at 50%).

9.9.5

Scale palette for entire run The color palette that is used to represent result data along the wellbore is relative to a minimum and maximum value. For each point along the wellbore, a color is assigned based on the result value at that depth relative to the minimum (dark blue) and maximum (bright red). If this switch is on, the minimum and maximum colors will at any given time represent the global minimum and maximum values for the entire simulation run thus far. So, for pressure, bright red corresponds to the maximum pressure that occurs anywhere in the well throughout the simulation. Other magnitudes are scaled and colored correspondingly. If this switch is off, the minimum and maximum colors are representative of the minimum and maximum values in the well at this point in time. The highest value along the well right now will be bright red, the lowest dark blue, regardless of the levels in prior steps. This coloring mode emphasizes where deviations occur rather than the scale of the deviations. Working with Kick results

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This is illustrated in Figure 9-17. The wellbore plot on the left side does not use palette scaling, and shows the position of the current free gas peak in bright red. The wellbore plot on the right side uses palette scaling, and therefore shows the situation in the wellbore relative to the overall maximum and minimum. The position of the peak is at the same position, but the intensity is scaled to show that the magnitude is only about a third of its maximum level. This corresponds to the profile and maximum curves in the profile plot on the right side.

Figure 9-17: Wellbore free gas plots with “scale palette” off (left) and on (right).

9.10

Multiple runs – keep results A very useful feature in Kick 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, it can be different case files or it can be imported results from other Drillbench applications. The example plots given below are taken from Presmod, and illustrate the effect of changing mud system. The same possibilities as shown in these figures are available in Kick. To perform multiple runs: Go to Results  Keep previous results. When the Reset button is pressed the time is set back to zero, but all the old results in the plots are still in place. 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.

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Figure 9-18 ECD as function of mud system. Figure 9-18 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.

9.11

Improved results view During a simulation the results of every time step are stored on a result stack. The results can be exported and imported at any time, also across to other Drillbench applications. Previous plot states can be accessed using a time slider. Time plots display an optional vertical indicator line – the timeline – according to the position of the slider. Depth profile plots show the profile state that corresponds to the slider position. By default, the slider is set to follow the simulation, i.e. plots show the results of the latest time step. Disabling this will allow you to inspect results at an earlier point in time while the simulation is running. Follow simulation is automatically disabled if you drag the slider during simulation. If you re-enable the option, the plots will again show the latest results.

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Figure 9-19, Time slider in operation. Profile plot shows results at 40 minutes. In a profile plot, the slider can be reconfigured to operate on pumped volume or bit depth instead of time. This is done on individual plots using the plot right-click menu (see 9.7.6 on page 79). This can be useful when comparing profiles from several runs that differ only in pump rate or rate of penetration.

9.12

Well schematic The flow areas of the well schematic can be colored in respect to the values of a profile plot by selecting Results  ; select None to switch off the coloring. Just like for profile plots, the values shown depend on the position of the time slider, so it is possible to slide manually backwards and forwards in time, or animate the display by having the slider follow an ongoing simulation.

Figure 9-20: Selection of the profile data to be visualized

The colors for minimum and maximum and the value range to be colored can be customized in the Data tab of the properties window, see Figure 9-21. Working with Kick results

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Figure 9-21: Well schematic showing actual free gas

9.13

Create presentation graphics Drillbench plots 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.

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Figure 9-22 Reconfigured temperature plot

In Figure 9-22, we have applied a number of customizations to a plot. (The original is shown in Figure 9-7 on page 73.) A plot legend has been added, the line color of the modified temperature data has been changed from green to blue, the line thickness has been increased, and the font size has been modified.

Figure 9-23 Plot properties menu

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RHEOLOGY MODELS The rheology model defines the shear stress of the fluid as a function of shear rate. This in turn defines the frictional pressure loss.

10.1.1 Generalised Newtonian models There are many rheological models to describe the non-linear proportionality between shear stress and shear rate. Most of the drilling fluids behave like yieldpseudoplastics, that is a minimum force must be applied to impart motion to them. This force is known as yield-point. In the following the actual models will be described.

Bingham model This is a two-parameter model with direct proportionality between  and  , in addition to a yield-stress y. The equation is

   y   p ,   y

(1)

  0    y 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  .

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

(2)

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.

Robertson-Stiff model This is a three-parameter model which includes Bingham and power law as special cases.

  A (   C ) B

(3)

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 . Rheology models

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This introduces a yield stress equal to

 0  AC B

(4)

The model simplifies to the Bingham model if B  1, or to the power law model if C  0.

Pressure and temperature dependent rheology The pressure and temperature dependence of rheology is described by correlation based models that have been developed by Rogaland Research. It is assumed that the rheology curve that is specified by the user is valid at atmospheric pressure and 50 C. The correlation describes the rheology of: WBM below 50 C WBM above 50 C OBM above 50 C The form of the correlation reflects the fact that rheology at high and low shear rates behave differently. In the kick simulator, all correlation are normalised to unity at atmospheric pressure and the temperature which the user specifies in the rheology input window.

Friction factor Friction factor in laminar flow The friction factor defines a generalised Reynolds number NRe by

f 

16 NRe

Friction factor in turbulent flow Turbulent flow behaviour is usually described in terms of the two dimensionless groups, Fanning friction factor f and Reynolds number. The Fanning friction factor is calculated following Reed and Pilehvari [47]. An expression that combines the Colebrook function [19] and Dodge & Metzner equation [12] is used when the flow is turbulent.

Transition from laminar to turbulent flow

Turbulence starts for Newtonian fluids when the Reynolds number is approximately 2100. For Non-Newtonian fluids the onset of turbulence is depending on the value Rheology models

(5)

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of n, the flow behaviour index. If n is 0.4, turbulence would not start until the generalized Reynolds number NRe reached approximately 2900. The dependence of n is expressed in following relation for the critical generalized Reynolds number [13]

NRe,cr  3470  1370n

(6)

10.1.2 Frictional pressure loss model Single phase flow The general equation for the frictional pressure loss gradient is [13].

2 fv 2  P      L  f Deff

(7)

where f is Fanning friction factor and Deff is the effective hydraulic diameter of pipe or annulus. The Fanning friction factor is calculated according to the rheological model chosen, and the prevailing flow regime.

Two phase flow A number of correlation have been developed for the two-phase frictional pressure losses and two of these are available in the simulator. These have been developed for Newtonian fluids in vertical pipes.

Beggs and Brill correlation with angle correction for liquid hold-up [18], [19]. This is developed using a Newtonian medium. To use this on a Non-Newtonian medium, we introduce the following changes: 1. We use a friction factor correlation that is developed for Non-Newtonian fluids. 2. The equivalent liquid viscosity is calculated according to a Non-Newtonian equation.

Semi-empirical pressure loss calculation In our simulator case we know the liquid hold-up at any time in the annulus. Therefore basically we do not need any correlation for liquid hold-up. We can then calculate the frictional pressure drop by the general equations for friction pressure loss using the physical parameters of the mixture rather than one of the phases. The two-phase friction factor is correlated to a generalised two-phase Reynolds number

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N Re,tp 

 m vm Deff f n   mix

by an appropriate friction factor correlation.

Rheology models

( 8)

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11

COMPOSITIONAL PVT MODEL

11.1

Overview Any mixing ratio of reservoir fluid and drilling mud can occur after influx in a well. The objective of the model described here is to predict the physical properties of this mixed fluid. A finite amount of gas is soluble in a liquid, causing the liquid to swell. The gas solubility is much greater at high pressure. This is the basis for a description of the volumetric behaviour of gas-liquid systems in terms of volume factors and a solubility ratio.

P

UNDERSATURATED LIQUID

FREE GAS

SATURATED, GOR=Rs or P=Pb GOR Figure 11-1. The regions determining the swelling behaviour of the liquid phase. (Typical.) The under-saturated liquid volume factor is a function of GOR as well as T and P, whereas the saturated does not depend on GOR. An approximate treatment where constant under-saturated compressibility is assumed therefore greatly reduces the size of the PVT-data set. Such a simplified formulation is used in Kick. Further discussion below.

11.1.1 Under-saturated liquid compressibility When a liquid is pressurized in the presence of gas, it behaves radically different above the pressure where all the gas is dissolved. This is the under-saturated region corresponding to P>Pb or, equivalently, GOR