Drillbench Kick User Guide Page i
TABLE OF CONTENTS
Page 1 GENERAL 1 1.1 Overview 1 2 MAIN ENVIRONMENT 2 2.1 Overview 23 CREATING A CASE FILE 4
3.1 Overview 4
3.2 The data model - DEML 4
3.3 New session (.dml) file 5
3.4 Editing an existing session (.dml) file 5
3.5 Library 6 3.5.1 Library editor 7 4 INPUT PARAMETERS 8 4.1 Summary 8 4.2 Description 9 4.3 Survey 9 4.4 Wellbore geometry 12 4.5 String 15 4.6 Surface equipment 17 4.7 Fracture pressure 19 4.8 Mud 21 4.8.1 Component densities 23 4.8.2 PVT model 24 4.8.3 Rheology 27 4.9 Reservoir 29 4.10 Temperature 34 4.10.1 Measured 34
4.10.2 Holmes and Swift 35
5 EXPERT INPUT PARAMETERS 36
5.1 Model parameters 36
5.2 Sub-models 39
6 RUN CONFIGURATION 40
6.1 Batch configuration 40
6.1.1 Drillers method 41
6.1.2 Wait and weight 41
6.2 Sensitivity configuration 42
7 MENUS AND TOOLBARS 44
7.1 File 44 7.1.1 New 44 7.1.2 Open 44 7.1.3 Reopen 44 7.1.4 Save 44 7.1.5 Save as 44 7.1.6 Save as template 45 7.1.7 Save library 45
7.1.8 Import 45 7.1.9 Export 46 7.1.10 Exit 46 7.2 Edit 46 7.2.1 Cut 46 7.2.2 Copy 46 7.2.3 Paste 46 7.2.4 Undo 46 7.3 View 46 7.3.1 Well schematic 46 7.3.2 Survey plot 48 7.3.3 Log view 49 7.3.4 Navigation bar 50 7.3.5 Input 50 7.3.6 Expert input 50 7.3.7 Run configuration 50 7.3.8 Simulation 50 7.4 Simulation 50 7.4.1 Start/Pause 51 7.4.2 Step 51 7.4.3 Reset 51
7.4.4 Load state from file 51
7.4.5 Save state… 51
7.5 Results 52
7.5.1 Keep previous results 52
7.5.2 Import results 52 7.5.3 Export results 52 7.5.4 Manage results 53 7.5.5 Add page 53 7.5.6 Current page 53 7.5.7 Load/save layouts 54 7.6 Tools 54 7.6.1 Take snapshot 54 7.6.2 Report 55 7.6.3 Validate parameters 56
7.6.4 Edit unit settings 56
7.6.5 Options 57 7.7 Help 60 7.7.1 Help topics 60 7.7.2 About 60 8 RUNNING A SIMULATION 61 8.1 Overview 61 8.2 Controlling a simulation 61 8.3 Simulation window 61
8.4 Interactive simulation mode 63
8.5 Batch simulation mode 65
8.6 Sensitivity simulation 66
9 WORKING WITH KICK RESULTS 68
9.1 Plot page operations 68
9.2 Plot management 68
9.2.1 Set and plot selection 68
9.2.2 Add 69
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9.2.4 Remove plot 70
9.3 Plot operations 70
9.3.1 Maximize plot 70
9.3.2 Normalize 71
9.3.3 Swap with selected plot 71
9.3.4 Track values 71
9.3.5 Print 72
9.3.6 Import 72
9.3.7 Export 73
9.3.8 Copy image to clipboard 75
9.3.9 Plot properties 75
9.4 Profile plot operations 76
9.4.1 Take snapshot 76
9.4.2 Create trends at observation points 76
9.5 Curve operations 77
9.5.1 Copy curves 77
9.5.2 Paste as custom curves 77
9.5.3 Clear custom curves 77
9.6 Trend plot switches 78
9.6.1 Show timeline 78
9.6.2 Show previous results 78
9.6.3 Flip axes 78
9.6.4 X axis 78
9.7 Profile plot switches 78
9.7.1 Show pore/fracture pressure 78
9.7.2 Show casing shoe 79
9.7.3 Fade recent results 79
9.7.4 Show minimum/maximum 79
9.7.5 Show previous results 79
9.7.6 Slider 79 9.8 Zooming 80 9.9 3D wellbore plots 80 9.9.1 General functionality 80 9.9.2 Select run 80 9.9.3 Select curve 81
9.9.4 Holdup fraction view 81
9.9.5 Scale palette for entire run 81
9.10 Multiple runs – keep results 82
9.11 Improved results view 83
9.12 Well schematic 84
9.13 Create presentation graphics 85
10 RHEOLOGY MODELS 87
10.1.1 Generalised Newtonian models 87 10.1.2 Frictional pressure loss model 89
11 COMPOSITIONAL PVT MODEL 91
11.1 Overview 91
11.1.1 Under-saturated liquid compressibility 91
11.1.2 Two-liquid formulation 92
11.1.3 Influx characterisation 92
11.1.4 Mud characterisation 94
12 LOST CIRCULATION 96
12.2 Fracturing 96
12.2.1 Fracturing the formation 96
12.2.2 The Fracture Volume 97
12.2.3 Fracture Closing 97
12.2.4 Mud mixing 97
13 KEYBOARD SHORTCUTS 98
Drillbench Kick User Guide Page 1
1
GENERAL
1.1
Overview
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 well-control 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.
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.
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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
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.
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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.
3.5
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.
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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.
4
INPUT PARAMETERS
The input parameters are divided into ten main groups.
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
4.1
Summary
The summary window is an overview of the most important information entered for the case.
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4.2
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 Description window
4.3
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.
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.
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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.
The survey profile can be previewed in 3D, by selecting View Survey plot.
Figure 4-7 3D survey plot
4.4
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.
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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
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.
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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.
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.
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4.6
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.
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
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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.
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.
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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.
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.
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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').
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.
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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
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
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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.
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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4.9
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.
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.
Table 1 Properties for predefined fluids Reservoir fluid Oil density [kg/m³] Gas density [kg/m³] GOR [Sm³/Sm³] Oil Compressibility [1/bar] Oil volume factor [-] Viscosity [cp]
Black oil 839 1.235 106 1.623E-04 1.341 0.536 Volatile Oil 830 1.041 486 3.165E-04 1.787 0.245
Dry Gas - 0.680 - - - Methane - 0.659 - - - Reservoir fluid Oil density [lbm/ft³] Gas density [lbm/ft³] GOR [scf/stb] Oil Compressibility [1/psia] Oil volume factor [-] Viscosity [cp]
Black oil 52.38 0.0771 595 1.119E-05 1.341 0.536 Volatile Oil 51.82 0.0650 2729 2.182E-05 1.787 0.245
Dry Gas - 0.0425 - - -
Methane - 0.0412 - - -
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, PVT-reports 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
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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.
4.10 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
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.
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.
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
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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.
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.
Time
Pr
essure gradient
Hydrostatic head Formation pressure
Flowing bottomhole pressure
kick intensity underbalance
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
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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.
7
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
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7.1.6
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.
7.1.9
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.
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
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.
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7.4.1
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
