Fault Seal Potential Variables page

This is the Next >> page accessed in WizGen (in "Flexible project" mode) from the Miscellaneous Options page or by selecting the Goto... button for Define fault seal potential variables from the Contents page.

The Fault Seal Potential Variables page of WizGen offers options to:-

set the instructions for calculating up to 5 Fault Seal Potential (FSP) measures for the fault wall rock in a single Transgen run.

The settings on this page of WizGen are used to construct the TGFSP string in the TGDATA runfile. It is recommended that the TGFSP strings are constructed/edited via this page in WizGen, rather than hand-editing the TGDATA file which can easily lead to mistakes.

NOTE:- If the current TransGen Project has already been worked on as a "Basic project" which has been upgraded to a "Flexible project", the Current FSP setting will be either csp or sgr (as shown below) as set on the Fault Rock Properties page of WizGen in "Basic project" mode. Whereas, if the Project is accessed for the first time in "Flexible project" mode, no FSPs will exist and the page will initially be blank - select the the File, New option, enter a new FSP name and then continue to set the variables as shown below.

The settings on this page in WizGen set the TGFSP keyword record in the TGDATA runfile. The TGFSP keyword can be followed by up to 5 Fault Seal Potential definitions including, for example, any of the following:- basic Shale Gouge Ratio, Clay Smear Potential (Yielding et al. 1997), Clay Smear Potential (Fulljames et al. 1997), Vshale weighted Clay Smear Potential, Shale Smear Factor (Lindsay et al. 1993), Shale Smear Factor for multiple shale beds. The instructions for each FSP measure in the TGFSP keyword are based on the general equation:-

Adding/Editing Fault Seal Potential measures

All Fault Seal definitions are added as Plugins Files under the TGFSP keyword in the TGDATA runfile via the File, New option on the Fault Seal Potential Variables page.

1. Enter new FSP name:

Click on the current File setting at the top of the Fault Seal Potential Variables page to access the following drop-down menu.
Click on New to open the Plugin prompt window.

Click in the currently empty box and type in the required new FSP name, e.g. csp_yielding

NOTE:- The name should be input in lower case and can include any combination of letters and numbers, but without spaces. The name will be the first item of each FSP definition below the TGFSP keyword in the TGDATA runfile.

Click on OK to close the Plugin prompt returning to the Fault Seal Potential Variables page of WizGen where the Current FSP box has been updated to the new FSP name.

2. Input/Edit Equation constants

Having created a new FSP file name or selected an existing FSP file for editing, you need to input/edit appropriate Equation constants
where:-

Exponent l is the power to which "throw" is raised.

Exponent m is the power to which "thickness" of a shale source bed is raised.

Exponent n is the power to which "distance" is raised.

Exponent p is the power to which "eVshale" (i.e. the effective Vshale content) is raised.

Valid values need to be input for each Equation constant. Even parameter(s) not needed in a particular FSP measure (e.g. Distance for Shale Gouge Ratio or Throw and Effective Vshale for Clay Smear Potential) must have a valid exponent, i.e. set an exponent to 0.0 to exclude that parameter and all associated settings from the current FSP measure.

So, for example for Clay Smear Potential, the Equation constants should be set as shown below, given CSP is defined as:-

NOTE:- When an exponent is set to zero, the options for that particular component are irrelevant to the calculation. However, all associated settings must still be defined, e.g. even if exponent p is set to 0.0 as above in a CSP equation, a valid Effective vshale setting must be selected (even though never used), otherwise ViewGen using the generatedTGDATA runfile will stop with an error message.

3. Select appropriate Distance option

When the Current FSP is Clay Smear Potential, it is important to select the correct Distance options setting:-

For CSP after Yielding et al. 1997 this method uses Centre of beds as the distance option.
For CSP after Fulljames et al. 1997, the distances are measured to the Far-side of beds.

NOTE:- Selecting the Near-side of beds option can result in incalculable connections between two non-shale layers if the N exponent is set to < 0.0 (for example as in CSP calculations), resulting in FSP values of infinity at certain connection vertices. This problem has been overcome by introducing the concept of "undefined" vertices and connections - see section on Inactive FSP values.

Maximum from layers then sum

With this option selected, the FSP term (as defined by the other settings on the Fault Seal Potential Variables page) for each shale layer in the footwall and hangingwall are compared and the maximum value from each layer is included in the summations. This option is recommended by Yielding et al. (1997) for calculating Clay Smear Potential.
So, for example, where two shale layers a and b have been displaced past a particular vertex on a fault, if the FSP Term for shale layer a is greater in the hangingwall than in the footwall, while the same FSP Term for shale layer b is greater in the footwall, then the final FSP calculated at the vertex is:-

In certain instances this method can result in numerical ambiguities, in which case TransGen will issue an error warning and stop.

HINT:- Do not use this Combination option setting with the Shale definition set to either Effective Vshale cutoff or Based on user-property as these introduce ambiguity into the FSP calculation, resulting in the TransGen run failing with an error message. See Invalid FSP options in the section on Issues associated with FSP calculations.

Sum layers then take maximum

With this option selected, the FSP terms are summed independently in the hangingwall and footwall sides of the fault. The final FSP is then the larger of these two values. This combine option is used in the definition of Clay Smear Potential published by Fulljames et al. (1997).

Maximum value

No summation of the individual FSP terms for the shale layers displaced past a particular vertex on a fault. The final FSP value is the maximum calculated for that vertex.

Minimum value

No summation of the individual FSP terms for the shale layers displaced past a particular vertex on a fault. The final FSP value is the minimum calculated for that vertex.

Mean value

The final FSP is the average of all the individual FSP terms for all the shale layers displaced past a particular vertex on a fault.

Sum layers then take average

With this option selected, the FSP terms are summed independently in the hangingwall and footwall sides of the fault. The final FSP is then the average of these two values.

Sum in footwall

The final FSP is the sum of the individual FSP terms for all the shale layers displaced past a particular vertex in the footwall of the fault.

Sum in hangingwall

The final FSP is the sum of the individual FSP terms for all the shale layers displaced past a particular vertex in the hangingwall of the fault.

5. Select Effective vshale method

Which grid blocks are treated as shales in the current FSP measure depend on the Effective Vshale (Evshale) values of the grid blocks. The Effective vshale can be calculated in one of the 4 following methods dependant on the availability of Net-to-Gross and/or Vshale data or another User property:-

HINT:- A valid Effective vshale setting must be selected even if evshale is not used in the current Equation, i.e. when Exponent p = 0 such as in the calculation of Clay Smear Potential.

User Property - Transgen takes the user-defined Effective Vshale grid values assigned to a user-defined keyword. These values should all ideally lie between 0.0 and 1.0. If the user-defined Effective Vshale grid contains values less than 0.0 or greater than 1.0, these values will still be included in the FSP calculation, but the results cannot be guaranteed meaningful. Meaningful FSP values are assumed to have a range from zero to infinity and all numbers entering the summation are either zero or positive.

Select the appropriate option, depending whether Net-to-Gross (NTG) and/or Vshale (TGVS) data or a User property to define shale content has been included for the current Project (see Included Data page).

6. Set the Plunge correction switch

By default, TransGen reports the FSP measures in 3D (i.e. Three dimensional option "on"), by measuring all distances, thicknesses and throws parallel to the COORD lines bounding the faulted connection faces. TransGen assumes implicitly, therefore, that the displacement vector of the fault is parallel to the COORD lines used to construct the 3D model geometry.

By selecting the alternative Strike projection option, the FSP measures can be reported on a vertical projection of the fault.

7. Set Shale definition

This setting defines which cells to use in the Current FSP calculation. Shale faces (see the section on FSP calculation in TransGen Version 3) are not constructed for non-shale cells. Non-shale cells are simply ignored in the FSP calculation.

NOTE:- To correctly calculate the values of FSP measures based on the concept of discrete shale layers (e.g. CSP), Shale face bunching is used to combine multiple, vertically adjacent shale faces into a single face for use in the FSP calculation. This operation (described in the section on Issues associated with FSP calculations) is ALWAYS applied, EXCEPT when the Shale definition is Based on all cells.

Select the option appropriate to the Current FSP using the following as a guide:-

Based on all cells

With this option selected, every cell is treated as shale, with the FSP calculation being equivalent to that performed for Shale Gouge Ratio in TransGen Version 2. Selection of this option automatically deactivates shale bunching.

Layers

With this option selected, named layers define the cells treated as shales. This setting is necessary when calculating Clay Smear Potential as per Yielding et al. 1997.
The named layers should be input as a list separated by commas. Multiple adjacent layers can be defined by a hyphen separating the first and last of these layers, e.g. `1,2,3,5,7,8,9,10' can be input as `1-3,5,7-10'. The list can be up to 256 characters long. Spaces are ignored (indeed spaces are removed by WizGen to shorten the length of the string).

Effective Vshale cutoff

Select this option and input an Effective Vshale cutoff value (e.g. 0.5) to be applied to the Effective vshale values defined by the current Effective vshale setting. Cells with eVs below the specified cutoff are designated shale cells and used in the current FSP calculation.

TGSHALE keyword

Select this option to use data defining the shale (set to 1) or non-shale (set to 0) status of every cell in the current model. Only shale cells are used in the current Fault Seal Potential calculation.
NOTE:- To use this option, the file containing the TGSHALE keyword and all the associated data must be added to the TGDATA run file via the Included Data page.

User-property

Select this option to use a user-defined keyword to assign shale cells. The keyword must have been added via the User-defined keywords page and the file headed by this keyword and including binary values of 0.0 or 1.0 (or any other value) for each cell in the current model included via the Included Data page. Any user-supplied grid cell value that is non-zero is considered to represent a shale.

8. Add other FSPs to be calculated

Return to point 1 and repeat the procedure to include up to 5 FSP calculations in the current TGDATA run file.

Refer to section on Typical Fault Seal Potential Variable settings to calculate Shale Gouge Ratio, Clay Smear Potential as per either Yielding or Fulljames, Shale Smear Factor as per Lindsay or combining multiple shale beds.

Select New to input a name for a new FSP.

Select Save to save the Current FSP definition to the FSP library file. This file is stored in the user's home directory (file location is <HOME>/.transgen/fsp.lib). The 'fsp.lib' file contains the user's favourite FSP definitions that can be stored and retrieved when required. A corporate fsp.lib file may be created and copied into each user's home directory.

Select Library to open up a list box containing the user's stored FSP definitions. The box would be similar to this:

A selected entry can be deleted from the library or loaded into the FSP page.

Select Remove to remove the current FSP from the TGDATA file and from the list of selectable Current FSPs - displayed top right of page (the previous FSP, if one exists, becomes the Current FSP). If there are no FSPs defined on the page, all the controls become insensitive except the File menu which allows a new FSP to be created or loaded from the library.

When the Fault Seal Potential Variables page is set as required, click on the Next>> button to view/edit the User-defined plugins page.

Alternatively, click on the << Back button to return to the Miscellaneous Options page to view/edit the Lower limits for Multiplier and/or Cell volume cutoff and whether to perform calculation or not via ViewGen.

Or click on the Contents button to access the Contents page to view/edit any of the current TGDATA file settings, inspect the project's TGDATA file and/or inspect the log generated by last ViewGen calculation.