Written by In GVERSE Petrophysics you can create, edit, or personalize petrophysical equations using the User Defined Equation (UDE) or the Petrophysics External Model (PEM) tools. The UDE will allow you to edit (pre load equations) or create petrophysical equations directly in GVERSE Petrophysics. On the other hand, the PEM is an interpretive model written as an executable file in a programming language (C, C++, or Visual Basic) outside of the GVERSE Petrophysics application. The model contains a list of required and optional input curves. All required input curves must be present in a well to execute the PEM in GVERSE Petrophysics. Here’s a step-by-step guide on how to activate a PEM and where to find an External Model Dev Kit:
- Start a GeoGraphix project and open GVERSE Petrophysics by clicking on the GVERSE Petrophysics icon on the GVERSE GeoGraphix modules tool bar.
- The Open Session window will open if a session was saved; otherwise the well list with curve data will appear. Select the well and click Open. Select the session and click OK.
- GVERSE Petrophysics interpretation will now be available. By default, the well curve will be displayed using the Raw Curves template.
- To activate or load a PEM, go to the Interpretation tab and click on Select User Defined Equation Set.
- The Select User Defined Equation Set window will open.
- If you need to import a PEM, click New Set to open the New User Defined Set window.
- In the New User Defined Set window, select Petrophysics External Model.
- Add a name on the User-Defined Set Name. If you want to use a pre-loaded PEM, click the drop box under Petrophysical External Model.
- Click Add External Model if you have a PEM and want to use it.
- The Select Petrophysics PDK Executable window will now open. Search for the PEM executable file. Click Open.
- Click OK.
- The new PEM will appear on the list.
- Select the PEM from the list and click OK.
- If you do not see the model display, create a new template. If you have a template, go to the Project tab and click Interpretation Sets.
- The interpretation set window will open. Under Set Name, select the template. Click OK.
- The equation and the template will be displayed (if you only see the curve display click Apply Selected UDE Set in the interpretation tab).
How to open the External Model Dev Kit
- To edit or create a new PEM, go to C:\Program Files (x86)\GeoGraphix\Utilities\Prizm External Model Dev Kit or to the place where you installed the GeoGraphix Utilities kit.
- Click in DevKit in the External Model dev Kit folder.
- A world document will open explaining how to use the PrizmAPI and how to create a PEM equation.
- To open the kit to create equations, click on PrizmAPI.
- You can open this kit by using: Microsoft C, C++, or Visual Basic programming languages.
The PEM model is divided into four sections:
- Header/Declaration Section: The C/C++ Header or Visual Basic Declaration Section provides declarations for PDK constants and functions for the “Curve Data” API.
- Run Calculation Section: The Run Calculation section reads curves and parameters, performs curve computations, and handles NULL propagation. NULL propagation comprises a major portion of the calculation code.
- Define Input/Output Section: The “DefineInputOutput” routine defines curves and parameters used in the model.
- Initialization Section: The initialization section has procedures to run calculations, register the PEM, and perform debugging operations. It is suggested that this code be copied from the source files shipped with the PDK. Edits to the copied code will commonly be made to the model name (Register procedure) and the hardwired data file used in the debug procedure.
Curves are defined with the following information:
- Mnemonic
- Units
- Description
- Required Input, Optional Input, or Output designation
When the PEM is added to GVERSE Petrophysics, input curve definitions are stored in the UDE Set. Input curves need to use Default Curve mnemonics to make use of GVERSE Petrophysics alias curve functionality.
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