Objective
The Inversion module provides a means to calculate mineral volumes based on a user specified mineral model, the mineral properties, and the input data. The primary results are a total porosity (from a sum of the fluids) and a grain density (based on the mineral volumes). The mineral volumes can also be used or exported.
Key Parameters
Displaying a matrix layout for each mineral model necessitates a different layout for this module than other modules. As such, when users are setting up mineral models they have the option of setting up a “Default” model and to then make customizations to that model for each zone.
Mineral matrix:
- Zone: Select the zone (or default) for modification.
- Mineral: The name of the mineral in the model.
- Enabled: Checkbox to specify if the mineral will be used in the inversion for the active zone.
- Grain: Specify if the mineral is part of the matrix (checked) or a fluid (unchecked).
Note that the mineral properties given on each row correspond to the curve listed in the Curves matrix.
Curves matrix:
- Curve: Dropdown menu with available curves. User can also type in a curve name.
- Mode: Specifies how the curve will be used in the inversion.
- Conf. Int: Places a weight on the curve in the inversion. Smaller weights increase importance. Should be set relative to curve value range.
Output Curves
Most important curves shown in bold.
- MINV_GRAIN_DENSITY: Grain density from the mineral inversion.
- MINV_POROSITY_STRICT: Sum of the fluids from the mineral inversion.
- RHOB_PRED: Predicted density from the mineral inversion for model QC.
- NPHI_PRED: Predicted neutron from the mineral inversion for model QC.
- PE_PRED: Predicted photoelectric factor from the mineral inversion for model QC.
- SONIC_PRED: Predicted sonic from the mineral inversion for model QC.
- COND_PRED: Predicted conductivity from the mineral inversion for model QC.
- VWCL_PRED: Predicted clay volume from the mineral inversion for model QC.
- V_KER_PRED: Predicted kerogen volume from the mineral inversion for model QC.
- MINV_MODEL_TOTAL_ERROR: Sum of errors between predicted curves from inversion and actual curves.
- MINV_MODEL_AVG_ERROR: Average error between predicted curves from inversion and actual curves.
CPI Config Reference
The relevant configuration file is 07_inversion.yaml.
Display
- Mineralogy track.
- Grain density track.
- Total porosity track.
- Bulk density inversion QC track.
- Neutron inversion QC track.
- Photoelectric inversion QC track.
- Compressional sonic inversion QC track.
- Conductivity inversion QC track.
- Clay volume inversion QC track.
- Kerogen volume inversion QC track.
- Inversion error track.
Associated cross-plots
- Rt-Clay cross-plot.
- DT-Clay cross-plot.
Associated maps
None.
Recommendations
- When setting the parameters expand the window so that the mineral and curve matrices are aligned.
- Set the default mineral model first and then make zone-by-zone modifications as necessary.
- Use the minimum number of minerals possible to prevent / minimize non-unique solutions due to being underdetermined.
- Remember that most mineral properties are well established. The clay and fluid properties have the most potential variation from the defaults.
