TOC Analysis Module

Objective

The TOC Analysis module provides several methods for estimating the total organic carbon (TOC) content of a system. The TOC (reported in weight fraction) result is also converted to a volume of kerogen.

Key Parameters

The various TOC estimation methods use different parameters that can be set on a zone-by-zone basis. Parameter visibility is based on TOC method selection. Parameters set zone-by-zone include:

• Calc. TOC: Specify if TOC should be calculated.
• TOC Method: Specify the method that should be used for the TOC calculation.
• Rwb: Bound water resistivity (Modified Passey method).
• ResD Baseline: Resistivity of inorganic shale (Passey overlay methods).
• DT Baseline: Sonic value of inorganic shale (Passey DT method).
• RhoB Baseline: Bulk density value of inorganic shale (Passey RhoB method).
• Nphi Baseline: Neutron value of inorganic shale (Passey Nphi method).
• Vre: Vitrinite reflectance (or equivalent). Note this is converted to “level of maturity” using the required correlations.
• Schmoker A: Parameter for Schmoker method.
• Schmoker B: Parameter for Schmoker method.
• RhoB Clay: Bulk density of clay (Vernik’s method).

The key parameters that operate across zones are:

• Min GR Shale: Values below this will be forced to zero TOC.
• TOC Conversion: Specify the method for converting from TOC to Kerogen.
• Kerogen Density: Density of kerogen to be used in conversion.

Output Curves

Most important curves shown in bold.

• TOC_FINAL: Final TOC result using method selected for zone.
• V_KER: Volume of kerogen derived from the TOC_FINAL curve.
• TOC_SCHMOKER: TOC result from Schmoker method.
• TOC_SLOGR: TOC result from Passey sonic method.
• TOC_DLOGR: TOC result from Passey density method.
• TOC_NLOGR: TOC result from Passey neutron method.
• TOC_VERNIK: TOC result from Vernik method.
• TOC_FAUST: TOC result from Faust method.
• TOC_MOD_PASSEY: TOC result from Modified Passey method.
• TOC_COMBINED: TOC result from average of twelve empirical Schmoker-like methods.

CPI Config Reference

The relevant configuration file is 06_toc.yaml.

Display

1. Gamma ray track with minimum GR shale parameter overlay line.
2. Depth track.
3. Resistivity track with ResD Baseline parameter overlay line.
4. Sonic overlay track with DT Baseline parameter overlay line.
5. Density overlay track with RhoB Baseline parameter overlay line.
6. Neutron overlay track with Nphi Baseline parameter overlay line.
7. Resistivity / Ro track with Rwb parameter overlay line.
8. TOC results track with outputs from Schmoker, Vernik, and Avg. Density methods.
9. TOC results track with outputs from Passey DT, RhoB, and Nphi overlay methods.
10. TOC results track with outputs from Modified Passey and Faust methods.
11. Results track showing final TOC result.

Associated cross-plots

None.

Associated maps

• Avg_toc: Average TOC estimate for the selected zone.

Recommendations

• Identify the key properties in an inorganic shale interval and use those properties to set the key parameters for the methods of interest.
• Set the parameters for each of the methods to try and minimize the variance among methods. This will make it easier to change methods between wells if the data requires it.
• The “Schlumberger method” for TOC to kerogen conversion has been reported to show the best results from several clients.