--> ABSTRACT: Complete Suite of Geochemical Values Computed using Wireline Logs, by James R. Lancaster and Asher Atkinson; #91019 (1996)

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Complete Suite of Geochemical Values Computed using Wireline Logs

James R. Lancaster and Asher Atkinson

Geochemical values of "black shale" source rocks can be computed from a complete suite of wireline log data. The computed values are: Total Organic Carbon (Wt%), S1, S2, S3, Hydrogen Index, Oxygen Index, Atomic H/C and O/C ratios, Genetic Potential (S1+S2), S2/S3, and Transformation Ratio (S1/(S1+S2)).

The results are most reliable when calibrated to laboratory analyses of samples in the study area. However, in the absence of samples, reasonable estimates can be made using calibration data from analogous depositional and thermal environments and/or professional judgement and experience. The evaluations provide answers to critical geochemical questions relative to:

- Organic Matter Quantity; TOC (Wt%), S1, and S2.

- Kerogen Types; I, II, and III, based on TOC vs S2 cross plot and the van Krevelen diagram of Atomic O/C vs Atomic H/C ratios.

- Thermal Maturation levels; Transformation Ratio can be converted to Level of Organic Metamorphism (LOM), pyrolysis Tmax (degC), Vitrinite Reflectance (Ro), Time Temperature Index (TTI) and others.

Various analog plots and cross plots can be prepared for interpretation. Case history examples are shown and discussed.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California