Method for formation evaluation of organic shale reservoirs using well logging data

A system comprising:

• at least one well logging tool configured to acquire formation bulk density data, nuclear magnetic resonance (NMR) porosity data, and organic carbon content data from an earth formation;
• a processor cooperating with the at least one well logging tool and configured to:
• determine a bulk density of the earth formation from the formation bulk density data, determine a total NMR porosity of the earth formation from the NMR porosity data, and determine a total organic carbon content of the earth formation from the total organic content data;
• estimate a gas filled porosity of the earth formation as a function of the bulk density and the total NMR porosity;
• estimate a kerogen volume of the earth formation as a function of the gas filled porosity and the total organic carbon content of the earth formation;
• determine a bitumen filled total porosity of the earth formation as a function of the estimated kerogen volume and an estimated total porosity of the earth formation;
• and
• determine a corrected kerogen volume of the earth formation as a function of the estimated kerogen volume and the estimated total porosity of the earth formation.

A method comprising:

• estimate a gas filled porosity of an earth formation as a function of bulk density and total NMR porosity of the earth formation, using a processor;
• estimate a kerogen volume of the earth formation as a function of the gas filled porosity, using the processor;
• determine a bitumen filled total porosity of the earth formation as a function of the estimated kerogen volume and an estimated total porosity of the earth formation, using the processor;
• and
• determine a corrected kerogen volume of the earth formation as a function of the estimated kerogen volume and the estimated total porosity of the earth formation, using the processor.