Simulation of coal resistivity dynamics during methane adsorption and desorption using an electrical rock physics...

Area of Science:

• Geophysics
• Rock Physics
• Petroleum Engineering

Background:

• Accurate prediction of coal resistivity is vital for coalbed methane (CBM) extraction and mine safety.
• Existing empirical models lack a mechanistic understanding of resistivity changes during methane adsorption/desorption.

Purpose of the Study:

• To develop a dual-coefficient electrical rock physics model for predicting coal resistivity.
• To integrate inorganic mineralogy, organic matter, methane adsorption, and pore structure into the model.
• To validate the model's predictive capability through experimental data.

Main Methods:

• Developed a dual-coefficient electrical rock physics model incorporating mineral composition, organic resistivity, and methane adsorption-desorption.
• Introduced correction coefficients for adsorption heterogeneity and structural complexity.
• Experimentally validated the model using coal samples, measuring resistivity during methane adsorption and desorption.

Main Results:

• The model demonstrated strong agreement with experimental resistivity data during both adsorption (R²=0.9815) and desorption (R²=0.9956).
• Sensitivity analysis showed mineral composition and inclusion shape significantly influence resistivity.
• Organic content inversely correlates with resistivity, with pore structure effects diminishing at high organic fractions.

Conclusions:

• The developed model provides a robust, physics-driven framework for understanding coal resistivity.
• This research offers a predictive tool for CBM resource assessment, CO2 sequestration monitoring, and mine hazard management.
• The model's adaptability to various coal types enhances its applicability in industry and research.