Multiphysics modeling of thermal–fluid–solid interactions in coalbed methane reservoirs: Simulations and optimization strategies

This study constructs a fully coupled thermal–fluid–solid multiphysics model using the finite element method in COMSOL Multiphysics to systematically investigate the complex interactions among thermal, fluid, and solid processes in coalbed methane (CBM) reservoirs. By integrating gas desorption kinetics, thermal expansion effects, and dynamic permeability evolution, the model effectively captures the nonlinear feedback mechanisms governing hydrocarbon recovery under variable thermo-mechanical conditions. Numerical simulations validated against field data from the Barnett Shale (with a prediction error of <5% in gas production rate) reveal that enhancing permeability from 5.125 × 10−17 to 5.125 × 10−16 m2 doubles cumulative gas production, highlighting the critical role of transport efficiency in controlling recovery performance. Further analysis shows that elevated reservoir temperatures (293–453 K) accelerate desorption rates by up to 40% by reducing adsorption energy barriers by approximately 30%, significantly improving recovery; specifically, thermal expansion dominates porosity evolution at high temperatures (>313 K), while desorption-induced matrix shrinkage prevails under low pressures (≤2 MPa). Additionally, Langmuir adsorption constants are found to critically regulate the timescale of pore pressure equilibration, with higher Langmuir volumes extending the stability period of gas production. This work enhances the predictability of CBM extraction by quantifying thermal–fluid–solid coupling mechanisms, providing theoretical support for optimizing stimulation strategies (e.g., fracturing parameter design) in heterogeneous reservoirs, and offering scientific guidance for the development of high-temperature reservoirs and applications of permeability enhancement technologies.