Enhancing shale gas recovery: An interdisciplinary power-law model of hydro-mechanical-fracture dynamics.

This study explores the efficiency of using carbon dioxide (CO₂) to extract shale gas, highlighting its potential to enhance extraction while mitigating environmental CO₂ pollution. Given the intricate microstructure of shale, CO₂ injection inevitably induces deformation within the shale reservoir's internal microstructure, thereby impacting gas displacement efficiency. The organic matter (kerogen) network and fracture network in shale, serving as primary spaces for gas adsorption and migration, exhibit complex microstructural characteristics. Thus, we developed a dynamic coupled hydro-mechanics permeability model for binary gas displacement, and three novel, interdisciplinary fractal power-law parameters are proposed to represent the distribution of shale fractures, considering the adsorption–desorption strength of the kerogen network. Numerical simulations analyzed the changes in gas seepage, diffusion, shale stress, permeability, and factors influencing displacement efficiency during the CO₂–EGR (enhanced gas recovery) projects. Key findings include (1) CO₂ injection leads to a nonlinear increase in the number of shale fracture networks, thereby enhancing the CH₄ output efficiency. (2) Compared to traditional fractal theory, the proposed power-law model is applicable to a wider range of reservoir fracture distributions and effectively characterizes the density (by α), size (by r), and complexity (by n) of the fracture network during the CO₂–EGR process. (3) Changes in the proposed interdisciplinary power-law parameters significantly alter CO₂ and CH₄ adsorption capacities and, in turn, significantly affects displacement efficiency and shale deformation. According to calculations, these parameters have the greatest impact on the CO₂–EGR process, ranging from 16.3% to 68.1%. [ABSTRACT FROM AUTHOR]