Multi-physics modeling of fracture-driven gas migration and its application to precision borehole arrangement in coalbed methane development

This study aims to address the challenge of precisely determining the optimal spacing for gas extraction boreholes following hydraulic fracturing. Laboratory experiments and theoretical modeling were conducted to analyze the gas adsorption/desorption characteristics of coal with preexisting fractures, investigating the influence of reduced matrix scale on gas desorption behavior. This provides more accurate parameters for modeling the post-fracturing gas desorption-diffusion–seepage processes. Ultimately, a fluid–solid coupling model was developed, incorporating the impact of coal damage on gas flow. Field trials of hydraulic fracturing in coal seams were carried out, and the model's validity was verified through analysis of the gas extraction results. Numerical simulations indicate that, compared to pre-fracturing conditions, the effective extraction rate of boreholes increased by over 50%. Hydraulic fracturing significantly enhanced coal seam permeability and improved gas extraction efficiency. This research provides a basis for the optimized design of gas extraction boreholes in coal mines.