Study on the Sensitivity of Gas Extraction Parameters and the Dynamic Evolution of the Effective Extraction Radius Under Multiphysics Coupling

To investigate the sensitivity and underlying mechanisms of key parameters for gas extraction, a three-dimensional numerical model was established. Using the control variable method, the effects of critical extraction parameters on gas pressure evolution, the effective extraction radius of drilling, and cumulative gas production were systematically analyzed. The results indicate the following: Extraction time is the primary factor controlling the expansion of the pressure disturbance zone, and gas extraction exhibits a significant characteristic of diminishing marginal returns. Increasing the extraction negative pressure and drilling diameter mainly improves near-drilling flow conditions and contributes only marginally to the overall extraction effectiveness. Drilling length determines the gas resource volume controlled by a single drilling operation and its sustained extraction capacity while exerting only a limited influence on the effective extraction radius. The initial porosity of the coal seam is the dominant factor controlling both the effective extraction radius and extraction efficiency. Field extraction data verified the model’s reliable representation of extraction patterns and parameter influence characteristics. A synergistic gas control strategy integrating long drilling coverage, enhanced permeability, reasonable negative pressure, and continuous extraction was proposed. These research results can provide a theoretical basis and technical support for the optimization of gas extraction parameters.