The efficiency of gas extraction in coalbed methane extraction is governed by coal seam permeability and borehole structural integrity. Over prolonged extraction, some boreholes become ineffective owing to degraded performance, necessitating precise identification criteria. In this study, a mathematical model for cumulative gas production under borehole failure was developed based on a gas flow decay function. Numerical analysis and data visualization were conducted via MATLAB, with mean values for collapsed/blocked boreholes adopted to eliminate the interference of unstable intervals. The analysis produced an equation that correlates the critical borehole flow rate with the time of loss of stability, providing a quantitative criterion for identifying ineffective boreholes in coal mining operations.
Han et al. (Tue,) studied this question.