Optimization and Engineering Application of In-Seam Borehole Predrainage Technology for Coalbed Methane Based on Response Surface Methodology

Abstract

To advance the optimization of engineering parameters in in-seam borehole predrainage technology, this study developed a comprehensive analytical framework integrating theoretical modeling, numerical simulation, and field validation. Taking Pingdingshan Tian’an Coal Mine No. 1 as a practical case study, we established a gas-bearing coal seam drainage model based on fluid–solid coupling theory. A multifactor optimization scheme was implemented using response surface methodology (RSM) complemented by an evaluation system focusing on the gas extraction efficiency coefficient (K). Numerical simulations through COMSOL Multiphysics 6.0 enabled detailed investigation of single-factor influences and multifactor coupling effects, ultimately identifying field-verified optimal parameters. Key discoveries include the following: (1) Spatiotemporal evolution patterns of gas drainage compliance zones showing stabilized interborehole pressure gradients and enhanced regional connectivity after 300-day extraction; (2) a parameter sensitivity hierarchy for K-value defined as drainage duration (primary) > borehole spacing > borehole diameter > extraction negative pressure; (3) an optimized configuration (4.5 m spacing, 113 mm diameter, 18 kPa pressure) achieving a 54.2% pressure reduction with a 0.98 efficiency coefficient. Field data demonstrated only 2.1% average deviation from model predictions, validating the methodology’s effectiveness for gas control parameter optimization in coal mining operations.