Study on Fracture Evolution Mechanisms and Stress Wave Dynamics in Supercritical CO2 Gas Explosion

Supercritical CO2 gas explosion is an important technique for enhancing permeability in low-permeability coal seams, as it can improve gas drainage efficiency while avoiding the open-flame hazards of conventional explosion and the high water consumption associated with hydraulic fracturing. This study aims to reveal the crack propagation patterns and stress-wave dynamics under different hole configurations. Using LS-DYNA, fracture models were established for three configurations under supercritical CO2 explosions: single-hole, symmetrical double-hole, and symmetrical double-hole with a control hole. The fracture processes were analyzed to investigate the effective fracture radius of single-hole explosions, the optimal spacing for symmetrical double-hole explosions, and the influence of control holes on crack development and connectivity. The simulation results indicate that the effective fracture radius of a single-hole explosion reaches up to 2.6 m under the modeled conditions. Compared with the single-hole gas explosion case, the symmetrical double-hole configuration with a spacing of 7 m significantly enhances fracture interaction and connectivity, resulting in an approximately 98% increase in the effective damaged area. Permeability enhancement was further quantified by introducing a damage–permeability mapping (k/k0) based on the simulated damage factor, and the permeability-enhanced zone was evaluated using the criterion of k/k0 ≥ 2.