Given the background of significant Coal Mine gas disasters
worldwide,
the research and development of efficient gas control technologies
have become critical to ensuring mining safety. CO2 gas
fracturing (CO2–Frac), an innovative technology
for Coal Mine gas control, has demonstrated efficiency in various
mining areas across China. However, its application in outburst-prone
coal seams is not yet fully understood. This study presents a field-scale
CO2–Frac project conducted in an outburst Coal Mine
in China, specifically the Pingshu Coal Mine, where the previously
employed dense-borehole gas extraction technology failed to efficiently
achieve gas extraction and outburst prevention. The CO2–Frac plan was evaluated through fracture propagation experiments
utilizing both single-hole and dual-hole configurations, highlighting
the advantages of the dual-hole CO2–Frac method.
Subsequently, on-site gas extraction tests were conducted to further
assess the efficacy of the CO2–Frac plan. The results
indicate that (1) In the dual-hole CO2–Frac scheme,
the fractured and pressure relief area expanded to approximately 26.82
m2, which is 220% larger than that of the single-hole scheme.
(2) The dual-hole CO2–Frac significantly enhanced
gas extraction effectiveness, increasing the flow rate from 0.026
to 0.216 m3/min in a 100m borehole, a 7.3-fold improvement.
Additionally, the gas extraction period to reach the standard was
reduced from 20 to 6 days. These findings conclusively demonstrate
that the dual-hole CO2–Frac technique is an effective
method for safe excavation in outburst-prone coal seams, providing
both theoretical and practical validation for its application in similar
geological settings.