Improving the permeability of coal seam with CO₂ gas phase fracturing technique: a case study in Jining Coal Mine

In order to solve the technical problems of gas treatment in complex low-permeability and high-gas coal seams, this paper takes the 2203 working face of No.2 coal seam in Jining Coal Mine, Huajin, Shanxi Province as the research object. By adopting the CO₂ gas phase fracturing anti-penetration technology, the gas extraction concentration and gas extraction purity of 4 groups （12） of extraction boreholes are analyzed, the effective extraction radius is inferred, and the effective fracturing range is determined. Then evaluate the effect of gas extraction and outburst prevention. The results show that: the influence range of effective cracking fractures in this geological unit is 6-7 m. The average gas extraction purity of the four groups of boreholes is 0.179 m³/min, which is 9.9 times higher than that of the conventional extraction holes of 0.018 m³/min. In the attenuation area, the average gas extraction concentration is 64.7% and the average gas extraction purity is 0.150 m³/min. In the stable region, the average gas extraction concentration is 73.2%, and the average gas extraction purity is 0.188 m³/min. It is found that the gas extraction parameter value in the stable region is higher. This technology can effectively increase the gas permeability of No.2 coal seam, improve the efficiency of gas extraction and the speed of coal roadway driving, reduce the investment of drilling construction, and relieve the tense situation of mining succession.