关键词: 穿层钻孔, 相变致裂, 抽采半径, 抽采效率

Abstract: In order to improve the gas drainage efficiency of soft and low permeability coal seam, liquid CO2 phase-transition fracturing test was carried out by drilling holes through bottom drainage roadway. The results show that the diameter of the fracturing borehole increases obviously and the radius of gas drainage is 10m after the fracturing of the coal seam. Both the pure gas quantity and gas concentration of borehole gas were greatly increased, although they show a certain degree of attenuation at the later stage of each fracturing, they still remained at a high level. Compared with the measure of hydraulic piercing, liquid CO2 phase-transition fracturing has better effect on enhancing permeability in the early stage. Liquid CO2 phase-transition fracturing not only enhances the gas drainage efficiency, but also improves the speed of mine tunneling, which has significant safety and economic benefits.