Abstract The efficiency of gas drainage in deep coal seams is generally poor because of their typically low-gas permeability and high-geostress characteristics. Therefore, we conducted a test study on the permeability enhancement of cross-measure boreholes using liquid CO2 phase-transition blasting (LCPTB) to identify an effective method for enhancing coalbed methane reservoir. Through a numerical simulation of LCPTB, the fracture propagation in the coal seam after blasting was analysed. Subsequently, a field test arrangement for boreholes of LCPTB was designed, and the range of enhanced permeability after blasting as well as the efficiency of gas drainage were investigated. The results indicate a significant increase in the permeability of the coal seam and the efficiency of gas drainage following LCPTB. The amount of gas extracted from the blast holes was 1.8–8 times greater than that extracted from boreholes without LCPTB. The practical spacing between boreholes was deemed to be 2.5–3 m. In addition, with decreasing measuring distance from the blast hole, the efficiency of LCPTB was improved by increasing the permeability of the coal mass surrounding the observation hole. The observation holes arranged around the blasting holes could increase the efficiency of gas drainage. In summary, this technology uses the energy released by LCPTB to increase the permeability of the coal surrounding the blast hole, and to displace methane in the coal seam, thereby improving the efficiency of gas drainage and providing economic and environmental benefits.

中文翻译：

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液态 CO2 相变爆破与交叉测量钻孔强化煤层气

摘要 深部煤层瓦斯抽采效率普遍较差，具有典型的低瓦斯渗透率和高地应力特征。因此，我们对使用液态 CO2 相变爆破 (LCPTB) 的交叉测量钻孔渗透率进行了测试研究，以确定提高煤层气储层的有效方法。通过LCPTB的数值模拟，分析了爆破后煤层中的裂缝扩展。随后，设计了LCPTB井眼现场试验布置，研究了爆破后增透范围和瓦斯抽采效率。结果表明，LCPTB 后煤层的渗透率和瓦斯抽采效率显着增加。从爆破孔中提取的气体量是从没有 LCPTB 的钻孔中提取的气体量的 1.8-8 倍。钻孔之间的实际间距被认为是 2.5-3 m。此外，随着距炮孔测量距离的减小，LCPTB 的效率通过增加观察孔周围煤体的渗透率而提高。在爆破孔周围设置观察孔可以提高瓦斯抽采效率。综上所述，该技术利用LCPTB释放的能量，提高炮孔周围煤层的渗透率，驱替煤层中的甲烷，从而提高瓦斯抽采效率，提供经济和环境效益。钻孔之间的实际间距被认为是 2.5-3 m。此外，随着距炮孔测量距离的减小，LCPTB 的效率通过增加观察孔周围煤体的渗透率而提高。在爆破孔周围设置观察孔可以提高瓦斯抽采效率。综上所述，该技术利用LCPTB释放的能量，提高炮孔周围煤层的渗透率，驱替煤层中的甲烷，从而提高瓦斯抽采效率，提供经济和环境效益。钻孔之间的实际间距被认为是 2.5-3 m。此外，随着距炮孔测量距离的减小，LCPTB 的效率通过增加观察孔周围煤体的渗透率而提高。在爆破孔周围设置观察孔可以提高瓦斯抽采效率。综上所述，该技术利用LCPTB释放的能量，提高炮孔周围煤层的渗透率，驱替煤层中的甲烷，从而提高瓦斯抽采效率，提供经济和环境效益。在爆破孔周围设置观察孔可以提高瓦斯抽采效率。综上所述，该技术利用LCPTB释放的能量，提高炮孔周围煤层的渗透率，驱替煤层中的甲烷，从而提高瓦斯抽采效率，提供经济和环境效益。在爆破孔周围设置观察孔可以提高瓦斯抽采效率。综上所述，该技术利用LCPTB释放的能量，提高炮孔周围煤层的渗透率，驱替煤层中的甲烷，从而提高瓦斯抽采效率，提供经济和环境效益。