Comprehensive technology of roof cutting roadway protection and gas extraction based on staged fracturing with directional drilling

CHEN Liang; YU Hongyang; BAI Yajun; WANG Dongwei; QIN Ruichen; WANG Dongpan

doi:10.11799/ce202509015

Abstract：Aiming at the problems of serious deformation of gob-side entry retaining wall and large amount of gas leakage from goaf in outburst coal seam with composite key strata,we took the No.20107 working face of Qincheng Coal Mine in Shanxi Province as an example,and studied the influence mechanism of fracturing fracture line position on stress propagation and wall deformation by theoretical modeling and mechanical analysis,and provided the analytical solution of the key horizontal position of roof cutting by staged fracturing.Combining with the theory of key strata,the middle and low bearing key strata of overburden rock were analyzed and identified,and the horizontal position and vertical interval of staged fracturing of directional drilling were comprehensively determined.It was pointed out that the triangle-like area between the fracture line and the natural caving line of overburden rock is the pressure relief gas enrichment area in goaf.Then the reasonable layer of gas extraction borehole in the fracture zone was optimized.The key parameters such as fracturing initiation,propagation pressure,fracturing duration and flow rate of staged fracturing were established using non-seepage fracturing theory and in-situ stress field test,which were verified by engineering test.According to the test results,the vertical deformation of the optimized retaining wall is 65%lower than before.The single-hole gas extraction volume of the directional drilling field is increased by 72%,and the total amount of each group is increased to 7.46 m3/min,realizing collaborative treatment of the deformation and instability of the retaining wall and the gas in the goaf.