Gas drainage technology and practice analysis of large diameter high position directional long borehole

Aiming at the problem of large gas emission and gas accumulation in the upper corner of the fully mechanized caving face in Wangjialing coal mine of high-strength mining field. Based on the theory of key strata controlled by strata, the roof caving trend and the development of inclined mining fissures are studied. At the same time, the numerical simulation method is used to study the evolution process of the goaf fracture with the working face push mining, analyze the development height of the roof fracture, determine the best hole arrangement layer and structure of the high-level directional drilling, and carry out engineering practice. The results show that the high-level directional drilling is effective according to the theoretical calculation and numerical simulation. The maximum extraction purity of one hole is 2.10 m³/min, and the maximum extraction concentration of one hole is 31.39%. The total amount of gas extracted by high-level directional drilling is 289 900 m³. The lowest gas concentration in the upper corner of the working face is 0.46%. The gas control effect of the working face is remarkable.