Application of surface well gas extraction technology in mining area of steeply dipping coal seam in Xinjiang

On the basis of in-depth analysis of the extraction effect of surface well in mining area and the stability of surface well structure, combined with the occurrence characteristics of Xinjiang coal seam with high dip angle and gas occurrence conditions, the well location is selected and arranged near the turning point of the working face with the minimum casing shear displacement. At the same time, the rational combination of the well structure in mining area and drill bit specifications is optimized. Five design and protection concepts of “avoid” “resist” “let” “thin” and “protect” surface wells are used in well structure, drilling and completion technology and safety protection devices to form a set of suitable design technology of gas surface extraction well in mining area of steeply dipping coal seam. After that, a mining surface well is constructed at 24223 working face of No.4 coal seam in 2130 Coal Mine to carry out gas extraction. The test results show that in the mining area, the average gas extraction concentration of surface wells is 31.5%, the average pure gas extraction volume of daily gas extraction is 850 m³/d, and the cumulative gas extraction volume reaches 605 200 m³, and the gas recovery of surface wells accounts for 56.67%, which reduces the pressure of wind exhaust gas and ensures the smooth mining of working face. When the working face is pushed over 90 m, an intelligent borehole imager is used to carry out on-site observation of the surface well. No abnormal deformation of the drilling casing is found in the process of lowering the second casing, and no deformation and damage occurred in the surface well, indicating that the structure of the surface well is stable after the working face is pushed, and the structural design of the well is reasonable, which could ensure the continuous extraction of the surface well.