Research on surface well design and engineering application of coalbed methane under multiple mining conditions

On the basis of analyzing the influence of multiple mining on surface well deformation and failure, the comprehensive deformation and failure mechanical model of surface well based on the main deformation forms of well body is constructed, and the single maximum shear displacement formula of surface well is deduced. Then the well location is designed and the well structure suitable for multiple mining is selected. The applicability of this technology is verified by field surface well extraction test. The results show that the surface well remains intact without obvious deformation and damage during the mining process of 1303 upper and lower working faces. At the same time, the average coal seam gas extracted by the surface well is 15 800 m³/d, the average extraction concentration is 33.71%, and the cumulative extraction volume is 36.55 million m³, which greatly alleviates the gas control pressure of the 1303 working face. Compared with the surface well before operation, the average gas concentration of the working face decreases by 30% after operation. The gas concentration in the return air roadway decreases by 58.75%, the average gas concentration in the return air roadway is only 0.33%, and the gas exhaust volume decreases to 70% of that before the surface well is in operation, which significantly reduced the gas concentration in the corner of the mining face and in the return air roadway, and successfully eliminated the restriction of gas gushing to the mining face. It provides a reference for the design and operation of surface well under multiple mining conditions.