Study on the optimization of well location and extraction life in mining disturbed zone of Yuecheng mine in Jincheng

The aim of the study is to reduce the coalbed gas accumulation in the upper corner caused by U-type ventilation in the working face of Yuecheng Coal Mine, Jincheng City, and improve the production and extraction life of coalbed methane surface wells in the mining disturbed area and goaf. Based on the research of surface mining test wells in Chengzhuang Mine and Sihe Mine, and taking the geological conditions of coalbed methane in Yuecheng Coal Mine as the engineering design basis, this paper puts forward that the well location in the surface mining disturbed area should be close to the roadway location as far as possible, and the design scheme of large hole surface drilling method and optimization of wellbore structure was proposed. The field test shows that some wells in the mining area disturbed are optimized by avoiding the unloading area of mining stress and the relatively high stress area of in-situ coal seam, and the mining includes three stages, pressure relief area drainage, stable drainage in the mining area, drainage in the old goaf, so as to prolong the service life of the drainage wells. However, there are still some wells in the mining area whose gas drainage volume decreases rapidly after the working face is pushed over the wellhead until no gas is produced, the production cycle only includes two stages, pressure relief area extraction and stable extraction in mining area, or even only one stage of pressure relief area extraction. The research shows that the optimized large hole drilling technology and three split casing well structure design have a certain effect on maintaining the well stability in the mining area, prolonging the mining period, ensuring the smooth migration channel of gas production in the mining area, and improving the extraction rate. There is a significant negative correlation between the gas extraction amount and the distance from the wellbore position to the return air roadway in the mining area. Under the premise of good communication between wellbore and fracture zone, high-power pumping equipment should be selected for pumping, which can effectively expand the pressure drop funnel area, and its pumping influence radius can extend over 500 m horizontally. Yuecheng Mine surface mining pumping tests achieved good results, which can provide reference for mining areas with similar types of conditions.