Surface drainage technology and application of CBM in key mining areas of Shanxi Province

In order to solve the problem of gas overrun in the upper corner of the coal mining working face caused by the substantial increase of the mining speed in the modern high-yield and high-efficiency coal mine, and break through the limitation of the single gas control method in time and space existing in the traditional underground gas drainage measures, relying on the National Science and Technology Major Special Demonstration Project, the mining activities of coal mining face in key mining areas of Jincheng, Yangquan and other mines in Shanxi key coal mines areas are simulated and observed on the formation mechanism of coal seam fissures in the three stages of advanced abutment pressure transfer, repeated disturbance of mining overburden and basic stability of mining overburden when the mining face is different from the surface well in the mining area. Based on this, the migration channel and enrichment area of pressure relief gas in the mining areaswere determined and verified. Research and engineering demonstrations have determined that the ground vertical well in the mining area of Shanxi key coal mine should be located in the area between the connection of the ground subsidence inflection point and the center line of the stope. The layer of L-type horizontal wells in the mining area should be preferentially arranged in the middle of the fissure zone and the rock stratum with large thickness and strength.According to the simulation of the deformation and failure of the surface wells in the mining area, it is found that the shear slip displacement and the tensile displacement of the strata are the key parameters that affect the structure of the surface wells. Therefore, the diameter of the surface vertical well in the mining area is increased and and the effective diameter of the surface well is improved by improving the cementing technology to enhance its tensile and shear resistance. Through the production practice, the optimal triple-shaft structure of the vertical well is developed so that the surface vertical well in the mining area should pass through the coal seam and the production casing should be arranged from the upper edge of the mining fracture zone to the caving zone. In the mining areas of Yuecheng Mine, Tashan Mine, Xinjing Mine, more than 100 drilling and drainage engineering demonstrations "drilling only, not fracturing" in the disturbance zone were performed. Most of the wells have achieved good gas drainage effect and the average total gas production of a single surface well is about 2 million m3, up to more than 30 million m3. The surface well in the mining area also played a very important role in the gas control in the upper corner of the coal mine working face. The gas concentration in the upper corner of the working face decreased by about 50% on average, which has significant effects in both coalbed methane drainage and gas emission control at working faces, and has good promotion and application value.