Spatial division of abandoned mine methane reservoir: Taking 12501 working face of Tunlan Coal Mine as an example

The accurate division of the disturbance space of abandoned mine methane(AMM) reservoir is an important basis for the evaluation, development and utilization of AMM resources. In this paper, taking the No. 2 coal 12501 working face of Tunlan Mine in the Xishan mining area of Shanxi as an example, numerical simulation of stress field, numerical simulation of fracture field and physical similarity simulation are used. The distribution law of stress field and fracture field during the mining process and after the goaf is stabilized is comprehensively studied. The research results show that the physical similarity simulation and the numerical simulation have a high degree of agreement. Combining the above three methods, the CBM disturbance reservoir space in the abandoned working face 12501 is finally divided into floor fracture area, recompaction area, gas conduction fracture area and bearing fracture area. The floor fissure area is located just below the working face in the coal seam. The overall mining fissure development area presents an inverted trapezoidal platform with the bottom surface close to the mined coal seam. The numerical simulation results of the fissure field show that its vertical depth is 22.3 m, Its depth is 5.58 times the thickness of the coal mined. The pressure-bearing area is located in the unexploited coal reservoir around the working face. It extends 70 m outward from the boundary of the working face inclination and 100 m from the boundary of the working face strike. The numerical simulation results show that the peak value of vertical stress of coal reservoir in the pressure bearing zone is much larger than the stress value of the original state of the coal seam, but smaller than the average compressive strength of the coal sample in the vertical seam. The main part of the gas-conducting fissure area is located at the edge of the coal seam working face. The bottom is a rock caving zone with a height of about 13.2 m, and the upper part of the caving zone is a rock stratum fault zone with a height of about 33.6 m. The vertical cracks in the fault zone continue to expand and penetrate through. Separation cracks. The overall shape of the gas-conducting fracture area is a trapezoidal platform, Its height is 11.7 times the thickness of the coal mined.. The main body of the recompaction area is distributed in the middle part of the goaf of the mining face, with a dip width of 110 m and a strike length of 1 268 m. This area is mainly composed of curved and caving overlying rocks, and the overall shape is a trapezoidal platform, which is located inside the gas-conducting fracture area. The gas-conducting fracture area is a favorable area for the development of legacy coalbed methane resources.