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废弃工作面遗留煤层气扰动储层空间划分以屯兰煤矿12501工作面为例

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

  • 摘要: 废弃矿井扰动空间精确划分是遗留煤层气资源评价和开发利用的重要基础,以山西西山矿区屯兰煤矿2号煤12501工作面为例,采用应力场数值模拟、裂隙场数值模拟和物理相似模拟的方法,综合研究了采动过程中及采空区稳定后的应力场、裂隙场的分布规律。研究结果显示:物理相似模拟与数值模拟吻合度高,综合以上3种方法,最终将12501废弃工作面遗留煤层气扰动储层空间划分为底板裂隙区、重新压实区、导气裂隙区和承压区。底板裂隙区位于煤层中工作面的正下方,整体采动裂隙发育区域呈现出靠近开采煤层为底面的倒梯形台,裂隙场数值模拟结果显示其垂向深度为22.3 m,其深度为开采煤厚的5.58倍。承压区位于工作面四周的未开采煤储层,在工作面倾向的边界起分别向外延伸70 m,在工作面走向的边界起分别向外延伸100 m的位置上,数值模拟结果显示承压区煤储层垂向应力峰值为远大于煤层原始状态的应力数值,但小于垂层煤样的平均抗压强度。导气裂隙区主体位于开采煤层工作面边缘区域,底部为高度约为13.2 m的岩层垮落带,紧邻垮落带上部为高约33.6 m的岩层断裂带,断裂带内竖向裂缝不断扩展贯通离层裂缝。导气裂隙区整体形状为梯形台,其高度为开采煤厚的11.7倍。重新压实区主体分布于开采工作面采空区的中间部分,倾向宽度为110 m,走向长度为1 268 m。此区域主要为弯曲垮落的覆岩构成,整体形状为梯形台,位于导气裂隙区内部。导气裂隙区为遗留煤层气资源的开发有利区。

     

    Abstract: 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.

     

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