水力压裂裂缝对煤层回采工作面应力的影响

The Influence of Hydraulic Fracturing Fissures on Coal Seam Mining Face Stress

以山西省晋城矿区寺河煤矿3#煤层某个回采工作面为例,通过矿井煤层压裂效果观测,采用有限元方法,模拟了煤层气井水力压裂对煤炭安全生产的影响。结果表明:在水力压裂裂缝延伸的端部处出现了局部应力集中区域和局部应力减少区域并存的现象;水力压力产生的裂缝宽度以及在围岩作用下支持剂的力学性质对煤层开采应力分布具有一定影响,随着压裂裂缝宽度的增加,采动应力随煤壁距离增加的变化规律不同以往,呈现"双峰"的变化模式,采动应力峰值表现后移动趋势;随煤与充填材料差异系数k的增加,最大、最小水平主应力都表现指数变化规律。总体而言,压裂裂缝宽度和差异系数k增加有利于压裂裂缝卸压。

Taking one mining face in Sihe Coal Mine No.3 coal seam of Jincheng Mining Area of Shanxi province as an example,simulation works are done by finite element method based on the observation of the hydraulic fracturing underground to research the effect of hydraulic fracturing and mining safety.Results indicate that local stress release and local stress concentration places are presented at the extension end of hydraulic fracturing.The width of hydraulic fracturing produced in the coal and the properties of proppant under the original stress have some relations with the distribution of mining stress.Namely,the distribution of mining stress is different with the mining without hydraulic fracturing and presents bimodal pattern variation as the distance of the coal wall increasing.The peak value of mining stress is obviously backward transferred.As the material difference coefficient k of coal and proppant is increasing,the maximum and minium horizontal principal stresses flows exponential function.Generally,increasing of fracturing width and the coefficient k is well for releasing stress in the coal reservoir.