千米深井煤层水力压裂作用下裂隙应力场演化规律的数值模拟研究  

Numerical simulation study on evolution law of fracture stress field under the action of hydraulic fracturing of coal seams in kilometer-deep wells

作　　者：李延辉[1] Li Yanhui(No.1 Coal Mine,Pingdingshan Tian′an Coal Industry Co.,Ltd.,Pingdingshan 467000,China)

机构地区：[1]平顶山天安煤业股份有限公司一矿,河南平顶山467000

出　　处：《能源与环保》2024年第4期32-37,43,共7页CHINA ENERGY AND ENVIRONMENTAL PROTECTION

基　　金：中国平煤神马控股集团科技板块重点研发计划项目(WSBG2022028)。

摘　　要：为了掌握千米深井煤层水力压裂作用下煤体内部裂隙应力场演化规律,更科学地开展超千米矿井煤层水力压裂增透瓦斯综合治理工作,以平煤股份一矿超千米埋深的戊8-31240工作面为建模背景,采用RFPA-2D数值模拟软件,建立了煤体内部裂隙发育—应力场扰动数值模型,模拟得到了水力压裂作用下深部煤体内部裂隙应力场演化过程。研究结果表明,深部煤体内部在水力压裂作用下,首先由水流浸润煤体,微裂隙在压裂孔四周区域萌生,在孔左上、右上两侧区域形成“V”形主级宏观裂隙呈扇形继续扩展发育,然后在孔左下、右下两侧区域微裂隙贯通形成“Λ”形次级宏观裂隙,最后孔两侧主、次级宏观裂隙贯通,呈现“X”形裂隙扩展主导压裂,并产生更多微裂隙,使深部煤体受水力压裂的影响范围不断扩大;深部煤体水力压裂开始阶段,内部破坏向压裂孔四周随机发生,随着压裂压力升高,煤体破坏开始向压裂孔上下区域延伸,但远小于向压裂孔两侧破坏速度,煤体破坏更多集中在煤层上部,表明水力压裂将会对煤层顶板造成较大冲击;深部煤体受水力压裂作用,条带状剪应力、块状拉应力主要集中在裂隙的尖端附近区域,剪应力从13.5 MPa卸压到1.1 MPa,卸压降幅91%,而拉应力从11.0 MPa卸压到2.2 MPa,卸压降幅80.0%,其拉应力卸压效果要小于剪应力的卸压效果,随着压裂的裂隙向煤体深部延伸转移,最终在单个压裂孔前后25 m范围区域形成剪—拉双重作用卸压区,使地应力得到释放,大大提高了深部煤体的透气性。数值模拟研究可为千米矿井深部煤层水力压裂技术工艺参数优化实施提供一定参考。In order to understand the evolution law of the crack stress field inside the coal body under the action of hydraulic fracturing of coal seams in kilometer-deep wells,and carry out comprehensive treatment of gas permeability enhancement more scientifically through hydraulic fracturing of coal seams with a depth of more than 1000 m,taking theⅤ8-31240 working face with a depth of more than 1000 m in Pingdingshan No.1 Coal Mine as the modeling background,the RFPA-2D software numerical simulation method was used to establish a numerical model of internal fracture development and stress field disturbance in coal bodies,and the evolution process of internal fracture stress field in deep coal bodies under hydraulic fracturing was obtained in the simulation.The research results showed that under the action of hydraulic fracturing,the deep coal body was first infiltrated by water flow into the coal body,micro-cracks sprout in the area around the fracturing hole,and a"V"-shaped main-level macro was formed in the upper left and upper right areas of the hole.The cracks continued to expand and develop in a fan shape,and then the micro-cracks in the lower left and right sides of the hole connected to form"Λ"-shaped secondary macro-cracks.Finally,the main and secondary macro-cracks on both sides of the hole connected,showing an"X"-shaped crack expansion dominant fracturing,and generate more micro-cracks,so that the range of deep coal bodies affected by hydraulic fracturing continues to expand.At the beginning of hydraulic fracturing of deep coal bodies,internal damage occurs randomly around the fracturing holes,and as the fracturing pressure increases,the coal body damage begins to extend to the upper and lower areas of the fracturing hole,but the damage rate is much smaller than the damage rate to both sides of the fracturing hole.The coal body damage is more concentrated in the upper part of the coal seam,indicating that hydraulic fracturing will cause a greater impact on the coal seam roof.The deep coal body is subjected

关 键 词：千米深井 水力压裂 裂隙应力场演化 剪—拉双重作用卸压区 数值模拟 

分 类 号：TD713.3[矿业工程—矿井通风与安全]