含层理页岩水压致裂特性及对破裂压力的启示  

Hydraulic fracturing characteristics of laminated shale and its enlightenment to fracture pressure

作　　者：沈仲辉 周令剑[1] 李希建[2] 张胜跃 周雷[4] SHEN Zhonghui;ZHOU Lingjian;LI Xijian;ZHANG Shengyue;ZHOU Lei(School of Emergency Management and Safety Engineering,Jiangxi University of Science and Technology,Ganzhou 341000,China;Mining College,Guizhou University,Guiyang 550025,China;College of Electronic Engineering,Xi’an Shiyou University,Xi’an 710065,China;State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China)

机构地区：[1]江西理工大学应急管理与安全工程学院,江西赣州341000 [2]贵州大学矿业学院,贵州贵阳550025 [3]西安石油大学电子工程学院,陕西西安710065 [4]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044

出　　处：《煤炭科学技术》2023年第11期119-128,共10页Coal Science and Technology

基　　金：国家自然科学基金资助项目(52264018);江西省教育厅科学技术资助项目(GJJ2200871);江西理工大学博士科研启动基金资助项目(205200100605)。

摘　　要：水力压裂是页岩气开发中常用的储层改造技术,破裂压力的准确预测对于现场压裂施工设计至关重要。为探究页岩层理对水力压裂的影响机制,以四川长宁地区黑色页岩为研究对象,对含层理的页岩进行巴西劈裂抗拉强度测试,利用GCTS岩石力学试验机开展不同层理角度下页岩的水压致裂试验,结合X射线CT机和三维扫描仪对页岩的扩展形态及裂缝表面粗糙度进行表征,并对页岩水力压裂的破裂压力进行分析。结果表明:(1)页岩的抗拉强度随层理角度变化呈先减后增的变化趋势,各向异性明显;(2)层理的存在对页岩水力压裂的破裂压力影响较大,不同层理角度条件下页岩水力压裂的破裂压力与抗拉强度的变化规律相似,在30°最小,90°最大;(3)层理面对水力压裂裂缝扩展的影响较小,主要是拉伸破坏产生的单裂缝,裂缝面粗糙度较高且与层理方向无关;(4)通过数值仿真确定了压裂井筒塑性区的存在,解释了试验中观察到异常高的破裂压力,说明水力压裂裂缝起裂后存在一定的临界起裂特征长度,岩石需要经过裂纹孕育阶段才能完全破裂,不同层理角度页岩通过临界起裂特征长度来影响起裂压力,采用新的模型能较好预测页岩水力压裂的破裂压力。研究结果对于了解深部页岩裂缝起裂扩展机理、压裂施工设计等具有一定的参考意义。Hydraulic fracturing is a common reservoir reconstruction technology in shale gas production.Accurate prediction of hydraulic fracture break pressure is of great significance to on-site fracturing construction.In order to explore the influence mechanism of shale bedding on hydraulic fracturing,taking the black shale in Changning area of Sichuan Province as the research object,the Brazilian splitting tensile strength test of the laminated shale was carried out.The hydraulic fracturing test of shale with different bedding angles was carried out using GCTS rock mechanics testing machine.The extension morphology and the roughness characteristics of the shale fractures were characterized combined with X-ray CT and three-dimensional scanner,and the fracturing pressure in hydraulic fracturing of shale was analyzed.The results shown that:①The tensile strength of shale decreased firstly and then increased with the variation of bedding angle,and the obvious anisotropy was exhibited;②The bedding had a great influence on the shale fracture pressure,the change of fracturing pressure and tensile strength of shale hydraulic fracturing under different bedding angle shown a similar trend,with the minimum at 30°and the maximum at 90°;③The bedding planes had a little influence on fracture extension of hydraulic fracturing,mainly single fracture produced by the tensile failure,and roughness of the fracture surface was higher and independent of the direction of bedding;④The existence of the plastic zone in the fractured wellbore was determined by numerical simulation,which also explained the abnormally high fracture pressures observed in the test,and suggested that there was a of hydraulic fracturing.Shales can be completely broken only after a very short time of crack inoculation.Fracture pressure was affected by the certain characteristic length of critical fracture initiation of shale with different bedding angle,and the new model can better predict the fracturing pressure of hydraulic fracturing in shale.The research re

关 键 词：页岩气开发 水压致裂 页岩层理 破裂压力 抗拉强度 扩展形态 裂缝粗糙度 

分 类 号：TU45[建筑科学—岩土工程]