页岩气储层岩石力学特性及脆性评价

Rock Mechanical Properties and Brittleness Evaluation of Shale Gas Reservoir

李庆辉 陈勉 金衍 侯冰 张家振

Li Qinghui Chen Mian Jin Yan Hou Bing Zhang Jiazhen

中国石油大学(北京)石油工程学院,北京 102249; 中国石油川庆钻探工程有限公司钻采工程技术研究院,四川成都 618300

College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing,102249,China; CCDC Drilling & Production Engineering Technology Research Institute,CNPC,Chengdu,Sichuan,618300,China

页岩气储层的岩石力学特性对开发影响极大,进行页岩破坏机理、力学特性和脆性评价方面的研究,可以为页岩气钻井和压裂设计工作提供技术支撑。采用室内试验和测井分析相结合的方法,在黑色页岩力学特性研究的基础上,分析了其脆性破坏特征及影响因素,提出了一种利用岩石弹性参数和矿物组成综合评价页岩脆性的方法,并介绍了利用测井资料计算单井脆性剖面的流程。研究表明,页岩普遍具有脆性破坏的特征,破坏类型与页岩种类、取心深度、取心方位和加载条件相关,低围压下标准试样以劈裂式破坏为主,全应力应变曲线经历极短的塑性屈服阶段即发生破坏,高围压时多出现双剪式和单剪式破坏,页岩的脆性与试样的弹性参数和矿物组成关系密切。实例分析表明,脆性特征影响压裂效果,与压裂造缝能力和产气情况吻合良好。综合脆性评价既是储层岩石力学特性分析的重要内容,也是压裂选层的重要依据。

Rock mechanical properties of shale gas reservoir are vitally important for exploitation.It’s necessary to conduct laboratory study on failure mechanism,mechanical properties and brittleness evaluation of shale,which can provide technical support for drilling and fracturing design.Based on rock mechanical properties of black shale,in combination with laboratory experiments and log analysis,the analysis of brittle failure characteristics and influential factors are performed.Comprehensive brittleness evaluation method utilizing elastic parameters and mineral compositions are proposed.Brittleness calculating process of single well utilizing logging data is introduced.Study results show that shale generally has a brittle fracture characteristic,and failure modes are related to shale type,coring depth,coring direction and loading conditions.Failure mode under low confining pressure is predominantly splitting failure;overall stress-strain curve has a very short plastic yield section before failure.Double shear and single shear failure modes are dominant under high confining pressure.Brittleness of shale samples has a close relationship to elastic parameter and mineral composition.A case study shows that brittleness affects hydraulic fracturing results,and coincides well with width generation capacity and deliverability.Comprehensive brittleness evaluation is useful for understanding reservoir mechanics and selecting fracture section.

国家重点基础研究发展计划("973"计划)项目"深井复杂地层安全高效钻井基础研究"(编号:2010CB226700)、国家科技重大专项"力学与化学耦合井眼稳定技术研究"(编号:2011ZX05031-004-005HZ)和国家自然科学"超低渗透页岩多井多裂缝同步压裂机理研究"(编号:51074171) 部分研究内容。

https://doi.org/10.3969/j.issn.1001-0890.2012.04.004