川南地区志留系龙马溪组页岩力学性质及微观破裂机理  

Mechanical properties of the Silurian Longmaxi Formation shale,southern Sichuan Basin and its microfracturing mechanisms

作　　者：龚训 金之钧 马新华 刘钰洋[3,4] 李关访 缪欢[6] GONG Xun;JIN Zhijun;MA Xinhua;LIU Yuyang;LI Guanfang;MIU Huan(Institute of Energy,Peking University,Beijing 100871,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China;National Energy Shale Gas R&D(Experiment)Center,Langfang,Hebei 065007,China;Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Unconventional Petroleum Research Institute,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]北京大学能源研究院,北京100871 [2]北京大学地球空间与科学学院,北京100871 [3]中国石油勘探开发研究院,北京100083 [4]国家能源页岩气研发中心,河北廊坊065007 [5]中国科学院地质与地球物理研究所页岩气与地质工程重点实验室,北京100029 [6]中国石油大学(北京)非常规油气科学技术研究院,北京102249

出　　处：《石油与天然气地质》2024年第5期1447-1455,共9页Oil & Gas Geology

基　　金：中国石油基础性前瞻性课题(2021DJ2005,2022DJ8004,2024DJ87)。

摘　　要：为揭示页岩力学性质和微观破裂机理,对川南地区志留系龙马溪组页岩开展了X射线衍射、三轴压缩、微米CT扫描和扫描电镜测试。研究发现:页岩矿物成分和围压对其力学性质和储层物性具有显著影响。随着脆性矿物含量的增加,页岩弹性模量和峰值应力增大,指示两者具有正相关关系。随着黏土矿物含量的增加,页岩塑性增强,岩石强度降低。随着围压的增加,页岩中的裂缝逐渐闭合、孔隙变形收缩、孔隙度减小,围压越大,压缩越严重。页岩在破坏过程中主要发育矿物颗粒边界裂缝和矿物颗粒内部裂缝两种裂缝。对于力学性质相近的页岩,随着围压的增大,页岩从矿物颗粒边界裂缝占主导演变为矿物颗粒内部裂缝占主导。围压增大导致矿物颗粒内部和颗粒边界裂缝向破碎带演变,页岩发育更多的裂缝。To reveal the mechanical properties and microfracturing mechanisms of shales,we investigate shales in the Silurian Longmaxi Formation in the southern Sichuan Basin using X-ray diffraction(XRD)analysis,together with triaxial compression,micro-computed tomography(micro-CT)and scanning electron microscopy(SEM)tests.The results indicate that the mechanical properties and reservoir physical properties of shale are significantly influenced by its mineral composition and confining pressure.Specifically,an increase in the brittle mineral content enhances its elastic modulus and peak stress,indicating positive correlations between these mechanical properties and the brittle mineral content.In contrast,higher clay mineral content increases the shale plasticity while reducing its rock strength.As confining pressure increases,fractures in the shale gradually close,and the pores deform and contract,leading to reduced porosity.A higher confining pressure results in greater compression.Two dominant types of fractures form during shale damage:boundary fractures occurring at interfaces between mineral grains and internal fractures occurring within grains.For shales with similar mechanical properties,increasing confining pressure shifts their dominant fracture type from boundary to internal fractures.Additionally,higher confining pressure causes the boundary and internal fractures to evolve into fracture zones,leading to an increased fracture density in the shale.

关 键 词：微观破裂机理 裂缝 岩石力学 页岩 龙马溪组 志留系 川南地区 

分 类 号：TE122.2[石油与天然气工程—油气勘探]