Damage Characteristics Analysis and Fractal Study of Shale With Prefabricated Fractures under Thermal-mechanical Coupling

To study the damage and failure of shale with different fracture inclination angles under uniaxial compression loading,in this work,RFPA2D-Thermal,a two-dimensional real failure process analysis software,was used for numerical simulation.Numerical simulation results show that quartz in shale mainly affects the tensile and compressive strength of shale by increasing rock brittleness.The coupling of temperature and pressure will cause lateral and volume destruction of shale,which enables the shale body to be more easily broken.Fracture inclination is the key factor affecting shale damage patterns.The failure mode of shale with low-and high-angle fractures is mainly shear failure,and the compressive strength does not vary with crack inclination.The damage mode of obliquely intersecting fractured shale is slip damage along the fracture face,the compressive strength decreases and then increases with the fracture inclination,and a minimum value exists.The acoustic emission simulation results of the damage process effectively reflect the accumulated internal damage and macroscopic crack appearance until fracture instability when the prefabricated fractured shale is subjected to uniaxial compressive loading.The crack inclinations of 0°and 120℃ corresponds to the most complex"N"shape damage mode.The crack inclinations of 30°and 60°,and the damage mode is an inverted"λ"shape.

贵州西部地区石炭系祥摆组煤系气储层特征分析

根据威宁地区钻探揭露情况,结合测井等资料,通过有机地球化学测试分析、核磁共振、电镜扫描和岩芯解吸实验,对黔西威宁地区煤储层特征及含气性进行分析。研究表明:煤层热演化程度较高,显微组分以镜质组为主,宏观煤岩类型主要为半亮煤,煤层孔隙和裂缝较发育,以溶蚀孔、粒间孔为主;泥页岩孔隙中介孔对总孔容的贡献远远大于大孔和微孔,祥摆组煤系页岩显示出较好的含气性,超过评价开发的最低标准。

不同围压下页岩微观破裂过程与量化研究

为揭示不同围压下页岩微观结构的破裂机理,基于RFPA2D-DIP对页岩微观结构进行单/双轴压缩试验,利用数字图像技术对页岩裂纹进行量化统计。结果表明,围压对页岩微观结构裂纹萌生、扩展及贯通具有重要影响,随着围压的增大,页岩微观结构存在V型(0 MPa、2 MPa、4 MPa)和倒V型(6 MPa、8 MPa、10 MPa)两种破裂模式,低围压(0 MPa、2 MPa、4 MPa)下微观结构破裂面粗糙,高围压(6 MPa、8 MPa、10 MPa)下微观结构破裂面平整。围压对裂纹量化指标影响显著,分形维数随围压的增大呈线性减小趋势,裂纹条数和裂纹总长随围压增大变化趋势具有一致性,呈M型,裂隙率和裂纹均宽随围压增大而减小,且变化速率越来越小。