石油实验地质2024，Vol.46Issue(4)：683-697,15.DOI:10.11781/sysydz202404683
深层页岩微观力学特征及控制机理
Micromechanical characteristics and controlling mechanism of deep shale:
摘要
Abstract
The deep shale gas in the Fuling area is characterized by complex structures,high crustal stress,significant stress differences,high formation temperatures,high compaction levels,low porosity,low permeability,and complex porosity-permeability variation patterns.One reason for the significant production differences between wells is the insufficient understanding of the geomechanical features and controlling mechanisms of deep shale gas reservoirs,and the inaccurate identification of sweet spots for hydraulic fracturing.This study focuses on the marine shale of the Wufeng-Longmaxi formations in the Fuling area,investigating the micromechanical characteristics and controlling mechanisms of deep shale gas reservoirs through five series of experiments:micro rock mechanics experiments,digital speckle experiments,X-ray diffraction,total organic carbon content measurement,and scanning electron microscopy(SEM).Coupled with digital image processing technology,the changes in stress field and displacement field,and microcrack propagation processes in the Longmaxi shale under loading condi-tions were meticulously depicted.The deformation and fracture characteristics of the Longmaxi shale were analyzed.Experimental results indicated that the total organic carbon content in the deep shale is approximately 4.2%,with quartz content at 55.4%and clay mineral at 26.9%.The study identified five stages of microdamage evolution in deep shale:compaction,elasticity,uniform crack propagation,crack propagation failure,and brittle failure.Under the influence of brittle minerals such as quartz,and soft components such as organic matter,the microcracks in deep shale exhibit various propagation modes,including transgranular,intergranular,and laminated layer cracks.Additionally,the fracture toughness indices of the deep shale samples were calculated,with Mode Ⅰindex being 8.279 MPa·(√m) and ModeⅡindex being 1.243 Mpa·(√m).These experimentally obtained fracture toughness indices can be applied to evaluate the brittleness of deep shale,providing guidance for deep shale frac-turing modification.关键词
微观力学特征/脆性特征/压裂改造/深层页岩/涪陵地区Key words
micromechanical characteristics/brittleness characteristics/fracturing/deep shale/Fuling area分类
能源科技引用本文复制引用
孔令运,宋广朋,蒋恕,王子航,李继庆,时贤..深层页岩微观力学特征及控制机理[J].石油实验地质,2024,46(4):683-697,15.基金项目
国家自然科学基金(42130803)、国家自然科学基金面上项目(42072174)和湖北省自然科学基金(2023AFB110)联合资助. （42130803）
