含气页岩组分构成与岩石力学特性

摘要

Mechanical properties of shale gas reservoir affect drilling rate .Studying textures and me-chanical properties of gas shale can help to provide technical support for drilling designs and operations . Mineral composition ,microstructure and mechanical properties for shale cores from southern Sichuan and shale outcrops in Longmaxi Formation ,were investigated through X-ray diffraction analysis ,electron mi-croscope scanning ,triaxial rock mechanical test ,etc .The study shows that Longmaxi Formation shale has clay mineral contents of 16.3% to 64.3% ,in w hich illite accounts for 74.0% ,but no smectite ,indicating low water sensitivity shale ;matrix mineral less than 5 μm in grain size accounts for an absolute majority with a small amount of silt-sized debris or grains ;uniaxial compressive strengths of parallel and perpendicu-lar to bedding plane are 137.0 M Pa and 132.4 M Pa respectively ,and uniaxial compressive strength in the direction with 45°offset is 66% of that parallel to bedding plane .The study results show that shale mechan-ical properties are obviously anisotropic .%页岩气储层的岩石力学特性能够影响钻井速度，进行含气页岩组构与岩石力学特性研究，可以为钻井设计和施工提供技术支持。采用X射线衍射分析、氩离子束剖光后扫描电镜观测和三轴岩石力学试验等方法，从矿物组分、微观结构、岩石力学性质等方面对蜀南页岩气钻井所取岩心和龙马溪组页岩野外露头进行了岩石力学特性研究。结果表明，龙马溪组含气页岩中黏土矿物的质量分数为16.3％～64.3％，伊利石占黏土总量的74.0％，不含蒙脱石，属于低水敏性页岩；粒径小于5μm的基质矿物含量占绝对优势，其中分布少量细粉砂级碎屑或颗粒；平行于层理面方向和垂直于层理面方向的单轴抗压强度分别为137.0和132.4 M Pa ，45°方向抗压强度为平行层理面方向的66％，表明页岩力学性质存在明显的各向异性。