层状页岩力学参数的各向异性研究

Deep Layered Shale Mechanical Parameters Anisotropy Study

页岩具有明显的层理性质,使页岩的力学特性有明显的各向异性特征,其复杂的力学性能对页岩气资源开发带来了严重挑战。本文通过不同层理角度页岩试样的单轴、三轴压缩实验和超声波实验,研究了页岩力学参数的各向异性特征,揭示了其力学性能和强度特征。研究结果表明:随着层理角度逐渐变大,各页岩试样的单轴和三轴压缩强度均表现出两边高中间低的"U"型变化规律;强度各向异性度随着围压的增加逐渐降低并趋于稳定;不同层理角度页岩试样在不同围压下的弹性模量和泊松比各向异性特征明显;随着层理角度逐渐增加,页岩试样的纵横波波速、动剪切模量和动Lame模量也逐渐增大。研究结果对充分认识页岩力学性能、推动页岩气开采中的井壁稳定、水力压裂等技术有一定的指导意义。

The Shale has obvious bedding properties,causing the shale’s mechanical properties having obvious anisotropic characteristics,and its complex mechanical properties have brought serious challenges to the development of shale gas resources.In this paper,the anisotropy characteristics of shale mechanical parameters were studied through the uniaxial,triaxial compression tests,and ultrasonic experiments with different bedding angles,revealing their mechanical properties and strength characteristics.The results show that as the bedding angle became larger,the uniaxial and triaxial compressive strengths of the shale specimens showe a U-shaped change pattern.The strength anisotropy gradually decreases with the increase of confining pressure and tends to be stable.Young’s modulus with different bedding angles under different confining pressures and Poisson’s ratio are obvious anisotropy.When the bedding angle gradually increasing,wave speed,dynamic shear modulus and dynamic Lame modulus also gradually increases.The research results have certain guiding significance for the understanding of shale mechanical properties,promote shaft wall stability and hydraulic fracturing in shale gas production.