基于CT扫描的含方解石脉填充页岩损伤破裂数值仿真试验

Numerical Simulation on Damage and Fracture of Calcite Vein-Filled Shale Using CT Scanning

为研究黔北地区牛蹄塘组的含方解石脉填充页岩的破裂演化过程,通过CT扫描获取页岩内部的图像,采用阈值分割技术辨别出页岩基质与方解石脉,结合RFPA-3D数值仿真软件重构页岩三维数值模型,并对4个角度的方解石脉页岩进行单轴压缩数值模拟试验。试验结果表明:页岩的力学性质随方解石脉倾角呈现出明显的各向异性,其中方解石脉为0°时抗压强度达到最大值45.05 MPa,方解石脉为60°时抗压强度达到最小值37.02 MPa。含方解石填充页岩试样在单轴压缩下表现出多种破坏模式,分别为沿方解石脉的剪切滑移破坏、多条沿方解石脉的复合破坏和“V”型拉伸剪切复合破坏。研究成果对方解石脉填充的页岩储层裂缝起裂和扩展预测具有重要的参考价值。

To study the rupture evolution of the calcite vein-filled shale in the Niutitang Formation in northern Guizhou,this paper obtains the image of the shale interior by the CT scanning.The shale matrix and calcite veins are identified by using the threshold segmentation technique.The three-dimensional numerical model of the shale by combining with the numerical simula-tion software of RFPA-3D is established.The numerical simulations of the uniaxial compression tests on the calcite vein-filled shale with four angles are conducted.The test results show that the mechanical properties of the shale show obvious anisotropy with the inclination angle of the calcite veins,in which the compressive strength reaches the maximum of 45.05MPa when the calcite veins are 0°.The tensile strength reaches the minimum of 37.02MPa when the calcite veins are 60°.The calcite-filled shale samples show two damage modes under the uniaxial compression,which are the shear-slip damage along the calcite veins,composite damage and the"composite damage"veins and"V"-shaped tensile-shear composite damage.The research results have an important reference value for the prediction of the fracture initiation and the extension in calcite vein-filled shale reser-voirs.