摘要
The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions.In this work,considering the different combinations of confining pressure and bedding plane inclination angle(α),biaxial mechanical loading experiments were conducted on shale containing circular holes.The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes.The instability of shale containing circular holes can be classified into five types:tensile failure along the bedding planes,tensile failure through the bedding planes,shear slip along the bedding planes,shear failure through the bedding planes,and block instability failure.Furthermore,the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks.The crack initiation criterion for shale containing circular hole was established,providing a new method for evaluating the trajectory of shale hole wall fractures.This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.
页岩裂缝的演化直接影响页岩气的有效开采。然而,对于深部致密页岩在不同应力条件下裂纹起裂的特征,目前还缺乏研究。本文考虑了围压和层面倾角(α)的不同组合,对含圆孔页岩进行了双轴力学加载实验。研究结果表明,围压和层面倾角对含圆孔页岩的破断模式有显著影响。含圆孔页岩的失稳可分为五种类型:沿层面的拉伸破坏、通过层面的拉伸断裂、沿层面的剪切滑移、通过层面剪切破坏和块体失稳破坏。此外,发现圆孔周围应变场和应力场的演变是页岩裂纹起裂特征和位置变化的根本原因。建立了含页岩圆孔裂纹起裂判据,为评价页岩孔壁裂缝轨迹提供了一种新方法。本研究对于评估页岩储层中裂缝网络的演化和稳定性具有重要意义。
基金
Projects(52104143,52109135,52374099)supported by the National Natural Science Foundation of China
Project(2025YFHZ0323)supported by the Natural Science Foundation of Sichuan Province,China。
