Investigation on failure behavior and hydraulic fracturing mechanism of Longmaxi shale with different bedding properties

Abstract

Research on the failure behavior and hydraulic fracturing mechanism of Longmaxi shale is vital for deep shale gas exploitation. The anisotropic properties of shale, especially bedding properties, significantly affect its cracking behavior. In this study, by embedding the smooth joint model (SJM) into the parallel bond model (PBM) in two-dimensional particle flow code (PFC2D), uniaxial compression and fluid–solid coupling hydraulic fracturing models with different bedding properties were quantitatively established, and the effects of bedding properties on the failure behavior and hydraulic fracturing mechanism of Longmaxi shale were investigated. The results demonstrated that bedding properties significantly affect the failure pattern, strength response and hydraulic fracture propagation of shale. Shale failure is controlled by bedding inclination, bedding strength, and maximum principal stress, which mainly depends on their competition mechanism. In addition, it is found that the secondary induced fractures associated with primary through-bedding fractures tend to have larger fracture networks compared with those associated with primary along-bedding fractures.