Peridynamic modeling and analysis of interfacial crack propagation by hydraulic fracturing in layered shale

Hydraulic fractures at the bedding interface in layered shale will give rise to various phenomena including penetration, diversion and offset which significantly influence the production of shale gas exploitation. It is persistent challenge to simulate the uncertain fracture propagation paths induced by hydraulic fracturing when encountering interfaces. In this study, an alternative peridynamic model is proposed to investigate the interfacial crack propagation by hydraulic fracturing in layered shale. The water pressure loading process is described through equivalently transforming the water pressure applied on fracture surfaces into the water pressure density on broken bonds. The interface model and its cracking criterion are derived by employing bilinear cohesive zone model, which effectively characterize the interactions between rocks with different properties on different sides of the bedding plane. The proposed model is validated through comparison with experimental results, and then is further employed to investigate the complex hydraulic fracture propagation near bedding interfaces. It is found that smaller angle between hydraulic fracturing direction and bedding may lead to better fracturing effects and higher gas extraction in layered shale.