XFEM modeling of multistage hydraulic fracturing in anisotropic shale formation

The aim of the present study is to understand hydraulic fracture propagation behavior in shale formations through numerical simulation. The propagation regime of shale fractures is first analyzed based on shale rock properties and the slick-water fracturing condition. Within the formation conditions we discuss in this paper, the transition regime is a dominant propagation behavior. Based on this knowledge, we establish an XFEM-based hydraulic fracture propagation model. The orthotropic nature of shale is taken into account. An iterative approach is successfully used to deal with the solid-fluid interaction problem. The model is verified by several analytical solutions. A Five-stage hydraulic fracturing is simulated to understand the mechanical interaction of fractures with each other. Results show that on-going hydraulic fractures are attracted by the pre-existing hydraulic fractures as a results of the change direction and magnitude of the local stress state. Further, the fracture deflection becomes extensive when the fracture spacing and horizontal stress difference is decreased and Young’s modulus ratio is increased.