thanks to Mao Sheng, China University of Petroleum
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 assuming the slick-water fracturing condition holds. Among the formation conditions we discuss in this paper, the transition regime appears as a dominant propagation mechanism. 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 discrete 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 result of the change of direction and magnitude of the local stress. Further, fracture deflections become extensive when the fracture spacing and horizontal stress difference decrease and Young’s modulus ratio increases.
— Stéphane P.A. Bordas