A novel hybrid model for hydraulic fracture simulation based on peridynamic theory and extended finite element method

The development of subsurface hydrocarbon reservoirs is highly dependent on hydraulic fracturing technology, and it is of great significance to use numerical simulation approaches to explore the propagation characteristics of hydraulic fractures. A novel hybrid model for investigating the hydraulic fracturing problem is proposed in this paper, wherein the crack segment is described using the extended finite element method (XFEM), and the region of the crack tip and potential fracture propagation is described using peridynamic (PD) theory. The fluid flow is governed by the continuity equation and the momentum equation, and the permeability in the fracture is calculated by the cubic law. The proposed model takes advantage of the small computational complexity of XFEM, and uses the stretch in the PD theory to determine whether the bond is broken, avoiding the need to obtain the stress intensity factor. The importance of the hybrid model is the coupling strategy for the transition region from XFEM to PD. Then the model is validated against two classic problems with available analytical solutions. The issue of hydraulic fractures intersecting natural fractures is also addressed. Meanwhile, the mesh size and the coupling region size is studied in this work. The model proposed in this paper is of benefit to provide a new perspective for numerical simulation of hydraulic fracture.