Phase field method to model hydraulic fracturing in saturated porous reservoir with natural fractures

In the present work, phase field model has been implemented for simulating hydraulic fracturing in porous reservoir which consists of several poorly connected natural fractures. We have used the finite element method (FEM) for solving the poro-elastic deformation and phase field equation, while the finite volume method (FVM) has been considered for solving the flow field. The validations of the numerical model with existing analytical and numerical solutions of fracture propagation are presented for an elastic medium subjected to incremental external loads and a poro-elastic medium undergoes hydraulic fracturing due to the increase of fluid injection pressure. The simulation results in this study show the ability of the phase field method based hydraulic fracturing (HF) model to obtain complex fracture propagation patterns including crack branching, merging, curving, and interacting with pre-existing natural fractures. Numerical simulation results suggest that for high injection pressure it is possible to get crack branching which is a desirable in the context of hydraulic fracture to create multiple high permeable flow paths with improved connectivity among the natural fractures for fluid circulation among injection and production wells. In the present study the values of aperture along the newly created hydraulic fracture and pre-existing fracture are determined from the displacement and phase fields at the end of hydraulic fracture simulations. The enhancement of effective transmissivity of the reservoir after hydraulic fracturing is compared for different network of pre-existing natural fracture. These results may be very insightful for industrial applications of hydraulic fracturing.