Numerical Simulation of Hydraulic Fracture Propagation using Fully-Coupled Peridynamics, Thin-Film Flow, and Darcian Flow

A numerical model is presented for the simulation of the evolution of hydraulic fracture in general geological media that couples a peridynamic mechanical model and finite element models for porous flow and fracture flow. The two-dimensional model captures porous flow through rock; thin-film flow through hydraulic fractures; mechanical deformation due to applied loads, pore pressure, and fracture pressure; and fracture growth and deformation. The fracture mesh is built dynamically as the fracture grows, connecting broken peridynamic bonds. While a simple finite element model of Darcian flow is employed in the presented results, the formulation and implementation of the peridynamic and fracture models allows the code to be easily coupled to any other hydrogeological code. The dynamic evolution of the system is solved by implicit Runge-Kutta integration. The mechanical deformation, matrix pore pressure, and fracture pressure fields are solved fully-coupled in staggered nonlinear iterations at each Runge-Kutta stage, and the damage field is updated sequentially at each time step. The accuracy and convergence rates of the peridynamic model is studied by comparing numerical results to analytical solutions in linear mechanics, and the fully-coupled model is benchmarked against Terzhaghi's consolidation problem. Applications of the model to simulating pressure-driven hydraulic fracture extension of a lone fracture and a fracture interacting with preexisting natural fractures are presented.