Parallel PD-FEM simulation of dynamic fluid-driven fracture branching in saturated porous media

Abstract

The dynamic hydraulic fracture in porous media is often characterized by crack diverting and/or branching that affects the connectivity of the fracture network. There is a need to understand the crack branching mechanism for enhancing the unconventional resource production. In the present manuscript, the dynamic fluid-driven fracture branching in saturated porous media is studied by a parallel PD-FEM coupling approach. Under the assumption of negligible relative acceleration of the fluid with respect to the mixture, the two-field u-p model is derived based on the Biot’s theory. The dynamic coupled system is discretized into two layers with the non-ordinary state-based peridynamics layer characterizing the deformation and fracture of the solid skeleton and finite element layer representing the fluid flow. A fully implicit scheme for the time integration of the dynamic coupled system within a nonlinear framework based on the Newmark method is employed and an alternate grid/particle updating OpenMP parallel programming scheme is proposed. The efficiency and accuracy of the coupled method is first verified by several benchmark examples with either experimental data or analytical solutions, followed by a study of crucial factors affecting dynamic hydraulic fracturing branching. The parametric study shows that in general the following factors favor the crack branching: lower critical energy release rate, higher injection rate, lower Young’s modulus, higher Poisson’s ratio, lower viscosity of the fluid and higher compressibility of the fluid.