Finite element modelling of viscosity-dominated hydraulic fractures

Hydraulic fracturing is a highly effective technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to developing more efficient application of this technology, and also presents a significant technical challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on existing pore pressure cohesive finite elements has been established to simulate the propagation of a viscosity-dominated hydraulic fracture in an infinite, impermeable elastic medium. Selected results of the finite element modelling and comparisons with analytical solutions are presented for viscosity-dominated plane strain and penny-shaped hydraulic fractures, respectively. Some important issues such as mesh transition and far-field boundary approximation in the cohesive finite element model have been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by fluid viscosity demonstrates the capability of the cohesive zone finite element model in simulating the hydraulic fracture growth.