Modeling of Hydraulic Hractures with Poromechanical Coupling Using an Assumed Enhanced Strain Method

Abstract:

When modeling hydraulic fractures, it is often necessary to include tightly coupled interaction between fluid-filled fractures and the porous host rock. Further, the numerical scheme must accurately discretize processes taking place both in the rock volume and along growing fracture surfaces. This work presents a three-dimensional scheme for handling these challenging numerical issues. Solid deformation and fluid pressure in the host rock are modeled using a mixed finite-element/finite-volume scheme. The continuum formulation is enriched with an assumed enhanced strain (AES) method to represent discontinuities in the displacement field due to fractures. Fractures can be arbitrarily oriented and located with respect to the underlying mesh, and no re-meshing is necessary during fracture propagation. Flow along the fracture is modeled using a locally conservative finite volume scheme. Leak-off coupling allows for fluid exchange between the porous matrix and the fracture. We describe an efficient and scalable preconditioning process that leads to rapid convergence of the resulting discrete system. The scheme is validated using analytical examples and monitoring data from a real fractured reservoir.