XFEM-EDFM-MINC for Coupled Geomechanics and Flow in Fractured Reservoirs

Unconventional reservoirs are often naturally and hydraulically fractured with characteristically small pores and low permeability within the matrix. The underlying fracture networks can have a wide range of length scales and complex geometries. While hydraulic fractures may be propped, natural fractures are predominantly supported by pore pressure. A timely topic in the simulation of unconventional petroleum resources is in devising models that can accurately capture the coupling between the geomechanics of the fractured media and the multiphase fluid flow and transport. We develop a mixed discretization approach to adequately resolve the fracture system while accurately and efficiently modeling both flow and geomechanics. An extended finite element method (XFEM) is applied to approximate the geomechanics, and an embedded-discrete-fracture model (EDFM) is used for the multiphase flow equations. The two schemes are fully coupled, and the time discretization for flow is fully-implicit. Moreover, a hybrid fracture representation concept is employed where the multiple interacting continua (MINC) approach is used in conjunction with the embedded discrete representation in order to capture small-scale fracture networks efficiently. Several validation and computational results are presented. We also apply the proposed method to production scenarios with horizontal wells and hydraulic fractures in reservoirs with secondary fractures.