Determination of effective transport properties of fractured rocks using the extended finite element method and micromechanics

In the paper, two modeling strategies for the computation of the effective permeability of heterogeneous, fractured rocks utilizing homogenization over a representative elementary volume (REV) are proposed and compared. One method is based on a new continuum micromechanics model. Here, the REV represents distributed fractures idealized as penny shaped inclusions in a porous matrix. The effective properties computed by this model are anisotropic and depend on the intrinsic properties of the porous matrix and the topology and density of the fractures. We propose a novel Cascade Continuum Micromechanics model (CCM), which is able to predict a fracture percolation threshold for a particular fracture density as a function of the topology of the fractures. The second modeling strategy is based on an Extended/Generalized Finite Element model (XFEM-GFEM) recently developed for numerical simulations of hydraulic fracturing in deep geothermal reservoirs. The predictions for the effective permeability from both models are compared for a REV containing distributed fractures with different aspect ratios and crack densities.