Multiscale mixed finite element, discrete fracture–vug model for fluid flow in fractured vuggy porous media

Abstract

Numerical simulation in naturally fractured-vuggy media is challenging because of the coexistence of porous media, fractures and vugs on multiple scales that need to be coupled. We present a new approach to reservoir simulation, based on the discrete fracture–vug network (DFVN) model, which gives accurate resolution of both large-scale and fine-scale flow patterns.In this work, we use a multiscale mixed finite element method (MsMFEM) for fluid flow in fractured-vuggy media using the discrete fracture–vug model. By combining MsMFEM with the discrete fracture–vug model, we aim towards a numerical scheme that facilitates fractured vuggy reservoir simulation without upscaling. MsMFEM uses a standard Darcy model to approximate the pressure and velocity on a coarse grid, whereas fine scale effects are captured through basis functions constructed by solving local flow problems using the discrete fracture–vug model. The accuracy and the robustness of MsMFEM are shown through several examples. In the first example, we consider Beavers–Joseph model and then compare the analytic solution. We use the MsMFEM in more complex models. The results indicate that the MsMFEM is a promising path toward direct simulation of highly resolution geomodels.