Multiscale finite volume method with adaptive unstructured grids for flow simulation in heterogeneous fractured porous media

The multiscale finite volume method for discrete fracture modeling in highly heterogeneous porous media is developed. Multiscale methods are sensitive to the heterogeneity contrasts in both matrix and fracture networks. To resolve this, efficient algorithms for generating adaptive unstructured coarse grids are devised. First, primal coarse grids are independently constructed for the matrix and lower dimensional fractures. Then, flexible dual coarse grids are generated based on the fracture and matrix permeability features. Since the proposed algorithms employ the equivalent graph of unstructured grids, the same coarse grid generation strategy is applied for the fractures and matrix domains. Permeability-adapted coarse grids significantly improve the monotonicity behavior of MSFV method in highly heterogeneous fractured porous media. The performance of the method is assessed through several challenging test cases with highly heterogeneous permeability field in both fractures and matrix domain. Numerical results indicate that the extended MSFV method with adaptive unstructured coarse grids is a significant development for accurate flow simulation in heterogeneous fractured media using DFM approach.