Multiscale simulation of flow in fractured porous media using unstructured grids

In this paper for flow simulation in fractured porous media, a multiscale finite volume method on unstructured grids is developed. To this end, algorithms for generating coarse scale unstructured grids for the matrix and fracture networks are presented independently. The presented algorithms for generating coarse scale unstructured grids are adaptable based on local changes in permeability field. Unstructured grid adaption based on permeability field has significant effect on improving the multiscale solution results in highly heterogeneous permeability fields. For the first time in this research, applying adaptive unstructured grids in fractured porous media is done. Coarse scale grid cells are generated such that strong variation of permeability along their boundaries and also the placement of coarse scale vertices in low permeability region are prevented. To reduce the computational cost, fracture-matrix coupling is considered only for the calculation of basis functions in the matrix domain. In order to evaluate the proposed algorithms, various 2D test cases are designed and solved. Finally, it is shown that the multiscale finite volume method with the proposed algorithms is an efficient numerical method for flow simulation in heterogeneous fractured porous media.