Generation of coarse‐scale continuum flow models from detailed fracture characterizations

A procedure for developing coarse‐scale continuum models from detailed fracture descriptions is developed and applied. The coarse models are in the form of a generalized dual‐porosity representation, in which matrix rock and fractures exchange fluid locally while large‐scale flow occurs through the fracture network. The methodology developed here introduces local subgrids to resolve dynamics within the matrix and provides appropriate coarse‐scale parameters describing fracture‐fracture, matrix‐fracture, and matrix‐matrix flow. The geometry of the local subgrids, as well as the required parameters for the coarse‐scale model, are determined from local flow solutions using the underlying discrete fracture model. The method is applied to two‐ and three‐dimensional single‐phase and two‐phase flow problems, and the accuracy of the coarse models is assessed relative to fully resolved discrete fracture simulations. For the cases considered, it is shown that the technique is capable of generating highly accurate coarse models with many fewer unknowns than the detailed characterizations, and speedups of about a factor of 100 are achieved.