Investigating the effects of intersection flow localization in equivalent-continuum-based upscaling of flow in discrete fracture networks

Abstract. Predicting effective permeabilities of fractured rock masses is a crucial component reservoir modeling. Its often realized with the discrete fracture network (DFN) method, whereby single-phase incompressible fluid flow modeled in representations individual fractures network. Depending on overall number fractures, this can result high computational costs. Equivalent continuum models (ECMs) provide an alternative approach by subdividing into grid continuous medium cells, over which hydraulic properties are averaged for simulations. While methods have advantage lower costs and possibility including matrix properties, choosing right cell size to discretize ECM accurate results conserve anisotropic properties. Whereas several techniques exist map onto complexity related intersections ignored. Here, numerical simulations Stokes simple utilized analyze their effect permeability. It demonstrated that intersection lineaments oriented parallel principal direction increase permeability process we term localization (IFL). We propose new method generate ECMs includes directional pipe parameterization: fracture-and-pipe model. Our compared against does not take IFL account performing ECM-based upscaling massively parallelized Darcy solver capable representing anisotropy cells. at local scale (fracture scale), its effects network-scale minor. investigated test cases orthogonal formations various scales, lengths, apertures, densities. Only global porosities above 30 % start systems For densities, smeared out process. However, noticed strong dependency resolution. Resolution tests suggests that, as long smaller than minimal length larger maximal aperture considered network, resulting anisotropies resolution-independent. Within range, applicable upscale networks.