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The Finite-element-centered Finite-volume Discretization Method (FECFVM) for Multiphase Transport in Porous Media with Sharp Material Discontinuities
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, ECMOR XIV - 14th European Conference on the Mathematics of Oil Recovery, Sep 2014, Volume 2014, p.1 - 22
Abstract
Simulation of coupled pressure-, buoyancy- and capillary driven multiphase fluid flow in geological media is challenging as they are aggregates of many rock types with sharp interfaces and extremely variable flow properties. Geological features have variable orientations, complex intersections, and aspect ratios up to >1000:1. Hence, realistic discretization is only possible with adaptively refined unstructured grids. Finite-element schemes for such meshes are not locally conservative and therefore ill suited for the simulation of transport processes. To overcome this restriction we developed a hybrid Finite-Element Node-Centered Finite Volume scheme (FEFVM). In this method, however, interface finite-volumes include multiple materials and smearing of transport variables occurs.
Here we present a new hybrid discretization technique that permits computation of conservative interelement fluxes. Finite elements are simultaneously used as finite volumes for a piecewise constant discretization of transport variables. This Finite Element-Centered Finite Volume Method (FECFVM) has the advantage that saturation discontinuities at material interfaces are honored without having to add extra degrees of freedom as in the embedded discontinuity method (DFEFVM), our earlier solution resolving the smearing problem. The FECFVM brings additional benefits regarding upwinding. The implementation presented here further allows representation of fractures or sand lenses by lower dimensional elements. This simplifies model construction, meshing, and fracture aperture modeling. It also speeds up computations. gradients allow accurate computation of interface fluxes and capillary effects on global pressure can be considered because it can be discontinuous.