A higher resolution edge-based finite volume method for the simulation of the oil-water displacement in heterogeneous and anisotropic porous media using a modified IMPES method

In this article, we present a higher-order finite volume method with a 'Modified Implicit Pressure Explicit Saturation' (MIMPES) formulation to model the 2D incompressible and immiscible two-phase flow of oil and water in heterogeneous and anisotropic porous media. We used a median-dual vertex-centered finite volume method with an edge-based data structure to discretize both, the elliptic pressure and the hyperbolic saturation equations. In the classical IMPES approach, first, the pressure equation is solved implicitly from an initial saturation distribution; then, the velocity field is computed explicitly from the pressure field, and finally, the saturation equation is solved explicitly. This saturation field is then used to re-compute the pressure field, and the process follows until the end of the simulation is reached. Because of the explicit solution of the saturation equation, severe time restrictions are imposed on the simulation. In order to circumvent this problem, an edge-based implementation of the MIMPES method of Hurtado and co-workers was developed. In the MIMPES approach, the pressure equation is solved, and the velocity field is computed less frequently than the saturation field, using the fact that, usually, the velocity field varies slowly throughout the simulation. The solution of the pressure equation is performed using a modification of Crumpton's two-step approach, which was designed to handle material discontinuity properly. The saturation equation is solved explicitly using an edge-based implementation of a modified second-order monotonic upstream scheme for conservation laws type method. Some examples are presented in order to validate the proposed formulation. Our results match quite well with others found in literature. Copyright (C) 2016 John Wiley & Sons, Ltd.