Modelling of 3D viscous fingering: Influence of the mesh on coreflood experiments

Abstract

The modeling of Viscous Fingering (VF) is of interest to the study of multiphase flow in porous media, especially in the O&G industry, where this phenomenon is one of the root causes of high-water production and low sweep efficiency. In this study, 3D coreflood experiments found in the literature were simulated with CFD, and nine different structured and unstructured meshes were compared to determine which one gives the best description of this phenomenon. The meshes included the structured orthogonal mesh, commonly used in reservoir simulation, up to unstructured hexahedral, polyhedral, and tetrahedral meshes, among others. On the other hand, the CFD model, which was based on the Volume of Fluid (VOF) model and the porous media model, was validated against experimental data for the oil recovery profile with an absolute error below 7% for the best cases. It was found that VF is severely affected by the type of mesh and the Courant–Friedrichs–Lewy (CFL) number used. It was concluded that the unstructured polyhedral and structured hexahedral meshes gave the most reliable description of the finger growth dynamics and oil recovery compared to experimental data. Finally, a mesh independence test using the Grid Convergence Index (GCI) methodology, along with a CFL number analysis, allowed to determine that the modeling of this phenomenon should be made using an average CFL number of 0.25.