Performance of combined vorticity-based gridding and dual mesh method for gravity dominated reservoir flows

This paper presents a new combined method for accurate upscaling of two-phase displacements in highly heterogeneous reservoirs. The method has the capability to retain its high performance for various flow regimes, from viscous to gravity dominant displacements, without the need for further modifications and computational steps. Two different grids are incorporated for simulation. The grid on fine scale is used to recognize the complicated physics of flow which depends on dominated driving forces and their interaction with heterogeneity. However, to achieve a fast simulation, the global flow calculation is performed on the coarse scale grid using upscaled equivalent properties. The communication between two different scale grids is achieved by the dual mesh method (DMM) procedure. A simple geometric mean upscaling technique is used to assign effective permeability for coarse grid blocks which introduces a significant error due to homogenization. As a result, DMM is incorporated in conjunction with the vorticity-based coarse grid generation technique to limit the homogenization error. The distribution of the coarse grid is optimized by the vorticity preservation concept which attempts to preserve single-phase vorticity between fine and coarse grid models. To demonstrate accuracy and efficiency, the combined DDM–vorticity method is applied to highly heterogeneous systems in two dimensions with and without gravity. The results reveal that the flow regime has only a minor impact on the performance (accuracy and speed up) of the method.