Analytical dual mesh method for two-phase flow through highly heterogeneous porous media

Abstract

Detailed geological models of a reservoir may contain many more cells that can be handled by reservoir simulators due to computer hardware limitations. Upscaling is introduced as an effective way to overcome this problem. However, recovery predictions performed on a coarser upscaled mesh are inevitably less accurate than those performed on the initial fine mesh. Dual mesh method is an approach that uses both coarse and fine grid information during simulation. In the reconstruction step of this method, the equations should be solved numerically within each coarse block, which is a time consuming process. Recently, a new coarse-grid generation technique based on the vorticity preservation concept has been applied successfully in the upscaling field. Relaying on this technique for coarse-grid generation, a novel method is introduced in this paper, which replaces the time-consuming reconstruction step in the dual mesh method with a fast analytical solution. This method is tested on challenging test cases regarding upscaling, in order to examine its accuracy and speed. The results show that the simulation time is decreased noticeably with respect to the conventional simulation methods. It is also 2–4 times faster than the original dual mesh method with almost the same accuracy.