Comparison of a Double-Scale Method and the Pebi Grid Method in Near-Well Flows Simulation

Although the use of radial logarithmic-distributed grids are popular in the case of the reservoir simulation with high saturation changes around the wells, this method is limited to the reservoirs with single-well. On the other hand, the necessity of applying fine-grid around the wellbore is approved in such phenomena. Therefore, a robust solution may be using both the Cartesian and the radial grid. In this paper, a Double-Scale method by using the concept of overlapping grids is presented. The main idea in this method is a coarse Cartesian grid overlapped by a radial grid connected by using the interpolation between the results of grids on the outer boundary of the radial grid. The method is implemented in the open-source Matlab Reservoir Simulation Toolbox (MRST). To show the performance of the presented Double-Scale method, the results of the second SPE comparative study simulation are compared with those obtained by PEBI (perpendicular-bisectional) grid. The results clearly show the good agreement between these methods in case of water cut and oil production rate while the advantage of the new Double-Scale method is in computational time which is about 1.7 times faster than PEBI.