Scaling-Up Fine Grid Models Using Pseudo Functions in Heterogeneous Porous Media

Abstract

To obtain a reliable characterization of complex reservoirs, geoscientists and petroleum engineers commonly build geologic or geostatistical reservoir models which contain more than a million grid cells. However, for flow simulation such a detailed description demands a great deal of information and processing time. Therefore, less complex models are usually preferred where the number of grid cells must be reduced by a factor of 10 or more. Such scaling up necessarily involves a loss of information that must be captured through upscaling porosity permeability and the use of pseudofunctions. The main objective of this paper is to determine a general methodology for using pseudofunctions for upscaling multiphase flow in 3D anisotropic heterogeneous reservoirs with different capillary and gravity numbers and applying the method to a real field case "Hassi Messaoud Field -Algeria".The performance of different kinds of pseudofunctions is evaluated under different capillary and gravity numbers, and upscaling levels. A variety of homogeneous fine grid models representing different existent flow regimes were considered in this study and the performance of several pseudofunction methods was compared. All the pseudo function methods succeeded in reproducing the fine grid water cut and oil production plateau for the capillary dominated, equilibrium, viscous dominated flows, however, for the gravity dominated flow they failed to match the fine grid curve exactly. Although this shortcoming of the pseudofunction curves gives better results than the rock curves.Next in this study, the results of the waterflood of a heterogeneous 3-D model of HMD Zone 17 are presented. This real field model confirmed the homogeneous case results: for high flow rates the pseudofunctions can be applied successfully to upscale from fine to coarse grid simulation.