Waterflood simulation of stratified sandstone reservoirs using dynamic pseudo curves

Abstract

Many studies have shown that pseudo relative permeability curves can be used in one-dimensional (1-D) linear models to successfully match simulation performance of two-dimensional (2-D) cross-sectional models. Additional studies have shown that pseudo relative permeability curves can be used in 2-D areal models to match 3-D model performance. The techniques, however, used in the latter studies were laborious and complex and often required multiple sets of pseudo relative permeability curves. This study shows that a 2-D areal model that uses only one set of pseudo relative permeability curves (generated from a cross-sectional model) allows accurate simulation of waterflood performance for highly stratified reservoirs that would otherwise require 3-D simulation or 2-D simulation with multiple sets of curves. The cases examined are waterfloods in reservoirs with repeating 5-spot patterns for several sandstone stratifications from beach, fluvial channel, and delta margin environments of deposition. Reservoir simulation in this study makes use of lab-derived capillary pressure curves and the method of Jacks et al. to compute pseudo relative permeability curves. Gravity numbers were developed to characterize cross-sectional and 5-spot (areal) displacements. These gravity numbers were correlated for several geological stratifications to minimize the need for iterative simulations of each particular cross-sectional model to obtain pseudo relative permeability curves. Two of these correlations were applied to field cases to demonstrate their utility.