A numerical simulation of the accuracy of present engineering methods for predicting waterflood performance of stratified reservoirs

Abstract

A two dimensional two phase (water-oil) numerical model has been used to investigate the accuracy of present engineering methods for predicting the waterflood performance of stratified reservoirs. The model includes the effects of gravity and capillary pressure. Also, investigations were made of the sensitivity of waterflood performance to factors not accounted for by present theory. Most important of these is the sensitivity to flooding rate and permeability ordering. The waterflood performance of stratified systems approximating actual field conditions was only slightly, but not significantly, sensitive to flooding rate, and was found to approach that of a uniform system with a flow capacity equal to that of the stratified system. The waterflood performance of a randomly heterogeneous system was found to be nearly rate insensitive. Further, the waterflood performance of such a system may be approximated by a uniform system with an absolute permeability equal to the geometric mean of the individual permeabilities. Hence, the oil recovery performance of a randomly heterogeneous reservoir may be predicted fairly well by the immiscible displacement theory of Buckley and Leverett, particularly at favorable mobility ratios.