Application of Empirically Derived Oil Recovery Factor Regression Equations to Water Drive Reservoirs in Niger Delta

Abstract

Abstract In order to make sound investment decisions with regards to oil field appraisal and development, it is crucial to be able to properly predict reservoir performance and hence oil recovery factor. Oil recovery factor is the recoverable fraction of the initial oil in place. It varies across different reservoirs depending on depositional environment, drive mechanism, rock and fluid properties. Over the years, a variety of methods have been used for the estimation of oil recovery factors vis (Analytical, Simulation, Empirical e.t.c). The thrust of this paper will focus on the use of empirically derived recovery factor regression equation for estimating oil recovery factor for water drive reservoirs in the Niger Delta. This method was first developed by the American Institute of Petroleum (API) subcommittee on recovery efficiency in Nov., 1967 with the publication of API Bulletin D14 "A Statistical Analysis of Recovery Efficiency" The subcommittee used case histories from some 312 producing oil reservoirs with sandstone lithology from which certain empirical relationships were derived by regression analysis. Specific regression equations were developed for Water-drive and Solution gas reservoirs. This paper presents the practicality of using the regression equation for water drive reservoirs in the Niger Delta, which have similar lithology. Firstly, a form of robustness check was done with mature reservoirs to see how well prediction from the regression equations line up with reality. Secondly, the equation was used to predict recovery efficiency in green reservoirs and results compared with other recovery factor estimation methodology noting the standard deviation in both cases. The results compared favorably and could be used as an additional robustness check when estimating reservoir recovery factor for water drive reservoirs in the Niger Delta.