Quantitative Analysis of Performance of Polymer Slug Injection

Abstract

ABSTRACT The literature reveals a number of criteria used to screen oil reservoirs for polymer injection. The qualitative response of polymer injection process for a given field parameter is also implied. This paper presents a quantitative analysis of the performance of an oil reservoir undergoing polymer slug injection due to variations of parameters used for screening. The reservoir performance is represented by the behavior of oil recovery, WOR and oil production rate. These performance parameters are usually used to determine the economics and economic limit of an enhanced oil recovery project. The field parameters considered for analysis in this study include reservoir permeability (230 – 2300 md), oil viscosity (25 – 100 cp), polymer viscosity (1.45 – 4.8 cp), rock adsorption characteristics (0 – 0.0001 lb/lb rock), polymer slug size of constant concentration (0.1 – 0.4 PV), combination of polymer slug size and concentration such that the injected polymer is constant, and polymer slug program. In this study a number of numerical exercises were conducted using the reservoir rock and fluid data for the Lower Huntington Beach Garfield zone in two dimensions. A field parameter is varied within the limits of the screening criteria and the response of the reservoir is analyzed. It is found that the reservoir permeability is of paramount importance to the success or failure of polymer injection as an enhanced oil recovery method. The analysis of the behavior of sandface pressure for low permeability reservoirs provides interpretation of the plugging effects observed in the field. The performance of polymer injection is improved when a polymer slug program aiming at protecting the initial slug by graded buffers is implemented. Finally, our numerical experimentation confirms the widely held view of using 0.70 pore volume injected as a criterion to terminate a polymer injection project.