Evaluation of polymer flooding in multi-layered heterogeneous reservoir: the study of viscosity and injection rate of polymer solution

Abstract

In polymer flooding, mobility ratio is substantially reduced, improving areal sweep efficiency as well as wellbore profile. Breakthrough time is obviously extended. This technique seems to be suitable for heterogeneous reservoir. This study emphasizes on effects of viscosity and injection rate of polymer solution on effectiveness of polymer flooding in reservoir containing certain range of heterogeneity. Optimization is performed first to verify injection scheme. After that, viscosity (related to polymer concentration), polymer injection rate, and double-slug injection mode are studied. Different heterogeneity is prepared by Lorenz coefficient to have value ranging from 0.25 to 0.46. From the results, it can be concluded that pre-flushed water is required increase injectivity before polymer injection. The optimal pre-flushed water is 0.15PV, whereas optimal polymer slug size is 0.20 PV. This combination results in high oil recovery efficiency at short time of production. Injecting big slug of low polymer concentration yields better results than small slug of high polymer concentration. Too high polymer concentration results in low injectivity, whereas too low concentration of polymer yields low oil recovery due to improper mobility control. High polymer injection rate provides benefit on low heterogeneous reservoir, while injection rate does not show different on heterogeneity higher than 0.4. Double-slug injection results in low injectivity and is not recommended in this study.