Evaluation of Sequential Polymer Flooding in Multi-layered Heterogeneous Reservoir

Abstract

Polymer flooding is a well-known technique used for controlling mobility ratio from both viscosity enhancement and reduction of effective permeability to water, leading to improvement of sweep efficiency as well as wellbore profile. This study emphasizes on effect of sequential polymer flooding together with residual resistance factor on multi-layered heterogeneous reservoir. Effectiveness of sequential polymer flooding is evaluated by comparing results with single-slug polymer flooding. In this study, pre-flushed water is not required since polymer adsorption results in water slug functioning as pre-flushed water. High polymer concentration and large slug size tend to yield favorable results. However, too large slug size could result in unsatisfactory in economic point of view. Benefit of sequential polymer flooding is shortening total production period and reducing total water production. To design sequential polymer flooding scheme, first polymer slug should be high in polymer concentration and large in slug size to maintain stability of displacement. High contrast in reduction of concentration results in more concern on first slug size compared to low contrast in reduction of concentration. Sequential polymer flooding is even more effective in case of high value of residual resistance factor. Increment of oil recovery can be obtained from optimal scheme. However, sequential polymer flooding is more suitable with low heterogeneity reservoir since high heterogeneity tends to decrease it effectiveness due to poor permeability distribution.