Review of Injection Profile Reversal during Polymer Flooding

Abstract

As a core enhanced oil recovery technology, polymer flooding has been widely applied in the mid-to-late stages of reservoir development, particularly during high-water-cut production phases. This technique increases the viscosity of injected water and optimizes the mobility ratio between water and oil, thereby expanding the sweep efficiency of the displacing fluid within the reservoir and effectively suppressing water channeling through high-permeability zones. However, the migration of polymers in heterogeneous reservoirs can lead to significant redistribution of fluid uptake capacity across different layers—a phenomenon commonly known as waterflood profile reversal. During polymer flooding, polymers preferentially enter high-permeability layers, where they adsorb and become trapped, creating residual resistance that gradually reduces permeability in these zones and subsequently drives more injected fluid into medium- and low-permeability layers. Moderate profile reversal can enhance vertical sweep efficiency and mobilize residual trapped oil; however, excessive polymer retention may cause formation damage and result in inefficient fluid redistribution. This study systematically investigates the fundamental causes and key influencing parameters of waterflood profile reversal during polymer flooding, including reservoir heterogeneity, permeability variation coefficient, polymer rheological behavior, adsorption/trapping characteristics, polymer solution concentration, injection rate, and depositional facies architecture. Based on this analysis, practical technical approaches for profile adjustment and reservoir adaptive management are further explored. To improve overall development efficiency in polymer flooding, this paper proposes an integrated technical framework combining high-resolution geological modeling, numerical simulation of polymer displacement, real-time monitoring of waterflood profiles, spatially resolved estimation of residual oil, and iterative optimization of development strategies.