Low-Cost Quaternary Chemically Enhanced Oil Recovery - Alkali Polymer Flooding Pilot Results

Abstract Polymer flooding has matured into a commercially viable Enhanced Oil Recovery (EOR) method. Yet, substantial volumes of oil often remain trapped post-polymer injection, and economically feasible solutions for further recovery are limited—with no widely reported successful field implementations to date. This study presents field results from Alkali-Polymer (AP) injection following long-term polymer flooding. In this approach, alkali reacts with reactive crude oil to generate in-situ soaps that mobilize residual oil, while polymers maintain sweep efficiency and enhance microscopic displacement. Prior to field implementation, a comprehensive laboratory program was conducted to optimize alkali and polymer selection, concentrations, and rheological properties—while addressing interactions with reservoir rock, near-wellbore area effects, geomechanics, and reservoir architecture. Scale inhibition strategies and water quality controls were also developed to mitigate operational risks. Field pilot outcomes confirm that such preparation enables substantial incremental oil recovery even after prior polymer flooding. The simplified chemistry of alkali and polymer compared with more complex Alkalis Surfactant Polymer (ASP) formulations reduces surface facility complexity and operating expenditures. Scaling was prevented in injection wells using softened water, and managed in producer wells through targeted inhibitor dosing. Economic evaluation reveals that AP injection post-polymer flooding can achieve Unit Technical Costs below €35/bbl, with further cost reduction and performance optimization possible through chemical and operational refinement. Additionally, direct AP injection—without preceding polymer flooding—shows promise for reactive oil reservoirs, offering superior Net Present Value (NPV) through higher incremental oil recovery and accelerated revenue realization.