Enhancing Surfactant-Polymer Flooding with Sacrificial Surfactants: Reducing Adsorption and Boosting Oil Recovery in High-Salinity Reservoirs

Abstract Surfactant polymer flooding is frequently constrained by the adsorption of high-cost primary surfactants onto reservoir rock, which lowers chemical efficiency and increases operational costs. This work presents a systematic laboratory assessment of sacrificial surfactants used as adsorption inhibitors to enhance surfactant polymer flooding performance in a Russian clastic reservoir with highly saline formation water. A comprehensive experimental workflow was implemented, integrating compatibility screening, static and dynamic adsorption measurements supported by high-precision HPLC analysis, and final verification through coreflood displacement experiments. An initial screening of twelve commercially available sacrificial surfactants was conducted in combination with a base surfactant polymer formulation. Seven candidates were selected based on solution stability and favorable interfacial tension characteristics. Static adsorption experiments performed on disaggregated reservoir rock with elevated specific surface area provided insight into adsorption behavior. Sacrificial surfactants №719, SPEMA-4, and SPESC-4 exhibited pronounced competitive adsorption effects, reducing adsorption of the primary anionic surfactant №102 by up to 33.6% after 72 hours. In contrast, several candidates led to increased adsorption, indicating unfavorable rock–fluid interactions. Dynamic adsorption tests under flow conditions confirmed the trends observed in static experiments. Sacrificial surfactants №719 and SPEMA-4 reduced anionic surfactant adsorption by 33.8% and 29.8%, respectively. Coreflood displacement experiments further demonstrated the effectiveness of adsorption mitigation. The formulation containing sacrificial surfactant №719 achieved an incremental oil recovery of 29.28%, exceeding the baseline surfactant polymer flood by 7.41%. The SPEMA-4 formulation also delivered a notable improvement, yielding 26.9% incremental recovery. These results confirm that appropriately selected sacrificial surfactants can substantially reduce primary surfactant losses through competitive adsorption and improve displacement efficiency. Among the evaluated agents, sacrificial surfactant №719 exhibited the most consistent performance across all experimental stages and is identified as the most promising candidate for further application.