Rheological and thermal properties of novel surfactant-polymer systems for EOR applications

In this work, two surfactant-polymer (SP) systems were evaluated for enhanced oil recovery applications. The first SP system contained partially hydrolyzed polyacrylamide and alkyl polyethylene glycol ether-based non-ionic surfactant. The second SP system consisted of the same polymer and alcohol propoxylate sulphate-based anionic surfactant. Rheology, thermal stability, interfacial tension (IFT), and core flooding experiments were performed to evaluate the SP systems at different temperatures, surfactant concentrations, and salt concentrations. The anionic surfactant reduced the viscosity of the polymer. However, the effect of the non-ionic surfactant on the rheological properties was not significant. The non-ionic surfactant was found to be stable at 80 °C while the structural changes were identified in the anionic surfactant after aging. IFT values of both surfactants were measured at various temperatures and salinities. Due to poor thermal stability and IFT increasing with temperature, the SP system containing the propoxylated anionic surfactant is recommended for applications in low-temperature reservoirs only. However, the SP system containing the ethoxylated non-ionic surfactant showed promising results at high-temperature and high-salinity conditions and 26 % additional oil recovery was obtained.