The Impact of Salt Concentration on the Screening of Surfactant Packages for EOR Applications

Abstract

This study focuses on improving surfactant solubility for enhanced oil recovery (EOR) in high-temperature, high-salinity reservoirs, addressing challenges in chemical flooding. Surfactant performance is influenced by wettability, contact angle, capillary forces, and interfacial tension (IFT). We systematically examined the effect of salt concentration on surfactant properties using solubility tests, emulsion stability analysis, and oil displacement experiments. Additionally, we explored surfactant formulations incorporating high-HLB components to enhance solubility. Our results showed that individual surfactants exhibited varying solubility in brines of different salinities. Some were insoluble even in low-salinity brine, while others remained soluble under high-salinity conditions. Surfactant formulations significantly improved solubility, with most combinations dissolving in high-salinity environments. Among them, one surfactant package (K-6) demonstrated the highest water solubility and salt tolerance, making it particularly suitable for EOR. Emulsion stability tests revealed that at 25°C, some individual surfactants formed stable emulsions in low-salinity brine, with up to 70 V/V% emulsion phase retention after 1 h. Their effectiveness decreased at higher temperatures, while other surfactants remained stable. In medium-salinity brine, some retained 90 V/V% of the emulsion phase at 80°C, while in high-salinity brine, the most stable emulsions retained 55–60 V/V%. Surfactant packages outperformed individual surfactants, achieving nearly 100 V/V% emulsion retention across salinity levels. Oil displacement tests indicated that surfactant packages were more effective, with the best formulation achieving > 20 mm displacement. Our findings confirm that tailored surfactant packages are essential for EOR in extreme reservoir conditions. By addressing solubility challenges and providing a structured selection approach, this study contributes valuable insights for optimizing surfactant formulations in EOR applications. Overall, our findings confirm that reservoir oriented surfactant packages are necessary for EOR in high-salinity and high-temperature reservoirs. By addressing a widely recognized solubility challenge and providing a structured approach for surfactant selection, this study contributes valuable insights into optimizing surfactant formulations for improved oil recovery.