Abstract:The enhancement of oil recovery by altering the salinity and ion composition of injected water has become a focal point of numerous studies. However, there is relatively less attention given to techniques combining surfactants with the quality injected water. To investigate the synergistic effects of different cations and surfactants on recovery efficiency, micro-scale displacement experiments were conducted to simulate the displacement process, along with experiments measuring interfacial tension and viscoelasticity modulus at the oil-water interface. Results from the micro-scale displacement experiments showed that 10,000 mg/L NaCl solution and 50,000 mg/L CaCl2 solution exhibited the best oil recovery efficiencies, reaching 64.51% and 59.27% respectively. After adding surfactants, the efficiency improved further with 10,000 mg/L NaCl + 0.2% dodecyl dimethyl ammonium betaine solution and 50,000 mg/L CaCl2 + 0.2% hexadecyl trimethyl ammonium bromide solution achieving the highest recovery rates at 87.28% and 80.92% respectively. Results from the interfacial tension and viscoelasticity modulus experiments indicated that when anionic and nonionic surfactants were added to NaCl and CaCl2 solutions, the interfacial tension reached the magnitude of 10-1 mN/m. However, with the addition of amphoteric and cationic surfactants, the interfacial tension decreased to the magnitude of 10-2~10-3 mN/m, accompanied by a significant decrease in viscoelasticity modulus. This study explores the mechanisms of the synergistic effects of different cations and surfactants on the displacement process, considering factors such as interfacial tension, viscoelasticity modulus, and wettability, and microscale oil displacement behaviors thus providing a comprehensive analysis of the relationship between multiple factors and recovery efficiency.