In order to enhance oil recovery from high-salinity reservoirs, a series of cationic gemini surfactants with different hydrophobic tails were synthesized. The surfactants were characterized by elemental analysis, infrared spectroscopy, mass spectrometry, and 1 H-NMR. According to the requirements of surfactants used in enhanced oil recovery technology, physicochemical properties including surface tension, critical micelle concentration (CMC), contact angle, oil/water interfacial tension, and compatibility with formation water were fully studied. All cationic gemini surfactants have significant impact on the wettability of the oil-wet surface, and the contact angle decreased remarkably from 988 to 338 after adding the gemini surfactant BA-14. Under the condition of solution salinity of 65,430 mg/L, the cationic gemini surfactant BA-14 reduces the interfacial tension to 10 23 mN/m. Other related tests, including salt tolerance, adsorption, and flooding experiments, have been done. The concentration of 0.1% BA-14 remains transparent with 120 g/L salinity at 50 8C. The adsorption capacity of BA-14 is 6.3-11.5 mg/g. The gemini surfactant BA-14 can improve the oil displacement efficiency by 11.09%.

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