The extended amphoteric surfactant (named C12P3E3NS), characterized by FTIR and 1H NMR, was prepared by amination and sulfonation in order to enhance oil recovery (EOR) for the low-permeability oil reservoirs. The surface and interfacial tensions of its combination systems with nonionic surfactant (APG0810, an Alkyl Polyglycoside), obtained by tension meter, were evaluated to obtain an optimized surfactant system for enhancing oil recovery. The compound system (named C12A) with 40 % mole fractions of C12P3E3NS, exhibiting the strongest interaction behavior and highest expansion modulus, possesses the best abilities of reducing the interfacial tension to ultra-low (10-3 mN/m order of magnitude) at a salinity of 10 wt%, and owns certain abilities of emulsifying crude oil. Meanwhile, the contact angle, measured by the contact angle measuring instrument, can be altered from 108.50°to 55.07°by the compound system C12A, confirming its better wetting alteration ability of transforming the capillary force from resistance to driving force. Eventually, displacement efficiency, obtained from core displacement tests, reveals that the compound surfactant system C12A can decrease the pressure by 15.80 % and its corresponding oil recovery factor is 15.25 % after water flooding, demonstrating its favorable displacement performance and potential application in medium or high salinity reservoirs.
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