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Abstract
This paper focused on surfactant evaluation targeting the harsh reservoir conditions (high temperature and high salinity fractured reservoir). Six kinds of surfactants were selected and evaluated in terms of interfacial tension (IFT) and contact angle. . S-6 and S-7 presented the best potential ability in IFT reduction among all kinds of surfactant solutions, which were in the 10−2mN/m magnitude. The experiment results showed that the contact angle on oil-wet glass slide at the concentration of 0.2% S-6 was 58°, which is in water-wet region; while other surfactants cannot change the surface wettability. . Finally, the micromodel flooding tests were conducted using S-6, S-7 and S-8 to study both effects of wettability alteration and IFT reduction ability on EOR. The micromodel work was based on an oil-wet etched glass. Compared with S-7, the recovery increase of S-6 was about 12%, indicating that with the similar abilities of IFT reduction for surfactant solutions, the one with stronger wettability alteration ability could lead to a higher oil recovery. As a result, S-6 had better potential in providing higher oil recovery as an imbibition agent. Numerical simulation using UTCHEM suggested that with the increase of injection rate and the decrease of IFT, the imbibition recovery is increased.
Graphical Abstract
Acknowledgements
The authors also would like to express sincere gratitude to Dr. Ming Han, Dr. Zhixue Sun and Dr. Ziyuan Qi for their instructive advice and useful suggestions on this paper.