Wettability alteration and surfactant adsorption study of methyl ester sulphonate/nano-silica nanofluid on sandstone reservoir rock

Abstract

This research project set out to investigate low salinity water/Methyl Ester Sulphonate (MES) surfactant/nano-silica synergy to enhance oil recovery from sandstone reservoir. A Series of experimental works, including contact angle measurements (Sessile drop technique) and UV-vis spectrophotometer tests, were conducted to ascertain the effect of the synergy solution on wettability alteration and surfactant adsorption reduction. Results showed that MES surfactant at 750 ppm and 1000 ppm reversed oil-wet sandstone to a water-wet state. Further reduction was observed at low salinity (250 ppm CaCl2) under high pH conditions. The lowest contact angle measured was 18 degrees with the synergy solution of 750 ppm MES and 250 ppm CaCl2 at high pH conditions. The maximum adsorption capacity was used as criteria to measure surfactant adsorption loss reduction. It was observed that surfactant adsorption capacity reduced from 4.66 mg/g to 0.85 mg/g when 25 ppm nano-silica was added at 70℃ temperature. This shows that the synergy was able to restore wettability to preferable water-wet conditions to support oil recovery and reduce the excessive loss of surfactant to the sandstone reservoir rock. Water-wet wettability condition and surfactant adsorption reduction are beneficial to the c-EOR project in terms of efficient cost savings on the quantity of surfactant usage for the project. At the same time, overall additional oil recovery is greatly improved.