Combination of a new natural surfactant and smart water injection for enhanced oil recovery in carbonate rock: Synergic impacts of active ions and natural surfactant concentration

Abstract

By increasing oil demand in carbonate reservoirs, enhanced oil recovery techniques play key role in improving oil production. Surfactant flooding and smart water injection are already well known as effective enhanced oil recovery techniques that increase oil recovery by reduction of oil-water interfacial tension and the alteration of rock wettability. In this work, a new plant-base natural surfactant, named Tribulus Terrestris is introduced and combined with smart water samples (i.e. synthetic seawater with different concentrations of active Ca2+, Mg2+ and SO42− ions) to determine their individual and integrated effects on reduction in interfacial tension, wettability alteration and oil recovery in carbonate rock samples.It was observed that increasing concentrations of SO42− up to 2.5 times resulted in maximum wettability restoration among active ions (by changing contact angle from 145.9° to 54.4°). Experimental results also showed that the effect of the concentration of active ions on wettability alteration was more significant compared to their effect on decreasing oil-water interfacial tension. In addition, the Tribulus Terrestris surfactant reduced oil-water interfacial tension considerably (from 45.3 mN/m to 13.5 mN/m at Critical Micelle Concentration of 0.3 wt %); hence, it was used as smart water modifier to integrate effects of wettability alteration (by smart water) and reduction in interfacial tension (by new natural surfactant). Core flooding experiments demonstrated increased oil recovery from 45.2% for distilled water injection up to 64% and 72% for smart water and combined smart water-surfactant respectively.