In this research, Cetyltrimethylammonium Bromide (CTAB) nano-emulsions were prepared at 0.05 and 0.1 wt% and evaluated in comparison with conventional CTAB emulsions. Particle size analysis showed that average CTAB nano-surfactant particle size was approximately 60 nm, much lower than that of the CTAB emulsions. Zeta potential analysis was used to evaluate the stability of the emulsion and demonstrated that CTAB nano-surfactant was more stable than the normal surfactant. CTAB Nano-surfactant also showed lower interfacial tension with the crude oil sample, in comparison with CTAB surfactant. The interfacial tension was more decreased by increasing the surfactant concentration. Wettability tests with carbonate rock powder, oil and CTAB emulsion/nano-emulsion showed that these surfactants are able to alter the rock wettability toward more water-wet condition. Spontaneous imbibition tests were performed at 50 0C on the oil saturated carbonate core samples with brine, surfactant and nano-surfactant, respectively. However, stable emulsions of oil in the aqueous phase made estimating the amount of oil recovery impossible.

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