Formation and characterization of nanoparticle assisted surfactant stabilized oil-in-water nanoemulsions for application in enhanced oil recovery

Nanoemulsions (NEs) are emerging as attractive injecting fluids for enhanced oil recovery because of their abilities to reduce interfacial tension, alter the rock wettability, improve the mobility ratio, become miscible with trapped crude oil, plug the pores, etc. The present study deals with the formulation, characterization, and performance of alumina (Al2O3) nanoparticle-aided AOS (alpha-olefin sulfonate) surfactant stabilized oil in water NEs in improving oil recovery. Dynamic light scattering (DLS) confirms the dispersion of nanoscale oil droplets with an average size of 192 nm and 172 nm for NEs stabilized by AOS surfactant and Al2O3 nanoparticle-aided surfactant, respectively. The corresponding Zeta potential (ζ) values are −60.2 mV and −63.4 mV, which indicate the higher kinetic stability of the NEs. The phase behaviour study shows a stable middle-phase emulsion with 0.75 wt% surfactant at optimum salinity of 0.5 wt% NaCl and the IFT values in the 10−5 mN/m range as measured by Chun Huh equation. On the other hand, the IFT between decane and nanoemulsion measured at 343 K by pendant drop is observed to be 26.42 mN/m, which is further reduced to 13.89 mN/m by inducing nanoparticles into the nanoemulsion. The NEs have significant potential to alter the wettability of sandstone rock from oil-wet to water-wet. It has been observed that the formulated NEs have good miscibility with crude oil, and the viscosity of crude oil is reduced significantly, which implies an improvement in displacement efficiency. Core flooding studies on two cores were performed by injecting both the formulated slugs to test their effectiveness in improving oil recovery. The injection of one pore volume of AOS-stabilized nanoemulsion and Al2O3 assisted AOS stabilized nanoemulsion increased oil recovery by 17.71 % and 23.97 % respectively over conventional water flooding.