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Synergistic Oil Displacement Effects of Dimeric Surfactant-Polymer-Silica Stabilized Nanoemulsions over Conventional EOR Fluids

Summary Nanoemulsion flooding is a promising chemical route towards enhanced recovery of hydrocarbon resources in mature reservoir formations, wherein narrow rock pore-spaces and high capillary pressure conditions are predominant. The present study delves into the synergistic effect of nanoemulsion-assisted enhanced oil recovery (EOR) over conventional flooding techniques. High-energy technique, i.e. ultrasonication was employed for the synthesis of oil-in-water nanoemulsions, consisting of hydrocarbon (n-heptane) shell dispersed in aqueous phase, and stabilized by {N,N’-bis(dimethyltetradecyl)-1,6-hexanediammonium bromide}+/{partially hydrolyzed polyacrylamide}+/{silica nanoparticle}. The presence of nano-sized oil droplets (< 500 nm) in nanoemulsions were confirmed by dynamic light scattering and cryo-microscopy imaging analyses. Wettability alteration studies showed that nanoemulsion fluids exhibited significantly fast spreading rates onto intermediate-wet sandstone surface. Analyzed chemical fluids showed pseudoplastic behavior, which is desirable for favorable oil mobility control during displacement studies. Nanoemulsions showed kinetic stability with slow droplet coalescence rates, as evidenced from light scattering results. Core-flooding studies showed that nanoemulsions showed better tertiary oil displacement efficiencies as compared to their aqueous fluid counterparts. Surfactant-polymer-nanoparticle (SPN) nanoemulsions showed enhanced recoveries of the order of ∼26%, after secondary water-flood. In summary, surfactant-polymer-nanoparticle assemblies contribute synergistically to strengthened mechanical stabilization effects in nanoemulsion fluids, which show favorability as EOR fluids.