The development of novel nanofluid for enhanced oil recovery application

Abstract

Recently, nanofluids' application in enhanced oil recovery (EOR) studies has been severely confined in low saline environments due to instability. In this study, a novel nanofluid was developed by conjugating an anionic surfactant to graphene oxide nanosheets (GONs) through electrostatic forces and compared with negatively charged colloidal silica nanoparticles. The surfactant conjugation on target GONs was confirmed by transmission electron microscopy, Fourier transforms infrared spectrometry and zeta potential. The developed nanofluid preserved a high salinity of 6 wt% NaCl and built more stable dispersions than bare silica nanofluid. The nanofluids' potential in recovering oil was comparatively studied by performing the viscosity, wettability, Pickering emulsion, and interfacial tension (IFT) experiments. Even though a tangible improvement of 1.48 cp was observed in the viscosity of Janus-GONs fluid after the dissolution of NaCl, this figure became negligible for silica fluid, by 0.07 cp. From the wetting values (θ), Janus-GONs changed the oil-wet wettability toward neutral-wet (89.9°), and silica nanoparticles toward partially water-wet (66.4°). Oil-in-water Pickering emulsions stabilized with the reinforced nanofluid remained fully stable compared to those of silica, which rapidly grew unstable. The reinforced nanofluid lowered interfacial tension by just under a third, which was attributed to its higher surface energy. In contrast, silica nanoparticles did not change interfacial tension sensibly. Micromodel experiments revealed that Janus-GONs yielded a considerable oil recovery of 79 % by restoring wettability to mixed-wet and reducing the viscous fingering phenomenon, compared to that of 53 % for silica. Based on the core flooding experiments, the percentage of oil recovered for Janus-GONs fluid was twice the silica nanofluid due to the higher capillary number (1 × 10−4) compared to the silica (8.7 × 10−6). Viscosity improvement was proposed as a new EOR mechanism next to wettability alteration and IFT reduction. Overall, the Janus nanofluid can be a ground-breaking nanomaterial for EOR.