Low-salinity nanofluid-A smart fluid enhanced oil recovery method

This paper proposes a novel Janus graphene nanofluid that enhances the low salinity water oil flooding performance. Two kinds of Janus hydroxylated graphene oxide (JHGO-1 and JHGO-2) were prepared by the high internal phase emulsion method. JHGO nanosheets were well dispersed in low salinity water, and their zeta potential was lower than -30 mV. Compared with JHGO-1, JHGO-2 has more excellent interfacial properties, remarkably reducing 73% of the oil-water interfacial tension and improving the interfacial viscoelastic modulus and shear viscosity. Furthermore, JHGO can form bubble film, interfacial film, and climbing film at the oil/water interface due to its amphiphilic nature, which endows it with intelligent oil-finding properties. JHGO nanofluid alters the rock surface into strong water-wet and changes the capillary force into the driving force of oil flooding. JHGO nanofluid can also rapidly peel crude oil from rock surfaces by reducing adhesion work and forming disjoining pressure. These excellent interfacial properties help low-salinity nanofluid to have a 15.4% enhanced oil recovery at the ultra-low concentration (50 mg/L). This smart fluid flooding lays the foundation for efficient oilfield development.