Hydroxyl-functionalized silicate-based nanofluids for enhanced oil recovery

Abstract

During the production life of the reservoir, wettability alteration from an oil-wet to a strongly water-wet condition and/or lowering the interfacial tension (IFT) between the water and oil phases is required at various stages to enhance oil recovery (EOR). Several chemical agents as potential wettability modifiers (e.g., surfactants and polymers) have been regarded and widely used in oil-wet systems. Recently, various nano-fluids, prepared by dispersing nanoparticles in brine solutions or solvents, have attracted attention as injecting fluid due to their unique properties. A large number of nanoparticles are being investigated for EOR applications either as stand-alone or in combination with surfactants and/or polymers. Because of its stability in brine even at low concentrations, totally or partially hydroxyl-functionalized nano-pyroxenes are capable of recovering additional oil after water flooding. However, the influence of their concentration on various parameters has not been previously investigated. Thus, in this study, we investigated the influence of nano-pyroxene on wettability, IFT and asphaltene aggregation. Wettability measurements were performed by contact angle measurements, imbibition experiments and wettability index to understand the underlying mechanisms. The interaction between nanopyroxene and asphaltene size distribution was investigated as a function of nanopyroxene concentration by dynamic light scattering (DLS) measurements. Results from the IFT measurements, contact angle, imbibition experiments and core flooding tests confirm that nanopyroxene affects oil recovery. Contact angle and wettability index measurements confirmed that adsorption of the nanoparticles on the rock surfaces alters the wettability from intermediate wet to stronger water-wet in the absence and presence of initial water films. In the presence of irreducible water saturation during wettability index measurements, depending on the brine composition and pH, initial alteration with aging resulted in a mixed or intermediate wet that changed to stronger water-wet as the nanopyroxene concentration increased. Moreover, increasing the concentration of nanopyroxene resulted in a noticeable IFT reduction but not an ultra-low range that can remobilize trapped oil due to higher capillary forces. Core flooding tests indicated that nanopyroxene-based nanofluid injection offers ~12–14.5% additional oil in addition to waterflooding.