In the past decade, nanoparticles (NPs) and surfactants have been extensively used as flooding additives to enhance the displacement of non-aqueous phase liquids (NAPLs) such as crude oils from subsurface formations. NPs are believed to improve NAPL recovery or removal through wettability alteration, viscosity reduction, and asphaltene dispersion, whereas surfactants show excellent performance in reducing the interfacial tension (IFT) between NAPL and brine. However, the limitations of traditional nanoparticles (i.e., toxicity, low stability), and surfactants (i.e., adsorption) have greatly hampered their efficiency. In this study, we present a novel approach to synthesize graphene-based amphiphilic Engineered Carbon Nanosheets (E-CNS) by asymmetrically modifying the surface of graphene oxide. One side of the nanosheets was grafted by an aliphatic straight carbon chain through an amine reaction, while the other side was protected using starch microsphere as a template. Due to their amphiphilic nature and nanoscale size, the E-CNS showed combined dual properties of both surfactants and nanoparticles. More specifically, E-CNS reduced the IFT by more than 60% (from 22.9 mN/m to 8.4 mN/m) and reversed the wettability of both calcite and quartz substrates towards a more water-wet state. The E-CNS also exhibited a unique self-assembly behavior at the NAPL/brine interface, flattening the curvature of both concave and convex menisci in glass tubes. Due to the combined impact of IFT reduction, wettability alteration, and interface self-assembly, NAPL recovery from E-CNS flooding increased by 13% and 6% for Edwards limestone and Berea sandstone, respectively, as compared to that of base brine conditions. These findings demonstrate the potential applications of engineered carbon nanosheets in enhanced oil recovery and aquifer remediation.<br/>

Engineered carbon nanosheets for enhanced NAPL displacement in porous media

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.