A novel nanofluid based on sulfonated graphene for enhanced oil recovery

In this study a novel nanofluid based on the sulfonated graphene (G-DS-Su) for enhanced oil recovery is developed. Nano porous graphene (NPG) synthesized by chemical vapor deposition method is sulfonated by a new route using 4-sulfobenzenediazonium salt and then chlorosulfonic acid. Presence of -SO3H group in G-DS-Su structure is confirmed by the Fourier transform infrared spectroscopy (FTIR) result. This stable functionalized graphene dispersion is applied in core flood experiments. Using G-DS-Su at concentrations of 0.5 and 2 mg/mL results in 16 and 19% increase in the oil recovery. Prior experiments show that G-DS-Su tends to migrate to the oil/water interface and form emulsions. Moreover, the IFT decreases about 11% in presence of G-DS-Su but an ultralow IFT is not achieved. The contact angle measurements show that the wettability of sandstone surface is altered from the oil-wet to the intermediate condition in presence of G-DS-Su. The wettability alteration may be due to both forming a wedge film in the oil/nanofluid/solid three-phase contact region and the adsorption of G-DS-Su onto the sandstone due to the pi-pi and pi-pi interactions between the functional groups of sand and G-DS-Su. Hence, the wettability alteration plays a dominant role in the oil displacement mechanism. (C) 2018 Elsevier B.V. All rights reserved.