▎ 摘　　要

Nanofluids based on nitrogen-doped graphene quantum dots (N-GQDs) are an emerging nanotechnology with potential applications in enhanced oil recovery (EOR). Herein, we report the EOR performances of N-GQDs that have different GQD-sizes and nanofluid concentrations. Wettability and hydrocarbons/water interfacial tension (IFT) studies establish that N-GQDs nanofluids at concentrations of 0.5 mg/mL and with the lowest mean GQDs size range (about 3.5 nm) lead to more wettability alteration of carbonate rocks and decrease the oil/water IFT and n-heptane/water IFT from 16.88 mN/m to 0.975 mN/m, and from 50.24 mN/m to 27.87 mN/m, respectively. Moreover, core flooding experiments show that the aforementioned nanofluid provided greater than 18% and 14% enhancements in the oil recovery factors from carbonate and sandstone core samples, respectively, versus water flooding. In the carbonate core, the alterations of wettability and IFT reduction simultaneously promote oil recovery factors. By comparison, for the case of sandstone core, only the reduction in oil/water IFT leads to higher oil recovery factors. (C) 2021 Elsevier B.V. All rights reserved.