Recently, using nanoparticles to change effective mechanisms in reservoirs, such as changes in wettability, reducing interfacial tension in sandstone reservoirs, are common methods for enhanced oil recovery. In this study, activated carbon ZnO nanocomposites (AC/ZnO) were synthesized, and different wettability alteration (WA), interfacial tension (IFT), and Zeta potential (ZP) tests at reservoir pressure and temperature (80 °C and 2500 Psi) were tested for obtaining an optimum concentration of AC/ZnO, and the results compared with pure ZnO nanoparticles. Then, series of spontaneous imbibition tests were designed at same operational tests at obtained optimum concentration. Fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET), and Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) tests were used to observe ZnO, and AC/ZnO structure. Different nanocomposites concentrations including30, 60, 90, 120, 150, and 180 ppm were analyzed during different IFT, WA, and ZP tests, and based on the maximum decrease in WA and highest ZP, 90 ppm was selected as an optimum concentration for ZnO, and AC/ZnO.AC/ZnO gave better results than ZnO during WA, IFT, and ZP tests, especially at optimum concentration of 90 ppm. At 90 ppm, CA was changed from 56.27° to 39.14°, and ZP was changed from -37.79 mV to -42.06 mV, respectively. For further investigations, both ZnO, and AC/ZnO were tested for increased oil recovery tests at optimum concentration of 90 ppm. Oil recovery factor (RF) for base, ZnO, and AC/ZnO were 38.38, 51.79, and 66.68 %, respectively after 15 days. The findings of this study can help for better understanding of main porous media mechanisms in the presence of AC/ZnO, and pure ZnO.
