Nanoparticles and nanocomposite have been used in recent studies to improve oil reservoir recov-ery. With the introduction of a newly constructed smart water injection scenario, this work inves-tigates the physico-chemical characteristics of polymeric carbon nitride/ZrO2 nanocomposite (ZrO₂/g-C₃N₄), and the results were compared with pure ZrO₂ nanoparticles as a known enhanced oil recovery agent. The effects of ZrO₂/g-C₃N₄ and ZrO₂ on wettability change, zeta potential, and interfacial tension under reservoir conditions (78 °C and 3800 psi) were determined after charac-terization experiments including x-ray powder diffraction (XRD), fourier iransform infrared spec-trometer (FTIR), transmission electron microscopy (TEM), field emission scanning electron micro-scope (FESEM), energy-dispersive x-ray testing (EDX), and brunauer–emmett–teller (BET) analysis. Based on the highest zeta potential and the greatest reduction in contact angle and interfacial ten-sion, optimum concentrations for ZrO₂/g-C₃N₄ and ZrO₂ were determined to be 30 and 40 ppm, respectively. Moreover, ZrO₂/g-C₃N₄ nanocomposite had better results in enhancing enhanced oil recovery parameters and was selected for low salinity flooding scenarios with three different sa-linities, including MgCl₂ + seawater (SW), CaCl₂ + SW, and MgSO₄ + SW, at 30 ppm of nanocom-posite. The best readings for ZrO₂/g-C₃N₄ nanocomposite in interfacial tension, contact angle, and zeta potential show that 1000 ppm has the best interfacial tension reduction among other tested concentrations of 500-50000 ppm. At 30 ppm, MgCl₂ + SW had maximum recovery (i.e., 49.36%), and it was due to better interfacial tension reduction, contact angle reduction, and stability in compared to other salinities.
