Using Polymeric Carbon Nitride/ZrO2 Nanocomposite for Low Salinity Water Flooding in Carbonate Porous Media at Real Reservoir Conditions

Nanoparticles and nanocomposites have been used in recent studies to improve oil reservoir recovery. With the introduction of a newly constructed smart water injection scenario, this work investigated the physicochemical characteristics of the 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 the wettability change, zeta potential, and interfacial tension under reservoir conditions (78 °C and 3800 psi) were determined after characterization experiments, which included X-ray powder diffraction (XRD), a Fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), a field emission scanning electron microscope (FESEM), energy-dispersive x-ray testing (EDX), and a Brunauer-Emmett-Teller (BET) analysis. Based on the highest zeta potential and the greatest reduction in the contact angle and interfacial tension, the optimum concentrations for ZrO₂/g-C₃N₄ and ZrO₂ were determined to be 30 and 40 ppm, respectively. Moreover, the ZrO₂/g-C₃N₄ nanocomposite demonstrated better results in enhancing the oil recovery parameters, and it was selected for low salinity flooding scenarios with three different salinities, including MgCl₂ + seawater (SW), CaCl₂ + SW, and MgSO₄ + SW, at 30 ppm of the nanocomposite. The best readings for the ZrO₂/g-C₃N₄ nanocomposite in its interfacial tension, contact angle, and zeta potential show that 1000 ppm has the best interfacial tension reduction among the tested concentrations of 500-50,000 ppm. At 30 ppm, MgCl₂ + SW had the maximum recovery (i.e., 49.36%), and this resulted from better interfacial tension reduction, contact angle reduction, and stability compared to other salinities.