Low salinity brine injection using a new green nanocomposite by considering the interfacial tension, contact angle, and spontaneous imbibition tests

Enhanced oil recovery in carbonate porous media is one of the main important matters among different researchers. This study examines the physico-chemical properties of ZnO/SiO2/xanthan/eucalyptus nanocomposites (NCs), a freshly synthesized enhanced oil recovery agent, by introducing low salinity flooding scenario in carbonate porous media. After performing characterization tests, as the main novelty of the present work, NCs optimum concentrations were obtained considering the reservoir conditions with the highest zeta potential and the greatest decrease in contact angle (70 °C and 3200 psi), which was 40 ppm. Then different solutions were obtained using different ions MgCl2, CaCl2, and MgSO4, and 40 ppm of NCs were prepared for further rock/fluid and displacement efficiency tests. According to the results in low salinity flooding scenarios, at 2000 ppm (as an optimum concentration), interfacial tension, contact angle, and zeta potential following this order, MgCl2 + 10 times sea water (10SW) + 40 ppm NCs (NC1) > CaCl2 + 10SW + 40 ppm NCs (NC2) > MgSO4 + 10SW + 40 ppm NCs (NC3). Next, spontaneous imbibition with NCs at the optimal concentrations (i.e., 2000 ppm salinity and 40 ppm NCs) shows the maximum recovery factor relates to NC1. Final recovery factors using NC1, NC2, and NC3 were 41.03%, 31.95%, and 27.72%, respectively, after a 28-day test.