Synergistic Effect of Zinc Oxide Nanoparticles and Methylene Blue on Enhancing the Hydrocarbon Potential of the Balkassar Oil Field in the Potwar Region, Pakistan.

Enhancement of residual oil recovery via nanoparticles is attributed to their high surface area, tunable size, and ability to alter wettability interfacial tension thereby facilitating the oil movement through the rock pore network. Nanoparticles can penetrate through small pores in reservoir rocks, may dislodge trapped oil, and stabilize emulsions, leading to a higher displacement efficiency. However, the effectiveness of nanoparticles over time can degrade due to several factors, such as retention of nanoparticles, pore throat plugging by aggregated nanoparticles, temperature changes, brine composition, and chemical instability caused by changes in pH, leading to the loss of oil recovery. To mitigate these effects, nanoparticles are being introduced into wastewater, e.g., methylene blue, which could significantly achieve the expected performance over time. Methylene blue, along with zinc oxide nanoparticles​,​ was used as a cost-effective and environmentally acceptable agent to improve the wettability of the carbonate rock. Despite the methyl blue's effectiveness in enhancing the oil recovery of carbonate rock, the fundamental mechanism remains poorly understood. Hence, to address this issue, the study primarily ​focuses on the effective use of methylene blue in combination primarily focuses on the effective use of methylene blue along with ZnO nanoparticles for enhanced oil recovery. Moreover, the study examines the combined effect of ZnO nanoparticles and methylene blue on the alteration of carbonate rock wettability under prevailing temperature and pressure conditions the wettability alteration of carbonate rock under the prevailing conditions of temperature and pressure. The findings of this study demonstrate that ZnO nanoparticles stayed well dispersed in the nanofluid solutions, exhibiting negligible sedimentation and agglomerations. This high colloidal stability was confirmed from the results of zeta potential values of ≤ -30 mV. Moreover, the synergistic effect of ZnO nanoparticles and methylene blue resulted in significant changes in wettability and a reduction in IFT. Furthermore, core flooding experiments showed an improvement in oil recovery of up to 56.50% at 25 °C under a constant injection rate when all effluents, i.e., the ZnO/methylene blue formulation, were combined. These findings demonstrate that methylene blue, along with ZnO nanoparticles, has strong potential for application in enhanced oil recovery processes in carbonate reservoirs.