Experimental Investigation of the Impact of Divalent Ions on Interfacial Interactions of Brine-Crude Oil

Smart water flooding is an enhanced oil recovery (EOR) technique which has gained more attention in research activities, recently. Despite many efforts on the study of fluids interaction in this process, most of the presented results are sparse, as they are not probing to the basics of transport phenomena between the involved phases. This work is aimed to bring new understanding of fluid-fluid interaction during smart water flooding through a series of organized experiments in which a crude oil sample with known properties was preserved in contact with different smart water composition for 45 days. Measuring brine pH illustrates the strong effect of the contact time and brine composition on partitioning of crude oil polar components. By increasing the concentration of divalent ions the dissociation of Naphthenic Acids (NAs) increase. To verify this important finding, ultraviolet-visible (UV-Vis) spectroscopy on aged brine samples were performed. Besides, the interfacial tension (IFT) measurements were conducted to identify the impact of the dissociation of crude oil polar components on interfacial interactions. Results show that the sulfate ion has the maximum effect on not although dissociation of polar components, but also on smart water-crude oil IFT reduction. Presence of a divalent cation is necessary for improving the effect of sulfate ion. Also the results show that presence of monovalent ions may affect the adsorption of polar components toward the interface, hence reduces the brine-crude oil IFT.