Effect of resin as a surface active agent (natural surfactant) on the interfacial tension of high and low salinity solutions prepared by chloride-based salts

Unfortunately, since crude oil is comprised of thousands of complex components, it is hard to extract a generalized conclusion for the effect of salinities on the interface phenomenon. So, it seems applicable if any investigation performs regarding the interactions between each component of the crude oil especially resin (known as natural surfactants), and the salinities. In this way, this study is designed to find the effect of resin fraction (with a concentration of 1–8 % wt) extracted from a crude oil and salinities including NaCl, MgCl2, KCl, and CaCl2 in the range of low and high salinity (0–45,000 ppm). The measured IFT values revealed that as the resin is dissolved in the toluene, IFT reduces compared with the toluene solution contains no resin. Besides, the results reveal that as the resin concentration increases from 1 % wt to 4 % wt, the IFT reduction is more evident in the overall viewpoint although the IFT reduction is different for each salt and even reduces if the resin concentration increases to 8 %wt. So, it seems that there is a shifting value for the resin concentration (which is about 4 %wt) which leading to the lowest IFT values or the highest IFT reduction effect. Moreover, the inspections reveal that for the low resin concentration (1 %wt), CaCl2 leading to the best IFT reduction behavior while for resin concentration of 4 %wt, KCl leading to the best IFT reduction behavior. •Increasing resin concentration from 1 to 4 %wt reduces the IFT while further increase to 8 %wt increases the IFT.•Optimum concentration for IFTmin is generally about 5000 ppm except for MgCl2 which is between 1000 and 5000 ppm.•CaCl2 had the highest impact on the IFT for resin = 1 %wt, while for 4 and 8 %wt no superiority was observed for salts.•4 %wt concentration for resin is a critical concentration in which the effect of salts on the IFT reach to the lowest impact.