Brine ions impacts on water-oil dynamic interfacial properties considering asphaltene and maltene constituents

Smart water flooding is one of the most promising methods for Enhanced Oil Recovery (EOR). However, the exact mechanism beyond is still unknown and the comprehensive knowledge for optimization of the composition of the ions needed for an effective flooding process is not available. In this manner, the interactions of different ions present in the aqueous phase with those components of the oil that can have a certain affinity to water (e.g. asphaltene and maltene) are of great importance. In this research work, the effects of monovalent and divalent ions of different charges (Na⁺, Cl⁻, Ca²⁺, Mg²⁺, and SO₄ ^2-) on dynamic interfacial properties of the water/oil system have been studied using profile analysis tensiometry (PAT) experimental method. It is demonstrated that participation of the ions from the water phase into the electrostatic interactions with oil, depends on the surface charge of different components of the oil that adsorb at interface. For a better understanding of this matter, separate solutions of the extracted asphaltene in toluene and maltene (de-asphalted oil using heptane) were prepared and used for comparative studies. The results illustrate a major role for the cations, while changes of the anions show negligible effects in our case studies. Among the cations, Mg²⁺ and Ca²⁺ show very significant effects on interfacial properties of the related brine-oil interface while Na⁺ shows negligible effects. The results also demonstrate more significant interaction of the resin components with divalent cations (Mg²⁺ and Ca²⁺) in comparison with the asphaltene components. In particular, Mg²⁺ shows a stronger interaction with both resin and asphaltene molecules in comparison with Ca²⁺. The measured interfacial elasticity results provide us very helpful complementary data for better understanding of the approximate size and concentration of the adsorbed molecules/aggregates, that support these findings well.