Interfacial tension of smart water and various crude oils

Abstract

The utilization of smart water in EOR (enhanced oil recovery) operations has drawn increased attention in recent years. Nevertheless, the variety and complexity of mechanisms during smart water injection require more research endeavors. In this study, interfacial tension (IFT) for the smart water/crude oil interacting system has been investigated. The investigated parameters included various salts with different salinity, pH, asphaltene type, and aged smart water with two crude oil samples. The results showed that the hydration of ions in smart water would play a key role to discern the primary mechanism of smart water. The interaction of acidic and basic asphaltene with hydration shell of different ions can be considered as primary mechanism for efficacy of smart water. Acidic and basic asphaltenes serve as intrinsic surfactants due to their interaction with OH− in the anion hydration shell and H+ in the cation hydration shell, respectively. The propensity of acidic asphaltene to interact with anions with high hydration energy and the tendency of basic asphaltene to interact with cations with high hydration energy led to an IFT of 0.2 mN/m and 11.3 mN/m for acidic and basic oils, respectively. The impact of pH also revealed that acidic and basic asphaltenes would have lower IFT in alkaline and acidic environments. Finally, it was found that changes in IFT for the aged smart water with crude oil depend on the asphaltene type as well as salt and salinity.