Effect of Polar Hydrocarbon Contents on Oil-Water Interfacial Tension and Implications for Recent Observations in...

For decades now, low salinity water flooding (LSWF) oil recovery has emerged as an environmentally benign and cost-effective method for improved oil recovery, where research findings have reported pH and interfacial tension effects. Considering the effect of oil chemistry on interfacial tension and the potential of this chemistry to have a direct relationship with LSWF, we measured the interfacial tension of four crude oils with composition varying from those of conventional to unconventional ones. We also characterized the crude oil samples using infrared spectroscopy and a wet chemistry method based on asphaltene precipitation. Our research approach has enabled us to relate the composition of crude oil to the interfacial tension trend at pH encountered in improved oil recovery schemes. Our research methodology, based on an integrated approach to using infrared spectroscopy and interfacial tensiometry, has also enabled us to propose a more robust theoretical explanation for current observations in LSWF related to pH and interfacial tension. In this regard, oil-water interfacial tension depends on the concentration of polar components, such that the higher the concentration of polar groups in crude oil, the higher the interfacial tension at a given pH of aqueous solution. We have also shown that the acid-base behavior of polar groups at the oil-water interface provides a theoretical interpretation of the explicit relationship between oil-water interfacial tension and the electrostatic components of interfacial tension as given by the energy additivity theory.