Interfacial property of the oil-brine system in the presence of asphaltene: Effect of ionic strength and asphaltene concentration
Volume Title: 1
Authors
Faculty of Petroleum and Natural Gas Engineering, Sahand University of Technology, Tabriz, Iran
Abstract
Asphaltene is one of the main polar components of the crude oil that exhibits surface-active property. In this paper, effects of salinity and asphaltene concentration on the interfacial property of oil/brine system was investigated by using dynamic interfacial tension (IFT). In order to track the surface activity of asphaltene molecules, oleic phase was simplified in the form of a miscible mixture of toluene and n-heptane (Heptol) with asphaltene concentration from 0.1 to 3 wt%. Seawater (SW) and its different concentrations (0.1SW and 2SW) were prepared to mimic low and high salinity water conditions.
Results showed that the effect of asphaltene on IFT profile of brine/Heptol system was characterized by an initial sharp decay followed by a gradual reduction toward an equilibrium value. As to ionic strength, the equilibrium IFT of brine/Heptol/asphaltene in the presence of SW was lower than that of 0.1SW, but such reduction was not pronounced in the presence of 2SW. This could be attributed to the presence of an optimum salinity range to facilitate migration of asphaltene molecules into brine/Heptol interface. In all salinity range, there was a positive impact on the IFT reduction by increasing asphaltene concentration up 0.5wt% such that at SW salinity, IFT diminished from 25 to 16.56 mN/m. But, beyond this concentration only a slight reduction in IFT was observed, 16.08 mN/m at 3wt% asphaltene. Such behavior could be reminiscent of the critical micelle concentration of the surface active materials that indicates brine/Heptol interface was almost occupied by asphaltene molecules at 0.5wt% concentration.
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