interfacial property of the oil-brine system in the presence of asphaltene: effect of ionic strength and asphaltene concentration

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#