Adsorption of asphaltenes at the water-oil interface contributes to the stability of petroleum emulsions by forming a networked film that can hinder drop-drop coalescence. The interfacial microstructure can either be liquid-like or solid-like, depending on: i) initial bulk concentration of asphaltenes, ii) interfacial aging time, and iii) solvent aromaticity.  The rheological nature of the asphaltene film is critical to understanding drop coalescence. When the interfacial microstructure is dominated by the viscous component, the coalescence time for two drops in intimate contact is rapid, on the order of seconds.  However, as the elastic contribution develops and the film microstructure is dominated by elasticity, the two drops in contact do not coalescence.  Such step-change transition in coalescence is thought to be related to the high shear yield stress (~104 Pa) and the increased elastic stiffness of the interfacial film that prevents mobility and rupture of the asphaltene film when in a solid-like state.

Petroleum emulsion stability governed by interfacial rheological properties

247th National Meeting (2014)

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