Influence of Aqueous-Phase Ionic Strength and Composition on the Dynamics of Water-Crude Oil Interfacial Film Formation

In this paper, we examine the impact of aqueous-phase ionic strength and ionic composition on viscoelastic properties of the water crude oil interfacial film by conducting interfacial shear rheological measurements under controlled water chemistry and aging time. A double-wall ring geometry is used in oscillatory mode to measure the film viscoelastic moduli. To further elucidate mechanisms controlling the kinetics of film formation, temperature-dependent interfacial rheological behavior is investigated as a function of time. Our results reveal that low-ionic-strength conditions are more conducive to film formation and, consequently, engender a more viscoelastic interface. This observation is consistent with our previous results on emulsion stability; i.e., increasing the ionic strength of the aqueous phase leads to the formation of less stable emulsions. On the other hand, the temperature dependence of the viscoelasticity buildup demonstrates that adsorption of polar materials onto the interface can be modeled as a diffusion-controlled process, affected by the temperature in two different ways: first, through viscosity temperature dependence and, second, directly through the diffusivity dependence. Our results provide insights into emulsion stability mechanisms as well as multiphase fluid interfacial processes.