On the interfacial properties of micrometre–sized water droplets in crude oil

Abstract

The remarkable stability of water-in-crude oil emulsions is due to the presence of a complex adsorbed layer at the surfaces of the dispersed droplets. Except for its role as a steric barrier, little is known about the in situ properties of this interfacial structure. In this study, new insights into the adsorbed layer are provided by direct micrometre-scale measurements. At low crude content in the bulk where, according to interfacial tension isotherms, there should be little or no surfactants on the droplet surface, the adsorbed layer displays pronounced rigidity and is capable of preventing coalescence and coagulation of the droplets. Such interfaces are highly dissipative and can be well described by the Boussinesq-Scriven model. As the supply of surface active materials in the bulk (i.e. the crude content) increases, the adsorbed layer transforms from a rigid structure to a fluid interface. This fluid layer continues to inhibit coalescence, although signs of weak interdroplet adhesion begin to appear. Under area compression, the fluid interface will discharge micrometre-sized emulsion droplets into the oil phase via a 'budding' mechanism.

Disjoining Pressure Isotherms of Water-in-Bitumen Emulsion Films

“…These effects became more severe over time. After the water and oil phases had been in contact for some time, film drainage would become negligible and the interfaces would appear more like the protective skins that have been observed in other studies (42,43). Normally the protective skin would appear after more than an hour of contact between the water and oil phases, although the protective skin would appear within a few minutes for more dilute asphaltene solutions.…”

Molecular Dynamics Simulation of Self-Aggregation of Asphaltenes at an Oil/Water Interface: Formation and Destruction of the Asphaltene Protective Film

“…Formation of a stable asphaltene protective film at the oil/water interface has been observed by using the micropipet technique. 15,61,62 The MD simulations clearly showed that the asphaltene molecules could well selfassemble to form ordered graphite-like aggregates in vacuum or at the vacuum/liquid and liquid/liquid interface (Figures 2−4). The asphaltene nanoaggregate generally consists of a few molecules, with the molecular PAHs face-to-face stacking together.…”

Understanding Water‐Based Bitumen Extraction from Athabasca Oil Sands

“…The recently developed micropipette technique under the NSERC Industrial Researc h Chair in Oil Sands Engineering at the University of Alberta (Moran et al, 1999;2000a,b;Moran 2001;Yeung et al, 1999Yeung et al, , 2000a) is one of the breakthroughs in measuring interf a c i a l properties of very viscous fluids such as bitumen. Application of advances in the measurement of zeta potential distributions of mixtures has made it possible to indirectly detect the heterocoagulation phenomena of fine solids with bitumen (Liu et al, 2002a,b;Xu et al, 2003a).…”