Mechanisms of Stabilization of Water-in-Crude Oil Emulsions

Abstract

The mechanisms of stabilization of water-in-crude oil emulsions have been investigated by changing the solvent-solute interactions in crude oil. Diluting the original crude oil with varying amounts of heptane, which is a poor solvent for asphaltenes, changes the solvent-solute interactions, leading to flocculation of asphaltenes and thus changing the emulsion stability. The interactions between the water droplets in an emulsion system have been quantified by measuring the radial distribution function and thereby the pair potential using the digitized optical imaging technique. It has been observed that the force of interaction between water droplets is oscillatory. This shows that non-DLVO forces, such as attractive depletion and repulsive structural forces, exist between the droplets. The interaction between the water droplets has been modeled by studying the properties of a thin liquid film sandwiched between the water droplets. Because of the film confinement effect, asphaltene-resin particles form a layered structure inside the thin liquid film. Also, the role of hydrodynamic interactions has been studied by using the film rheometer to measure the dynamic film tension and film elasticity. It has been found that, because of the adsorption of asphaltene at the film interfaces, the film elasticity plays a significant role in stabilizing these emulsions.

Adsorption Kinetics of Asphaltenes at Liquid Interfaces

“…These emulsions need to be destroyed after oil has been produced out of the reservoirs to recover the oil. A great deal of studies of these emulsions can be found in the literature (3)(4)(5), together with studies of the effect of various demulsifiers (6)(7)(8)(9). To obtain oil-in-water emulsions or to break the already existing water-in-oil emulsions, watersoluble surfactants need to be added and can possibly affect the interfacial structure.…”

Perspectives of Ionic Liquids Applications for Clean Oilfield Technologies

“…Most crude oils that contain asphaltenes and naphthenic acids, especially heavy crude oils form marine environments trend to form stable W/O emulsions, which are complex scattered systems (Kumar et al, 2001).…”

Demulsifying water-in-oil emulsions by ethyl cellulose demulsifiers studied using focused beam reflectance measurement

“…The presence of the demulsifier molecules at the oil-water interface favors the drainage of the thin liquid films between the approaching emulsified water drops. On the other hand, demulsifiers could also bridge water droplets and therefore lead to flocculation of the emulsified water droplets, enhancing coalescence and phase separation (Kumar et al, 2001;Liu et al, 2003;Rondon et al, 2008).…”