#Water in oil emulsion stability skin#
Rigid or solid films are like an insoluble, solid skin on water droplets characterized by very high interfacial viscosity.These films are classified into two categories on the basis of their mobilities. Concentration of polar molecules in the crude oilĪ good correlation exists between the presence of incompressible interfacial film and emulsion stability.Extent to which the adsorbed film is compressed.Type of crude oil (asphaltic, paraffinic, etc.).The properties of interfacial films depend on : 2 – Photomicrograph of an emulsion showing interfacial films (magnified). The presence of fine solids can also strengthen the interfacial film and further stabilize emulsions.įig. 1 and 2 show the persistent film in a water-in-oil emulsion. Highly viscous interfacial films retard the rate of oil-film drainage during the coalescence of the water droplets by providing a mechanical barrier to coalescence, which can lead to a reduction in the rate of emulsion breakdown. These films enhance the stability of an emulsion by increasing the interfacial viscosity. These films are believed to result from the adsorption of high-molecular-weight polar molecules that are interfacially active (surfactant-like behavior). Produced oilfield emulsions are stabilized by films that form around the water droplets at the oil/water interface. Surface films and stability to coalescence Oil demulsification discusses the mechanisms of emulsion breakup. Coalescence is the fusion of droplets to form larger drops with reduced total surface area. Aggregation or flocculation is the grouping together of water droplets in an emulsion without a change in surface area. Sedimentation is the falling of water droplets from an emulsion because of the density difference between the oil and water. These stabilizers suppress the mechanisms involved that would otherwise break down an emulsion. Their kinetic stability is a consequence of small droplet size and the presence of an interfacial film around water droplets and is caused by stabilizing agents (or emulsifiers). Water-in-oil emulsions are considered to be special liquid-in-liquid colloidal dispersions. 2 Factors affecting oil emulsion stability.1.1 Surface films and stability to coalescence.
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