Mousse emulsions viscosity

Some special problems arise at sea. When crude oil is spilled on the ocean, a slick is formed which spreads out from the source with a rate that depends on the oil viscosity. With sufficient energy an O/W emulsion may be formed, which helps disperse oil into the water column and away from sensitive shorelines. Otherwise, the oil may pick up water to form a water-in-oil emulsion, or mousse ( chocolate mousse ). These mousse emulsions can have high water contents and have very high viscosities, with weathering they can become semi-solid and considerably more difficult to handle, very much like the rag-layer emulsions referred to above. The presence of mechanically strong films makes it hard to get demulsifiers into these emulsions, so they are hard to break. See Chapter 9. 

A graphic and important example is furnished by the oil spill chocolate mousse emulsions formed when crude oil spills into seawater. These water-in-oil emulsions have high water contents that may exceed 74% and reach = 0.80 or more without inverting. As their common name implies, these mousse emulsions not only ha e viscosities that are much higher than the original crude oil but can become semisolid. With increasing time after a spill, these emulsions weather (the oil becomes depleted in its lower boiling fractions), and apparently the emulsions become more stable, more solidlike, and considerably more difficult to handle and break. 

Dispersal is usually aimed at creating an O/W emulsion so that the dispersed oil drops can settle out as described earlier. Emulsification of the oil also accelerates microbial degradation of the oil owing to its increased surface area. To achieve O/W emulsification, the dispersant (emulsifying agent) needs to be added within about the first 12 - 24 h after a spill, otherwise a maximum viscosity mousse emulsion will have formed making it extremely difficult to get the dispersant into the oil [79, 84]. Nevertheless, dispersants are commonly used in oil spill treatment. 

Extremely viscous so-called heavy oils are often produced from wells in Canada, Venezuela, and China. These oils often have reported viscosities in the range of (3-30) x 10 mPa s [38 0] and are often produced at the well head as a gas-in-oil emulsion with a gas volume fractions of from 0.05 to 0.40 [41], which has the appearance of chocolate mousse [38]. The foams formed from such gas-in-oil emulsions upon standing can be extremely stable, persisting for several hours in open vessels [38]. 

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