The name is absent

Chapter 2

2.5. Effects Ofasphaltenes and demulsifier selection

For water in crude oil emulsion, several mechanisms have been suggested
for the stability ^{[27L [281}: (a) steric repulsion due to the adsorption of asphaltenes
and resins, followed by formation of rigid films at the water∕oil interfaces; (b)
formation of long-range particle structure inside the film between two approaching
drops; (c) steric repulsion due to the adsorption of naphthenates at high pH.

For mechanism a), the thickness of such films can be several hundred
nanometers and the solubility of asphaltenes will affect the formation of rigid film.
ForAthabasca bitumen, the solvencies of the solvents are as follows ^t21j: paraffins
< olefins < napthenes < cycloolefins < condensed napthenes < aromatics <
condensed aromantics. By increasing the aromaticity of the oil phase and the
resin/ asphaltene ratio, the average number of asphaltene molecules present in
the colloid diminishes and therefore their solubilization in the oil phase will
increase. Conversely, decreasing the aromaticity of the oil and/or the
resin∕asphaltene ratio leads to an increase in the asphaltene aggregation number
and therefore to precipitation. If asphaltenes are less soluble in the solvents, they
will precipitate and adsorb at the water/ oil interface forming the film structure. The
thickness and concentration of these surfactant-active materials around the
droplet’s periphery build over time until the layer becomes a structural barrier

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