| Summary: | The recovered crude oil is often in form of an emulsion and the recovery is cut off when water to oil ratio exceeds a certain amount. The emulsions vary from water-in-oil to oil-in-water and the step that follows is to coalesce droplets to get two continuous liquids. This is often made difficult because crude contains naturally occurring surfactants, or the oil recovered is by enhanced oil recovery techniques which have additives that also stabilize the droplets. We have considered below a heavy oil (viscosity 650-750 mPa.s) to which has been added one of the three surfactants: a nonionic surfactant or a cationic surfactant or an anionic surfactant. In addition, the mix can have alumina or silica nanoparticles or none. Most of the results have straightforward interpretations. Cationic surfactants appear to give rise to a secondary haze. There is no apparent effect due to nanoparticles. If the system contains nonionic surfactant then it can be destabilized by raising the temperature, except for one notable case. There are also cases of precipitation of nanoparticles.
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