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[Propacket]

Hi Everybody,

Crude oil contains water in two forms
• Free Water
• Water in Emulsion with Oil
Three phase separator operation in hysys solely separates free water and does not take into account the water which is in emulsion with oil. This is due to the inability of hysys to consider the effect of various emulsifiers on the separation. Therefore, during process design how would we know the water load on dehydrator installed downstream of production separator .i.e. how would we know the water content which is in emulsion with oil and is actually carried with the oil downstream of three phase separator?

[daryon]

Hi Everybody,

Crude oil contains water in two forms
• Free Water
• Water in Emulsion with Oil
Three phase separator operation in hysys solely separates free water and does not take into account the water which is in emulsion with oil. This is due to the inability of hysys to consider the effect of various emulsifiers on the separation. Therefore, during process design how would we know the water load on dehydrator installed downstream of production separator .i.e. how would we know the water content which is in emulsion with oil and is actually carried with the oil downstream of three phase separator?

Hi P.Engr,
I don't think you can know with any certainty what the water load on the dehydrator will be. If you are expecting stable crude oil-water emulsions then it may be quite high. High process temperatures and chemicals will help to break the stable emulsion and allow phase separation. Electrostatic coalescers can handle water-in-oil contents of 15% (Vol) possibly higher. Where I have worked with stable emulsions in the past the client has supplied a fair bit of information from laboratory work, like gravity separation times between crude oil - water at various temperatures and with various quantities of demulisfier chemicals added.

One design approach (I'm not saying this is necessarily the best way) could be to specify the dehydrator with as high as practically possible inlet water load and work out what you need to do upstream (heat and chemicals) to ensure this is achieved.

One further point to highlight; be very wary of mixed fluid viscosities for stable oil-water emulsions. It was reported by Thompson et. al (1985) that the viscosity of a 50% water-in-crude emulsion can be 6 to 20 times that of the base crude oil. This has also been seen in practice, often where downhole ESPs are installed. High emulsion viscosities can have a very significant impact on line sizing and equipment sizing, especially heat transfer equipment.