CRUDE OIL STABILISATION AND ACCOUNTING FOR "MOUSSE" EFFECT 1

[compo]

I am trying to get more information and references from separation gurus out there regarding the mousse effect that can be apparent with certain crudes. The "mousse" effect wherein excess gas is trapped within the oil phase exiting say a production separator. The mousse is oil entrapped with small dispersed gas bubbles.

I appreciate that this tendency would be case specific and to understand crude characteristics tests are required for the particular crude in question. However I would appreciate any general feedback and references to correlations that you may know of that perhaps indicate what a respectable or common allowance is for moussing or gas volume carry-under with oil. In this case oil stream exiting a three phase separator (oil/water/gas) which then feeds a degasser where the gas is recovered and compressed. In designing the degasser and particularly selecting the compression capacity the allowance for moussing can be a critical parameter in the sense of over or under designing. In this case the crude is heavy 20°API and exhibits stable emulsion characteristics.

Thanks

 

[jay165]

Your asking for a generalization where one doesn't exist. There is no "common allowance" for gas carry under. What will determine the allowable amount will be specifications for maximum vapor pressure for the oil. This will come from either the pipeline company or the end user (the refiner) for your crude. In general you only want to stabilize the crude as much as you have to to meet the contract specifications.

You didn't ask, but the way to reduce gas carry under is with increased heat addition, reduced separator pressure, increased retention time, inlet swirl devices or chemical treatment.

 

[compo]

Appreciate your feedback. I am aware of the implications of RVP and methods to reduce foaming that's why I didn't ask those specific questions. In this case RVP is not the issue as a degasser will take care of any excess gas the issue is what excess is reasonable to design for regarding impacts/capex associated with downstream equipment rating. From my experience I have seen 50% v/v to 15% v/v carryunder quoted for design purposes and genrally without much basis or backbone behind the numbers.

 

[TexasPE]

The best way is to perform an actual test at operating temperatures and pressures. Talk to Pritham Ramamurthy or Chris Taylor at KBR's Park Ten Technical Research Facility in Houston Texas. They have designed a test setup for a client that allowed for testing to determine gas carryunder along with demulsifier dosage rates.