3 phase [oil, gas, water] flow pressure drop

[Wazobia]

Hi. I am doing some work on crude oil separation and am having problems finding correlations / methods on pressure drop calculations for the crude lines. Basically it's a design for a new flowstation, and i am trying to do some preliminary line sizing calculations.

Is it OK to assume a homogenous liquid flow, as opposed to an oil / water emulsion? What correlations are used, if an emulsion is assumed. Anyone who has experience with this, help would be very much appreciated.

I know software like OLGA can do this, but i would also like to know a manual process of solving this type of problem

Thanks.

 

[BigInch]

Gas/oil/water flow is usually only assumed as two phase flow, as it is only gas over liquid without solids (for the present anyway), for which the Lockhart-Martinelli correlation, among some others, may be of use to you. Google Two phase flow, Lockhart-Martinelli and you will find a number of articles detailing that method of analysis. What you need to consider as far as the water and oil phase is how much water you have in relation to oil and if you allow sufficient settling to occur after it is extracted from the wells, or if it goes directly into the pipeline. If the quantities are each significant and remain in roughly the same proportions and separated, you may be able to develop an effective viscosity factor then use an applicable friction factor equation with only that in mind. If the quantities of each fluid vary, and remain separate, you may have to model the hydraulics as two product flow cases. If you have an emulsion that does not separate, you will probably be able to treat the friction loss as pretty much any other liquid, once you have determined the viscosity of that emulsion. The tricky ones are those fluid combinations that will not remain in whatever state they enter the pipeline, ie, emulsions that separate, or two fluids that combine to make an emulsion in the pipeline, or those that never combine. Depending on the properties of the two fluids, various flow regimes are possible. There, you must be able to predict when such actions take place and adjust your friction equations to compensate. Some Venezulan heavy crudes are notorious for difficult transportation characteristics to the point where they must be transported as an emulsion surrounded by a water layer, so you may have to do some significant lab work to determine the most appropriate method for econimical transport.

"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com

 

[Wazobia]

Thanks for the advice BigInch. I havent started the line sizing calculations proper, hopefully i'll get my other stuff done before midday and start on that.