Oil Carryover 1

[Inchtain]

Dear engineers,

We have a 3-phase pressure vessel working at 3 bar and 65 degrees Celsius. We have very good crude oil outlet with only 0.3% water cut and the gas outlet is fine. On the other hand, the water outlet carries quite big quantities of oil.

What do you think is the probable reason?

It's worth to say that an emulsifier is injected to the crude oil before entering the Separator.

Thanks and best regards,

 

[LittleInch]

Lack of separation time for the water/ oil interface.

Did you really mean emulsifier or demulsifier?

The former will bind oil to the water to create an emulsion.....

So no wonder you have a lot of oil in your water needing secondary treatment.

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[horacio Torres]

You should check the design residence time for oil and water, they have to be on process according to the design. Otherwise you will have bad oil -- water separation.

You have to use a demulsifier, to break the water-oil emulsion. Some products have the behavior, if you overseed, promoted the emulsion doing the reverse effect.

If you have turbulence in the coalescer zone, it make less efficient the oil water separation, check it.

Horacio

 

[Inchtain]

Sorry, it is demulsifier.

So, how one can overcome the problem of not having sufficient time for the water/oil separation?

And how to check the turbulence in the coalescer area?

Regards,

 

[LittleInch]

Either lower flow or bigger separator. Or less water in the oil coming in

Also check the height of the oil water interface control. If you get too low sometimes you vortex or cone down oil into the water outlet.


There are lots of ways to post process the water coming off it including vortex separators, gravity separators, a further separators etc.

What is the residence time?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[horacio Torres]

Residence time ....  Time that the liquid has to be in the separator to let the drops  separate from the continuous phase.  If oil remains in the water phase it could be that the water flow is above the design, no given time to the oil drops to separate from the water phase.

Mr Inchtain
First check the design flow  for water and oil, calculated the resident time for them and compared  with the actual one. If you have water flow above the design means that  water residence time is less than the design.. Normaly  I set 10 min for each phase. GPSA set even 5 min for some oil water separation...
Solutions, you cannot reduce the flows... you need another water oil separator or install a gun barrel first than is cheaper.

Turbulence checking is quite difficult.. In an oil field with medium oil production, we review process conditions, design flow of water oil separator everything same to be fine. no reason for poor performance,  finally was set out of service and inspected inside, a big asphaltenes block was discovered. there was turbulence.


Horacio