3-phase Separator and Slug Catcher

[Khansahib]

Considering the limited space available on an offshore platform the task is to design a 3-phase separator that can accomodate possible slug of well fluid. Options available are: (unless someone has better idea)
(i) Have a slug catcher followed by a separator, but this option requires a great deal of space.
(ii) Built the slug catching capacity within the horizontal 3 phase separator, which may result in oversized separator and have weight problem, lifting and rolling on the platform as well as localized weight on the structure
(iii) Install a Control valve upstream of separator and control the separator liquid levels and pressure by controlling the upstream control valve. This option is more apealing as I can have a controlled flow to the separator and any slug can be mitigated with in the 24"x30 KM pipeline upstream of control valve.
Your expert opinion will be valuable.

 

[dcasto]

or put the control valve down stream of the slug catcher. If the level is to high, pinch the flow out. This is better because upstream the shreading of the water/oil through the valve causes an emulsion.

 

[Khansahib]

dcasto, u r right about the emulsion formation if the valve is provided upstream. ur second suggestion has a merit provided option-1 is considered. But there is a space limitation and two piece of equipment are difficult to accommodate. I am looking for an option that kills the two birds in one stone without sacrificing the space. Any other idea?

 

[dcasto]

I only use a slug catcher with the above control system.

Why not have 30" pipe hanging vertically as a "drip" leg on the line coming in. The foot print is 30" diameter and 40' tall.

 

[SNORGY]

Khansahib:

Where do the liquids go from the separator? Is there an existing downstream surge volume that you can set up to accommodate a "crash dump" or "panic dump" case (in the event the liquids are not too unstable)? That would involve twinning the liquid outlet valves and routing the bigger one(s) of the twin(s) to the surge volume (in whatever form that exists).

I suppose that would depend on your ratio of "liquid" to (presumably) "water". Panic dumping is not the best thing to do with 3-phase separators especially if there is downstream heat (e.g. produced water storage heater). I still see it done (albeit onshore), but less frequently these days.

Might be worth a quick review even if it doesn't withstand the first minute of scrutiny from a safeguarding perspective.

Regards,

SNORGY.

 

[Khansahib]

Thanks gentlemen for your interest.

SNORGY[/]The crash dump I am thinking to take it to the Flare Knock Out Drum unless there is good reason Not to use it.

decatocan you elaborat a little more keeping in mind that it is offshore platform, space and enornment are challenging.

 

[SNORGY]

Khansahib:

That's probably one of the better places to go if you are considering that option (panic dump provision). You would probably want to take a look at the knockout pump (if any) and see if you could re-run from there back to the separator after your slugging event.


Regards,

SNORGY.

 

[dcasto]

I've only worked onshore, but once the riser comes up, on the platform, why not just hang a piece of pipe as your slug catcher attached to a leg of the platform.

 

[atayto]

May be it is not profecional, but could you have look to this link. there is some separators for well service. footprint should be very very very small.

 

[Khansahib]

SNORGY I am going to ensure that the KOD pump is big enough to meet the requirement, Thanks, any other suggestion?

dcasto Your suggestion is valid and a way can be found to implement it but I want a paradigm. I believe that due to number of risers and may be vibration it may not be a good option or atleast I am not aware. May be someone on this forum can respond to this option.

atayto The way I understand this kind of separator/scrubber are normally used for wet gas to make it liquid free and could be used, Thanks may be I use it for the project I am working provided I convince the client.
need more literature on it

 

[SNORGY]

dcasto's suggestion is good, in my opinion, provided the "slug" therein caught is then routed to the separator to afford further phase disengagement, if required. Also, the elevation of the slug catcher pipe relative to the separator becomes important with respect to the mechanism by which the slug volume is transferred.

Regards,

SNORGY.

 

[Khansahib]

SNORGY Since there is no response from experts on the forum should I consider that my proposed option has a merit other than decasto which requires a paradigm?

 

[BigInch]

I assume you can't design a multiphase pipeline and put the slug catcher on land, right.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[SNORGY]

I would really like to see the P&ID, GA and elevations before offering a professional opinion as to which options have what merit.

Regards,

SNORGY.

 

[BigInch]

Its better to get in on the project still in time to draw them up. That's now, before he tells us anything usefull. That's why I put the equipment on the beach.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Khansahib]

I am working on the P&IDs, might take some time to finish