Slug Factor for 3 phase horizontal separator sizing.
Slug Factor for 3 phase horizontal separator sizing.
(OP)
Hi,
Senior engineer told me to keep 20% of vessel size for slug margin but SHELL DEP is saying 0.05D or minimum 0.3m. I would like to understand which method to be used for slug margin during three phase horizontal separator design.
Thanks
Senior engineer told me to keep 20% of vessel size for slug margin but SHELL DEP is saying 0.05D or minimum 0.3m. I would like to understand which method to be used for slug margin during three phase horizontal separator design.
Thanks





RE: Slug Factor for 3 phase horizontal separator sizing.
Predicting slug volumes isn't a hard and fast science, there is a lot of uncertainty in your value. 20% to me isn't a large margin, 0.05D is very little. Given that slug catchers are normally fairly large vessels 0.3m isn't much of a margin either.
How confident do you feel with your predicted slug volume? What happens if the slug is larger than you predict?
RE: Slug Factor for 3 phase horizontal separator sizing.
No slug catcher before separator, therefore, 20% of vessel volume is keeping as slug margin but i agree with you if more slug is coming then separation problem will be there.
Is this better to keep a big margin in separator sizing or put slug catcher, field is getting old and more sediments coming with production. Keeping 20-30% slug margin will increase the vessel size and cost will also go up, now comparing the cost of vessel and puting the slug catcher which is best option?
RE: Slug Factor for 3 phase horizontal separator sizing.
Maybe you should consider reference?
Is the margin form normal level to HH
or from H to HH
or from H to overfilled??
Best regards
Morten
RE: Slug Factor for 3 phase horizontal separator sizing.
My question is to seek the advise from members and I'm not considering Shell DEP is not a bible. Shell DEP is just for reference but your judgment is the final and best fit as per situation.
The best solution for this type of services is desanding option instead of increasing the vessel size.
Thanks for your valuable comments.
10815L
RE: Slug Factor for 3 phase horizontal separator sizing.
Anyway, what i was trying to say with regards to your margin for slugs is that you could consider the margin from NL or from HH and your rationale "would depend". So are your certain that the Shell DEP margin and your "senior engineer" has used the same reference?
You say that the " best solution for this type of services is desanding option instead of increasing the vessel size" - how does this solve a slug issue?
There are a number of issues wrt slugs:
-Quality of separation
-Level control (overfilling)
-Gas compressor control (large variation in gas flow)
-?
The sizing should consider your upstream design: Is it a separator connected directly to wells, or are there (long) sub sea flow lines, risers? Your margin should be justified based on these and not just a number (in a manual or otherwise). Should your separator be able to handle a slug when at HH or only when (near) NL? If you in addition to your estimated slug size and frequency ALSO want a margin then you maybe a manual will help. But in many cases adding "fat on fat" creates other problems (aside from the obvious cost issue)
Best regards
Morten
RE: Slug Factor for 3 phase horizontal separator sizing.
Every Shell project I have ever worked on, Shell have encouraged the EPC contractor(s) to recommend "industry standard" and "fit for purpose" optimizations to their voluminous documents. Every time, the effort is carried on - with their encouragement - right up until the first shop inspection meeting with various fabricators. At that point in time, we are dragged into a conference room, declared either incompetent or stupid or both, admonished for having the audacity to challenge the DEPs / Specifications / Standards, told to discard the optimized documents, and revert back to the originals.
That appears to be the "Shell" way.
RE: Slug Factor for 3 phase horizontal separator sizing.
Best regards
Morten
RE: Slug Factor for 3 phase horizontal separator sizing.
RE: Slug Factor for 3 phase horizontal separator sizing.
Yes, I agree. It is pointless to deviate from a Shell DEP when, in the end, the DEP will be upheld.
RE: Slug Factor for 3 phase horizontal separator sizing.
Good luck,
Latexman
RE: Slug Factor for 3 phase horizontal separator sizing.
RE: Slug Factor for 3 phase horizontal separator sizing.
What is the meaning of TA's,and please elaborate more in detail of your quoting,"Too many producer companies do not reward tech experts with the ability to make decisions - in other words, why deviate if the only reward to me is increased risk?"
Thanks
RE: Slug Factor for 3 phase horizontal separator sizing.
As to slug capacity, that should be absolutely dependent on upstream conditions and the impact of overrunning your separator on downstream processes. If all you have downstream is more pipe, then you get away with a higher probability of overtopping the separator. If you have a piggable gas line upstream of the vessel and a compressor with no suction scrubber downstream I'd put a VERY large factor for slugs (and a HH ESD, etc.). I did this "analysis" for a project in 1993 and turned a 30" X 12' vertical separator into a 90" X 25' horizontal vessel (that still slugged the compressor once in the intervening 19 years).
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
RE: Slug Factor for 3 phase horizontal separator sizing.
RE: Slug Factor for 3 phase horizontal separator sizing.
one more explanation, can I ask the vendor for fly change over the compartments after one or two year of operation, if Increase of water cut and water & oil compartment can be readjusted with out cutting and welding. And this easy for operation and save lot of time and cost. is this good option for integrity of the vessel or not.
Thanks
RE: Slug Factor for 3 phase horizontal separator sizing.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.