Slug Calculations and Slug catcher sizing
Slug Calculations and Slug catcher sizing
(OP)
Hi Everyone,
I am working on Gas condensate pipelines and need support to solve one problem.
Brief description:- The 12” pipeline system has lot of NGL in the flowing gas stream, and Pipesim is predicting dropout of the liquid. The gas stream is saturated leaving the 2-phase separator at a pressure of ~ 50-70 psig, and the line goes underground and cools, causing liquid dropout. Around 300bbl liquid hold up is calculated by Pipesim.
Objective is to size the slug catcher. What pigging frequency should be considered? How fast this liquid will accumulate? What will basis of slug catcher design? How much margin shall be considered in slug volume as slug calculated by dynamic simulation would be more? Can anyone enlighten on these?
Regards,
MTQ
I am working on Gas condensate pipelines and need support to solve one problem.
Brief description:- The 12” pipeline system has lot of NGL in the flowing gas stream, and Pipesim is predicting dropout of the liquid. The gas stream is saturated leaving the 2-phase separator at a pressure of ~ 50-70 psig, and the line goes underground and cools, causing liquid dropout. Around 300bbl liquid hold up is calculated by Pipesim.
Objective is to size the slug catcher. What pigging frequency should be considered? How fast this liquid will accumulate? What will basis of slug catcher design? How much margin shall be considered in slug volume as slug calculated by dynamic simulation would be more? Can anyone enlighten on these?
Regards,
MTQ





RE: Slug Calculations and Slug catcher sizing
If 300 bbls/day, then 7 days of ops would yield 2100 bbls. Still not an unreasonable sized vessel. Try 2 weeks, 4200 bbls. A month is 8400 bbls.. getting a little large. I'd use a safety factor of 2 for slug size, so 7 days of ops would need somewhere around a 5000 bbl vessel.
Always buy the biggest vessel size you can afford, or fit on the plot plan. That's a static cost, whereas operating costs go up for smaller size vessels, go on forever and will eventually surpass the cost of the vessel.
Independent events are seldomly independent.
RE: Slug Calculations and Slug catcher sizing
Actually this holdup is calculated from Pipesim (SS run) and it calculates volume only. It don't tell accumulation rate and that's what I am looking for to avoid dynamic simulation at this time.
I need to know how much pigging frequency should be considered in selection of slug catcher. How fast this volume will accumulate? Is there any rule of thumb for this type of application?
Regards
RE: Slug Calculations and Slug catcher sizing
All this gives you n idea of how fast you need to dump the fluid and some feel for the size of the vessel and dump valves.
RE: Slug Calculations and Slug catcher sizing
Independent events are seldomly independent.
RE: Slug Calculations and Slug catcher sizing
If you want a conservatve size for your slug catcher choose 300bbls, but in reality you could get a much smaller one once you do the design, which is a lot cheaper than a huge vessel or some type of finger slug catcher. Without a largest slug flow in either normal operation or start-up or the liquid pump out rate you can't size it properly. The other way to reduce voulme is to reduce pressure and increase gas speed to sweep more of the liquid out, but yu're starting at a fairly low pressure already so maybe that's not an option, but have you tried a different line size?. If your liquid accumulation rate is low, you could get away without a slug catcher providing you pig frequently, though this is normally not a recomended option due to the inherent hazards associated with pigging.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way