Dewatering gas lift pipe line
Dewatering gas lift pipe line
(OP)
Hi all,
I am looking for a procedure of dewatering gas lift pipe line.Can some one help me on this issue.
Best regards
tbvn
I am looking for a procedure of dewatering gas lift pipe line.Can some one help me on this issue.
Best regards
tbvn





RE: Dewatering gas lift pipe line
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
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RE: Dewatering gas lift pipe line
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"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/
RE: Dewatering gas lift pipe line
I am a brand new in this area and I am trying to learn from you all as much as possible.
Actualy we are preparing dewatering gas lift pipe line from Subsea tie in point to our facility.After we have complted hydrotest this pipe line, there is apr 360m3 water left inside.The hole lenght of this pipe is 7 km and ID is 10 inch.we have installed a bi-dir pig and pressure upstream of pig is 100bar.
I am looking for a procedure of dewatering gas lift pipe line for prepare our procedure.
Hope this clear and you can help me.
BR,
tbvn
RE: Dewatering gas lift pipe line
http://www.eng-tips.com/viewthread.cfm?qid=258654
**********************
"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/
RE: Dewatering gas lift pipe line
So to "dewater" your line I would:
1. Determine a legal way to dispose of the water removed. This can be a bigger problem than anything else since the nice clean water you used to fill the line is now "waste" and many countries will no longer let you dump it on the ground. I've had to haul my test water to disposal wells (your project is around 2,200 bbl so this is not a small thing).
2. Then I would run a couple of foam pigs towards whichever end the disposal method is on. There will be some bypassed water with two pig runs, but your line will either use dehydrated gas (which will evaporate the left-behind water within a few days or weeks) or you will need to regularly pig the line and the left-behind water will get pigged out with that.
You dry a line down to less that 50% relative humidity when it has something that liquid water can hurt, I don't think that is the case for a gas-lift line.
David
RE: Dewatering gas lift pipe line
He can stop the procedure whenever he thinks its dry enough to run (mostly) gas and probably do it again the next month or so.
**********************
"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/
RE: Dewatering gas lift pipe line
I got solution now.
BR,
tbvn
RE: Dewatering gas lift pipe line
My apologies, I feel this assumption is incorrect and need to point out the following:
High concentrations of methane, ethane, propane (i.e. lean export/lift gas) and the very likely presence of free water even after dewatering (10" ID is not a small line, in fact HUGE for gas lift) combined with low ambient temperatures (Subsea line) and high (enough) pressures @ approx 100 barg represent perfect hydrate formation conditions. Even if the lift gas is dehydrated, the free water in the line will be ready & waiting for it.
The dewatering procedure needs to address this issue. In fact, in most cases, this is mitigated against by the use of a suitable mix of MEG/Water as the initial hydrotest fluid.
I hope we are not too late in pointing this out...
The only saving grace is that, if the 10" ID is correct, it will take HUGE amounts of hydrates to block it completely...
Nick McCarthy
Flow Assurance Consultant
http://www.linkedin.com/in/flowassurance
RE: Dewatering gas lift pipe line
For ongoing injection, the OP needs to look at the mix of gases (I rarely see anything heavier than methane in gas lift gas because the other stuff is too valuable as NGL and is less effective in gas lift) and the amount of water vapor in that gas (again, it is pretty common to use dehydrated gas for gas lift from shore for the issues you raised).
David
RE: Dewatering gas lift pipe line
I agree with NMcC's comments above.
Bulk de-watering off subsea gas lift lines is not sufficient ensure that hydrates don't form.
Generally due to terrain, sufficient water can collects at low points leading to hydrates in the line or downstream of gas lift chokes on the tree.
Generally you would use a train of b-dir, foam or gel pigs with MEG/water [80/20] between the pigs. The driving force provided by Nitrogen or product gas.
In UK, BG guidelines are used to calculate MEG quantities required in the pig train. I will have a look if I can get extract from these guideline.
Regards
Al
RE: Dewatering gas lift pipe line
Glycol Swabbing
See attachment for claculating glycol volumes.
Regards
Alph