Offshore Pipeline Leak : Preservation Method 6

[ek4putr4]

Dear Pipeliners,

What is the best method to preserve a leaked offshore pipeline? The leakage is at the dogleg bend's weld (parted), therefore cannot be clamped. The pipeline is currently shut down, and already exposed to sea water for about 4 month. Next 5 month will be expected to carry out the replacement.

Rgds
WYN

 

[SJones]

thread338-210090


Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[rconner]

I could well be the only one who doesn't understand exactly what you're talking about/wanting, but I was just curious what you mean by "preservation" in the context of an apparently long inactive pipe line that (apparently came somewhat apart maybe more than 4 months ago and) will shortly be replaced?

 

[ek4putr4]

The pipeline was parted 4 months ago, and there is an option to replace part of it instead of replacing the whole line. To avoid further corrosion, it is required to stop it corroded or to do preservation. Due to no equipment available currently, the fastest time to repair will be next 5 months.

 

[rconner]

Thanks. While I have no experience with such, if the concern has been/is salt water/oxygen etc. migrating into the line, was it/would it have been advisable to if at all possible somehow at least put something temporarily over breech (concrete, or maybe at least sand bags, etc.?) to minimize this transfer? I don't really know whether in the end this would help or hurt, but I am curious of others thoughts.

 

[BigInch]

Why worry about corrosion now when the line has failed? Corrosion control is best practiced as a preventive measure.

Are there impressed current options? Can you attach temporary anodes? In any case, with no equipment available, its probably difficult to do anything now, and whatever it might be is probably not very cost effective either.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[Sid7]

4 month on and still 5 months more to go. and this is estimate. At what stage of the design life is the pipeline? As BigInch has said already this is not going to be cost effective anyways.

Can the leaking bend be contained by two pigs from either sides? May be using some sort of rubber swell item either with the aid of pig or diver and temporary seal the leak till repair assessed completed?



Siddharth
These are my personal views/opinions and not of my employer's.

 

[JT100]

i came across a company called brinker technology that uses platelets to locate and block leaks using the difference in pressure, dont know too much about it but might be worth looking into. they can inject platelets of various sizes into the pipeline, and if required inject a radioactive material to locate the leak, but by the sounds of it that is not required in this case.

 

[Ussuri]

We have used brinker platlets before. They worked well. You inject a gel into the flow and the leak 'sucks' the platelets towards it. They gradually overlay the leak creating a longer leak path and eventually sealing the leak. They are a temporary fix and allow you time to develop a more appropriate system.

I dont think they would work in this instance as the pipeline is already shut down so there is no medium to inject the platelet rich gel into, and no pressure differential to cause them to migrate to the leak.

 

[ek4putr4]

Two options are currently come up, using continuously chemical injected/treated sea water and using smart plug pig from both side. I dont think platelets will work due to the line has been parted (openned 75% of circumferential at KP 0.3 of 6" 7.1 km total pipeline length).

 

[BigInch]

You'd probably add more oxygen to the process by pumping down fresh seawater to the damaged area and the rest of the pipe as well. Ya I think we can eliminate platelets.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[ek4putr4]

Thanks all, it means that smart plug pig is the only way.

 

[Sid7]

ek4putr4

Whatever the method you will adopt, we would appreciate if you can come up with the same with the results later.

Thanks in advance.

Siddharth
These are my personal views/opinions and not of my employer's.

 

[narenr]

Brinker platelets works only if there is a small leak not on parted pipes.

Assuming there is diver access, the diver can insert an inflatable plug [

http://www.inpipeproducts.com/products/testing_isolation/

], but before that corrosion inhibitor has be be injected from the other end of the pipeline for preservation. From experience I can say that if you have planned for the repair in the next 5 months, it might as well take a year, so preservation is important if you intent to repair or replace the parted sections.

Rgds Naren

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.