Offshore pipe-in-pipe installation

[Yves22]

Hi,

I am looking at the risk assessment of pipe-in-pipe lay methodology and practically new to this concept. Would appreciate your feedback.

1) What are the challenges in Pipe-in-pipe lay as opposed to the single pipelay?
2) How is wet buckling detected in the inner pipe?
3) Based on limited references, is it reel-laid from the surface and positioned on the seabed in a snake lay configuration? Is this the preferred method?
4) What are the repair technology in the event of wet buckle in deep to ultra-deep waters? What is the likelihood of abandonment and then resuming from the shallow end of the pipeline?
5) Any references/websites to gather more information on its installation and nightmares would be much appreciated.

Thanks in advance.

 

[LittleInch]

You might have more chance of a response if you post in the mechanical engineers pipeline forum, but you may also get more input from someone like ITP who make this and have experience on their website. AFAIK, PIP is normally reeled from onshore facility onto a reel vessel. Wet buckle you'll find out if the pipe weight suddenly increases.... Snake lay is sometimes used to take out the issue of inner pipe expansion versus outer pipe, but is subject to issues of concentrating stresses after a few cycles, i.e. S lay can become Z lay.
Repair in deep water - forget it.
As said look at vendors and instalation contractors like allseas, subsea 7, technip etc google search, Institute of marine engineering lectures, papers from internaitonal forums.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way