Method of laying lined pipeline
A method lays lined pipeline which actively and successfully removes air pockets which might be trapped in the annulus between the liner and the host pipe by progressively flooding the lined pipeline. Further, the liner is brought into closer contact and engagement with the host pipe. The removal of air in the annulus enables the pipeline test pressure to stabilize more quickly and avoids the risk of potential collapse during operational service life in the event the pipeline pressures fluctuate or a vacuum is created during an emergency shutdown.
1. A method of laying lined pipeline on a seabed, the method comprising providing a lined pipeline having a continuous annulus between an internal polymer liner of the lined pipeline and a steel host pipe, lowering the lined pipeline towards the seabed while keeping a lower end of the pipeline closed, and subsequently opening the lower end of the pipeline while an upper end of the pipeline is open, to allow seawater to progressively flood the lined pipeline.
2. The method according to claim 1 , wherein the lined pipeline is lowered to the seabed before opening the lower end of the pipeline to allow seawater to progressively flood the lined pipeline.
3. The method according to claim 1 , wherein the lower end of the pipeline is opened when a effective pressure differential is obtained.
4. The method according to claim 1 , comprising continuing to lay the pipeline while the lower end of the pipeline is open.
5. The method according to claim 1 , wherein the lined pipeline is laid using a pipe lay vessel.
6. The method according to claim 5 , wherein the pipe lay vessel is a reel lay vessel, and the lined pipeline is disposed on and deployed from a reel.
7. The method according to claim 5 , wherein the pipe lay vessel is an s-lay or j-lay barge, and the lined pipeline is constructed length-by-length.
8. The method according to claim 5 , wherein the pipe lay vessel tows the lined pipeline into position.
9. The method of claim 5 , wherein the flooding of the lined pipeline is controlled from the pipe lay vessel.
10. The method of claim 1 , wherein the lined pipeline comprises a plurality of lined pipe sections having respective linings that are joined to provide the continuous annulus between the linings and the pipes along the length of the joined pipe sections.
11. The method according to claim 10 , wherein providing a lined pipeline comprises joining sections of lined pipe, and joining respective linings of the lined pipe sections to preserve the continuity of the annulus.
12. The method according to claim 10 , wherein the respective linings are joined using one or more electrofusion fittings to preserve continuity of the annulus.
13. The method according to claim 12 , further comprising testing the integrity of interfaces or welds between the electrofusion fitting or fittings and respective liners.
14. The method according to claim 10 , wherein the respective linings are joined using one or more butt fusion welds to preserve continuity of the annulus.
15. The method of claim 12 , wherein the electrofusion fitting or fittings comprise an inner diameter concentric with an inner diameter of respective liners.
16. The method of claim 12 , wherein the electrofusion fitting or fittings comprise an outer diameter concentric with an outer diameter of the liner.
17. The method according to claim 13 , wherein the integrity of an interface or weld is tested prior to laying the corresponding section of pipeline.
18. The method according to claim 1 , comprising filling the lined pipeline with seawater at atmospheric pressure before lowering the lined pipeline towards the seabed.