Replacement of gas export line

The challenge

Our client operates the F2-A Hanze platform in the Netherlands, which is located around 200 kilometres north of Den Helder in the Dutch part of the North Sea. The platform is connected via a 4-inch flexible gas pipeline to the A6-F3B gas pipeline, while a control umbilical has been piggybacked to the flexible pipeline. This pipeline needed to be replaced, but an additional challenge was that the existing control umbilical needed to remain in place.

The solution

We were asked to install the new 4-inch flexible gas export pipeline in water 42 metres deep. The project was executed from the DP2 DSV Stril Server, which was fitted out by Bluestream with a full suite of air diving, ROV and flexible lay equipment. 

The scope of the project included:

• Removal of rock dump with an airlift, subsea dredge and excavator

• Preparation of two crossings by installing mattresses

• Isolation and valve testing

• Disconnection of old flexible pipeline

• Installation of new flexible pipeline including bend restrictors

• Tie-in of new flexible pipeline including dewatering of spools and valves

• Leak testing and dewatering of the new flexible pipeline

• Installation of dropped objects protection and stabilising rock bags

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