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Last phase of sea-bed testing for Ormen Lange

April 10, 2006, 09:00 CEST
Norwegian Sea will be finished by the end of May. All equipment which is to be installed at a sea depth of 850 metres is being thoroughly tested by the Grenland Group in Tønsberg.

Since January, the 120-metre long Hall C in the Framnes area of Tønsberg has been filled with subsea production equipment, intended for the Ormen Lange field.

In this hall, supplier FMC Kongsberg and its subcontractors have been able to try out all the operations that are to be carried out this summer, using remote-controlled subsea equipment at a depth of 850 metres.

"Many people ask if such extensive testing is necessary, but we have found that the thorough preparations have revealed surprises, which we will now avoid encountering out at sea. In that way, the costs of testing have already paid off many times over," says engineer Per Magne Almdahl. He is responsible for following up the testing at the Grenland Group on behalf of Hydro.

Hall C is dominated by a 35-metre long and 30-metre wide terminal that is used to connect the production pipes running into the land-based facility at Nyhamna with two templates on the sea bed. The terminal is a so-called PLET - Pipeline End Termination.

The PLET system in Hall C is a replica, which is solely to be used during testing. The system that will actually connect the 30-inch pipes from Nyhamna to the production equipment on the sea bed was already installed in the field last August.

"The replica is identical to the system on the sea bed, and here we are able to test that all the modules really can be assembled correctly," says engineer Øivind Leon Eriksen. Together with Almdahl, he has followed up the testing on Hydro's behalf.

During the testing, the task is to evaluate what can happen in a worst case scenario when installing the equipment on the sea bed. Everything from base frames to valves has been thoroughly tested. This includes, for instance, two huge valve modules that each weigh 130 tonnes, and are to be mounted on the PLET system.

"In this work, it's actually important to have a negative attitude - all the time you have to base your work on what's the worst thing that can happen, and prepare the processes accordingly. When equipment is to be installed at a depth of 850 metres, you only get one chance. Here we get to test that all the parts really do fit together," says Eriksen.  

The production equipment will be installed on the field from the end of April until the end of the summer. Helge Hagen, who is in charge of this subsea operation, says that the pull-in of the production pipes towards the terminal is one of the most important processes to be tested in the hall.

"This will be a critical moment during installation on the sea bed, and among other things we are testing how different degrees of incline for the pipes affect the operations we are to carry out at sea. We also simulate as much as we can of other processes, such as so-called pigging, which is carried out during gas pipeline maintenance operations," says engineer Helge Hagen.

Incidentally, this year's testing in Tønsberg comes in addition to the work that was carried out last year, before the two sea-bed templates were installed on the sea floor.

"We are now approaching the end of an intensive test phase, and are looking forward to the equipment being installed on the field," says the head of Hydro's testing process in Hall C.