Britain's first field development in the West of Shetlands offshore area faces further delays because installed subsea equipment failed during pressure testing.
BP Exploration Operating Co. Ltd. initially intended to produce first oil from Block 204/24a Foinaven field late in 1995, but the operator once more must revise its schedule.
BP has decided it must retrieve a subsea manifold and five christmas trees from the seabed. The operator believes valve seals have been damaged and would leak oil if used.
What happened
The problem was spotted when BP carried out high pressure testing of subsea equipment using water and dyes. Four out of 48 valve stems on one of two subsea manifolds leaked, as did three trees from one drilling center and two from the other.
A BP official said high differential pressure between the outside and inside of the equipment affects how the valve seals seat, and leakage suggests the seals have been damaged.
All the equipment that failed was supplied by the Aberdeen unit of Cooper Cameron Corp., said the official, and both BP and the supplier will investigate the cause of the failures.
Equipment will be retrieved using the Iolair construction semisubmersible vessel, which installed it. BP has not said when it expects the repair work to be completed.
Golar-Nor Offshore AS, Trondheim, Norway, which is leasing its Petrojarl Foinaven production/storage/off- loading ship to BP for the development, has told the Oslo stock exchange it expects recovery, repair, and installation will take 3-4 months.
Last year, BP had to retrieve the first subsea manifold it installed in Foinaven after cracks appeared on hubs during leak testing (OGJ, Nov. 11, 1996, p. 28). This had caused the start-up target to be pushed back to April 1997.
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