This incident investigation report refers to a hydrocarbon leak occurred September 2008 on Statoil Hydro’s Oseberg C installation. This leak occurred in the production manifold area. The initial escape was estimated at 26 kilograms per second. The immediate cause was a sudden and unintended opening of the test manifold valve leading to the unpressurised test manifold. The consequent pressure shock tore off a two-inch pressure equalisation pipe between the test and production manifolds. The direct cause of the pressure shock was the rapid opening of a well to the unpressurised test manifold. The fail-safe position of the activated control block opened the valve, while the deactivated one closed the valve in its fail-safe position. That meant a rapid and unintended opening of the valve when hydraulic fluid was introduced to the control block. The total hydrocarbon volume was estimated at 1,500 kg. No people were injured and material damage was slight.
Officer of the Watch 