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BP proves diverless connection method in Foinaven

Sept. 1, 1997

Tooling used to re-install flow-line termination assemblies in BP's Foinaven development. [15,714 bytes] Once the flanges were positioned by the alignment frame, an ROV put studs and nuts in position for tightening in a torque tool. Photos courtesy of Sonsub. [15,118 bytes] BP Exploration Operating Co. Ltd. has speeded recovery work in Foinaven oil field in U.K.'s West of Shetland area, by means of the world's first diverless reconnection of a standard flanged subsea assembly.

BP Exploration Operating Co. Ltd. has speeded recovery work in Foinaven oil field in U.K.'s West of Shetland area, by means of the world's first diverless reconnection of a standard flanged subsea assembly.

Development of Foinaven has been delayed by failure of installed subsea equipment during pressure testing. Much of the equipment has had to be recovered (OGJ, May 19, 1997, p. 33).

The reconnection involved a tool developed by Aberdeen's Sonsub International Ltd. and McDermott Subsea Constructors Ltd. in 14 weeks, under a contract to disconnect and re-install termination assemblies to an 8-in. and a 10-in. flow line.

Connection to the assemblies was originally done onboard a pipelay vessel prior to installation, since Foinaven lies too deep for divers in 480 m of water.

Without the tooling, said Sonsub, the only alternatives would have been expensive mechanical pipe connectors or recovery of pipeline ends to the surface.

The tooling allowed re-installation of the assemblies without changes to existing field equipment. It was carried out using two Sonsub remotely operated vehicles (ROVs) deployed from MSV Iolair construction vessel.

Derek Cruickshank, Sonsub sales and marketing manager, said, "As the industry moves into deeper waters, there will inevitably be requirements to undertake diverless intervention on flanged assemblies. There is tremendous potential for the application of the cost-effective solution provided by our new system in all water depths, mainly because it does not require modifications to be made to clients' existing equipment."

BP owns the tool, with design rights held by BP, Sonsub, and McDermott. Its alignment frame can handle equipment as heavy as 20 metric tons, including assemblies, manifolds, and pig launchers and receivers.