Ahead of the arrival of the BW Athena FPSO, subsea mooring specialist First Subsea has supplied the Ballgrab connectors used to moor the FPSO's submerged turret production buoy in 440 feet (134 meters) of water in the Ithaca Energy (UK) Limited, Athena field located on Block 14/18b in the UK sector of the North Sea at the end of 2011.
First Subsea has supplied 4+1 Ballgrab Series II subsea mooring connectors with a minimum breaking load (MBL) of 6,594 kN to moor the FPSO's 220 tonne, submerged turret production (STP) buoy. In total the buoy has nine R4 studless chain mooring lines attached to suction anchors. Five mooring lines use chain and wire, while the remaining four lines comprise chain, mid-line Ballgrab connector and wire to the buoy.
"The geometry of the STP buoy's mooring lines meant that four of the nine lines needed a diverless solution. The Ballgrab connector has an excellent track record for this kind of shallow water mooring in the North Sea," said Brian Green, general manager, First Subsea Ltd.
Each Ballgrab mooring line installation involved the use of a temporary docking porch or mud mat holding the connector's female receptacle attached by 240m chain to the suction anchor. When the buoy was in position, the male connectors, attached to the mooring lines, were lowered from the surface into the female receptacles to complete the mooring installation, and the mud mats recovered to the surface.
The Athena STP Buoy is supplied by Advanced Production and Loading (APL), a National Oilwell Varco company.
The Athena STP buoy is First Subsea's sixth STP buoy mooring project. Recent projects have included the shallow water Maersk Peregrino FPSO and the Petrobras Cascade Chinook FPSO, the world's deepest STP buoy mooring.
The Athena Joint Venture Partners are Ithaca Energy (UK) Ltd (operator, 22.5%), Dyas UK Ltd (47.5%), EWE AG (20.0%) and Zeus Petroleum Limited (10.0%).
For more information on First Subsea's range of Ballgrab subsea mooring connectors visit www.firstsubsea.com, e-mail firstname.lastname@example.org and call +44 (0)1524 387777.