BP chartered a large semi-submersible accommodation vessel for mooring alongside a platform at the Valhall Oil Field in the Northern North Sea.

Longitude were instructed to prepare a mooring analysis report for the 240,000 tonne displacement Safe Scandinavian semi-submersible vessel in alongside wave heights of up to 9.5 metres and stand-off wave heights of up to 11.4 metres. The analysis included the preparation of a hydrodynamic model of the semi-submersible and verification against response amplitude operators provided by the vessel owners.  The spread mooring system comprised of a mix of polyester, steel wire, chain and buoyancy elements and the mooring analysis was performed to NORSOK standards and included two line failure scenarios.