Global Marine Systems has announced the successful completion of the Gjøa power cable installation. Gjøa is the first ever floating platform to have power supplied by a direct link from shore, and will contribute to a greener source of energy, reducing carbon emissions by an estimated 210 000 tpy.
Working together, Global Marine Systems and ABB installed the submarine cable, which brings electricity from the Mongstad refinery, north of Bergen, Norway, to the oil and gas company’s floating production platform in the North Sea.
Gjøa’s 100 km high voltage AC power cable passes through up to 544 m depth of water and is the world’s longest power link to an offshore platform. Installation of a cable to such a depth, over subsea cliffs and very rough subsea terrain, poses significant challenges requiring the utilisation of innovative installation techniques.
As senior project manager, Bruce Manning explains, ‘When laying this type of heavy cable in deep water, control of the lay tension is vital to ensure the cable is not damaged. This is principally achieved by monitoring the point that the cable touches the seabed using a remotely operated vehicle,’ he said. ‘The installation process needed to be highly controlled as waves can exceed 7 m in height (even in summer) and pose a significant challenge. Lay vessel motion would induce unacceptable stresses into the cable, which were alleviated by use of a heave compensated lay chute - the first time this has ever been done.’
To guarantee a successful outcome further protection for storm conditions was also made through temporary buoyancy systems, which could be rapidly deployed immediately before a storm hits.
Read the article online at: https://www.oilfieldtechnology.com/exploration/03092010/global_marine_systems_installs_cable_for_gj%C3%B8a_floating_platform/