Geotechnical Design and Installation of Suction Anchors for the Goliat FPSO, Offshore Norway

Abstract

Goliat is the first oil field to be developed in the Barents Sea, and thus sets the industry standard as activity migrates ever further north. Eni, together with partner Statoil, has chosen to develop the field using Sevan Marine's cylindrical FPSO concept. This FPSO is designed for operations under the challenging conditions encountered in the Barents Sea and is equipped to meet the strict environmental requirements stipulated for operations in the Arctic climate. The FPSO is moored using 14 suction anchors, with 6 anchors in the west cluster, 4 in the north cluster and 4 in the southeast cluster. The soil layers of relevance for the suction anchor design are a surface layer of very soft sandy clay and a soft to firm slightly sandy clay with some gravel to at least 20 m depth. All 14 suction anchors were designed with the same geometry to allow flexibility during the installation phase. The anchor holding capacity was evaluated using Finite Element analyses. The successful installation of the suction anchors was performed in spring 2013 to allow hookup of the FPSO as planned. This paper describes details of the suction anchor design and installation process as a reference for further work in Arctic regions.