Aasta Hansteen spar

The Aasta Hansteen platform is a truss spar type allowing condensate to be stored in the hull below sea level and offloaded to a shuttle tanker. The produced gas is exported to the shore with steel catenary risers (SCR). The production risers are also SCRs, with these being the first time SCRs have been used in the Norwegian Sea.

The spar hull was designed by Technip, with the topsides being designed by CB&I, with both being fabricated by Hyundai Heavy Industries in South Korea before being transported to Norway for installation.[2] Once on site it was partially submerged by filling ballast tanks to 177 m and anchored to the seabed, leaving only the top 21 m above the surface. The seabed moorings are primarily made of cut resistant polyester and steel chain.

At a height of 198 m (of which 177 m will be submerged) and a diameter of 50 m it is the biggest spar platform hull ever built in terms of diameter and displacement.[3]

The Aasta Hansteen spar exports the natural gas from the field through the Polarled[4] pipeline to the Nyhamna processing plant on the Norwegian coast. The project cost approximately 37.5 billion NOK.[1]

The Aasta Hansteen spar was built on its side in the dry dock on barges. Once built it was floated off the barges and then floated onto the heavy transport ship Dockwise Vanguard and shipped to a fjord near Stord in Western Norway. The spar was upended in the fjord, after which the topsides were installed using the floatover technique. It was then towed vertically to the Aasta Hansteen gas field 300 km off Bodø at the northwest coast of Norway. The spar will be moored north of the Arctic Circle using polyester moorings to the seabed 1200m below.[1][5][6]

The Aasta Hansteen began producing on 17 December 2018.[1]

Originally called the Luva gas field and later renamed after Aasta Hansteen, it was discovered in 1997 approximately 300 km off the coast of Norway. During start up of the platform, the production from the surrounding Luva, Haklang and Snefrid gas fields will be exported to the platform. Future fields already discovered are planned to be tied back to the Aasta Hansteen platform through SCRs. Future expansion of additional risers and topsides facility are built-in in the design of the platform. The field is located north of the Arctic Circle, and is subject to perpetual darkness and sub-zero temperatures in the winter months. [1]