Aasta Hansteen spar

The Aasta Hansteen FPSO spar is a spar gas platform engineered by CB&I, currently being built by Hyundai Heavy Industries in South Korea.

Design

Once on site it will be partially submerged by filling ballast tanks to 177 m and anchored to the seabed, leaving only the top 21m above the surface. The seabed moorings will be primarily made of cut resistant polyester and steel chain.

At a height of 198m (of which 177m will be submerged) and diameter of 50m this will be the biggest spar platform hull ever built in terms of diameter and displacement.[1] The spar hull will be a truss spar type allowing condensate to be stored in the hull beneath sea level and offloaded to a shuttle tanker. The produced gas will be exported to the shore with rigid Steel Catenary Risers (SCR). The Production import risers will also be SCRs, first time of application of SCRs in the Norwegian Sea.

The Aasta Hansteen spar will export the natural gas from the field through the yet to be built Polarled[2] pipeline to the Nyhamna processing plant on the Norwegian coast. The project costs 31 billion NOK.[3]

Transport and installation

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 than towed vertically to the Aasta Hansteen gas field 300 km off Bodø at the northwest coast of Norway. The spar will be tethered north of the Arctic Circle using polyester moorings to the seabed 1200m below.[4][3][5]

Aasta Hansteen gas field

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. [3]

References

  1. ↑ "Det meste er ekstremt på Aasta Hansteen". Retrieved 30 November 2017.
  2. ↑ "Polarled project description". Retrieved 22 February 2017.
  3. 1 2 3 "Aldri før har det blitt installert utstyr så dypt i Norge". Teknisk Ukeblad. Retrieved 10 April 2017.
  4. ↑ "Aasta Hansteen (Luva)". Subseaiq. Retrieved 18 February 2013.
  5. ↑ "Den er 200 meter høy og veier 46.000 tonn. Nå skal den til Stord". Teknisk Ukeblad. Retrieved 10 April 2017.
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