Five tugs with a combined 150,000 horsepower have started the 500 nautical mile tow-out of the giant Aasta Hansteen spar platform from Stord, Norway to the Aasta Hansteen field in the Norwegian Sea.
Located in approximately 1,300 meters of water and 300 km from land, the Aasta Hansteen gas field is being developed with a Spar FPSO platform that will be the first on the Norwegian Continental Shelf and largest in the world.
A spar is a floating installation consisting of a vertical cylindrical hull that is moored to the seabed.
The departure of the Aasta Hansteen platform is the biggest tow-out operation since the Troll A platform was moved offshore in 1996. The voyage, which is expected to take 12 days, is being managed by Subsea 7 and involves the tugs Skandi Vega, Skandi Iceman, Normand Ranger, Normand Prosper and Siem Opal.
The Aasta Hansteen discovery was made in 1997 and actually comprises three separate discoveries; Luva, Haklang and Snefrid South, with recoverable reserves estimated at 51 billion standard cubic meters of gas.
The field is characterized by its remote location far from land and established infrastructure, as well as its significant water depth and challenging weather conditions.
The spar installation itself features conventional topsides with processing facilities. Pure steel risers will transport the gas from the seabed to the platform and onward to shore via the new 480 km Polarled gas pipeline. The hull will be equipped with storage for condensate which will be loaded onto shuttle tankers at the field.
Here is a video of the tow-away: