Boskalis connects Aasta Hansteen topsides to spar hull

Boskalis has completed a dual vessel float-over of the topsides for Statoil’s Aasta Hansteen spar platform in the Norwegian Sea.

Statoil is developing the Aasta Hansteen gas/condensate field, 300 kilometres (186 miles) offshore, via the world’s largest production and storage spar platform.

Earlier this year Boskalis’s Dockwise Vanguard transported the hull from the yard in South Korea to a fjord near Stavanger.

The cylindrical buoy, 50 metres (164 feet) in diameter, is 198 metres (649 feet) long and weighs 46,000 tons.

Subsequently, Boskalis transported the 24,300-ton topsides, also built in South Korea, onboard the White Marlin.

Once the vessel arrived in Norway, the topsides was transferred onto two S-class vessels, the smallest in the Dockwise fleet.

After positioning these vessels on either side of the White Marlin, they started un-ballasting while the White Marlin ballasted down and manoeuvred out from underneath. The result was a catamaran-type structure with the topsides linking the two hulls.

Last weekend, the catamaran structure and topside were towed out to the vertical spar hull.

Once the load was in position above the substructure, mating of the hull and topsides was completed.