Early yesterday morning (11 December), Boskalis completed an impressive dual vessel float-over operation of the Aasta Hansteen topside.
Over the last number of years, Boskalis has played a critical role in the transportation of the Aasta Hansteen SPAR from South Korea to Norway and the topside installation through its subsidiary Dockwise. With this achievement, Boskalis has broken many engineering records with the transport of the largest and heaviest SPAR ever, the largest catamaran topside float-over and more than 100,000 worked hours with zero lost time injuries.
Aasta Hansteen FPSO SPAR
The Aasta Hansteen FPSO SPAR is a gas production and storage platform that will be operated by Statoil on the Aasta Hansteen field approximately 300 km off the coast of Norway. The SPAR consists of a lower part, referred to as the hull or substructure, and the topsides on top of the SPAR hull.
The SPAR hull was transported horizontally by Boskalis from the yard in South Korea to a fjord near Stavanger in Norway (see picture below). This enormous cylindrical buoy with a diameter of 50 m, 198 m length and weight of 46,000 t was transported by the Dockwise Vanguard earlier this year.
Transport of SPAR hull on board of the Dockwise Vanguard (by Flying Focus).
Topside Transport
Subsequently, Boskalis transported the 24,300 tons topside which was also built in Korea (see picture below). This operation was carried out with the White Marlin, the newest and second largest vessel in the Dockwise fleet.
Transport of the topside on board of the White Marlin (by Flying Focus).
Installation of the Topside
The third and final phase was the installation of the topside on top of the SPAR hull. Once the White Marlin arrived in Norway, the topside was transferred onto two S-class vessels, the smallest in the Dockwise fleet (see picture below).
Topside transfer onto the S-class vessels creating a catamaran structure (by Espen Rønnevik/Boskalis).
Catamaran Structure
After accurately positioning these two vessels on either side of the White Marlin, they started un-ballasting whilst the White Marlin ballasted down and manoeuvred out from underneath. The result was a sort of catamaran structure with the topside linking the two hulls.
Over the weekend, the catamaran structure with the topside was towed out to the vertical SPAR hull (see picture at the top). Once everything was in position above the substructure, the mating operation between the hull and topside was successfully completed (see picture below).
The end result – the topside neatly installed on the SPAR hull (by Espen Rønnevik/Boskalis).
Watch a time-lapse of the float-over installation as well as an animated version of the operation below.
Picture (top): Topside float over installation with the tip of the SPAR hull above the waterline in between the S-class vessels (by Espen Rønnevik/Boskalis).
