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Unique dual vessel float-over operation Aasta Hansteen topside

When Boskalis successfully completed a unique, dual vessel float-over operation of the Aasta Hansteen topside owned by Statoil, several engineering records were accomplished. Besides the topside installation, Boskalis was also responsible for the transportation of the Aasta Hansteen SPAR substructure and topside from South Korea to Norway. Project Director Bas Polkamp outlines the challenges of this phase of the project.

Bas, could you outline the challenges of the transportation phase of the project?

“To provide some background first. The Aasta Hansteen SPAR-FPSO is a gas production and storage platform, which will be operated at the Aasta Hansteen field, approximately 300 kilometers off the coast of Norway, above the Arctic Circle in depths of more than 1,300 meters. The SPAR consists of the hull/substructure and a topside.”

“Hyundai Heavy Industries (HHI) contracted Dockwise to carry out the transport of the SPAR hull from the fabrication yard in Ulsan, South Korea, to a fjord near Stavanger in Norway. As such, a ‘relatively straightforward’ part of the operation, even though it is a huge structure. Just the hull alone is an enormous cylindrical buoy with a diameter of 50 meters, length of 198 meters and weight of 46,000 tons. The hull was transported horizontally on our semi-submersible heavy transport vessel Dockwise Vanguard via the Cape of Good Hope in 59 days, arriving in Norway at the end of June.”

“Subsequently, we transported the 24,300-ton topside from Ulsan. This operation was carried out with the White Marlin, the newest and second largest vessel in the Dockwise fleet. With the design and detailed engineering carried out at the company’s offices in Shanghai, Houston and at our headquarters in the Netherlands, a project site team was then based at a Chinese outfitting yard supervising the construction and installation of four big skid tracks on the White Marlin. In the meantime, the topside was placed on skid tracks on the quayside. Once all the preparations were finalized the topside was pulled onto the vessel using dozens of strong wires.”

Watch the video of the float-on operation of the world’s largest spar platform Aasta Hansteen, Dockwise Vanguard, South Korea.