STAVANGER -- The deck and four-legged hull of the Gjøa semi-submersible have been mated together in Norway, according to the field’s development operator Statoil. The operation was undertaken by Aker Stord in a fjord just outside the town of Stord.
Among the exacting requirements, the guide pins had to be inserted into their slots with a tolerance of only 25 mm (0.98-in.) in all directions. The guide pins were engineered to take the load in case the platform lists, allowing it to be towed to shore prior to welding of the deck to the hull. This in turn meant that mechanical testing and commissioning of the platform could get under way more quickly.
The hull’s ballast tanks were filled with water to submerge the structure to a depth of 35 m (115 ft) in the fjord. Only 5 m (16.4 ft) of the hull was above the waterline when the barge transporting the deck was towed from the quay. The barge was then guided into place between the hull columns.
As the ballast water was slowly discharged, the hull rose towards the deck, allowing mating to be effected. At this point the hull draught was 13 m (42.6 ft). The mated platform was subsequently towed to the quay to allow mechanical completion to proceed.
According to Statoil, over 2,000 personnel have worked continuous shifts on this project over the past few months to ensure the platform would be ready for its tow-out to the field location in the Norwegian North Sea in April. Once production has started next October, GDF Suez E&P Norge will take over as operator.