During the past few days, the deck and hull of the Gjoa platform have been mated together in the fjord outside of the Norwegian town of Stord. Located on Blocks 35/9 and 36/7 in the Norwegian North Sea, 45 kilometers offshore Norway in water depths of 360 meters, Gjoa is the largest field development project on the Norwegian Continental Shelf today. The field is estimated to contain 82 million barrels of oil and condensate and 1.4 Tcf (40 Bcm) of gas.
There were exacting requirements for precision and weather conditions during the operation, which was a success. Four guide pins had to meet their respective slots with a tolerance of just 25 millimeters (1 inch) in all directions. The operation was carried out by Aker Stord.
The four-legged hull rose from the sea offshore Stord and 'spiked' the deck of the new North Sea giant, Gjoa. The guide pins are designed to take the load should the platform list, so that it can be towed to shore before the deck is welded to the hull, allowing mechanical testing and commissioning of the platform to start sooner.
Carried by Special Barge
During the night, the ballast tanks in the hull were filled with water in order to submerge the structure to a depth of 35 meters. Only five meters of the hull protruded from the water when the barge carrying the platform deck was towed from the quay. The barge carrying the platform deck was manoeuvred into place between the columns of the hull.
Lifting the Deck
Slowly but surely, the ballast water was discharged; the hull rose towards the deck and they were mated into one. When the operation was completed, the draught of the hull was 13 meters. The mated platform was then towed to the quay, so that the work of mechanical completion could continue.
Planning Saved Time
"I am impressed by this operation. It was well-planned, safe and efficient and carried out with the utmost precision," said Kjetel Rokseth Digre, project manager for Gjoa. The mating was carried out by Aker Stord, who are constructing the platform for Statoil.
Building for a New Operator
"It was extremely important for us to get this done now. We now have a complete platform structure to work on, and we are doing everything in our power to get Gjoa ready by the agreed date," said Digre.
Statoil is operator during the development phase of the Gjoa field. The plan is for the platform and the field to be handed over in October 2010, to GDF Suez E&P Norge AS, who will be operator during the production phase. Gjoa will be GDF Suez's first operatorship for a field in operation.
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