Mating the topside and hull for Statoil's Åsgard B gas platform began in Åmøy Fjord outside Stavanger in the afternoon of 18 October.
The heaviest topside section, weighing 21,000 tonnes, left the Kværner Rosenberg yard in Stavanger around 15.00 on the Castoro XI barge.
This "topside east" unit was towed by several tugs to the fjord, where the semi-submersible hull has been moored.
During the mating operation, the hull has been ballasted down until only the tops of its support columns are visible above the water.
Around 17.00, the barge carrying the topside was guided between the columns until its load was in the correct position.
Preparations for the actual mating then continued during the evening.
Odd Mosbergvik, operations vice president for the Åsgard development in the Norwegian Sea, monitored the first phase of the operation together with his core team and representatives from the other licensees.
"This is a milestone for the project," he says. "I'm relieved that we've come so far. At the same time, it's a pleasure to be able to watch this encounter between engineering art and good seamanship."
The next step will be to hang a riser gallery from the outside of the topside east section, while the final stage involves attaching the west section with the living quarters and helideck.
Plans call for all work to be finished and the mated platform returned to the Kværner yard by 3 November.