Crane ship Sea Troll at Statfjord A

Norwegian Petroleum Museum

US crane barge Atlas was originally supposed to lift the 32 big modules onto Statfjord A. When the lifting programme began in June, however, it turned out that this vessel was unsuited to North Sea conditions.

— Crane ship Sea Troll rented in for use at Statfjord A coped better with the North Sea weather than the barges often used at the time. Photo: Odd Noreger/Norwegian Petroleum Museum

It came from the Gulf of Mexico, and could only operate in calmer waters than the North Sea offered. Even at midsummer, when conditions were at their best, not a single module was lifted.[REMOVE]

Fotnote: Lavik, Håkon. Statfjord. Nordsjøens største oljefelt. Stavanger 1997: 30.

Sea Troll, a newly built Norwegian crane ship, was hired to replace Atlas. Its hull design was much better suited for working in North Sea weather.

But contractor Brown & Root was not keen to be forced to take on a new crane vessel, and made minimal use of Sea Troll at first. By the end of August, several key modules – including the flare boom and drilling rig – had still not been lifted aboard, and work had to be postponed until the following spring.

Although Sea Troll coped better with the North Sea weather, it was not like modern crane vessels which can whip the largest and heaviest modules onto a topside more or less regardless of sea conditions. Sea Troll could operate in maximum wave heights of 1.5 metres.

The final modules were positioned in the spring and summer of 1978. Sea Troll moored on the field again on 1 February, now as a combined accommodation, work and crane vessel. It performed 10 lifts before 10 May, three involving temporary units to be removed from Statfjord A and seven with new modules being placed on board. One of the key modules was the actual drilling rig.

Sea Troll was replaced in June by a larger crane ship, the Dutch Narwahl, which performed the four final lifts.[REMOVE]Fotnote: Status no 1.1978. These were also the largest and heaviest. On 13 June, Narwahl placed the 1 850-tonne compressor unit during particularly good weather conditions.

The last module was lifted aboard as early as the following day. This was the 122-metre flare boom, and both lift and installation were extremely complicated. It took 20 hours from starting to lift the boom until it was fully installed on Statfjord A.

To learn more, see: Statfjord A – Hook-up and commissioning .