The Gullfaks A and B platforms operated by Statoil in the North Sea are shutting down for their last turnarounds on the old model.
Maintenance work requiring a complete halt will be carried out every other year in future, rather than annually, to reduce the loss of revenue involved.
Oil production will be suspended today, 31 July, on the B platform, with Gullfaks A following on 1 August. They are both due to be back on stream by 19 August.
Work on the A platform includes a replacement of the flare system and boom, reports Norvald Henjum, head of the Gullfaks field services department.
In addition come a number of major and minor tasks in all disciplines which depend on production being stopped.
A workforce of almost 500 people is due to devote just under 40,000 hours to Gullfaks A and roughly 12,000 to the B platform.