Technical Drawings and Documentation of the Valhall Platforms

Seabed subsidence on Ekofisk was first observed in the autumn of 1984, when its installations were clearly lower in the water. The same phenomenon was also found on Valhall, and action had to be taken to counteract its effects. The problem was most obvious with the Ekofisk tank. It was easy to see that more of the rows of holes in its concrete breakwater had become submerged than when it was first installed.

Installations on the outer edges of the field were included in the plans for Valhall from as early as the 1960. Although the initial proposals were dropped, two flank platforms arrived in 2003-04. White Paper no 92 (1976-1977) on the Valhall development included plans for a third development phase from 1982, with a platform on the south-western part of the field. A fourth stage scheduled for 1983 envisaged another installation to the south-east. But these plans were dropped in favour of a focus on improving recovery from the field centre.