Ekofisk tank installed

This operation was prepared down to the smallest detail. The most critical part of the route was the passage from Hillevåg on the Gands Fjord to the Høg Fjord further north. Since the concrete structure drew 66 metres, the water depth was carefully measured and the correct channel buoyed.

The weather was fine and completely calm when the tow began in the early morning of 21 June. Many people had gathered along the shore to watch the event. Six tugs with a combined 45 000hp began to move the 215 000-tonne structure from Stavanger to Ekofisk.

Arriving on the field on 1 July, the tank was slowly ballasted down until it stood on the seabed. The Norwegian Geotechnical Institute had already investigated conditions on the site, but Det Norske Veritas – responsible for approving the operation – feared that the topography was too uneven for the tank to stand in a stable position.

At the last moment, its position was slightly adjusted. This meant that the Ekofisk Complex acquired a characteristic kink, rather than running in a straight line from south to north. A steel skirt under the tank also ensured that currents would not undermine it.

The choice of concrete as the construction material for the Ekofisk tank kicked off a completely new era in the history of Norwegian offshore history.

In the very same year this structure was towed out, work began on building the first Condeep gravity base structure (GBS) in Stavanger.

Oil platforms positioned on slender concrete shafts became a normal solution for Norwegian offshore production until the mid-1990s, when floating units and/or subsea technology became established as good replacements.