Ekofisk tank receives its first oil

It would serve as a buffer until the pipeline to Teesside in the UK had been completed, and its most important function thereafter would be as a process facility for oil and gas.

Once the tank had been positioned during the summer of 1973, the work of installing its topside systems began. It was ready to receive oil for the first time in December 1974.

Before being towed out from Hinnavågen near Stavanger, the tank had been given an extra “20-metre” concrete deck covering 0.71 hectares to carry the process equipment on board. Once out on the field, work started on installing an upper “30-metre” deck.

During this period, the construction personnel lived in temporary accommodation on the tank. At its peak, this housed 520 people who lived, ate and slept there.

At that time, the tank lay like an island without fixed links to the neighbouring platforms. Building bridges to Ekofisk 2/4 P and on to Ekofisk 2/4 C and FTP was a separate project.

Things went wrong with one of the bridges. The crane could not take its weight, and it landed in the sea. But the whole system of links was in place by 23 June 1974 and work could begin on connecting the pipelines carried on the bridge roofs.

That job was finished during November, and first oil flowed to the tank on 3 December – well timed, because the winter storms had now started and offshore loading had to cease.

The tank was able to demonstrate its capabilities over the next 20 days, and its storage cells held 900 000 barrels by 23 December.

Offshore loading had to cease for 40 per cent of the time between December 1975 and October 1975, when the oil pipeline to Teesside came on line. Thanks to the tank, however, production continued at full pitch for 99 per cent of that period.

This facility then ceased full storage operation after just one year, and subsequently served as a buffer tank if failure of a pump or other technical equipment restricted pipeline capacity.

Separating wellstreams into oil, gas and water was thereafter its most important function, with the crude passing through fiscal metering before being piped to Teesside.

The gas called for more treatment as well as compressors to reach the necessary pressure. Before being piped to Emden in Germany, it had to meet certain quality specifications. A big dehydration plant removed water and a separate stage extracted the natural gas liquids (NGL).

Comparable with a big refinery squeezed into a very small space, the process plant was assembled offshore. It became fully operational with completion of the gas pipeline in the autumn of 1977.

The tank became a hub for all Ekofisk production, receiving output from Eldfisk, Edda, West Ekofisk, Albuskjell, Cod and Tor. Other fields, such as Valhall, Ula and Gyda, were later tied in, as was the Statpipe system. This installation thereby served as a key component in Norwegian offshore production for many years.