Observed Behavior of the Ekofisk Oil Storage-Tank Foundation (original) (raw)

1976, Journal of Petroleum Technology

The Ekofisk oil field was the first North Sea oil discovery to be produced commercially. The discovery, made by the Phillips Norway Group in 1969, pro~ed to be a major oil reservoir. This success initiated efforts by others in the North Sea, and the search has s~ccessfully resulted in several major discoveries. In the hostile North Sea environment, the exploration and production of oil have offered great engineering chtdlenges. One challenge has been the design and construction of the Ekofisk storage tank, 93 m (305 ft) in diameter and 90 m (295 ft) high, which rests on the sea floor in 70 m (230 ft) of water in mid-North Sea, The Ekofisk tank is the first of a number of concrete gravity structures to be placed in the North Sea. Since its placement, 12 other such structures have been ordered. These platforms will be used for drilling, production, and oil storage. Placed in water depths up to 150 m (492 ft), some of them are likely to experience sea conditions worse than those experienced by the Ekofisk tartk. Artificial Island When production began at the Ekofisk field, oil was loaded onto tankers from buoys. With rough sea states, such loading is not possible; therefore, the Phillips Norway Group decided to construct a 160,000-cu m (5.7-MMcf) storage tank to maintain production in bad weather. The tank probably will not be required for oil storage after pipelines from the Ekofisk field are completed to Teeside in the United Kingdom and to Emden, West Germany, in i 975. However, the tank carries two decks with a total area of 11,000 sq m (1 18,000 sq ft), thus making an artificial island in the midd!e of the North Sea with valuable space for processing and pumping equipment,