In the deepest, axial part of the Viking subbasin of the North Sea, the Frigg field, one of the world's largest offshore gas fields, straddles the border of the British and Norwegian continental shelf at lat. 60°N. The discovery well was drilled in 1971 on Norwegian block 25/1 in 100 m of water. Gas was discovered at a depth of 1,850 m in a lobate submarine fan representing the ultimate phase of a thick Paleocene deposit.

Sealed by middle Eocene open marine shales, the structure is mainly submarine-fan depositional topography enhanced by draping and differential compaction of sands. The area of structural closure is underlined by a typical "flat spot" on seismic sections and the gas column lies on a heavy oil disk. Chromatographic analysis shows that both oil and gas could be coming from underlying Jurassic source rocks.

Recoverable gas reserves are estimated to be about 200 billion cu m (7 Tcf). Production began September 15, 1977; the gas is brought ashore at St. Fergus in Scotland by a 360-km pipeline.