In the deepest, axial part of the Viking sub-basin 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 60° N lat. 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 underlain by a typical "flat spot" on seismic sections, and the gas column lies on a heavy oil disc. Chromatographic analysis shows that source of both the oil and gas could be the underlying Jurassic section.

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.