More than 200 wells now have been drilled in the North Sea basin and major gas production is established in the Permo-Triassic section. More recently, wet gas was discovered in early Tertiary strata in Norwegian waters (Cod field).

The geology of the North Sea basin is illustrated for the first time with data from exploration wells 42/23-1, 44/21-1, 48/6-1, 49/17-1, 49/22-1, and 53/10-1 together with cross sections of the four major gas fields--West Sole, Leman, Indefatigable, and Hewett. The largest field is Leman 18 × 5 mi (29 × 8 km) which produces from the Lower Permian Rotliegendes, as do West Sole and Indefatigable. Production at Hewett comes largely from two zones in the Lower Triassic Bunter. Producing depths range from 3,000 ft (900 m) at Hewett to 9,000 ft (2,750 m) at West Sole. Published reserves show more than 1 trillion ft³ to be present at West Sole, with larger reserves present in the other fields, up to 12 trillion ft³ at Leman.

Other fields have been found offshore and onshore in the North Sea basin. The largest onshore discovery at Groningen (Netherlands) has reserves of 58 trillion ft³ in the Rotliegendes sandstone. The Cod basal Tertiary discovery only enhances the future of a fascinating new hydrocarbon province where the opportunities for geologic exploration extend far into the future.