Four years of exploration activity offshore Troms has resulted in four gas discoveries, with total resources of 170 x IO9 cu m (6,000 x IO9 cu ft) recoverable gas. Shows of heavy, waxy oil are present in most wells. Recent regional studies on structural evolution and organic geochemistry suggest that, in parts of the area where exploration activities have been concentrated so far, the oil-prone source rock has not been mature enough to expel the generated oil. In other parts, all potential source rocks became overmature 100 million years ago because of extreme subsidence during the Early Cretaceous. The...