Neptune 7 anchored in block 25/1 on 30 March 1971 and spudded the first well on this acreage four days later. Since it was important to secure an overview of geology in the area, the well was drilled to a total measured depth of no less than 4 570 metres.
A petroleum reservoir was discovered as early as the end of April, in a sandstone layer. This structure initially appeared to contain only water, but analyses and testing determined that the reservoir contained gas.
The gas-bearing sandstone was discovered on 28 April at a depth of 1 812 metres below the drill floor. After passing through a 135-metre-thick gas column, the drill bit penetrated an oil-bearing sandstone layer at a depth of 1 947 metres. This layer was seven-nine metres thick. Well 25/1-1 terminated on 20 July. Production testing yielded a flow of 2.38 million standard cubic metres of gas per day through a 5/8-inch choke. That same spring, the Petronord group named the field Frigg after the most prominent goddess in Norse mythology.
Four appraisal wells were drilled during the summer and autumn of 1971 to provide further information about the discovery.National supervision and controlElf moves to Stavanger