In case of any doubt about Norway’s commitment to maintain – and expand – its production of gas and oil offshore, the energy minister, Terje Aasland, has a pithy response: “We will develop, not dismantle, activity on our continental shelf.”

This week, to the alarm of environmental campaigners, he announced that three gasfields off the country’s southern coast would reopen by the end of 2028 – nearly three decades after they closed – to meet a shortfall caused by the impact of the war in Ukraine and disruption to supplies from the Middle East.

The decision will help keep gas and oil production at about the 2025 level – which has been stable for almost 20 years – and stay broadly the same for the rest of this decade. Norway has 97 offshore oilfields, three of which came on stream last year, and its Norwegian Offshore Directorate expects “100 and beyond” within the next two years, still producing at least the present level of 2m barrels of oil daily.

The Barents Sea, in the high north, is the new gas and oil frontier – with the prospect of mining for seabed minerals between northern Norway and Greenland, a more distant prospect after initial surveys by the Norwegian Offshore Directorate – an agency of Aasland’s department – showed potential.

“Norwegian offshore production plays an important role in ensuring energy security in Europe,” Aasland tells the Guardian. “The world, and Europe, will have a need for oil and gas for decades to come and it is crucial that Norway continues to develop its continental shelf to remain a reliable and long-term supplier … and (with) a high level of exploration activity.”