Named Aker BP, the new entity will hold 97 licenses on the Norwegian continental shelf, including 46 as the operator. It will produce around 122,000 barrels of oil equivalent per day, based on 2015 figures, with reserves estimated at 723 million barrels.
It will be 40-percent owned by Norwegian group Aker, the holding group that owns Det Norske, and 30-percent owned by BP. The remaining 30 percent will be held by Det Norske's other shareholders.
"With this transaction, we provide Det Norske with operational strength, a robust capital structure and two solid industrial owners, thereby creating a platform for further growth on the Norwegian continental shelf and near-term capacity to pay out quarterly dividend," Kjell Inge Rokke, Aker's main owner, said in a statement.
In practice, Det Norske will issue 135.1 million new shares at 80 kroner apiece which will go to BP, which will in exchange turn over its Norwegian assets. Aker will then acquire 33.8 million of these shares.
BP will also receive a cash payment of $140 million.
Because of the weak oil price, oil companies have been trying to reduce their expenses and financial commitments while optimising their portfolios.
"The direct impact on BP will be less costs in the immediate term, less capital, (and) reduced headcount (BP has around 850 employees in Norway)," Bloomberg News quoted BP's upstream director Bernard Looney as saying.
In 2014, Det Norske acquired the Norwegian assets of US company Marathon Petroleum for $2.1 billion.