Energy firm Det norske has agreed to buy Marathon Oil Corp's Norwegian business for $2.1 billion in cash and has secured the financing needed to pay for its share of the $20 billion Johan Sverdrup field in the North Sea, it said.Det norske, controlled by billionaire Kjell Inge Roekke, said the deal would increase its output by around 80,000 barrels a day (bpd), more than 20 times its current production, giving it stakes in 13 more licences with 10 operatorships.The deal transforms Det norske from an explorer with a heavy capital budget to a major producer with significant cashflow and also solves its financing problems, which have weighed on the shares as investors worried about how it would pay for developments like Sverdrup, the biggest North Sea find in decades."Adjusted for (contingent recourses), you come down to a price per barrel of around $17," said Oeyvind Hagen, an analyst at brokerage ABG Sundal Collier. "On a comparable basis we had assumed it to be around $15.8 per barrel. So this was on the higher end. They are not buying cheap barrels here."For Marathon, the deal is a mixed success as it received no acceptable offers for its UK business, which has been for sale since December, and the firm said it would retain those assets.To pay for the deal, Det norske has secured a loan and was also in talks with four banks over a seven-year, $2.75 billion loan. It would also issue $500 million worth of shares in a fully underwritten rights issue, with Aker ASA, its biggest shareholder, agreeing to subscribe for 49.99 per cent of the new shares."With this equity issue, the company has secured the financing of its current work programme until first production from the Johan Sverdrup field," it added.Det norske was advised by JP Morgan while Scotia Waterous advised Marathon.