Marathon Oil Corp . is selling its Norwegian business for more than $2 billion in cash to Det Norske Oljeselskap AS A as part of a drive by the Houston-based energy company to sell its North Sea oil-and-gas operations to focus on the U.S. “The sale of our Norway assets advances one of our key 2014 priorities and further demonstrates our commitment to rigorous portfolio management to simplify and concentrate our business,” Marathon Chief Executive Lee M. Tillman said Monday. In December the company said it would increase in capital spending to boost output while also lifting shareholder returns with a $2.5 billion buyback program. Marathon said the Norwegian deal was worth $2.7 billion but that after adjustments for debt, net working capital and interest the net proceeds would be $2.1 billion. Since 2011 Marathon Oil has sold $6.2 billion worth of assets in a bid to improve growth […]