CAIRN Energy is reported to be a frontrunner to buy a portfolio of North Sea assets that could be worth as much as $2 billion (£1.6bn). The Reuters news agency said Edinburgh-based Cairn is in talks with Denmark’s Dong Energy about acquiring its interests in a range of North Sea fields, which have attracted attention from chemicals giant Ineos and the EIF Global Energy Partners private equity firm. Cairn Energy, led by chief executive Simon Thomson, declined to comment on the report. Mr Thomson has said that Cairn could increase its exposure to the North Sea, where the company has stakes in giant fields that Enquest and Premier Oil expect to bring onstream in coming months. Mr Thomson has said Cairn expects that these fields will operate very profitably, even at relatively low crude price levels. Dong plans to focus on renewable energy.