U.S. energy investor Kimmeridge has offered to buy natural gas producer Ascent Resources for $6 billion amid a heated battle over plans of the gas driller’s private equity backer to transfer its stake from one of its funds to another, Kimmeridge’s managing partner Ben Dell told the Financial Times. The Energy & Minerals Group, a private equity firm focused on natural resources, plans to transfer its more than 30% stake in Ascent Resources into a newly formed continuation vehicle, which is estimated to value the gas producer…