Exxon Mobil reported a dip in fourth-quarter earnings Friday as a gain from Norway oil and gas assets blunted the impact from weak chemical and refining results. Earnings came in at $5.7 billion, down 5.2 percent from the year-ago period. Revenues fell 6.6 percent to $67.2 billion. Production of oil and natural gas was essentially flat, with the oil giant highlighting higher output from the Permian Basin in the US as a strength. The upstream business was boosted by the $3.7 billion one-time accounting of the sale of Exxon's stakes in 20 producing fields to Norwegian company Var Energi, part of the US giant's plan to downsize secondary investments as it pumps more funds into US shale fields. Exxon cited weak profit margins in its chemical and refining businesses as a drag on results in those segments. Shares declined 0.6 percent to $64.42 in pre-market trading. jmb/bgs