The move represents a setback for oil companies active in Canada’s arctic waters and follows a similar decision by Chevron Corp. CVX 0.26 % in December to halt its own exploratory drilling program in the Beaufort Sea . Those projects have been stymied by regulatory hurdles and some of the world’s highest extraction costs. Imperial Oil Ltd. IMO 0.60 % , Exxon Mobil’s Canadian affiliate, informed federal regulators in Canada of its decision to suspend its Beaufort Sea exploratory program on Friday and said it would seek to have its current lease extended retroactively to 16 years. “If approved, the extension would provide sufficient time to undertake the necessary technical studies and develop the technology and processes to support responsible development in the Beaufort Sea,” Imperial Oil said in a letter to Canada’s National Energy Board. The Arctic holds billions of barrels of untapped oil reserves, but offshore-drilling costs […]