Chevron is refocusing investment on tight assets in the US. : Chevron Corp. has decided to exit shale rock production in Canada as it refocuses investment on tight assets in the United States. The US energy major is divesting its 70 percent stake in the Duvernay play in the oil province of Alberta. “Chevron will be soliciting and reviewing expressions of interest, but there are no assurances of any sale”, San Ramon, California-based Chevron said in a recent statement.