The giant Tengiz oilfield in Kazakhstan saw its oil production drop by 11% in early March compared to February due to unscheduled maintenance at the massive field that typically pumps more than 600,000 barrels per day (bpd), industry sources told Reuters on Tuesday. U.S. supermajor Chevron holds a 50% interest in Tengizchevroil (TCO), the operator of the Tengiz oilfield, the world’s deepest producing supergiant oil field and the largest single-trap producing reservoir in existence. The Tengizchevroil joint venture…