Oil has climbed about 30 percent in London this year with consensus growing that the Organization of the Petroleum Exporting Countries and its allies’ output-cut deal will probably be extended. Unplanned supply losses from Iran and Venezuela are also increasingly tightening the market. But as clouds linger over the global economy, and a new flood of shale-oil pours in from the U.S., the rally has failed to reach last year’s highs.
