The Globe and Mail reports in its Tuesday edition that global oil markets now face supply constraints that are providing revenue gains for Canadian producers. The Globe's Shawn McCarthy writes that crude prices jumped last week as traders fretted over the continuing emergency shutdown at Alberta's Syncrude Canada and prospects for lower exports from members of the Organization of the Petroleum Exporting Countries Iran, Libya and Venezuela. The higher prices would be a tonic -- if sustained -- for Calgary's oil companies. However, many of the factors propelling prices higher are either short-term or political in nature, and are hard to count on for the long term. Analysts worry about a supply squeeze as the Trump administration pressures global importers to end their purchases of Iranian oil while Venezuela's production slumps with the South American country's deepening crisis. Canadian oil producers are reaping the benefits, and their share prices are climbing. The S&P/TSX Capped Energy Index posted a 15-per-cent gain in the quarter that ended on Friday. Adding to energy companies' wary sense that a corner has been turned was the approval last week of Enbridge's Line 3 pipeline expansion.