Sunday, April 17th was the designated moment. The world’s leading oil producers were expected to bring fresh discipline to the chaotic petroleum market and spark a return to high prices. Meeting in Doha, the glittering capital of petroleum-rich Qatar, the oil ministers of the Organization of the Petroleum Exporting Countries (OPEC), along with such key non-OPEC producers as Russia and Mexico, were scheduled to ratify a draft agreement obliging them to freeze their oil output at current levels.