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. In anticipation of such a deal, oil prices had begun to creep inexorably upward, from $30 per barrel in mid-January to $43 on the eve of the gathering. But far from restoring the old oil order, the meeting ended in discord, driving prices down again and revealing deep cracks in the ranks of global energy producers.