Bruce March, chief executive of Imperial Oil Limited of Canada, speaks during CERAWeek, a high profile world energy conference, in Houston March 8, 2011. Top executives from some of the world's biggest energy companies on Tuesday said global oil supply is plentiful in spite of Libyan supply disruptions, and urged U.S. policymakers not to tap strategic oil stockpiles. REUTERS/Richard Carson (UNITED STATES - Tags: BUSINESS ENERGY)