Exxon Mobil, ChevronTexaco and Royal Dutch/Shell curbed their first-quarter oil production by a combined 474,000 barrels a day, according to the companies. The downturn offset a 500,000-barrel-per day production increase by Organization of Petroleum Exporting Countries, or OPEC.

That trend "could be problematic" because the global oil supply cushion is already thin, said Refco Group energy analyst Marshall Steeves. "If we don't see non-OPEC production growth ... that's going to put more of a burden on Saudi Arabia and other OPEC members."