FILE - This Oct. 26, 2006, file photo shows an Exxon logo at a gas station in Dallas. Exxon Mobil said Thursday, April 26, 2012, that it earned $9.45 billion, or $2 per share, in the first quarter, down from $10.7 billion, or $2.14, a year earlier. Revenue rose 8.8 percent to $124.1 billion. (AP Photo/LM Otero, File)

In this March 16, 2012 photo, oil rigs belonging to PetroChina are seen near the banks of a snow covered lake in Daqing in northeastern China's Heilongjiang province. A big shift is happening in Big Oil: an American giant now ranks behind a Chinese upstart. Exxon Mobil is pumping less oil than PetroChina, a company formed just 13 years ago by the Chinese government to better compete for the world's oil and natural gas. On March 29, 2012, the shift is expected to become official when the Beijing company announces that it produced more crude last year than its 130-year-old Texas rival. (AP Photo) CHINA OUT

This Feb, 13, 2012 photo shows gas prices at Exxon and BP Mini-mart in Scott Township, Pa. Consumer prices rose a modest 0.2 percent in January, pushed up by higher gas, clothing costs. (AP Photo/Gene J. Puskar)

FILE - In this June 30, 2011 file photo, a motorist pumps gasoline into his vehicle at an Exxon gas station, in Farmers Branch, Texas. For the first time in months, retail gasoline prices have fallen below $3 a gallon in places, including parts of Michigan, Missouri and Texas. And the relief is likely to spread thanks to a sharp decline in crude-oil prices. (AP Photo/Tony Gutierrez, File)

Farmland is saturated with both floodwaters from the swollen Yellowstone River as well as oil leaked from a broken Exxon Mobil pipeline upstream, Sunday, July 10, 2011, near Laurel, Mont. A week after 1,000 barrels of oil leaked into the river, clean-up crews are still working to soak up the oil which has collected in farmland along the river's banks, back channels and islands. (AP Photo/Julie Jacobson)

A sheen from spilled oil in the Yellowstone River is seen from above a back channel, Sunday, July 10, 2011, near Billings, Mont. It may be two or three weeks before Montana officials can safely launch boats on the Yellowstone River to determine the extent of damage to wildlife from the July 1 oil spill caused by an Exxon Mobil Corp. pipeline failure near Laurel, Mont. (AP Photo/Julie Jacobson)

Cleanup workers use oil absorbent materials along side the Yellowstone River in Laurel, Montana, Wednesday July 6, 2011. An Exxon Mobil pipeline near Laurel, Montana ruptured and spilled an estimated 1,000 barrels of crude into the Yellowstone. (AP Photo/Jim Urquhart)

FILE - In this Jan. 27, 2011 file photo, an Exxon sign is displayed atop a mini-market in Carnegie, Pa. Exxon said Thursday, April 28, 2011, it earned nearly $11 billion in the first quarter, a performance that will likely land it in the center of the national debate over high gasoline prices.(AP Photo/Gene J. Puskar, file)

In this Jan. 27, 2011 photo, Exxon and Mobil oil products are displayed on a shelf in an Exxon mini-market in Carnegie, Pa. Exxon said Monday, Jan. 31, net income grew 53 percent in the fourth quarter as oil prices rose and the company increased production.(AP Photo/Gene J. Puskar)

A Mobil logo is seen at a gas station on Wednesday, Oct. 27, 2010, in Los Angeles. Exxon Mobil Corp. said Thursday, Oct. 28, income jumped 55 percent in the third quarter on higher oil prices and increased production.(AP Photo/Damian Dovarganes)

In this Aug. 3, 2010 photo, a boat motors near oil sheen in the Gulf of Mexico, between the Deepwater Horizon Oil Spill site and the Louisiana coast. BP claimed a key victory Wednesday in the effort to plug its blown-out well as a government report said much of the spilled oil is gone _ though what's left is still nearly five times the amount that poured from the Exxon Valdez. (AP Photo/Gerald Herbert)

In this photo taken on Sunday, July 25, 2010, a worker cleans up the oil at the Nantuo Fishing Harbor after the oil spill in Dalian in northeast China's Liaoning province. An American oil spill expert says China's worst-known oil spill is far larger than the government has reported. China's government has said 1,500 tons of oil spilled after an explosion two weeks ago near the northeastern city of Dalian. But Rick Steiner estimates that 60,000 to 90,000 tons spilled into the Yellow Sea. He says the spill is at least as large as the 1989 Exxon Valdez oil disaster in Alaska. (AP Photo)**CHINA OUT**

Prices are displayed at an an Exxon gas station in Heidleberg, Pa., Tuesday, June 8, 2010. Oil prices rose to near $75 a barrel Wednesday, after Fed Chairman Ben Bernanke said European debt problems should not have a major impact on the U.S. economy.(AP Photo/Gene Puskar)

FILE- This April 21, 2010 aerial photo taken in the Gulf of Mexico more than 50 miles southeast of Venice on Louisiana's tip shows the Deepwater Horizon oil rig burning. Teams of lawyers from around the nation are mobilizing for a gargantuan legal battle over the massive Gulf Coast oil spill, filing multiple lawsuits in recent days that together could dwarf the half-billion dollars awarded in the Exxon Valdez disaster two decades ago. (AP Photo/Gerald Herbert, File)

FILE - In this Jan. 30, 2009 file photo, an Exxon tanker truck operated by Corey Moorer, right, of Clinton, Md., makes a refueling stop at an Exxon station in Arlington, Va. Exxon Mobil said Monday, Feb. 1, 2010, its fourth-quarter earnings tumbled 23 percent as higher oil prices squeezed profit margins in its refining business.(AP Photo/J. Scott Applewhite, file)

FILE - In this July 26, 2006 file photo, an Exxon sign glows at an Exxon station in Richmond, Va. Exxon Mobil said Monday, Dec. 14, 2009, it will acquire XTO Energy in an all-stock transaction valued at $31 billion.(AP Photo/Steve Helber, file)

In this Oct. 27, 2009 photo, a sign is seen at a Mobil gas station in East Montpelier, Vt. The world's largest publicly traded oil company said Thursday, Oct. 29, third-quarter profit tumbled with crude prices, but like other big energy companies, production is bouncing back. (AP Photo/Toby Talbot)

FILE - In this May 1, 2008, file photo, a customer pumps gas at an Exxon station in Middleton, Mass. Exxon Mobil said Thursday, July 30, 2009, its second-quarter profit fell a surprising 66 percent from a year ago as the world's biggest publicly traded oil company, like the rest of the industry, saw crude and gas prices fall sharply and refining margins tighten. (AP Photo/Lisa Poole, file)