NEW YORK (Bloomberg) Exxon Mobil Corp. and Europe's Royal Dutch Shell Plc, Eni SpA and Repsol YPF SA posted declines in second-quarter output, the latest failures by major oil producers to boost crude and natural-gas supplies.

All but Shell, which was helped by record refining profit, also reported drops in net income in earnings statements issued yesterday. The profit decline at Irving, Texas-based Exxon Mobil, the world's biggest oil company, was the first in more than three years and came as a surprise to analysts.

Production is falling, contributing to near-record energy prices, as oil-rich nations limit access to reserves and, in the cases of Venezuela and Russia, force companies to cede control of some projects. Companies such as BP Plc and ConocoPhillips, which also reported drops in production this week, are expanding their search for crude to deeper oceans and remote corners of the globe as output wanes from fields tapped decades ago.

"There's still not enough prospects to drill, even at these higher-threshold prices, and make those projects economical, so you're seeing all the majors on a global basis having declining production," said Ben Halliburton, chief investment officer at Tradition Capital Management in Summit, New Jersey. Tradition manages $525 million, including shares of ConocoPhillips and Marathon Oil Corp.

Second-quarter net income at Exxon Mobil dropped to $10.3 billion from $10.4 billion, and per-share profit of $1.83 was 13 cents below the average of 17 analyst estimates compiled by Bloomberg. Oil and gas output fell 1 percent to the equivalent of 4.12 million barrels of crude a day.

Shell, based in The Hague, said its profit rose 18 percent to $8.67 billion, or $1.38 a share, even as production fell 2.3 percent. Profit excluding one-time items and gains from holding inventories beat analyst estimates.

Eni, Italy's biggest oil company, had a 1.5 percent decline in profit, to 2.27 euros ($3.11 billion), and a 0.7 percent drop in production. Net income at Repsol, Spain's largest oil producer, fell 11 percent to 818 million euros. Output tumbled 6.4 percent.

London-based BP, second only to Shell among Europe's oil companies, on July 24 said its profit rose 1.5 percent, to $7.38 billion, as a jump in refining earnings made up for a 5.3 percent decline in oil and gas output.

ConocoPhillips, the third-largest U.S. oil company, yesterday reported a 94 percent drop in net income and a decline of more than 9 percent in production. The Houston-based company said costs to write off assets seized by Venezuela's government reduced net income by $4.51 billion.

"The obvious issue is access, Venezuela being the poster child, cutting ownership and volumes," said Doug Hohertz, an analyst at the Mitchell Group in Houston, which owns Exxon Mobil and Chevron shares.

Chevron Corp., the second-largest U.S. oil company, was only able to end a three-year slide in production after it acquired Unocal Corp. in 2005. The San Ramon, California-based company is scheduled to report its second-quarter results tomorrow.

Major oil companies are seeing production undercut by high prices, said John Parry, an analyst at John S. Herold Inc. in Norwalk, Connecticut. Output from overseas fields is often tied to production-sharing contracts that specify how much money they can earn over time. As prices rise, he said, it takes less production to reach that financial limit.

Crude-oil futures in New York yesterday traded as high as $77.24 a barrel, the highest in 11 months and close to the record of $78.40 set last year. Before 2004, the futures had never traded as high as $50 a barrel.

"The higher the oil prices, the less production you're entitled to" under overseas contracts, Parry said.

Shares of Exxon Mobil, the world's largest company by market value, fell $4.25, or 4.6 percent, to $88.54 at 11:16 a.m. in New York Stock Exchange composite trading. Shell fell 24 pence to 1,945 pence in London. Eni dropped 22 cents to 26.33 euros in Milan, and Repsol declined 1.15 euros to 27.01.

Producers also must contend with disruptions in output, such as those caused by militant attacks and kidnappings in the Niger Delta. Shell said it has no firm date for when it can resume full output in Nigeria, where the company's share of idled output was 195,000 barrels a day at the end of the second quarter. Eni said crude shipments from its Brass export terminal in Nigeria are still reduced.

In more stable parts of the world, producers are fighting to make up for depletion from fields discovered when new deposits were easier to tap, analysts said. "Production is falling for everyone because of physical decline in aging oil fields," said Fadel Gheit, an analyst at Oppenheimer & Co. in New York.

Exxon Mobil has spent about $7.5 billion per quarter on stock buybacks. U.S. Energy Secretary Samuel Bodman has called on producers to increase spending on new sources of energy.

"A lot of critics are saying the industry is spending far too much money repurchasing stock, but it's an issue of access," said Parry, the John S. Herold analyst. "The industry would love to drill in the Rocky Mountains, to drill off the coast of Florida, to drill in Alaska, but the legislatures won't let you drill.

"You're really running up a hill constantly, and it's not necessarily how much money you can throw at it. You just run out of geology."