International oil firms also worry that their government-sponsored competitors receive unfair advantages. During the bidding war over Unocal, for instance, Chevron complained Cnooc could offer more money because the Chinese government was helping finance the bid by providing low- and no-interest loans.
One result of government ownership of oil supplies, analysts said, is that they often manage oil fields less efficiently than big international firms -- resulting in less oil for everyone. "The national oil companies are not really investing and developing oil fields," said Muhammad-Ali Zainy, senior energy economist at the Centre for Global Energy Studies in London.
There are roughly 60 national oil companies worldwide. Nearly half of them own reserves outside their home country, or hold ambitions to do so, analysts said.
Peter J. Robertson, vice chairman of Chevron, worries about the increasing dominance of national oil firms. Given that they already control more than three-quarters of the world's oil reserves, "if governments can come along and gobble up the rest of it at a percent or 2 percent at a time, pretty soon the commercial business looks pretty thin," Robertson said.
Government-controlled oil companies in China -- including China National Petroleum Corp. and Cnooc -- have been expanding internationally. Malaysia's Petronas now has business interests in 35 countries. Brazil's Petrobras has been active outside its home country and has developed expertise in deep-water production.
International oil companies and national companies, while sometimes rivals, often work together. In many cases, national oil companies lack the money, technology or managerial skill needed to develop big projects and seek to work with the bigger firms.
But some national oil companies have gained enough know-how to begin closing that gap. According to PFC data, more deals are being made between national oil companies, allowing one to operate in another's home country -- leaving the international firms out altogether.
Nowhere is the thirst for oil rising faster than in China and India. Both countries are aggressively seeking oil supplies, making deals in countries such as Sudan and Iran, where international companies have shied away for political reasons.
China consumed 4.8 million barrels of oil a day in 2000. The U.S. Energy Information Administration expects it to use up 7.2 million a day this year -- far less than current U.S. consumption of about 20 million barrels a day but rising more rapidly. In 2010, China is expected to consume 9.2 million barrels a day, according to the EIA.
The Chinese government wants to lock up supplies in part due to its belief that big oil companies and the United States are manipulating the market to choke China's economy, said Wenran Jiang, a political science professor at the University of Alberta.
"They feel it's not fair for China to depend on the commercialized, manipulated, artificially driven up price," said Jiang, who is part of a working group on energy cooperation between the Canadian and Chinese governments.
International oil companies also fear competition from their national rivals. In a speech in April, the chief executive of Shell, Jeroen van der Veer, said that "virtually every week" the national companies cut deals to acquire production assets.
Even so, officials from Shell and other large international oil companies, sometimes known as IOCs, said they still have advantages in operating big oil fields.
"Governments will need IOCs as much as we need them," van der Veer said.
