Such purchases have prompted suggestions that Beijing is using its state companies to lock up foreign supplies. But industry analysts say the oil market is too complex for most deals to work that way.
"This is definitely not about buying up oil resources in order to ship the oil into China," Norrish said.
"Basically, China's interest is in ensuring growth in energy supplies," he said.
By buying stakes in foreign projects, "it can assist in ensuring that investments take place and projects go ahead," he said.
And deals currently being signed by oil-producing countries only give foreign investors a share in output for a limited time, rather than control of the oil field, said Leo Drollas, chief economist for the Center for Global Energy Studies in London.
"If they think that by investing in Sudan and Venezuela and elsewhere they've secured oil somehow, I'm not so sure of that, from a strategic standpoint," he said.
Drollas said that in some cases, it might be cheaper and safer for China to sign long-term contracts to buy oil on the open market.
"Given the volatility of some regions, who is to guarantee that your assets might not be worthless one day?" he said.
China suffered just such a setback when a US$1.2 billion deal signed by a state firm to develop an oil field in Saddam Hussein's Iraq became worthless after his government was toppled.
Beijing has tried to curb oil imports by raising output from its own wells.
The government reported modest success last month, announcing that imports last year fell by 5 percent to 953.2 million barrels, while output from domestic wells rose 3.7 percent to 1.27 billion barrels.
China's booming oil needs have pushed up average long-term prices on world markets, according to financial analysts. But they say other factors are to blame for the recent price spike, noting that China's consumption stayed nearly flat last year.
"You can't blame China for US$70-a-barrel oil," Norrish said.
Beijing launched a Cabinet-level commission last year headed by Premier Wen Jiabao (溫家寶) to coordinate energy policy.
It has announced plans to start building a petroleum reserve to cushion against interruptions in foreign supplies. Similar to one operated by the US, it is to stockpile 100 million barrels of fuel -- the equivalent of almost a month's consumption -- in four tank farms scattered throughout the country.
The government also is pushing conservation measures and more use of nuclear power, wind turbines, hydroelectric dams and other alternative sources. Plans call for building 30 nuclear plants by 2020.
But its goals are modest, calling for nuclear power to supply 4 percent of the country's needs by 2010, with another 5 percent from wind and solar generators.
And with economic growth forecast above 9 percent in coming years, China's total oil and gas imports are expected to rise sharply.
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