But most analysts believe the country's recoverable reserves are well over 100 billion barrels.
They doubled the field's output and increased proved recoverable reserves to 20 million barrels.
The Energy Information Administration (EIA) puts it at around 37tcm of recoverable reserves, two-thirds of which is shale gas and the rest tight gas and coal-bed methane.
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Back on land, mining-company engineers say new techniques, such as dissolving minerals and sucking them up through a pipe or extracting ore with high-powered water jets, could increase recoverable reserves.
As part of its proven crude reserves, Ecuador has an estimated 900 million barrels (and 1.3 billion barrels of potential recoverable reserves) in the Ishpingo-Tapococha-Tiputini (ITT) block in the Amazon rainforest.
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The U.S. Energy Information Administration estimates that China's shale formations hold 1, 275 trillion cubic feet of gas that can be extracted using current drilling technology, or more than the recoverable reserves in the U.S. and Canada combined.
They are estimated to contain recoverable oil reserves of more than 45 million barrels.
Recoverable gas reserves have been estimated anywhere between 35-65 trillion cubic feet.
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Based on these estimates, the EIA concludes that the U.S. will not exhaust its recoverable coal reserves at current mining levels for 222 years.
The United States boasts an estimated 2.2 trillion cubic feet of technically recoverable natural gas reserves.
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In 2002, the U.S. Geological Service pegged technically recoverable Marcellus shale reserves at 1.9 trillion cubic feet.
The US Geological Survey estimates that the Arctic has around a quarter of the world's undiscovered and recoverable oil and gas reserves.
Published reserves are those amounts that everyone knows are there, are recoverable at current prices.
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