In 2002, the U.S. Geological Service pegged technically recoverable Marcellus shale reserves at 1.9 trillion cubic feet.

FORBES: Just How Long Will U.S. Gas Supplies Last?

But a report by the British Geological Survey to map out where Britain's gas reserves are has been commissioned by the Department of Energy.

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The world has plenty of potash 610 years worth, which ensures centuries more of fertilizer-making, and 590 years of known iron-ore reserves, according to U.S. Geological Survey estimates.

WSJ: Exhausting the Earth's Resources? Not So Fast

The expert working group will begin with the perspective that geological resources are an important element of development and that biosphere reserves are much more than just protected areas.

UNESCO: Basic Sciences

But a joint survey by the state-run Petrobangla corporation and the United States Geological Survey (USGS) suggests that Bangladesh's gas reserves could reach as much as sixty-one trillion cubic feet (tcf).

BBC: Bangladesh edges toward gas exports

But by accounting for further development, continual technology advances such as horizontal drilling and supportive prices, the U.S. Geological Survey calculates that 86% of total U.S. proven reserves are additions to original numbers.

FORBES: Crude Awakening

" Dorian notes that Chinese estimates of its reserves "have been downsized tremendously over the last 15 years because the original geological estimates were incorrect, " adding: "This is a company in which the valuation is influenced not only economic measures but also political and social factors, so it's very complicated.

CENTERFORSECURITYPOLICY: Center For Security Policy

Last year, the US Geological Survey estimated the Arctic could be home to 30% of the world's undiscovered natural gas reserves and 13% of its undiscovered oil.

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The US Geological Survey estimates that the Arctic has around a quarter of the world's undiscovered and recoverable oil and gas reserves.

ECONOMIST: Arctic politics: Cosy amid the thaw | The