Apart from the sub-salt fields, Petrobras is exploring 270 blocks in the Gulf of Mexico and over 200 more onshore in Brazil.

ECONOMIST: Brazil's Petrobras

Chevron began drilling this ultradeep well over a year ago, with the objective of boring down to big sub-salt prospects 29, 000 feet beneath the surface.

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It is expected to propose vesting all unassigned rights in the sub-salt area (62% of the total) in a new, wholly state-owned, company which would partner Petrobras or any other firm that signs exploration contracts.

ECONOMIST: Brazil's Petrobras

Green aficionados are familiar with the statistic that the sun bathes the Earth in trillions of barrels of energy (in oil equivalent terms), and less familiar with the fact that total known hydrocarbon resources are also countable in the trillions of barrels (from the oil-sands and ultra-deep-water sub-salt fields, to methane hydrates and coal, not to mention shale gas).

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