Officials have argued that the discovery of so much oil in the Tupi field has eliminated geological risk.

ECONOMIST: Brazil's oil policy

Croesus' oil guru thinks that Brazil's Tupi and Jupiter fields will be minor blips in the grand scheme of rising demand and diminishing supply.

FORBES: The Croesus Chronicles

Yet this Cassandra can even spin Tupi into cataclysm.

FORBES: Crude Cassandra

In 2007, the vast new Tupi field in Brazilian coastal waters was discovered in 200 meters of water below a massive layer of salt in hugely inhospitable geological conditions.

CNN: The price of our oil addiction

Second, the government might be tempted to revisit existing contracts, which would be bad for confidence and disastrous for Petrobras and its partners (Britain's BG Group has a 25% stake in Tupi and Portugal's Galp Energia 10%).

ECONOMIST: Brazil

As the company begins to tap into the giant reserves of the Santos Basin (in December it began production in areas of the Tupi and Iracema fields), it seems like the only way Petrobras can go is up.

FORBES: Petrobras To Focus On Brazilian Production To Outstrip Exxon Atop Oil Markets, CFO Says

Recent discoveries, such as the Tupi Field, which is expected to hold between 50 and 100 billion barrels of oil equivalent, prompted Brazil's government-owned Petrobras to boast that they would double Exxon Mobil in size by 2020.

FORBES: Magazine Article