BRAZIL'S oil discoveries, including the Western Hemisphere's largest in three decades, may cost US$100 billion more to develop than the industry's most costly field.

The Tupi deposit and nearby offshore prospects probably will cost US$240 billion to exploit, said Peter Wells, director of British research firm Neftex Petroleum Consultants Ltd and a former Royal Dutch Shell Plc exploration manager.

The total exceeds the US$136-billion estimate for Kazakhstan's Kashagan field, led by Eni SpA, and would be enough to fund the United States space program for 14 years, Bloomberg News reported.

Brazil's state-controlled Petroleo Brasileiro SA will need to enlist international producers such as Exxon Mobil Corp to raise financing for the platforms and pipelines required to reach crude trapped beneath 10 kilometers of water and rock, Wells said in a telephone interview.

The prospects may hold US$6 trillion of petroleum and make Brazil one of the world's 10 largest oil producers.

"This oil is going to be difficult to get out of the ground and it will cost a lot," said Wells, who also was a chief negotiator for BP Plc in Azerbaijan. Petroleo Brasileiro "will need the capital expertise only found with the world's largest, most experienced oil companies."

Tupi, the biggest discovery in the Americas since 1976, will start pumping in April 2009, Chief Executive Officer Jose Sergio Gabrielli said in an interview last month. Gabrielli declined to estimate development costs for Tupi and adjacent fields, and a spokesman said the company wouldn't comment on Wells's projection.

The US$240 billion estimate assumes there are four to seven similar prospects nearby and includes costs to drill wells, lay pipelines and build production platforms over a period of about 20 years, Wells said.

Tupi alone could cost US$100 billion, said Wells, part of a Neftex team doing a six-year study to map all of the world's petroleum basins.