July 3 (Bloomberg) -- Petroleo Brasileiro SA's Tupi field is commercially viable at an oil price as low as $40 to $50 a barrel, according to the Brazilian state-controlled company's chief executive officer.

The field is viable ``in the range of one-third of the current price,'' Petrobras CEO Jose Sergio Gabrielli told reporters today at the World Petroleum Congress in Madrid. ``The field is viable at a very reasonable price.''

Oil was trading at $144.96 at 10:23 a.m. today in London.

Discoveries near Rio de Janeiro and Sao Paulo including Tupi will at least triple Brazil's oil reserves, Brazilian President Luiz Inacio Lula da Silva said in a June interview.

Rio de Janeiro-based Petrobras, holder of the Western Hemisphere's largest oil discovery since 1976, has about 13 billion barrels of proved reserves.

Tupi has as much as 8 billion barrels of recoverable oil equivalent, Petrobras said in November. The surrounding pre-salt region may contain as much as 50 billion barrels of oil, according to Peter Wells, director of U.K. research firm Neftex Petroleum Consultants Ltd.

Tupi, located in the Santos Basin southeast of Sao Paulo, may hold enough oil to supply every refinery on the U.S. East Coast for 15 years. The Santos Basin has the potential of ``very high production'' of hydrocarbons, Gabrielli said in a separate presentation earlier today.

To contact the reporters on this story: Fred Pals in Amsterdam at fpals@bloomberg.net

Last Updated: July 3, 2008 05:59 EDT