Libra, which has recoverable volumes estimated by oil regulator ANP at between 8 billion and 12 billion barrels, is located in the high-yield region off the coast of Rio de Janeiro.

Production began on Sunday and the floating production, storage and offloading (FPSO) vessel Pioneer of Libra has daily capacity to process up to 50,000 barrels of oil and 4 million cubic metres of gas, Petrobras said in a securities exchange filing.

French oil and gas major Total, said in a separate statement that the production start-up will generate revenue while collecting data for subsequent development phases of the field.

"Libra is a major asset in Total's portfolio and fits into our strategy of investing in highly competitive projects with low break-even points," Arnaud Breuillac, Total's exploration and production president, said in a statement.

Total estimates the technical cost of production for the field at about $20 (£14.98) a barrel.

A final investment decision on another FPSO with a capacity of 150,000 barrels per day would be made soon, Total said, adding that a third FPSO with the same capacity would follow soon after.

"In the years ahead other production units of similar capacity will be invested in so that the field can be developed to its full potential," Total said in the statement.

Brazil's Petrobras has a 40 percent stake in the field. Total and Shell hold 20 percent each, while China's CNOOC and CNPC hold 10 percent apiece.

(Reporting by Bate Felix and Jake Spring; Editing by Brian Love and David Goodman)

Stocks treated in this article : Total, Petroleo Brasileiro SA Petrobras