Jan. 13 (Bloomberg) -- BG Group Plc, the U.K.’s third- largest natural-gas producer, plans to invest $4 billion to $5 billion through 2012 to develop pilot projects in Brazil’s “pre- salt” oil fields of Tupi, Iara and Guara.

BG and partners in the field, including Petroleo Brasileiro SA, plan to start output in 2010 and pump as much as 300,000 barrels a day from three wells by 2012, BG Group Chief Executive Officer Frank Chapman said today in an interview in Brasilia.

Tupi, a field with an estimated 5 billion to 8 billion barrels of oil and gas, is the largest discovery in the Americas since 1976. It is part of the pre-salt region, which may contain 80 billion barrels of oil, enough for more than 10 years of U.S. consumption. Iara has 3 billion to 4 billion barrels of recoverable oil, according to Petrobras, as Brazil’s state- controlled oil company is known.

“We’re confident that these developments can be made economic at lower oil prices, but we’ll need to ensure the efficiency of the investment,” Chapman said. “Oil prices we see today are much more realistic.”

Crude oil futures in New York have plunged 58 percent in the past year. The price touched a record high of $147.27 on July 11.

The pre-salt area runs about 800 kilometers (500 miles) along Brazil’s coast, 160 miles offshore from Rio de Janeiro and Sao Paulo states. The oil is under a layer of salt in waters 2 miles deep.

Gustavo Gattass, an analyst at UBS AG in Rio, estimates it will cost $600 billion to extract the oil over the next 20 years.

BG owns 25 percent of Tupi and Iara and 30 percent of Guara. Petrobrasis the operator in the three fields, holding at least 45 percent of each. BG also owns Cia. de Gas de Sao Paulo, Brazil’s largest natural-gas distributor.

To contact the reporter on this story: Iuri Dantas in Brasilia at idantas@bloomberg.net; Andre Soliani in Brasilia at asoliani@bloomberg.net

Last Updated: January 13, 2009 11:50 EST