(Adds details on oil exports, destinations, factors behind expected growth)
RIO DE JANEIRO, May 13 (Reuters) - Brazil's state-run oil company Petrobras on Wednesday estimated nearly 50 percent growth in oil exports in 2015, thanks to new offshore output and as its refineries lack capacity to process more crude.
Petroleo Brasileiro SA, as the company is formally known, expects to export 350,000 barrels of petroleum per day in 2015, up from 231,500 bpd in 2014, crude oil manager Fernando Colares Nogueira said at an event on Wednesday.
China and India will be the main buyers, rather than the United States, once a principal destination of Brazil's excess crude, Nogueira told reporters at an event in Rio de Janeiro.
U.S. producers have ramped up domestic production, slashing the need for imports in the world's largest oil-consuming nation.
The exports could help Petrobras generate much-needed cash as it deals with lower oil prices and a development slowdown worsened by a massive corruption scandal. Heavy capital spending and years of fuel subsidies have caused borrowing to soar, making Petrobras the world's most indebted major oil company.
Petrobras output has been increasing this year, however, largely from offshore "subsalt" reserves south of Rio de Janeiro. All its refineries are operating at or near full capacity, with little room to process new output.
The subsalt region exploits oil trapped deep beneath the sea bed by a layer of salt and is home to some of the world's largest recent oil discoveries. While the oil is expensive to extract compared to less extreme environments, Nogueira said, operating there will be economically viable based on Petrobras' projections for oil prices this year and next.
At the same event, the director of oil agency ANP Magda Chambriard said Brazil should double its oil output by 2025.
Petrobras accounts for some 50 percent of Brazil's oil exports, Nogueira said, down from 70 percent in 2011. (Reporting by Marta Nogueira; Writing by Caroline Stauffer and Jeb Blount; Editing by Chizu Nomiyama and Richard Chang)