Petrobras declares two fields 'commercial'; hold 351 mln bbls

* Tartaruga Verde, Tartaruga Mistiça are new field names * Recoverable reserves equal to 19 days U.S. demand RIO DE JANEIRO, Jan 3 (Reuters) - Brazil's state-led oilcompany Petrobras said on Thursday that it declaredtwo offshore oil prospects with an estimated 351 million barrelsof oil and gas to be "commercially viable", opening the door tonew output. The Aruana and Oliva discoveries in the BM-C-36 concessionin the oil-rich Campos basin, will now be known as the TartarugaVerde, or "Green Turtle", and Tartaruga Mistiça, or "LoggerheadSea Turtle", fields, Rio de Janeiro-based Petrobras said. Tartaruga Verde has an estimated 230 million barrels ofrecoverable oil and natural gas equivalent (boe), the companysaid. Tartaruga Mistiça has an estimated 121 million boe ofrecoverable reserves. The fields hold enough oil to supply all needs in the UnitedStates, the world's largest oil consumer, for about 19 days,according to BP Plc and Reuters. Petrobras owns 100percent of each areas. The fields are about 125 km (78 miles) off Brazil's coastand about 275 km east of the city of Rio de Janeiro. Petrobras said the fields have medium-grade crude at 27degrees on the American Petroleum Institute scale, a "lighter"and more valuable grade of petroleum than most of the oilproduced in the Campos Basin. The Campos Basin is home to about 80 percent of Brazil's oiland natural gas output. The sites are about 125km (78 miles) offRio de Janeiro's coastline.