RIO DE JANEIRO, April 7 (Reuters) - Brazil's oil giant Petrobras (PETR4.SA) said on Wednesday it found light oil in a new well that confirmed its estimate of 5 billion to 8 billion barrels in the Tupi offshore field. The oil field is part of the country's massive offshore subsalt area, which Brazil hopes will turn it into a major player in energy markets. The new well, known as Tupi OW, is located at a depth of 2,131 meters (7,000 feet) and is 270 km (167 miles) from the coast of Rio de Janeiro. Petrobras holds a 65 percent stake in Tupi, Britain's BG Group (BG.L) has a 25 percent stake and Portugal's Galp (GALP.LS) 10 percent. (Editing by Marguerita Choy)