Preliminary drilling has confirmed that an offshore deposit discovered in March contains significant reserves of light crude, Brazilian state oil giant Petrobras said.

"New oil samples were collected at depth of up to 6,131 meters (19,000 feet)," according to a statement from Petrobras, which said the oil has a density of 31 degrees API.

The higher the degree on the 10-50 API scale, the less dense the oil and the more easily it can be refined into fuel.

The Carcara well has "an oil column of over 400 meters, showing reservoirs that are mostly continuous and connected," Petrobras said.

The well is located in the BM-S-8 block of the Santos basin, 230 kilometers (140 miles) off the coast of the southeastern state of Sao Paulo.

BM-S-8 lies within the pre-salt region, so-named because the tens of billions of barrels of reserves it is estimated to hold are located far beneath the ocean floor under a layer of salt as much as two kilometers (1.2 miles) thick.

Petrobras, with a 66 percent stake, is the operator of the BM-S-8 block, while Petrogal Brasil, a subsidiary of Portugal's Galp Energia, has 14 percent, and Brazilian firms Barra Energia do Brasil and Queiroz Galvao each hold 10 percent interests.

The pre-salt fields, which range across roughly 160,000 sq. kilometers (62,000 sq. miles), are estimated to hold between 50-80 billion barrels of crude and could potentially transform Brazil into a major crude exporter. EFE