UPDATE 1-Brazil's Petrobras finds more light oil in subsalt

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SAO PAULO, June 12 (Reuters) - Brazil's state-run oil company Petrobras (PETR4.SA) (PBR.N) said on Thursday that it struck light oil in another ultra-deep field under the subsalt layer in the Santos Basin.

This is the latest in a slew of promising deep-water light-oil discoveries over the past year that have helped more than double the price of Petrobras shares.

Petrobras said the find was in the Guara, the smaller of two fields in the BM-S-9 ultra-deep block, which also holds the so-called potential super-giant Carioca field. It also yielded light oil from an exploratory well sunk in September of 2007.

The oil from the Guara ranked 28 on the API scale, making it much lighter than the bulk of crude produced in Brazil, which ranges around 14 to 18 API.

Petrobras offered no reserve estimate for the new find, which lies at a very technically challenging ultra-deep depth, under 2,141 meters of water and another 5,000 meters under the ocean floor, including a salt layer.

The field lies 310 km off the coast of Brazil's Sao Paulo state in the Santos Basin.

Petrobras is operator at the BM-S-9 block with a 45 percent stake in the exploration and production concession. Its partners BG Group and Repsol YPF hold 30 percent and 25 percent stakes, respectively. (Reporting by Reese Ewing; editing Carol Bishopric)