Brazilian state-run energy giant Petrobras (PBR) said late Monday that its Abare Oeste prospect in the Santos Basin's prolific BM-S-9 block tested positive for oil and natural gas.

"The discovery was proved via oil, natural gas and carbon gas content sampling via a cable test carried out in reservoirs located at depth of some 5,150 meters," Petrobras said in a filing with stock regulators.

It's the fourth discovery in the BM-S-9 block, which also yielded the Guara prospect. Last week, Petrobras estimated Guara's recoverable reserves at between 1.1 billion and 2 billion barrels of crude oil and natural gas. Petrobras is the lead operator of the block, with a 45% stake. BG Group PLC (BG.LN) holds 30%, while Spain's Repsol YPF (REP) has the remaining 25%.

-By Jeff Fick, Dow Jones Newswires; 55-21-2586-6085; Jeff.Fick@dowjones.com