RIO DE JANEIRO (REUTERS) - A consortia led by Singapore's Keppel Shipyard offered Brazil's Petrobras the lowest price to build a floating platform for Buzios, Latin America's second-largest oil field, three people close to the competition said. Keppel offered to build P-78, a 180,000-barrels-per-day production unit that Petrobras plans for its deepwater Buzios field, for 12.52 billion reais (S$3.12 billion), the sources said, asking not to be named as the information is confidential. A winner has not been selected and the result is unclear, the sources said. Petroleo Brasileiro, as Brazil's state-controlled producer is known, declined to comment. Keppel did not immediately respond to requests for comment. The Singapore shipyard, which partnered with Hyundai Heavy Industries Holding and Brazil-based BrasFELS shipyard for the bid, beat two Asian competitors, sources said. A consortia led by Daewoo Shipbuilding & Marine Engineering offered to build the P-78 platform for 14.11 billion reais. Samsung Heavy Industries placed the highest bid, 15.15 billion reais, the people said. The competition marks Petrobras' comeback as a key customer for Asian shipyards, since Petrobras decided to re...