UPDATE 4-Exxon Mobil bets on Brazil, buys 10 oil blocks in auction

RIO DE JANEIRO, Sept 27 (Reuters) - Exxon Mobil Corp vastly expanded its presence in Brazil on Wednesday, winning 10 blocks in the country's 14th round of bidding for oil exploration and production rights, helping the cash-strapped nation fetch a record 3.8 billion reais ($1.19 billion).