CNOOC Ltd., China's third-biggest oil and gas group, is considering a bid of more than $13 billion for its U.S. rival Unocal Corp. in a deal that would mark the largest and most significant overseas acquisition by a Chinese company, the Financial Times reported Friday. Quoting people close to the situation, the British paper said the state-controlled group is interested in Unocal's Asian assets and has asked bankers to study a takeover of the whole company followed by a subsequent sale of the U.S. assets. Unocal's main attraction for CNOOC is its extensive operations in several Asian countries, including Indonesia,...