The most striking trend in oil and gas M&A in recent years has been the rise of bidders from emerging economies - a development that hit the headlines with the unsuccessful bid by CNOOC of China for Unocal of the US in 2005, write Ed Crooks and Lina Saigol .

The Chinese companies were quiet in 2007, but activity picked up again in 2008. Sinopec, the second biggest listed oil company, agreed a C$2.1bn (US$1.7bn) bid for Tanganyika Oil, a Canadian company operating in Syria, and is said to be looking for more deals.