Oil executive Jiang Jiemin rose to power in communist China in time-honored fashion: by hitching his star to a mighty mentor.

In Jiang's case, that patron was another oil man, Zhou Yongkang, who went on to become the chief of China's internal security apparatus and one of the country's most powerful men.

Like Zhou before him, Jiang rose to the top of the country's biggest oil producer, China National Petroleum Corporation. In return, say people familiar with his career, Jiang helped Zhou build power by using the oil giant to dispense patronage. In March last year Jiang ascended even higher, when he was named to run the agency that oversees all of China's biggest state-owned companies.