My bet would be PetroChina.
From the Financial Times' Energy Source blog:
Will BP, with its battered share price and reputation, become a genuine takeover target?
While it might be a technically viable, and attractive, target for some companies, there are enough drawbacks to make it difficult to see who might be seriously interested:
Shell and BP in particular have a long history of courtship, which the FT explores. In 1995 Shell approached BP, whose shares were then at a low ebb, but former BP chief executive Lord Browne describes in his memoirs that he stalled until the approach petered out....MORE