The announcement makes Bohai the nation"s biggest find in 40 years.

The China National Petroleum Corp. said Thursday that it now estimates the oilfield in the Jidong district at Tangshan City contains 7.3 billion barrels, compared to the 2.2 billion originally estimated, the state-run Xinhua news agency reported.

PetroChina, CNPC"s holding company, turned in $18.5 billion in net profits last year, making it Asia"s most profitable company.

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