TIANJIN, June 21 (Xinhua) -- China's largest offshore crude oil producer, Bohai Oilfield, has produced upwards of 500 million tonnes of crude oil so far, said China National Offshore Oil Corporation's Tianjin branch.

Since the Bohai Oilfield was put into production over a half-century ago, more than 50 oil and gas fields and more than 190 production facilities have been built.

A total of five oil fields with oil and gas reserves exceeding 100 million tonnes have been discovered in the Bohai Sea area during the past five years.