China National Offshore Oil Corporation announced Sunday that the secondary development project of the Liuhua Oilfield, the country's first deepwater oilfield, has fully commenced operation, a major breakthrough in China's ability to develop complex deepwater oil and gas reservoirs.

Located in the Pearl River Mouth Basin, the oilfield is China's largest offshore reef limestone oilfield in terms of proven geological reserves.

Since its initial commissioning in 1996, the oilfield has produced over 20 million metric tons of crude oil, said CNOOC.

The milestone enables the nation to exploit challenging deepwater resources and strengthen its domestic energy supplies, experts said.

The secondary development project comprises two oilfields, Liuhua 11-1 and Liuhua 4-1, situated in an area with an average water depth of about 305 meters. The project involves 32 production wells.

Since the first batch of wells began operation in September 2024, daily crude oil output has climbed to a record high of 3,900 tons, CNOOC said.