China National Offshore Oil Corp. announced production started at the Weizhou 6-12 oil fields in the northern South China Sea.
"The project has 10 producing wells and is expected to hit its peak production in 2013," the company said in a statement.
CNOOC gave no indication of the reserve potential. The U.S. Energy Information Administration said oil production from China is expected to reach about 4.5 million barrels per day this year.
"Over the longer term, EIA predicts a flatter incline for China's production, reaching 4.7 million bpd by 2035," its analysis states.
The Organization of Petroleum Exporting Countries, in its April report, said the largest share of growth in oil demand this year is expected to come from China.
China is at odds with its neighbors over the South China Sea. Michael Swaine, a Chinese expert at the Carnegie Endowment for International Peace, told U.S. lawmakers this month that maritime issues "constitute the single most likely and significant potential source of instability, and even military conflict," in the region.