China National Offshore Oil Corporation (CNOOC) has reported a significant discovery in the South China Sea, identifying oil and gas reserves in metamorphic buried hills for the first time off the coast of China.

The development is centred around the Weizhou 10-5 South Oil and Gas Field, situated in the Beibu Gulf, where the water depth averages 37m.

The exploration well, designated WZ10-5S-2d, has encountered an oil and gas pay zone measuring 211m. Drilling reached a total depth of 3,362m.

Testing of the well has revealed daily production capabilities of 165,000ft³ of natural gas and 400 barrels of crude oil.

CNOOC CEO Zhou Xinhuai said: "This represents the first major breakthrough in metamorphic sandstone and slate buried hills exploration offshore China, setting an important example for advancing deep plays and buried hills oil and gas exploration.”

CNOOC chief geologist Xu Changgui said: "In recent years, CNOOC has consistently intensified theoretical innovation and tackled key technology challenges in buried hills and deep plays exploration.

“Breakthroughs have been achieved in the exploration of Paleozoic granite and Proterozoic metamorphic sandstone and slate buried hills within the Beibu Gulf Basin.

“They demonstrate the vast exploration potential in buried hills formations, drive the secondary exploration process in mature areas, and mark the commencement of large-scale exploration of buried hills in the Beibu Gulf Basin."

The discovery follows CNOOC recently starting production at the Weizhou 5-3 oilfield development project in the Beibu Gulf Basin.

Situated in waters averaging a depth of 35m, the project is anticipated to achieve peak production of 10,000 barrels of oil equivalent per day by 2026.

Earlier this year, the company unveiled a substantial oilfield discovery in the eastern South China Sea at an average water depth of around 100m.