China’s CNOOC Ltd. has tapped commercial flows of oil and gas from a shale exploration well in the South China Sea, marking the first successfully drilled shale oil well offshore China, state media reported on July 28.

Exploration well Weiye-1, sunk at the southwestern trough of Beibuwan Basin in South China Sea, tested daily production of 20 cubic meters (126 barrels) of oil and 1,589 cubic meters of natural gas, Shanghai Securities Journal reported.

The whole Beibuwan basin could hold about 1.2 billion tonnes of prospective shale oil resource, the report added.

CNOOC’s press department did not immediately respond to a request for comment.

Under a central government call to boost domestic energy supply security, national oil companies are making greater efforts to tap shale deposits despite their geological challenges and higher cost.

By late 2021 China produced only 35,000 bbl/d of shale oil—extracted from shale rocks and is more complex and expensive to produce than conventional crude—mostly in onshore northern Ordos basin and northwestern Jungar Basin.

That equates to less than 1% of its total oil output.