(ECNS) - China has approved 235.7 billion cubic meters of proven geological reserves at an ultra-deep shale gas field in the Sichuan Basin, marking a major step in the country's push to expand domestic energy supplies, according to media reports.

State-owned oil giant Sinopec said the Ministry of Natural Resources had certified the reserves at the Ziyang Dongfeng shale gas field.

According to Sinopec, the discovery makes Ziyang Dongfeng China's first ultra-deep shale gas field with reserves exceeding 100 billion cubic meters. It also pushes the country's shale gas exploration to depths beyond 4,500 meters.

The gas field was discovered in Cambrian Qiongzhusi shale formation, which dates back around 540 million years, the company said.

Sinopec said the project faced major technical challenges, including unclear reservoir characteristics, uncertain gas accumulation mechanisms, and difficult drilling conditions caused by high temperatures and pressures at depths of 4,500 to 5,200 meters.

China has increased investment in domestic oil and gas exploration in recent years as part of broader efforts to strengthen energy security.

(By Zhang Jiahao)