Chinese oil major Sinopec announced on Wednesday that its Ziyang Dongfeng shale gas field in Southwest China's Sichuan Province has been certified by a panel of experts from the Ministry of Natural Resources as having proven geological reserves of 235.687 billion cubic meters(bcm),the Xinhua News Agency reported on Thursday.

This marks the birth of China's first hundred billion cubic meter ultra deep shale gas field,pushing shale gas exploration and development into the ultra deep range of over 4,500 meters below the surface.It represents a major leap in China's shale gas exploration from deep to ultra deep formations,according to the company.

Located in the Sichuan Basin,the Ziyang Dongfeng shale gas field is a large,integrated gas field discovered in the shale series of the Cambrian formation-the oldest shale formation in the world to have achieved large scale discoveries,dating back to 540 million years ago.

Buried at depths of 4,500-5,200 meters,the formation poses enormous engineering challenges,including unclear shale reservoir characteristics,poorly understood accumulation mechanisms,thick difficult to drill strata,and extreme high temperature/high pressure conditions,the oil company said.

Through innovations in geological theory and breakthroughs in a series of core technologies,the research team has developed a new understanding of the shale gas accumulation pattern in the formation,opening up a brand-new strategic replacement resource base for shale gas exploration in China.