China National Offshore Oil Corp (CNOOC) announced on Thursday that it has successfully drilled and discovered a high-yield volcanic oil and gas well in ultra-deep formations exceeding 5,000 meters in the Bohai Sea, marking a major breakthrough in ultra-deep natural gas exploration offshore China.

The well is located in central Bohai, adjacent to the Bozhong Sag, the largest hydrocarbon-rich sag in the Bohai Sea, according to the Science and Technology Daily.

The Bohai Sea area is an important natural gas production region in China and one of the key sources for natural gas supply to the Beijing-Tianjin-Hebei region and Bohai Rim region.

The project encountered a cumulative gas pay zone of more than 120 meters in volcanic formations and it was completed at a depth of 5,770 meters. The well tested at approximately 800,000 cubic meters of natural gas per day, revealing promising exploration prospects in the offshore ultra-deep volcanic rocks and effectively advancing the natural gas exploration process in the Bozhong Sag, according to CNOOC.

The discovery comes at a time when China is seeking to consolidate domestic oil and gas supply to underpin energy security.

In recent years, the company has continued to strengthen theoretical research on the enrichment of deep and ultra-deep oil and gas resources in basins with high heat flow and strong tectonic activity, while stepping up efforts to develop key technologies, Xu Changgui, chief scientist and chief geologist at CNOOC, said, adding that exploration in China's offshore areas has made a major leap from shallow formations to deep and ultra-deep ones. 

Xu noted that the success of this well has opened up a new exploration target for offshore ultra-deep natural gas and expanded the scope of deep oil and gas exploration in the Bohai Sea. 

"It is of great significance for accelerating ultra-deep exploration in the Bohai Sea and for building a trillion-cubic-meter-scale major gas province in the region," he said.

According to the company, the ultra-deep formations in the Bohai Sea are geologically complex, which makes reservoir estimation difficult. CNOOC said that it has independently developed key offshore deep multi-source broadband 3D seismic exploration technologies and created innovative methods for predicting high-quality reservoirs in ultra-deep buried hills. 

These technologies enabled the precise identification of favorable zones for ultra-deep volcanic natural gas enrichment in the Bozhong Sag, leading to the discovery of a high-yield oil and gas well, a significant breakthrough in ultra-deep volcanic natural gas exploration in the Bohai Sea.

The National Development and Reform Commission and the National Energy Administration have announced a five-year plan for oil and gas development, calling for intensified exploration and reserve expansion to solidify the "ballast stone" of independent supply, and targeting domestic oil and gas supply of 440 million tons of oil equivalent by 2030.

Data from the Ministry of Natural Resources showed that China's offshore crude oil output in the January-September period climbed 3.5 percent year-on-year.