China makes breakthrough in offshore ultra-deep gas exploration

China has drilled a high-yield gas well in volcanic rock formations at a depth of more than 5,000 meters in the central Bohai Sea, marking a major breakthrough in offshore ultra-deep natural gas exploration.

The well was drilled on Thursday to a depth of 5,770 meters and tested at a daily gas output of approximately 800,000 cubic meters.

During exploration, the well encountered more than 120 meters of gas-bearing formations in volcanic rock, demonstrating the vast exploration potential of offshore ultra-deep volcanic rock reservoirs.

Guo Tao, chief geologist at the Bohai Petroleum Research Institute of CNOOC Tianjin, said the reservoir temperature reached 150 degrees Celsius, while formation pressure exceeded 80 megapascals.

Facing challenging high-temperature and high-pressure geological conditions, teams from multiple disciplines worked together to improve operational quality under complex geological conditions, ultimately completing the drilling operation and obtaining a high-yield gas flow.

In offshore oil and gas exploration, formations buried deeper than 3,500 meters are generally classified as deep, while those exceeding 4,500 meters are considered ultra-deep.

The ultra-deep volcanic rocks in the Bohai Sea were formed by volcanic eruptions and subsequently underwent multiple phases of tectonic transformation. Their dense lithology and strong heterogeneity have made exploration particularly challenging.

Difficulty in accurately identifying complex formations, locating high-quality reservoirs and drilling through hard rock has long posed world-class technical challenges to exploration and development in the area.

The Bohai Sea is a major natural gas production region in China and an important source of gas supply for Beijing-Tianjin-Hebei and surrounding areas.

The successful drilling of the well opens up a new frontier for China's offshore ultra-deep natural gas exploration. It is expected to accelerate exploration in the ultra-deep Bohai region and support the development of a giant gas province with reserves of one trillion cubic meters.

The breakthrough also carries significance for increasing domestic oil and gas reserves and production, while ensuring a stable natural gas supply to regional markets.