China makes breakthrough in ultra-deep natural gas exploration in Bohai Sea

(ECNS) -- China has made a breakthrough in ultra-deep natural gas exploration in the Bohai Sea after a well drilled more than 5,000 meters (about 16,400 feet) below the seabed struck high-yield oil and gas in volcanic rock formations, China National Offshore Oil Corporation (CNOOC) said Thursday.

The well is in the central Bohai Sea, next to the Bozhong Sag, the largest hydrocarbon-rich depression in the sea. It cut through more than 120 meters of gas-bearing volcanic rock and reached a total depth of 5,770 meters.

Testing showed the well can produce about 800,000 cubic meters of natural gas a day, or about 28 million cubic feet, CNOOC said. The company said the result highlights the exploration potential of ultra-deep volcanic formations beneath the sea.

The project team said the geological conditions in the ultra-deep layers of the Bohai Sea are complex, making reservoirs hard to predict.

To overcome these difficulties, CNOOC developed offshore deep-layer seismic exploration technologies that use multi-source, broadband and three-dimensional seismic data. It also developed an improved method for predicting high-quality reservoirs in ultra-deep buried hills, which let researchers pinpoint areas favorable for natural gas accumulation in the volcanic formations of the Bozhong Sag.

Xu Changgui, chief scientist and chief geologist of CNOOC, said the discovery has opened a new area for ultra-deep offshore natural gas exploration and expanded the potential for deep oil and gas exploration in the Bohai Sea.

The discovery is expected to speed up exploration in the region and support development of a large-scale natural gas production base in the Bohai Sea, with estimated reserves of 1 trillion cubic meters, according to CNOOC.