China discovers 110 billion cubic meter deep methane mine

China National Offshore Oil Corporation announced on October 23 that it had discovered the first deep coalbed methane deposit with reserves exceeding 110 billion cubic meters.

Shenfu deep CBM mine in Yulin city, Shaanxi province. Photo: CMG — Shenfu deep CBM mine in Yulin city, Shaanxi province. Photo: *CMG*

The Shenfu deep coalbed methane deposit is located in Yulin City, Shaanxi Province, on the eastern edge of the Ordos. The new discovery is important for China’s energy security, helping to boost the country’s unconventional oil and gas reserves and production.

Methane is a natural gas found in coal seams. Unlike conventional gas deposits, it is stored through adsorption. Methane is mainly distributed at the grain surfaces of coal as adsorbed gas, but is also present in cracks and crevices as free gas or dissolved gas in water.

Coal-based methane is found at depths of over 1,500 m. China has abundant reserves of more than 30 trillion m3 located at depths of less than 2,000 m. Deep methane deposits account for about one-third of China's total methane reserves.

Compared with the medium and shallow types, the accumulation mechanism and geological conditions of methane in deep coal are more complicated. As the depth increases, the formation temperature, formation pressure and stress also increase significantly, making exploration more difficult and costly.

The coal seam of Shenfu Mine is about 2,000 m deep and the thickness of a single layer is 6-23 m, with an average gas content of 15 m3 per ton of coal. At present, more than 100 exploration wells have been dug in the area, with a maximum daily gas output of 26,000 m3 per well.

Shenfu is the second major deep methane field discovered by CNOOC, after Linxing, which has similar gas reserves. According to Xu Changgui, deputy chief exploration engineer at CNOOC, the new discovery shows great prospect for exploration and development in the eastern edge of the Ordos region. "This discovery lays a solid foundation for the company to build a large onshore gas production base, which can exploit up to 1 trillion cubic meters of proven gas in place," said Zhou Xinhuai, CEO of CNOOC.

Thu Thao (According to CGTN )

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