In the last ten years, China has imported numerous advanced technologies of gas extraction and oil exploitation from other countries, and it has made some achievements, especially for the coal seam with a better gas permeability. But for the most coalfield, the surface longhole drilling is not effectively used in original coal seam with poor gas permeability, low-gas pressure and low-saturation. These disadvantages also cause lower gas production and smaller gas- extraction range of the hole. In order to solve these problems, the ideas and technologies of the underground gas extraction are presented in this paper, which depends on the de-stressed zone and fracture zone caused by coal mining. These two zones could promote not only the gas desorption rate and the flow rate, but also could increase gas permeability. Under this condition, gas extraction along with the coal mining can be achieved at the same time, and it is called coal and gas co-extraction. The paper introduces the project case in Huainan coal area in central China, where the gas extraction technologies had been employed in upper and lower coal seam of first mining coal seam in the process of multi-seam mining.


The coal and gas co-extraction, which mainly depends on the de-stressed zone and fracture zone to increase gas desorption rate and permeability of coal seam, is one of the gas extraction technologies in the process of coal mining [1] In the recent ten years, this technology has been rapidly developing in China. It is in the coal seam with adsorption status. The calorific value of 1 m3 (35 ft3) pure gas is equivalent to the calorific value of 1.13kg (2.49lb) gasoline or 1.21kg (2.67 lb) standard coal, and it is equal to the calorific value of natural gas.

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