Present situation and technical research progress of coalbed methane surface development in coal mining areas of China

The exploration and development process of coalbed methane (CBM) in coal mining areas, which was implemented under the organization and cooperation of the coal enterprises in China, was reviewed in this paper. After more than 30 years of hard work and unremitting efforts, gratifying achievements have been made in the research, engineering experiments and industrial development on CBM surface development technology, including the successful CBM development of anthracite coal in Jincheng mining area, Shanxi Province, for the first time at home and abroad, the largescale commercial production of CBM, the major breakthrough made in the CBM development technology by horizontal wells in the roof of broken soft coal seam with low permeability in Huaibei mining area, Anhui Province, and the high and stable production of CBM in single horizontal well of broken soft coal seam with low permeability production. Besides, CBM well development in the active mining area of coal mine has been developed as large-scale engineering application in Huaibei, Huainan, Jincheng and other mining areas. At the same time, the main achievements and application results of the theoretical and technical research on CBM surface development in coal mining areas based on the major national science and technology projects from the 11th to the 13th five-year plans were summarized, such as the technology and equipment of sealed coring for CBM well, the enhanced production technology of surface vertical CBM well in broken soft coal seam with low permeability, the staged fracturing development technology in the roof and horizontal well of broken soft coal seam with low permeability, the stratified pressure control and multilayer gas drainage technology in multi-seam, the development technology of surface CBM in low rank coal seam with low gas content, the multi-hole rotary jet sidetracking technology of horizontal CBM well with tight radius and the prediction technology of CBM production in active mining area of coal mine. On this basis, according to the coal mining development trend and demand in the coal mining areas in China, it is pointed out that the future CBM research in coal mining area should focus on the following three aspects: the coordinated development of deep CBM and coal resources by way of the shallow goaf and active mining area, the coordinated development of CBM and coal resources in thick low-rank coal mining area with low gas content, and the CBM development in the abandoned/closed mine.