Key problems and countermeasures of CBM development through surface boreholes in abandoned coal mines of Shanxi Province

With the effective implementation of China's coal capacity reduction policy, a number of resource-depleted and under-developed mines will be abandoned. The plenty of coalbed methane resources still existing in abandoned mines, could be developed and utilized to realize clean, safe, efficient and low-carbon development of coal industry, promote safe production of coal mines, optimize energy structure, and achieve greenhouse gas emission reduction. Based on the relevant research of Shanxi Province Coal-based Key Science and Technology Targeting Project(Coalbed Methane Industry Chain), the author systematically expounds the key problems faced by coalbed methane development in abandoned coal mines, such as inaccurate resource evaluation, unsound drilling system, lack of surface and underground co-extraction, etc. In view of these problems, the following countermeasures are proposed: Accurate geological exploration of abandoned mines is an important basis for the design of surface drilling trajectory in goaf, especially for abandoned mines with backward coal mining technology such as blasting mining. In order to effectively reduce the risk of drilling into coal pillars, the precision of geophysical exploration should reach meter level. "L" –shaped coalbed methane surface boreholes are the best choice in abandoned mines, that is, selecting a certain distance of safe coal pillar around the goaf as the location of L-shaped boreholes and supporting special drilling technology. Coal mining enterprises should consider the development and utilization of abandoned mine resources during the whole life cycle planning of coal mines in advance, especially ensure the unblocked CBM pumping channels before the mine is abandoned, so as to realize the new combined mining mode of "one borehole for multi-purpose" of CBM boreholes and improve the CBM development efficiency of abandoned mines. Adopt backfire prevention device, various sensors and other devices, and set automatic alarm halt limit value for key parameters, so that coalbed methane surface extraction process in abandoned mine is safe and efficient; In order to improve the overall development and utilization value, it is necessary to adopt the corresponding cascading utilization mode for coalbed methane with different concentration in abandoned mines. Taking the abandoned mines in Shanxi Province as a demonstration area, the research and understanding has important guiding and demonstrative significance for promoting the development and utilization of coalbed methane in abandoned mines in the coal mining areas of China.