Key technologies for coordinated development of coalbed methane in inclined soft coal seam groups: a case study of Aiweigou Mining Area

Abstract

In order to clarify the key technologies for the coordinated development of coal and coalbed methane that are compatible with the mining conditions of inclined broken soft coal seams. Based on the characteristics of gas drainage and asymmetric mining of inclined crushed soft coal seam group gas drainage and coal seam group, a matching coordinated development mode of coal and coalbed methane was formed in the spatiotemporal synergy of “three holes, four zones and five quantities” of asymmetric pressure relief, and the coordinated development strategy of coal and coalbed methane under asymmetric mining was clarified, and the spatiotemporal synergy mechanism of coordinated development of combined coal and coalbed methane was clarified. In view of the problem of difficulty in eliminating the first mining seam of inclined crushed soft coal seam, the construction process of long drilling under inclined crushed soft coal seam was optimized, and a wireless measurement system of electromagnetic wave while drilling of drill bit was developed, which realized higher precision anti-biasing of drilling trajectory. Aiming at the problem of lack of pertinence of surface well protection in asymmetric mining area, the temporal and spatial evolution characteristics of asymmetric mining-induced pressure relief failure were clarified, the evolution characteristics of mining-induced fractures under asymmetric mining were obtained, the safe position of wells in the surface well of inclined coal seam was determined, and a three-open casing structure in the mining area was developed that could take into account the stability and extraction efficiency of surface wells. The application results show that the “three-hole, four-zone and five-quantity” mode of spatiotemporal synergy can realize the efficient extraction of coalbed methane and ensure the balance of extraction and mining of inclined coal seam groups. The progressive extraction method of downward drilling of inclined coal seam expands the application scope of progressive extraction and solves the problem of time incoordination in the extraction process of inclined coalbed methane. The optimized stability maintenance structure of the mining surface well can adapt to the asymmetric mining effect, and realize the efficient extraction of coalbed methane from the surface well in the mining area. The above results have been popularized and applied in the Aiweigou mining area of Xinjiang Coking Coal Group, and the key technology and typical model of coalbed methane extraction that conform to the characteristics of inclined coal seams in major high-gas mining areas in Xinjiang have been initially formed.

Keywords

• coalbed methane mining technology
• downward borehole
• surface borehole
• inclined coal seam
• mining-induced fracture