Exploration and research progress on the integrated technology of coalbed methane development, gas control, and methane emission reduction

Coal methane is a hydrocarbon gas with methane as its main component. This is a collective term for coalbed methane (CBM) and coal mine gas, which coexist with coal in coal seams. Given the “triple” attributes of coal methane as an energy source, a disaster gas, and a greenhouse gas, developing integrated technologies for its development, management, and emission reduction is vital to enhance efficient production and utilization and ensure energy, production, and ecological security. Aiming at problems such as the difficulty of coordinating the development of CBM and coal in the whole production cycle; optimizing the relationship between the successive deployment of projects and spatial configuration; mining CBM in the tectonic coal development coal-endowed area; and extracting coal mine gas, the large amount of gas in the air discharge, and the low utilization rate of low and ultralow concentration of coal methane, our team tries to explore and propose the idea of the integrated technology and the direction of the research. The temporal succession and effectiveness of coal methane development engineering during the entire production cycle, along with the configuration and optimal deployment of coal methane extraction engineering in the space between the surface and underground of coal mines, are key links for realizing the synergistic development and utilization of coal and CBM. Utilizing surface well “multipurpose” successive extraction technology ensures spatial and temporal coordination between CBM extraction and coal mining engineering. Considering the spatial and temporal constraints of coal mining projects, the depth and condition of coal seams, and other factors, surface and downhole drilling in the mining area are jointly deployed in advance to overcome the challenges of rapid and efficient CBM extraction and coal and gas outbursts that cannot be resolved by downhole pumping or surface wells using a single well deployment. To tackle the difficulties of developing CBM in structural coal and the propensity for gas outbursts, we propose a method for constructing cavities in structural coal reservoirs to promote gas drainage and reduce outbursts. Moreover, we systematically expound upon a new technology for stress release in horizontal wells to enhance the efficient exploitation and prevention of outbursts in CBM from structural coal (including broken, soft, and low-permeability coal seams). Given the varying concentrations of CBM (coal mine methane) resources across different coal mining periods, we adopt different CBM extraction and methane utilization technologies, adapting to the characteristics of full-space and -concentration methane gases in coal mining areas, and propose technologies for high, medium, low, and ultralow concentration methane gradient utilization. The author systematically reviews the current status, progress, and challenges of CBM development, gas management, and methane abatement technologies in coal mining areas. An integrated technology system for CBM development, gas control, and methane emission reduction is proposed, encompassing “coal premining, mining, and postmining surface well integrated deployment and continuous extraction technology,” “joint deployment and collaborative extraction technology of surface well-underground borehole in the coal mining area,” “integrated technology of CBM development and coal seam outburst reduction and outburst elimination in tectonic coal,” and “coal methane high, medium, low, and ultralow concentration cascade development and utilization and atmospheric emission control technology. This integrated technology system represents the direction for technological application and development in the coordinated development of coal and CBM, full-space joint extraction and gas management in mining areas, and full-concentration gradient utilization of methane throughout the coal mine production cycle.