Key technologies for surface control of gas dynamic disasters in coal mines and their application

Objective and SignificanceAs the coal mining depth increases, coal mining faces increasingly prominent challenges including coal and gas outbursts, rock bursts, and compound dynamic disasters. Deepening the understanding of disaster-causing mechanisms and developing diversified prevention and control technologies are significant for the safe production of coal mines. Employing the key technologies for coalbed methane (CBM) production to control gas-related dynamic disasters is an inevitable course for the safe production of coal mines. However, large-scale, suitable technology systems are yet to be developed. MethodsFrom the perspective of the application of key technologies for surface CBM production, this study systematically reviews the development history and research advances in technologies including well drilling and completion for CBM production and fracturing. From the angle of coal mine safety, this study organizes the disaster-causing mechanisms and critical control technologies for gas dynamic disasters over the past 70 years. In combination with the characteristics of CBM production technologies and the demand for the prevention and control of dynamic disasters in coal mines, this study proposes some suggestions for theoretical innovation and technological breakthroughs. Results and ConclusionsIn terms of theoretical research, it is necessary to deepen the comprehensive exploration of coals and CBM and conduct fine-scale geological studies by integrating multiple approaches. Regarding control technologies, efforts should be made to further explore the control technologies for coal and gas outbursts and rock bursts, with the former including (1) outburst elimination using cavity-type tube wells+high-pressure air/liquid nitrogen/CO2 scrubbing + negative-pressure drainage and (2) multistage fracturing of L-shaped surface horizontal wells+production and the latter including (1) multistage hydraulic fracturing of roofs using L-shaped wells and (2) proppant injection-based multistage hydraulic fracturing for roofs using L-shaped wells+production. Accordingly, advanced technologies such as multistage fracturing of L-shaped wells for CBM production should be employed to conduct on-site experiments on gas dynamic disaster control. It is necessary to explore the applicability of varying prevention and control theories and technologies under different geologic conditions based on scientific research and engineering integrated engineering and projects and develop technology systems for the prevention and control of gas dynamic disasters in coal mines, thus providing robust support for the safe production of coal mines in China.