Deep Coal Mine Methane Drainage in China with Lower Greenhouse Gas Emissions: Insights of Borehole Protection Technology

Abstract

Climate warming has currently been one of the most important global environmental issues. Coal mine methane (CMM) is a typical greenhouse gas with higher global warming potential and ozone depletion potential than CO2. Unfortunately, it should be noted that the CMM emission increases rapidly with the increasing coal consumption in China. Fast and whole protection technology of borehole is a recently developed method to maintain the drainage efficiency in deep mining level. However, the potential negative impact of screen pipes on CMM drainage efficiency has not been well studied. To investigate this impact, an innovative coal permeability model from elastic to post-failure state was deduced to develop our previous gas migration model. Then redistributed stress, coal permeability and gas pressure around a borehole were studied by implementing the mathematical model into Comsol Multiphysics. Numerical results indicate that the negative impact of screen pipes on drainage subpressure do not affect the drainage efficiency due to the stress redistribution. Engineering application shows that comparing to the traditional borehole protection technology, the gas concentration increases about 120% and the gas flux increases about 110% by using the fast and whole protection technology. The research will provide theoretical foundation of CMM capture and borehole protect technology and is of great significance for the CMM utilization and the global environment.