Some problems on the research and development of the application of methane draining boring technology to prevent hazards in underground coal mines in Vietnam

Abstract

Underground coal mining activities in the Quangninh coal basin (in the North of Vietnam) have been carried out at a depth of −130 m to −150 m, and in the near future this mining depth will become −300 m and −500 m. Together with the increasing coal output, the quantity of methane and other mine gases emitted from coal beds during mining activities will grow bigger and bigger. According to the forecast of the coal mining industry, if mines go deeper downward, all underground coal mines in the Quangninh basin will be classified into the mine group with the dangerous level of methane bearings. Mine gas control and management operations with conventional ventilation are less effective and entail high expenses. One of the main solutions is to carry out short, medium and long boreholes for controlling and recovering methane and other mine gases from coal beds before mining activities. Efficiency of drilling activities for methane gas recovery from coal seams with horizontal bore holes at underground coal mines depends on many factors including the mine gas draining borehole layout at the roadways, gas content in the coal beds, technologies for mine gas draining boring activities, and so on. Methane gas exists in the coal beds under the adhesive state with stable physical and chemical bonds. In order to recover these gases, it is necessary to carry out boreholes and create artificial joints (collecting pits) in coal beds with the impulse method (hydraulic separation method).