摘要: Gas emissions and problems in the Australian coal mines have lncreased significantly in recent years as mines reach greater depths and increase longwall production levels and panel sizes.Traditionally，the main objective of gas dr... 展开 Gas emissions and problems in the Australian coal mines have lncreased significantly in recent years as mines reach greater depths and increase longwall production levels and panel sizes.Traditionally，the main objective of gas drainage operations was to meet the safety requirements of the underground coal mines with respect to outburst and frictional ignition.However，with the recent focus on reducing greenhouse gas(GHG) emissions from the mining industry，gas drainage and improved gas capture has become one of the critical GHG mitigation strategies．It was identified that the wider application of gas drainage as a mitigation strategy depends on achieving drainage costs that are less than the combined value of the associated safety，greenhouse and gas revenue benefits．The technique of surface-to-inseam drainage (SIS) also known as Medium Radius Drilling (MRD) technology is gaining acceptance in the coal mining industry as an acceptable means of pre draining virgin underground areas prior to mining operations，although the design and application of the MRD technology is still being developed based on our ever increasing knowledge of coal seam gas behaviour．MRD techniques offer the most promising alternative to Conventional Inseam drilling or‘CIS’drilling．Numerous improvements in drilling techniques have allowed MRD drilling to become more productive and cost effective not the least of which is the management of bottom hole pressures during drilling operations．The control of pressure has improved drilling rates and minimised near surface damage to coal seams which is known to effect drainage performance．Studies by CSIRO have identified the major parameters effecting MRD performance as a result of a two year ACARP funded study into MRD techniques．These parameters are outlined in the following paper． 收起