A gas mixture enhanced coalbed methane recovery technology applied to underground coal mines

This paper presents a field trial for developing a gas mixture enhanced coalbed methane (GECBM) technology that can be integrated with underground coal mine methane (CMM) drainage systems. The field trial was carried out in a deep underground coalmine roadway in two stages, initially degassing using a conventional method for 30 days in three boreholes installed in the underground coal seam and then injecting the gas mixture from one of the boreholes for about 2 months. The field trial focuses on the investigation of the technical and economic feasibilities of G-ECBM technology applied to underground CMM drainage systems. The results revealed that the G-ECBM technology integrated with underground methane drainage systems can provide an effective method to enhance the coalbed methane (CBM) recovery from coal mines and the efficiency of underground gas drainage systems, and hence improve the mining safety. The field measurements showed that the single-borehole flow rate and concentration of CH₄ for the production boreholes with G-ECBM have increased by a factor of 4.73 and 1.68 on average, respectively, compared with the conventional production boreholes without G-ECBM. The results also showed the economic prospect of applying G-ECBM technology to underground CMM drainage systems.