三软中厚煤层
three soft in the thick coal seam
20m特厚中硬煤层
20 m VERY THICK AND MEDIUM HARD SEAM
CO2-N2赋存煤层
coal seam containing CO2 and N2
本煤层抽放
gas drainage in mining seam
变组分煤层气
Various component coal bed methane
various components coal bed methane
薄基岩浅埋煤层
the shallow buried coal seam of thin base rock