大倾角地层煤层气钻井
CBM well boring in strata at great inclination
煤层煤质
coal seam a nd coal quality
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
7种煤煤质
coal quality of seven coal samples
CO2-N2赋存煤层
coal seam containing CO2 and N2