Differential Impact on High and Low Rank Coal by the Main Factors of Coalbed Gas Enrichment

The distinct physical and chemical characteristics of different rank coal obviously influence the physical property of coal reservoir and the enrichment of coalbed gas.This paper analyzes some important factors,including coal seam conditions,tectonic,tectono-thermal events,hydrodynamic conditions,which have differently influenced the concentration of coalbed gas from different rank coal.High rank coal seams yield much more gas than low rank ones,with strong absorption ability and high gas content.With structures controling the regional distribution of different rank coal,the tectonic uplift leads to the increase of the coal seam permeability,and coalbed gas accumulating and migrating or dissipation of the gas.The gas generation are caused by tectono-thermal events,which would also have altered the coal reservoir.Hydrogeological conditions affect the preservation of different rank coalbed methane,and could accelerate the generation of the low rank coal.The differential control of the main factors on the diverse rank coalbed gas enrichment thus resulted in the mechanism of pool-forming.Hence,it is necessary to adopt different evaluation methods and mining technology to propect and explore different rank coalbed gas.