Pore Distribution Features of Different Rank Coal and Influences to Coal Bed Methane Development

In order to investigate the difference of the pore distribution in the coal reservoirs with high and low rank coal affected to the coal bed methane enrichment and the penetration migration,according to the pressurized mercury and balanced water isothermal adsorption experiment results of the high and low rank coal samples,the paper analyzed the pore development features of the high and low rank coal and compared the difference of the pore volume fractals in the high and low rank coal.The results showed that low porosity of the high rank coal,small content of the influent pore,inkstand type semi-sealed pore development would cause a connection reduction of the pore,a poor influent capacity,a high micro pore content,a low moisture content and a high adsorption capacity and would be favorable to the enrichment of coal bed methane.The porosity of low rank coal would be large.The specific pore volume of the large,medium and transition pore all would be large,the connection of the pores would be good and the influent capacity would be high.The small specific surface area and high moisture content would cause the adsorption capacity reduced.The coal bed methane development of high rank coal reservoir should improve permeability and coal bed methane development of low rank coal reservoir should be first to select methane enrichment zone.