Pore Features and Geological Significance of Low Rank Coal Reservoirs in Erdos Basin

As for the coal samples from the Jurassic System coal bed methane exploration development area in Erdos Basin,the pressurized mercury,low temperature liquid nitrogen test,microscope observation and other means were applied to study the pore type,pore connectivity and pore form of the coal reservoirs and the crack density,crack connectivity and crack development features of the coal core samples.The study showed that the like pore-throat ratio of the coal reservoirs in the south part of the Erdos Basin was low(generally lower than 15),the mercury withdrawal efficiency was quite high(higher than 50%),the mining recovery rate was high and the displacement pressure was generally higher than 0.7 MPa.The max mercury injection saturation was lower than 65%.The coal porosity was lower than 12%,the permeability of the coal reservoirs was lower than 0.01×10-3 μm2 and the production capacity would be high.Thus all above would be favorable to the coal bed methane development.The observation of the coal core samples from the coal bed methane well showed that the seams in the basin would be primary structure coal generally,the cracks in the coal in the Jiaoping and Dafosi Area,the south part of the basin were well developed and the connectivity was medium.All would be favorable to the coal bed methane development.