The exploration and development of coalbed methane（CBM）in the Permian Longtan Formation in south Chongqing is in the initial stage. In order to reveal the general geological conditions of coalbed methane in the coal seam C

25

by the experimental and geological data obtained from the coal mines and coalbed methane drilling

the geological characteristics such as coal rock and coal quality

coal pore penetration and gas content have been analyzed. The results show that the C

25

coalbed methane of Longtan Formation of Permian in th

e study area is characterized by “stable development

relatively large thickness

low pore permeability

high metamorphism and high gas content”. The development of the coal seam C

25

is stable throughout the whole area

showing the trend of “thick in the north and thin in the south”

and the thickness in the northern part of the coalbed is generally larger than 1.5 m. The coal quality belongs to semi-bright coal. The content of vitrinite in the organic component is 51.7%~72.2%; the vitrinite reflectance ranges from 1.8%~2.2%

and the metamorphism degree is high-over maturity. The porosity and permeability of the coal rock are relatively low

with the porosity ranging from 3.46%~8.46% and the permeability of mostly lower than 0.01×10

-3

μm

2

. The gas content of the coal bed is high

generally more than 10.0 m

3

/t; meanwhile

the top and bottom plates of the coal bed are good sealing layers. Based on the production of Q1 and Y2

it is believed that the coal seam C

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of Permian Longtan Formation in south Chongqing area has good geological conditions for CBM exploration and development.