Study on occurrence characteristics and controlling factors of coalbed methane in Zhaoguan Coalfield

Based on coal bed methane(CBM)information,tectonic condition,coal ash,lithology of the roof and floor,seam depth,hydrogeological condition and magmatic activity,this paper had a study on occurrence characteristics and controlling factors of CBM in Zhaoguan Coalfield.The results showed that the CBM content and gas saturation of upper group coal seams (No.7 and No.9)were obviously larger than that of lower group coal seams (No.11 and No.13).The geological structure of this area had no obvious influence on the occurrence of CBM.The ash content of coal seam was negatively correlated with CBM content.The top and bottom plates of the upper group coal seams had dense lithology and good integrity,which was beneficial to preservation of CBM.The roof of lower group coal seams was intruded by magmatic rock and had relatively poor integrity,which was propitious to emission of CBM.The CBM content was positively related to the buried depth of coal seam.The CBM content of upper and lower group coal seam respectively increased 3.67 m3/t and 0.53 m3/t by each hundred meters.Stagnant groundwater area had high salinity groundwater,that was favorable for the preservation of CBM.CBM in coal seam near magmatite diffused seriously.It was the basic reason of the lager difference of CBM content between the upper and lower coal seams.