Study on Main Control Factors Affecting Gas Content of Coal Seams in Liulin Mining Area

In order to clarifty the dominant factors controlling the coalbed methane (CBM) content in Liulin Mining Area, the paper focused on the hydrogeology and roof rock effects based on the analysis of sedimentology, burial depth, ash content, and other factors. The key roles controlling the CBM accumulation were acquired fro m the analysis of lithology combination within 20 m upon coal seams by methods of gray correlation, correlation analysis and other mathematical methods. Results sho wed that the gas content of No.3 + 4 coal seam in Shanxi Formation was accompany with the general rules, and was dominated by the Sealing Effect (mudstone) in the roof lithology combination. And the CBM reservoir was pressure closing reservoir in continental strata. The No.8 + 9 coal seams showed no direct connection with burial depth, ash content and roof rock. However, the gas content was closely related to the limestone thickness, and was controlled by the Dynamic Effect (limestone) . The CBM reservoir was hydraulic closing reservoir in paralic strata.