Analysis of main geological controls on coalbed methane enrichment and accumulation patterns in low rank coals

According to the status of the low rank coalbed methane distribution and enrichment in China affected by the multi geological factor control, an analysis was conducted on the sedimentary environment, tectonic role and the hydrogeologic condition as well as other key geologic factors. The results showed that in a low coalification stage, the vitrinite (huminite) could make a certain contribution role to the adsorption capacity of the coal and rock. The moisture content in the coal property would have a negative effect. A sedimentary environment would affect the thickness and total resource volume of the coal measure strata. A higher thickness of the seam roof and floor, the higher compact of the lithology would be more favorable to the keeping of the coalbed methane. The gas content of the seam would have a positive correlation to the seam thickness. A tectonic movement might cause a failure to the covered layer, would cause the releasing of the coalbed methane and might form a good lateral sealing. A hydrodynamic system would have a control role both to the formation and keeping of the low rank coalbed methane. The interested relation of the coalbed methane enrichment in the low rank coal basin should be distinguished with the coupling relationship between the hydrogeology and the tectonics. As for the low rank coalbed methane reservoir, the free gas content should not be ignored. On the favorable selection of the reservoir formation mode, a high attention should be made to the analysis on the tectonic dynamic condition and the evaluation of the tectonic traps.