Vertical diversity of coalbed methane content and its geological controls in the Qingshan syncline, western Guizhou province, China

The distribution of methane content in the coalbed is complex in the Qinshan Syncline of western Guizhou Province. Analyses of factors controlling on the distribution of gas content are made in this paper. Coal ranks and geo-structure in the region showed strong controls on the gas distribution. Coals with higher degree of metamorphism or located in syncline most likely have higher gas content. With the concept of coalbed methane content unite thickness (CBMCUT), those factors such as coal seam buried depth and coal structure present positive relations with gas content. Results indicated that the variation of CBMCUT is not fixed in different research areas or in different coal structures. Namely, the variation follows v-shaped correlation with the increasing coal buried depth in the region of Qinshan Syncline. However, the trend is smooth for the coals in the Panzhuang mining area. Usually, the critical value for primary-texture coal and mylonitized is different based on the analysis of the relationship between coal structure and CBMCUT in those two areas described above. The value is commonly higher in mylonitized coal and lower in those mainly primary-texture and fragmented coals.