The Spatial Distribution of CBM Systems under the Control of Structure and Sedimentation: The Gujiao Block as an Example

ABSTRACT A multilayer coal bed methane system with a complex superimposed relationship developed vertically in the Gujiao block. Taking the cumulative thickness of mudstone between neighbouring coal seams and open faults as object of research, the key strata for the division of different CBM systems was defined. The connection of an open fault for the fluid pressure system and the spatial distribution of the CBM system were analysed. The results showed that the porosity of compact mudstone is extremely low. When the mudstone thickness of the roof and floor increases, the gas content increases. Taking the Lijiashe and Wangzhimao faults as the boundary lines, the fluid pressure gradient between the Shanxi and Taiyuan formations is less than 0.08 MPa /100 m in the northern fracture zone, such as the Zhenchengdi, the Xiqu, the Tunlan, and the northern Dongqu well fields. The vertical gas units of different strata may belong to the same CBM system. The structure is simple in the southern Lijiashe fault. The vertical gas units in the southern Lijiashe fault belong to different CBM systems. Combined with the minimum thickness of the mudstone layer (2 m) and coal seam (0.5 m) standards, the spatial distribution of CBM systems was analysed.