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Abstract Coalbed methane was an important unconventional geological resource. There were abundant coalbed methane resources in the western margin of Ordos Basin, among which Weisan mine field in the central and southern part of Weizhou mining area was a typical representative. The mine field was located in the north-south fold thrust belt of Qinglongshan-Yunwushan in the western margin of Ordos. It was affected by the compression in the east-west direction as the main stress, and was generally located in the synclinal structure. Coal seams were widely developed in the mine field due to the influence of regional sedimentary metamorphism. The coal-bearing strata were Carboniferous-Permian Taiyuan Formation and Permian Shanxi Formation. In this paper, the contour maps of each coal seam of Taiyuan Formation and Shanxi Formation ( including cumulative thickness, coal ash content, gas content and coalbed methane content ) were provided. The accumulation law, coal seam chemical properties and coalbed methane origin characteristics of the well fieldwere analyzed in detail, and the exploration and development potential of the well field was discussed. The coal-bearing strata of Taiyuan Formation and Shanxi Formation were a set of thick marine-continental alternating coal-bearing clastic deposits, and their coal-forming environments were offshore delta plain swamps and bay lagoon swamps. Among them, the average thickness of the mineable coal seam of the Taiyuan Formation was 13.21 m, the mineable coal content coefficient was 2.41 %, most of the mineable coal seams were No.12, No.15, No.17 and No.20 coal seams, and the local mineable coal seams were No.10 and No.14 coal seams ;the average thickness of the coal-bearing strata in the Shanxi Formation was 125 m, the numbered coal seam was 4 layers, the average cumulative thickness of the coal seam was 8.92 m, the coal-bearing coefficient was 7.13 %, and the 4 coal seams that could be mined were No.0, No.2, No.3 and No.4 coal seams. The average yield of float coal ash in each mineable coal seam of Weisan mine field was 6.30 % -15.04 %, the total average was 9.06 %, and the average deashing rate was 60.81 % -70.11 %. The average recovery rate of floating coal was 9.53 % ~ 37.52 %, and the total average value was 27.93 %. Coal seam gas composition was mostly N2, composition of 7.44 % ~ 98.99 % ; cH4 accounted for 0 ~ 87.12 %. CO2 accounts for 0.50 % ~ 12.92 % ; heavy hydrocarbon composition was less than 1 %. The occurrence of coalbed methane in the Shanxi Formation was relatively small, while the No.0,1,2,3,4 and 10 coals of the Taiyuan Formation were poor gas areas, most of the No.12,15,17 and 20 coals were low gas areas, and local areas were medium gas areas.
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