Characteristics of High Rank Coalbed Methane Reservoir from the Xiangning Mining Area, Eastern Ordos Basin, China

Abstract

For the purpose of better estimating the CBM resource potential in the study area, the high rank CBM reservoirs were studied by geological surveys and laboratory measurements in Xiangning mining area, eastern Ordos Basin. Geological characteristics of coals in the Xiangning mining area provide favourable conditions for the development of CBM reservoirs. Coal seams are dominated by semibright coal, which are all low volatile anthracite coal with Rmax ranging from 2.22 to 2.50%. No. 2, 3 and 10 coal seams are vitrinite–rich (81.2%, averagely) and low to middle ash yield coals (16.86–21.49%, averagely). The permeability values of coal reservoirs range form 0.0067 to 0.268 mD, and the porosity is from 2.82 to 4.14% in the study area. Microfractures are mainly tensile structure, pores of coals are dominated by macropores, mesopores came next to it followed by micropores, and the great majority of induced porosity is stomas in the study area. No. 2, 3 and 10 CBM reservoirs are characterized by higher gas capacities (26.08 to 27.27 m3/t, VL). The gas content of CBM reservoirs has a positive correlation with the burial depth.