Characteristics and influence factors of pore structure of coal reservoirs in the eastern margin of Ordos basin

Based on the coal reservoir in eastern margin of Ordos basin, by vitrinite reflectance measurement and pressure mercury testing and cryogenic liquid nitrogen adsorption experiment, the characteristics and influence factors of pore structure were discussed and analyzed. The results show: the porosity of coal reservoir in the study area is low, and the trend of the north to south is obviously lower. The coal reservoir is mainly based on the transitional pores and micro pores. BET of coal reservoir is 1.26 m²/g, larger in the north. Due to the influence of the relative content of inertinite, the degree of compression and secondary pore, BJH of coal reservoir is 0.003 41 mL/g. With the increase of coal metamorphism, the porosity, BJH and BET of coal rank had a trend of “high-low-high”, and attained the minimal value when R_max was 1.5%. With the increase of stress of coal reservoir, the micro pores were closed, and the number of other types of pores was reduced, and the content of transitional pores increased relatively. In coal, the pore types of the adsorption changed from the closed type to open type. The stress acting on the development of coal had strong control effect, which is mainly reflected in the contribution of the large pores to CBM.