Abstract Middle-rank coal mainly refers to bituminous coal with the vitrinite maximum reflectance (Ro,max) between 0.65% and 2.0%. Based on the results of a proximate analysis, maceral composition, high-pressure mercury intrusion porosimetry (MIP) experiments and isothermal adsorption experiments, combined with gas content and permeability derived from well test, the pore size distribution (PSD), adsorption characteristics and the evolutionary paths of middle-rank coal were analyzed, and the influencing factors of the gas-bearing property and permeability were discussed. The results indicated that as Ro,max increases, the porosity shows first decreasing and then increasing, with the minimum values reached when Ro,max = ∼1.0%. The volume and specific surface area of the total pores have the same evolutionary paths with each class of pores, first decreasing and then increasing with the increases of Ro,max. The minimum value appears when Ro,max is between 1.2% and 1.3%. As Ro,max increases, VL increases while PL first increases and then decreases, the maximum value is again reached at near Ro,max = 1.3%. The gas content increases with the increases of Ro,max, first increasing and then decreasing with the increases of buried depth, and the buried depth at 950 m is the critical depth of gas content. There is a positive correlation between gas content and gas saturation; the permeability decreases with the increases of buried depth, and increases with the increases of coal reservoir porosity. Ground stress is the main controlling factor of reservoir permeability.

中文翻译：

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我国中煤储层物性及影响因素分析

摘要 中阶煤主要指镜质体最大反射率(Ro,max)在0.65%～2.0%之间的烟煤。基于近似分析、微晶成分、高压压汞孔隙度（MIP）实验和等温吸附实验的结果，结合试井得到的含气量和渗透率、孔径分布（PSD）、吸附特征和分析了中阶煤的演化路径，探讨了含气性和渗透率的影响因素。结果表明，随着 Ro,max 的增加，孔隙率呈现先减小后增大的趋势，当 Ro,max = ～1.0% 时达到最小值。总孔隙的体积和比表面积与每一类孔隙具有相同的演化路径，随着 Ro,max 的增大先减小后增大。当 Ro,max 介于 1.2% 和 1.3% 之间时，会出现最小值。随着 Ro,max 增加，VL 增加，而 PL 先增加然后减小，在 Ro,max = 1.3% 附近再次达到最大值。含气量随着Ro,max的增加而增加，随着埋深的增加先增加后减小，950 m处的埋深为含气量的临界深度。含气量与含气饱和度呈正相关；渗透率随着埋深的增加而降低，随着煤储层孔隙度的增加而增加。地应力是储层渗透率的主要控制因素。随着 Ro,max 增加，VL 增加，而 PL 先增加然后减小，在 Ro,max = 1.3% 附近再次达到最大值。含气量随着Ro,max的增加而增加，随着埋深的增加先增加后减小，950 m处的埋深为含气量的临界深度。含气量与含气饱和度呈正相关；渗透率随着埋深的增加而降低，随着煤储层孔隙度的增加而增加。地应力是储层渗透率的主要控制因素。随着 Ro,max 增加，VL 增加，而 PL 先增加然后减小，在 Ro,max = 1.3% 附近再次达到最大值。含气量随着Ro,max的增加而增加，随着埋深的增加先增加后减小，950 m处的埋深为含气量的临界深度。含气量与含气饱和度呈正相关；渗透率随着埋深的增加而降低，随着煤储层孔隙度的增加而增加。地应力是储层渗透率的主要控制因素。随着埋深的增加先增大后减小，950 m处的埋深为含气量临界深度。含气量与含气饱和度呈正相关；渗透率随着埋深的增加而降低，随着煤储层孔隙度的增加而增加。地应力是储层渗透率的主要控制因素。随着埋深的增加先增大后减小，950 m处的埋深为含气量临界深度。含气量与含气饱和度呈正相关；渗透率随着埋深的增加而降低，随着煤储层孔隙度的增加而增加。地应力是储层渗透率的主要控制因素。