Coal Geology & Exploration


In order to reveal the characteristics of nano-scale pores in coals with different metamorphic degrees, the small-angle X-ray scattering method (SAXS) is used to obtain the porosity, pore size distribution, specific surface area and fractal dimension of 15 samples whose vitrinite reflectance Rmax is 0.31%-6.24%, and the low temperature CO2 and N2 adsorption DFT model results are used to verify the pore size distribution. The results show: during coalification process, when Rmax is < 0.5%, the porosity and the specific surface area of coal increase with the increase of metamorphic degree, the micropores(< 2 nm) content increases seldomly, the mesoporous(2-50 nm) and microporous(50-100 nm) content increase greatly, and the surface of coal is gradually smooth. When Rmax=0.5%-1.4%, the porosity and the specific surface area decrease, and each type of pore content is reduced, and the surface of coal is gradually smooth. When Rmax=1.4%-4.0%, the porosity and specific surface area of coal rock increase, the microporous content increases, and the mesoporous and microporous content are nearly stable, and the surface of the coal is gradually rough. When Rmax > 4.0%, the porosity and specific surface area of coal increase, the microporous growth is slow, and the surface of coal is gradually smooth.


metamorphic degree, small-angle X-ray scattering, nano-scale pore characteristics, fractal characteristics, coalification




[1] SAKUROVS R, DAY S, WEIR S. Relationships between the critical properties of gases and their high pressure sorption behavior on coals[J]. Energy & Fuels, 2010, 24(3): 1781–1787.

[2] HE Lilin, MELNICHENKO Y B, MASTALERZ M, et al. Pore accessibility by methane and carbon dioxide in coal as determined by neutron scattering[J]. Energy & Fuels, 2012, 26(3): 1975–1983.

[3] MELNICHENKO Y B, HE Lilin, SAKUROVS R, et al. Accessibility of pores in coal to methane and carbon dioxide[J]. Fuel, 2012, 91(1): 200–208.

[4] SAKUROVS R, HE Lilin, MELNICHENKO Y B, et al. Pore size distribution and accessible pore size distribution in bituminous coals[J]. International Journal of Coal Geology, 2012, 100: 51–64.

[5] ZHAO Yixin, PENG Lei. Investigation on the size and fractal dimension of nano-pore in coals by synchrotron small angle X-ray scattering[J]. Chinese Science Bulletin, 2017, 62(21): 2416–2427. 赵毅鑫, 彭磊. 煤纳米孔径与分形特征的同步辐射小角散射[J]. 科学通报, 2017, 62(21): 2416–2427.

[6] TANG Shuheng, CAI Chao, ZHU Baocun, et al. Control effect of coal metamorphic degree on physical properties of coal reservoirs[J]. Natural Gas Industry, 2008, 28(12): 30–33. 唐书恒, 蔡超, 朱宝存, 等. 煤变质程度对煤储层物性的控制作用[J]. 天然气工业, 2008, 28(12): 30–33.

[7] WANG Qingwei, WANG Qinwang. Migration pathway discrepancy study of CBM in coal reservoirs with different coal ranks[J]. Coal Geology of China, 2012, 24(4): 24–26. 王庆伟, 王勤旺. 不同煤阶煤层气运移通道的差异性研究[J]. 中国煤炭地质, 2012, 24(4): 24–26.

[8] CHEN Yue, TANG Dazhen, TIAN Lin, et al. Coal metamorphism controlling regulation on the development of pores and fractures in low–medium rank coal reservoirs[J]. Natural Gas Geoscience, 2017, 28(4): 611–621. 陈跃, 汤达祯, 田霖, 等. 煤变质程度对中低阶煤储层孔裂隙发育的控制作用[J]. 天然气地球科学, 2017, 28(4): 611–621.

[9] LI Xiangchun, LI Zhongbei, ZHANG Liang, et al. Pore structure characterization of various rank coals and its effect on gas desorption and diffusion[J]. Journal of China Coal Society, 2019, 44(Sup. 1): 142–156. 李祥春, 李忠备, 张良, 等. 不同煤阶煤样孔隙结构表征及其对瓦斯解吸扩散的影响[J]. 煤炭学报, 2019, 44(增刊1): 142–156.

[10] BOUSIGE C, GHIMBEU C M, VIX–GUTERL C, et al. Realistic molecular model of kerogen's nanostructure[J]. Nature Materials, 2016, 15(5): 576–582.

[11] LIU Yu, ZHU Yanming, LI Wu, et al. Ultra micropores in macromolecular structure of subbituminous coal vitrinite[J]. Fuel, 2017, 210: 298–306.

[12] CLARKSON C R, FREEMAN M, HE L, et al. Characterization of tight gas reservoir pore structure using USANS/SANS and gas adsorption analysis[J]. Fuel, 2012, 95: 371–385.

[13] LI Zhihong, WU Dong, SUN Yuhan, et al. Analytic methods applied to slit smeared intensity data of SAXS[J]. Coal Conversion, 2001, 24(1): 11–14. 李志宏, 吴东, 孙予罕, 等. 小角X射线散射模糊数据解析方法[J]. 煤炭转化, 2001, 24(1): 11–14.

[14] LI Zhihong, GONG Y J, WU D, et al. A negative deviation from Porod's law in SAXS of organo-MSU-X[J]. Microporous and Mesoporous Materials, 2001, 46: 75–80.

[15] XIE Fei, LI Zhihong, WANG Wenjia, et al. In-situ SAXS study of pore structure during carbonization of non–caking coal briquettes[J]. Fuel, 2020, 262(C): 116547.

[16] RADLINSKI A P, MASTALERZ M, HINDE A L, et al. Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal[J]. International Journal of Coal Geology, 2004, 59(3/4): 245–271.

[17] SONG Xiaoxia, TANG Yuegang, LI Wei, et al. Pore structure in tectonically deformed coals by small angle X–ray scattering[J]. Journal of China Coal Society, 2014, 39(4): 719–724. 宋晓夏, 唐跃刚, 李伟, 等. 基于小角X射线散射构造煤孔隙结构的研究[J]. 煤炭学报, 2014, 39(4): 719–724.

[18] BALE H D, SCHMIDT P W. Small-angle X-Ray-scattering investigation of submicroscopic porosity with fractal properties[J]. Physical Review Letters, 1984, 53: 596–599.

[19] REICH M H, SNOOK I K, WAGENFELD H K. A fractal interpretation of the effect of drying on the pore structure of Victorian brown coal[J]. Fuel, 1992, 71(6): 669–672.

[20] NIE Baisheng, WANG Kedi, FAN Yu, et al. The comparative study on calculation of coal pore characteristics of different pore shapes based SAXS[J]. Journal of Mining Science and Technology, 2020, 5(3): 284–290. 聂百胜, 王科迪, 樊堉, 等. 基于小角X射线散射技术计算不同孔形的煤孔隙特征比较研究[J]. 矿业科学学报, 2020, 5(3): 284–290.

[21] LI Yang, ZHANG Yugui, ZHANG Lang, et al. Characterization on pore structure of tectonic coals based on the method of mercury intrusion, carbon dioxide adsorption and nitrogen adsorption[J]. Journal of China Coal Society, 2019, 44(4): 1188–1196. 李阳, 张玉贵, 张浪, 等. 基于压汞、低温N2吸附和CO2吸附的构造煤孔隙结构表征[J]. 煤炭学报, 2019, 44(4): 1188–1196.

[22] PRINZ D, LITTKE R. Development of the micro–and ultra–microporous structure of coals with rank as deduced from the accessibility to water[J]. Fuel, 2005, 84(12/13): 1645–1652.

[23] MATTHIAS T, KATSUMI K, ALEXANDER V, et al. Physisorption of gases with special reference to the evaluation of surface area and pore size[R]. IUPAC Technical Report, 2015, 87(9/10): 1051–1069.

[24] LIU Yang, YAO Suping, TANG Zhongyi. Characterization of nanopore of different metamorphic coals by SAXS[J]. Geological Journal of China Universities, 2019, 25(1): 108–115. 刘阳, 姚素平, 汤中一. 利用SAXS表征不同变质程度煤纳米孔隙特征[J]. 高校地质学报, 2019, 25(1): 108–115.

[25] ZHANG Hui. Genetical type of proes in coal reservoir and its research significance[J]. Journal of China Coal Society, 2001, 26(1): 40–44. 张慧. 煤孔隙的成因类型及其研究[J]. 煤炭学报, 2001, 26(1): 40–44.

[26] YAN Wenying, SHI Chenglong. On the gelatification and fusinitization of the brown coal in Luoci Basin[J]. Journal of Xi'an Mining Institute, 1987, 4(3): 11–18. 阎文英, 石呈龙. 论罗茨盆地褐煤的凝胶化作用和丝炭化作用[J]. 西安矿业学院学报, 1987, 4(3): 11–18.

[27] TANG Yuegang, WANG Jie. A new index of lignite maturity: Gel rate[J]. Coal Geology & Exploration, 1990, 18(4): 25–28. 唐跃刚, 王洁. 反映褐煤成熟度的新指标: 凝胶率[J]. 煤田地质与勘探, 1990, 18(4): 25–28.

[28] LI Wu, ZHU Yanming. Structural characteristics of coal vitrinite during pyrolysis[J]. Energy & Fuels, 2014, 28(6): 3645–3654.

[29] LIU Yu, ZHU Yanming, LIU Shimin, et al. Molecular structure controls on micropore evolution in coal vitrinite during coalification[J]. International Journal of Coal Geology, 2018, 199: 19–30.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.