Comparative experimental study on porosity, mechanical and CO<sub>2</sub> adsorption characteristics of coal and shale

doi:10.1007/s11707-022-1059-1

Front. Earth Sci.

2023, Vol. 17

Issue (3) : 788-796 https://doi.org/10.1007/s11707-022-1059-1

RESEARCH ARTICLE

Comparative experimental study on porosity, mechanical and CO₂ adsorption characteristics of coal and shale

Haitao LI¹, Guo YU², Xiaolei WANG³(

), Dongming ZHANG^3,⁴

¹. Exploration and Development Research Institute of PetroChina, Southwest Oil and Gas Field Company, Chengdu 610051, China
². PetroChina Southwest Oil and Gas Field Company Planning Department, Chengdu 610051, China
³. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
⁴. School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China

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Abstract

To compare the pore structure, mechanical and CO₂ adsorption properties of coal and shale, a series of experiments were carried out using nuclear magnetic resonance (NMR), uniaxial compression, Brazilian splitting, and high-pressure CO₂ adsorption. The results show that the total porosity of coal is 7.51 times that of shale, and shale is dominated by adsorption pores, while adsorption pores and seepage pores in coal are equally important. Moreover, it is found that the micropores in shale are more advantageous, while meso-macropore in coal are more significant. The adsorption pore surface of coal is rougher than that of shale, and the seepage pore structure of shale is more complex. The uniaxial compressive strength, elastic modulus and absorption energy of shale are 2.01 times, 2.85 times, and 1.27 times that of coal, respectively, indicating that shale has higher compressive capacity and resistance to elastic deformation than coal. The average tensile strength, Brazilian splitting modulus, absorbed energy and brittleness index of shale are 7.92 times, 6.68 times, 10.78 times, and 4.37 times that of coal, respectively, indicating that shale has higher tensile strength and brittleness, but lower ductility, compared with coal. The performed analyses show that under the same conditions, the CO₂ adsorption capacity of coal is greater than that of shale. The present article can provide a theoretical basis to implement CO₂-enhanced coalbed methane (CBM)/shale gas extraction.

Keywords coal shale NMR mechanical properties adsorption characteristic

Corresponding Author(s): Xiaolei WANG

Online First Date: 03 August 2023 Issue Date: 12 December 2023

Cite this article:

Haitao LI,Guo YU,Xiaolei WANG, et al. Comparative experimental study on porosity, mechanical and CO₂ adsorption characteristics of coal and shale[J]. Front. Earth Sci., 2023, 17(3): 788-796.

URL:

https://academic.hep.com.cn/fesci/EN/10.1007/s11707-022-1059-1
https://academic.hep.com.cn/fesci/EN/Y2023/V17/I3/788

Fig.1 Experimental sample.

Tab.1 Mineral composition of shale and coal (%)

Fig.2 Equipment of high-pressure gas adsorption with volumetric method.

Fig.3 Nuclear magnetic T₂ spectrum of coal and shale.

Fig.4 Nuclear magnetic pore size distribution of coal and shale.

Fig.5 Porosity ratio of coal and shale.

Fig.6 Fractal dimension of coal and shale.

Fig.7 Uniaxial compression curve of coal and shale.

Tab.2 Difference of uniaxial compression parameters of coal and shale

Fig.8 Brazil splitting curve of coal and shale.

Tab.3 Differences of Brazil splitting parameters between coal and shale

Fig.9 CO₂ adsorption isotherms of coal and shale.

Tab.4 Langmuir parameters of CO₂ adsorption isotherms of coal and shale

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