Anisotropic characteristics of nuclear magnetic resonance of pores and fractures in coal under uniaxial loading

LU Fangchao; ZHANG Yugui; JIANG Linhua

doi:10.3969/j.issn.1001-1986.2018.01.012

Volume 46 Issue 1

Feb. 2018

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COAL GEOLOGY & EXPLORATION > 2018 > 46(1): 66-72. > DOI: 10.3969/j.issn.1001-1986.2018.01.012

LU Fangchao, ZHANG Yugui, JIANG Linhua. Anisotropic characteristics of nuclear magnetic resonance of pores and fractures in coal under uniaxial loading[J]. COAL GEOLOGY & EXPLORATION, 2018, 46(1): 66-72. DOI: 10.3969/j.issn.1001-1986.2018.01.012

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Anisotropic characteristics of nuclear magnetic resonance of pores and fractures in coal under uniaxial loading

1. College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China;
2. Institute of Coalbed Gas Geology, Henan Polytechnic University, Jiaozuo 454000, China

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National Science and Technology Major Project(2016ZX05067-006)

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Received Date: February 28, 2017
Published Date: February 24, 2018

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Abstract

In order to study the anisotropy of coal pores and fractures, further reveal the microstructure and physical characteristics of coals, coal samples were collected from Pingdingshan eighth mining area for nuclear magnetic resonance(NMR)experiments, transverse relaxation time(T₂) and magnetic mesonance imaging(MRI) under uniaxial loading were compared and analyzed. The results showed that T₂ was remarkably anisotropic:parallel to bedding and in direction X of vertical main fractures, T₂ had three peaks, parallel to bedding and direction Y of main fractures, T₂ had two peaks, vertical to direction Z of bedding T₂ had one peak. After uniaxial loading, the spectral area of T₂ and the porosity decreased, the percentage of peak area induced by porosity variation in direction X and Y declined, but the fracture areas ascended, the fracture area in direction Z declined. The MRI revealed that under uniaxial loading, most pores and fractures parallel to bedding were closed, some fractures had radial deformation, most fractures of loading direction were closed, the compaction effects was remarkable. In summary, under uniaxial loading, the anisotropic characteristics of coal samples were remarkable, and the NMR was an effective method to study microscopic changes of coal pores and fractures.
- pores and fractures,
- NMR,
- anisotropic characteristics,
- uniaxial loading,
- MRI

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