Abstract
The microscopic pore structure of coal affects the content of adsorbed gas. The microstructure of coal sample before and after loading is different, which will affect the adsorption and permeability of coal seam gas. In order to study this difference, the authors carried out mercury intrusion experiments on coal containing different coal samples and used nondestructive nuclear magnetic resonance (NMR) techniques, scanning electron microscopy, and transmission electron microscopy, to study the microstructure of coal samples before and after loading. The experimental results show that the pores of coal samples are mainly micropores and small pores, and the mesopores and macropores are relatively few. The T2 spectrum area of the coal sample is significantly increased after loading, and the parallel-layer coal samples’ T2 spectrum area is 46735, which is 9112 more than the vertical layer coal samples. The T2 spectrum of the vertical coalbed of saturated water samples shows a three-peak shape, the peak of the T2 spectrum is 12692, and the parallel bedding shows a bimodal morphology. The peak area of the T2 spectrum is 11277. The permeability of the parallel bedding coal sample is good, and the coal sample exhibits anisotropic properties. The pores and cracks of the coal samples increased after loading, and the localized area of the coal sample collapsed and formed a fracture zone, which was not conducive to the occurrence of coal seam gas. Further explanation of the changes in the permeability of the coal sample before and after loading will affect the gas storage and transportation.
Highlights
Mine gas disasters have always been a problem that plagues the safe production of the coal industry
In the process of coal mining, the coal seam is affected by the coal mining machine, hydraulic fracturing, and other mining disturbances. e original equilibrium state of the coal seam is broken, the microstructure of the coal body changes, and the gas continuously desorbs from the coal and causes the coal to flow out, which leads to gas outburst accidents
Direct observations have been made by scanning electron microscopy and transmission electron microscopy. e most commonly used qualitative analysis method is scanning electron microscopy [3, 4]. e mechanical behavior of coal samples after different pressurization and unloading modes [5,6,7,8] hydraulic fracturing can increase the permeability of coal seams by injecting high pressure into the cracks [9]
Summary
Mine gas disasters have always been a problem that plagues the safe production of the coal industry. E mesostructure experiment of the permeability change caused by the coal sample after loading: CT scanning, infrared spectroscopy, etc., in which the scholar [30] studied the CT scan of the test piece before and after the coal penetration test under the full stress-strain condition and found that the through crack occurred. It was produced after the infiltration experiment. Erefore, the author uses the nondestructive nuclear magnetic resonance (NMR) technology, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to study the microstructure changes before and after the loading of the coal body and the relationship between the change and the permeability and the effective porosity, in order to grasp the coal microstructure change before and after the loading of the coal body and the impact of the gas storage and transportation
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