Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

Pan, Jienan; Zhao, Yanqing; Hou, Quanlin; Jin, Yi

doi:10.1007/s11242-015-0453-5

Cited by 84 publications

(44 citation statements)

References 21 publications

(37 reference statements)

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“…The reason could be the differences of the pore structure and wettability of coal. The pore structure (including volume, specific surface area, and pore connectivity) relates to coal ranks [31,48,49]. The rank of coal used in this study differs from that in our previous work.…”

Section: T 2 Distribution Of Coalmentioning

confidence: 94%

Variable Pore Structure and Gas Permeability of Coal Cores after Microwave Irradiation

et al. 2018

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The experimental work in this paper investigated the effect of microwave energy on pore structure and gas permeability of coal cores. Fifteen coal samples were irradiated under the condition of 2.45 GHz with 6 kW. The effect of microwave irradiation on the pore structure of coal samples was evaluated by nuclear magnetic resonance (NMR). The water saturation degree has little influence on transverse relaxation time (T2) distribution before the microwave treatment. By contrast, water saturation degree obviously affects the T2 distribution after the microwave energy treatment. Coal permeability increased after microwave energy treatment. But fractal dimension decreased after microwave energy treatment. The results show that microwave energy has a potential for degassing coal seams.

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Section: T 2 Distribution Of Coalmentioning

confidence: 94%

Variable Pore Structure and Gas Permeability of Coal Cores after Microwave Irradiation

et al. 2018

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“…The rank in Ôcoal rankÕ refers to the steps in a natural and slow process called ÔcoalificationÕ during the plant matter changes into the material which are denser, harder and more carbon-rich, including an-thracite, bituminous, sub-bituminous, lignite and peat (Keshavarz et al 2017;Pan et al 2015;Shi et al 2018). Samples of different coal ranks were selected in this study as follows: a Quaternary peat from Glastonbury, England, to assess the physical characteristics prior to coalification; Paleocene low-rank lignite from North Dakota, USA; Triassic sub-bituminous coal from Pingdingshan, Henan, China; Carboniferous medium-rank bituminous coal from Morgantown, West Virginia, USA; and a Carboniferous high-rank anthracite from Hazelton, Pennsylvania, USA.…”

Section: Methodology Samples and Sample Preparationmentioning

confidence: 99%

Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

et al. 2019

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Characterization of coal micro-structure and the associated rock mechanical properties are of key importance for coal seam exploration, coal bed methane development, enhanced coal bed methane production and CO 2 storage in deep coal seams. Considerable knowledge exists about coal chemical properties, but less is known about the nanoscale to the microscale structure of coals and how they change with coal strength across coal ranks. Thus, in this study, 3D X-ray micro-computed tomography (with a voxel size of 3.43 lm) and nanoindentation tests were conducted on coal samples of different ranks from peat to anthracite. The micro-structure of peats showed a well-developed pore system with meso-and micropores. The meso-pores essentially disappear with increasing rank, whereas the micro-pores persist and then increase past the bituminous rank. The micro-fracture system develops past the peat stage and by sub-bituminous ranks and changes into larger and mature fracture systems at higher ranks. The nano-indentation modulus showed the increasing trend from low-to high-rank coal with a perfect linear relationship with vitrinite reflectance and is highly correlated with carbon content as expected.

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“…At the time of the folds’ formation, interbed shearing and concentration of local stress, caused by the gangue, led to coal damage and brittle and ductile deformation. The organic composition and micro–nano pore structures of the coal rock were altered to varying degrees; the stronger the degree of deformation, the more significant the change to the nano structure (Bu et al., 2015; Ju and Li, 2009; Pan et al., 2015). Different degrees of deformation can lead to different characteristics in terms of fracture development, total pore volume, and the gas adsorption capacity of coal and rock, influencing their gas content and permeability (Ju et al., 2009; Majewska and Ziętek, 2007; Pan et al., 2012).…”

Section: Shear Deformation Of Fold Structures and Coal-gas Outburstsmentioning

confidence: 99%

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

Jia

Feng

Wei

et al. 2017

Energy Exploration & Exploitation

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The coal measure strata formed in the late Paleozoic era underwent tectonic movements on several occasions, leading to the development of a range of fold structures in the strata as a result of highly interlayered gliding and shearing deformation. In addition, brittle ductile tectonic coals were widely distributed in the reservoir, constituting one of the primary causes of coal-gas outbursts in Chinese mines. This indicates a strong connection between shear deformation and such outbursts. In this study, structural geology, gas geology, and rock mechanics are all taken into consideration to investigate the controlling effects of the fold structure formation process on coal thickness and tectonic coal formation. Numerical simulation, based on the stress test data, was deployed to identify the stress distribution law adjacent to fold structures under the modern stress field. Additionally, the mechanical mechanism underpinning coal-gas outbursts near the fold structure was determined by making a comparison with the distribution law relating to such outbursts. The results demonstrate that the formation and evolution of the fold structure not only form the material basis of outbursts but also control their power source. During the fold formation process, interbed sliding and shearing between strong and weak rock strata were caused by differences in the mechanical properties of the coal bed and rock layer, resulting not only in a change to the local thickness of the coal seam but also in its deformation and structural alteration. Interbed shearing and local stress concentration, caused by the coal gangue, led to coal damage and the development of layered tectonic coal of consistent thickness, simultaneously improving its ability to adsorb gas and providing the material basis for coal-gas outbursts. This reduced the seam's capacity to resist such events. The conditions for these outbursts are created 1 State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University), Jiaozuo, P.R. China 2 Institute of Gas Geology, Henan Polytechnic University, Jiaozuo, P.R. by the sudden desorption of excess gas as a result of formation pressure release during coal mining and the widespread distribution of tectonic coal. Under the modern tectonic stress field, the stress distribution characteristic is controlled by the fold structure shape; and because of the aforementioned differences in the mechanical properties of the coal bed and rock layer, the interlayer deformation is asynchronous. This causes shear stress concentration within a specific range of the anticline's two wings. This concentration zone happens to be exactly aligned with that of coal-gas outbursts, meaning that shear stress concentration is considered to be both the power source for and main cause of the region's outbursts.

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Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

Cited by 84 publications

References 21 publications

Variable Pore Structure and Gas Permeability of Coal Cores after Microwave Irradiation

Variable Pore Structure and Gas Permeability of Coal Cores after Microwave Irradiation

Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

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