The influence of long-time water intrusion on the mineral and pore structure of coal

Si, Leilei; Wei, Jianping; Xi, Yujun; Wang, Hongyang; Wen, Zhihui; Li, Bo; Zhang, Hongtu

doi:10.1016/j.fuel.2020.119848

Cited by 119 publications

(38 citation statements)

References 21 publications

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“…Among them, micropores, also referred to as adsorption pores, are the main space for gas adsorption. The commonly used methods to measure the pore structure characteristics of coal include high-pressure mercury injection, nuclear magnetic resonance, micro CT, low-temperature nitrogen adsorption, and transmission electron microscope [14][15][16][17][18][19][20]. Due to the limitations of different measurement methods, the pore structure of coal can hardly be accurately characterized with a single method [21].…”

Section: Introductionmentioning

confidence: 99%

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

et al. 2021

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In this study, the full-size pore structure characteristics of six different-rank coal samples were investigated and analyzed from three perspectives, namely, pore shape, pore volume, and pore specific surface area, by performing a high-pressure mercury injection experiment and a low-temperature nitrogen adsorption experiment. Next, the full-size pore volumes and pore specific surface areas of the six coal samples were accurately characterized through a combination of the two experiments. Furthermore, the relationships between volatile matter content and pore volume and between volatile matter content and pore specific surface area were fitted and analyzed. Finally, the influences of metamorphic degree on pore structure were discussed. The following conclusions were obtained. The pore shapes of different-rank coal samples differ significantly. With the increase of metamorphic degree, the full-size pore volume and pore specific surface area both decrease first and then increase. Among the pores with various sizes, micropores are the largest contributor to the full-size pore volume and pore specific surface area. The fitting curves between volatile matter content and pore volume and between volatile matter content and pore specific surface area can well reflect the influence and control of metamorphic degree on pore volume and pore specific surface area, respectively. With the increase of volatile matter content, the pore volume and the pore specific surface area both vary in a trend resembling a reverse parabola.

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Section: Introductionmentioning

confidence: 99%

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

et al. 2021

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“…Two types of gas flow in coal seams have been identified including the diffusion flow and the laminar flow targeting different types of coal seams [3][4][5]. Generally speaking, in the coal seam with a microporous structure or low permeability, the diffusion flow plays a critical role while in the coal seam with microporous structure or high permeability, the laminar flow dominates [6][7][8]. In this study, the gas flow in the process of drainage is treated as laminar flow, following Darcy's law.…”

Section: Gas Solid Coupling Analysis Of Coal Seammentioning

confidence: 99%

A Case Study on the Gas Drainage Optimization Based on the Effective Borehole Spacing in Sima Coal Mine

Sun

2021

Geofluids

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Based on the dynamic expressions of permeability and porosity of the coal seam derived in the paper, a multiphysical field coupling numerical model of gas migration under the interaction of stress field and seepage field was established. The gas drainage project #3 Coal Seam operated by Sima Coal Industry Co., Ltd., was selected as the study object. Taking different drainage time periods in various positions of drainage holes into consideration, combined with the advance situation of the 1207 working face in the Sima Coal Mine, a mixed layout gas drainage scheme featured with the effective borehole spacing was obtained through the COMSOL multiphysics simulation. In addition, a series of field industrial tests were performed to validate the research result, revealing that comprehensively considering the extraction time of coal and optimizing the layout of extraction boreholes can effectively improve the engineering economic benefits.

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“…Based on the LN2GA data, the fractal dimension can be determined by the fractal Frenkel-Halsey-Hill (FHH) equation (Ni et al 2020;Si et al 2021;Liu and Nie 2016). It can be described by the following expression:…”

Section: Fractal Characteristics Of Coal Pores Under Moist Conditionmentioning

confidence: 99%

Experimental Study on Pore Structure and Gas Desorption Characteristics of a Low Rank Coal: Impact of Moisture

Yang

Chen

Tian

et al. 2021

Preprint

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Coal and gas outburst is one of the most serious disasters for underground coal mining. The water adsorbed on coal can leads to that the pore structure of moist coal is different from that of dry coal, thereby affecting methane desorption characteristics of coal for the outburst risk prediction. In this paper, the impact of moisture on pore structure and methane desorption performance were investigated. The analysis on low-temperature nitrogen gas adsorption tests show that the micropores (pore diameter < 10 nm) are most affected by the adsorbed water. In particular, for water-equilibrated coal sample at 98% relatively humidity, the micropores less than 4 nm analyzed by DFT pore size distributions almost disappear probably due to the blocking effect of the formed water clusters and capillary water. In this case, the micropores can still contributes most sites for gas adsorption. Furthermore, the fractal dimension at relative pressure of 0–0.5 (D1) and 0.5–1 (D2) calculated by the Frenkel-Halsey-Hill model indicates that, when moisture content is less than 4.74%, D1 decreases rapidly while D2 shows a slight change; whereas, further increases in moisture content results in that D2 decreases significantly and D1 remains at about 2.32. Further investigation shows that, below the equilibrium moisture content, the ultimate desorption volume (A) and initial desorption rate (V0) are closely related to D1, while the desorption constant (Kt) mainly depends on D2. Therefore, the adsorbed moisture has significant negative impact on methane desorption performances by affecting characteristics of coal’s pores.

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The influence of long-time water intrusion on the mineral and pore structure of coal

Cited by 119 publications

References 21 publications

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

A Case Study on the Gas Drainage Optimization Based on the Effective Borehole Spacing in Sima Coal Mine

Experimental Study on Pore Structure and Gas Desorption Characteristics of a Low Rank Coal: Impact of Moisture

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