The influence of closed pores on the gas transport and its application in coal mine gas extraction

Si, Leilei; Li, Zenghua; Kizil, Mehmet S.; Chen, Zhongwei; Yang, Yongliang; Ji, Songtao

doi:10.1016/j.fuel.2019.06.013

Cited by 30 publications

(3 citation statements)

References 54 publications

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“…It has several advantages, including reducing gas emissions during mining, preventing gas from building up and beyond safe limits, preventing gas explosions, and putting an end to coal and gas outburst accidents. Furthermore, it can convert waste into a protective resource and make use of gas as a valuable coal-related resource [4][5][6][7]. The progress made by China in gas extraction technology has many benefits, including environmental protection, efficient resource utilization, and safe production.…”

Section: Introductionmentioning

confidence: 99%

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Wang,

Li,

Liu

et al. 2024

Advances in Civil Engineering

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Gas extraction is a major technique for regional gas regulation and coal and gas comining in China. Assuring effective gas extraction operations is a crucial step in ensuring the supply of energy. The effect range of extraction drilling, pressure relief degree, and standard period of gas extraction are all constrained because of the geological constraints affecting coal gas permeability and occurrence. Combined with the advantages of directional drilling and high-efficiency pumping technology and antireflection enhanced pumping technology of hydraulic fracturing, directional long-drilling hydraulic fracturing can effectively improve the efficiency of gas control and expand the scale of gas control. The present study focuses on the exploration of directional long-hole hydraulic fracturing technique in thick coal seams with high gas content using Dafosi Mine as a case study. The research findings demonstrate that hydraulic fracturing contributes to the enlargement of pore size, pore density, and pore connectivity in coal seams. In-depth research was conducted on the expansion of coal seam fractures during the hydraulic fracturing process using the RFPA3D-flow numerical simulation program. Additionally, a comprehensive analysis of stress distribution around the fractures under the flow-solid coupling condition was performed. To further improve the effectiveness of hydraulic fracturing technique, the research team optimized the fracturing tools and construction processes in the four coal seams of Dafosi Mine. The impact of segmented hydraulic fracturing in coal seam bare hole drilling was also studied. Furthermore, an investigation method specific to the coal seam bare hole segmented hydraulic fracturing effects applicable to Dafosi Mine was developed. The maximum fracture extension pressure, minimum fracture closure pressure, and fracture morphology change characteristics during drilling and fracturing were measured, and the fracturing influence radius of coal seam was determined to be 46−58 m, the gas extraction concentration after fracturing increased by 2.20–4.22 times, and the 100-m extraction flow increased by 4.93–11.03 times. It gives other mines technical assistance so they can keep advocating and utilizing the horizontal directional long-drilling stage hydraulic fracturing technique.

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Section: Introductionmentioning

confidence: 99%

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Wang,

Li,

Liu

et al. 2024

Advances in Civil Engineering

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“…The pore structure plays a crucial role in various fields such as coal mining, gas extraction, and hazard prediction [5][6][7]. The size and connectivity of pores directly impact the permeability and extraction rate of gas [8].…”

Section: Introductionmentioning

confidence: 99%

Joint Characterization and Fractal Laws of Pore Structure in Low-Rank Coal

Zhou

Bai

et al. 2023

Sustainability

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The pore structure of low-rank coal reservoirs was highly complex. It was the basis for predicting the gas occurrence and outburst disasters. Different scale pores have different effects on adsorption–desorption, diffusion, and seepage in coalbed methane. To study the pore structure distribution characteristics, which are in different scales of low-rank coal with different metamorphism grade, the pore structure parameters of low-rank coal were obtained by using the mercury injection, N2 adsorption, and CO2 adsorption. These three methods were used to test the pore volume and specific surface area of low-rank coal in their test ranges. Then, the fractal dimension method was used to calculate the fractal characteristics of the pore structure of full aperture section to quantify the complexity of the pore structure. The experimental results showed that the pore volume and specific surface area of low-rank coal were mainly controlled by microporous. The pore fractal characteristics were obvious. With the influence of coalification process, as the degree of coal metamorphism increases, fluctuations in the comprehensive fractal dimension, specific surface area, and pore volume of the pore size range occur within the range of Rmax = 0.50% to 0.65%.

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“…Beyond the pore geometry, closed pores play a pivotal role in the process of gas seeping and transporting. , As well known, the closed porosity can impact the coal’s reservoir nature. , The porosity is usually over 60% and even >80% for anthracite . While these pores are not connected with other pores, the gas can still diffuse to the neighboring pores via an intermolecular pore.…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Diffusion Behavior of CH₄ and CO₂ in Closed and Open Pores from Zhaozhuang Coal

Yang

et al. 2022

Energy Fuels

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The adsorption and diffusion properties of CH4, CO2, and H2O in a realistic coal molecule are essential to the study of carbon capture, utilization, and storage (CCUS). The molecular dynamics (MD) simulations and grand canonical Monte Carlo (GCMC) methods were used to investigate the adsorption, diffusion, and relative concentration of gases on the different styles of geometrical pores in closed and open pores under different moisture contents. The results showed that the amount of adsorption in the cylindrical pore was higher than that in the spherical pore. The closed-cylindrical pore had a stronger gas adsorption capacity. Under the same conditions, the diffusion coefficients of gases in the open pores were larger than in closed pores. Methane has a higher diffusion coefficient than CO2. The presence of water reduced the diffusion coefficients of the gases. In the meantime, the gap between the CH4 and CO2 diffusion coefficients gradually decreased as the water content increased. The water molecules occupied the surface and space of pores, leading to reduction in the adsorption capacity. Due to the increasing amount of water, the diffusion coefficient of CH4 and CO2 decreases due to enhanced interactions between C and the gases according to the radial distribution function (RDF).

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The influence of closed pores on the gas transport and its application in coal mine gas extraction

Cited by 30 publications

References 54 publications

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Joint Characterization and Fractal Laws of Pore Structure in Low-Rank Coal

Adsorption and Diffusion Behavior of CH₄ and CO₂ in Closed and Open Pores from Zhaozhuang Coal

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The influence of closed pores on the gas transport and its application in coal mine gas extraction

Cited by 30 publications

References 54 publications

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Research on Hydraulic Fracturing Technology of Long Boreholes along Strata of High Vast Thick Coal Seam

Joint Characterization and Fractal Laws of Pore Structure in Low-Rank Coal

Adsorption and Diffusion Behavior of CH4 and CO2 in Closed and Open Pores from Zhaozhuang Coal

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Product

Resources

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Adsorption and Diffusion Behavior of CH₄ and CO₂ in Closed and Open Pores from Zhaozhuang Coal