Experimental Ivestigation of the Temperature and Pore Pressure Effect on Permeability of Lignite Under the In Situ Condition

Niu, Shiwei; Zhao, Yangsheng; Hu, Yue

doi:10.1007/s11242-013-0236-9

Cited by 73 publications

(33 citation statements)

References 15 publications

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“…As shown in current work and supported by several previous studies e.g., [9][10][11][12][13][14][15]23], gas flow behavior in coal is governed by both temperature and effective stress. Consequently, permeability field beyond the gasification zone would be anisotropic.…”

Section: Implications For Ucg and Future Experimentssupporting

confidence: 88%

“…Fluctuations of coal permeability with temperature and σ 3 were reported by other researchers [19,20,22,23,25]. The general trend of permeability with temperature was ascending in those works.…”

Section: A Conceptual Model For Permeability Evolution Versus Thermalsupporting

confidence: 57%

“…Especially at ultra-high temperatures such as 500 °C or 600 °C, significant increase in permeability was observed. Nonetheless, at lower temperatures such as 100 °C or 200 °C, fluctuations in permeability were noted [23,25]. Based on our experimental results, a conceptual model was inferred for N2-permeability versus thermal deformation of the Alberta coal, which is depicted in Figure 17.…”

Section: A Conceptual Model For Permeability Evolution Versus Thermalmentioning

confidence: 81%

“…Several other researchers also conducted permeability test with one end open to the atmosphere e.g., [15,23]. The majority of permeability measurements were conducted in a constant pressure mode, where a constant differential pressure was maintained between top and bottom of the specimen.…”

Section: Permeability To Gasmentioning

confidence: 99%

“…The intention here was to quantify differences between the various methods to compute the stress-strain curves. It would provide some insights on the importance of measuring deformation during a HT test on coal which were not quantified by some other researchers [22][23][24][25].…”

Section: Stress-strain and Deformation Characteristics During Shear Amentioning

confidence: 99%

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Influence of High Pressure and Temperature on the Mechanical Behavior and Permeability of a Fractured Coal

Kasani

Chalaturnyk

2017

Energies

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Understanding mechanical behavior and permeability of coal at ambient and high temperature is key in optimizing high-temperature in-situ processes such as underground coal gasification. The main objectives of this study were to characterize thermal deformation, stress-strain behavior, and gas permeability of coal samples acquired from the Genesee coal mine in Central Alberta, Canada under various temperatures and confining stresses. These measurements were conducted in a high-pressure high-temperature triaxial apparatus. Initial thermal expansion of the coal was followed by contraction in both axial and lateral directions at about 140 • C. This temperature corresponds to occurrence of pyrolysis in the coal. All specimens showed brittle behavior during shear while forming complex shear planes. The specimens exhibited compressional volumetric strain responses at all temperatures. Deformation localization initiated at various stage during shearing. Specimens sheared at 200 • C showed higher peak stresses and larger axial strains compared to those tested at room temperature (24 • C). Fluctuations of permeability were observed with confining stress and temperature. Permeability dropped at 80 • C due to thermal expansion of coal and closure of initial fractures; however, it increased at 140 and 200 • C due to a combined response of thermal expansion and pyrolysis. Small axial strain during shear was observed to reduce permeability.

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Section: Implications For Ucg and Future Experimentssupporting

confidence: 88%

Section: A Conceptual Model For Permeability Evolution Versus Thermalsupporting

confidence: 57%

Section: A Conceptual Model For Permeability Evolution Versus Thermalmentioning

confidence: 81%

Section: Permeability To Gasmentioning

confidence: 99%

Section: Stress-strain and Deformation Characteristics During Shear Amentioning

confidence: 99%

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Influence of High Pressure and Temperature on the Mechanical Behavior and Permeability of a Fractured Coal

Kasani

Chalaturnyk

2017

Energies

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The mechanism of inward and outward expansion of multiscale dynamic permeability of coalbed methane at different temperatures

Hao

Liu

et al. 2023

Deep Underground Science and Engineering

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The multiscale micro‐nano pores in coal can result in the ultra‐low permeability of coal, which restricts the efficiency of gas extraction. It is difficult for the conventional seepage‐enhancement measures to affect the nanoscale pores within the coal matrix. Thermal stimulation can reach deep into the micro‐nano pores within coal matrix to improve the permeability. Therefore, it is important to study the diffusivity and permeability of the multiscale micro‐nano pores at different temperatures. In this study, the experiments of diffusion‐seepage measured by the methods of GRI (Gas Research Institution) and steady‐state were conducted using a cylindrical coal at different temperatures and pressures. The experimental results show that the apparent diffusion coefficient of cylindrical coal is not constant but variable dynamically; and the classical diffusion model fails to describe the full‐time process of gas flow accurately. On this basis, a model of multiscale dynamic apparent diffusion‐seepage that can accurately describe the full‐time flow process was proposed. As is observed, the apparent permeability attenuates dynamically with time without stress loading, and the initial apparent permeability and the attenuation coefficient increase monotonically with the rise of temperature. Under the stress constraint, the steady‐state permeability increases after a decrease as the temperature rises, displaying a “U‐shaped” pattern. Without stress constraint, the increasing temperature causes the exterior multiscale pores to expand outward by different degrees so as to increase permeability, while the interior micro‐nano pores show three inward and outward expansion mechanisms. Under stress constraint, at low temperature and high effective stress, the increasing temperature causes pores to expand inward and the permeability decreases accordingly. When temperature continues to increase, coal expands outward because the effective stress is counteracted by the thermal stress, leading to an increase in permeability. This study is of significance for thermal gas extraction engineering.

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Evolution law of pulsating seepage and thermal deformation by injecting high‐temperature steam into coal for thermal coalbed methane recovery

Li,

Chen

et al. 2024

Deep Underground Science and Engineering

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Chinese coal reservoirs are characterized by low pressure and low permeability, which need to be enhanced so as to increase production. However, conventional methods for permeability enhancement can only increase the permeability in fractures, but not the ultra‐low permeability in coal matrices. Attempts to enhance such impermeable structures lead to rapid attenuation of gas production, especially in the late stage of gas extraction. Thermal stimulation by injecting high‐temperature steam is a promising method to increase gas production. The critical scientific challenges that still hinder its widespread application are related to the evolution law of permeability of high‐temperature steam in coal and the thermal deformation of coal. In this study, an experimental approach is developed to explore the high‐temperature steam seepage coupled with the thermal deformation in coal under triaxial stress. The tests were conducted using cylindrical coal specimens of ϕ50 mm × 100 mm. The permeability and thermal strain in coal were investigated when high‐temperature steam was injected at 151.11, 183.20, 213.65, and 239.76°C. The experimental results reveal for the first time that as the amount of injected fluid increases, the steam permeability shows periodic pulsation changes. This paper introduces and explains the main traits of this discovery that may shed more light on the seepage phenomenon. When the injected steam temperature increases, the amplitude of pulsating permeability decreases, whereas the frequency increases; meanwhile, the period becomes shorter, the pulsation peak appears earlier, and the stabilization time becomes longer. The average peak permeability shows a “U‐shaped” trend, decreasing first and then increasing as the steam temperature increases. Meanwhile, with the extension of steam injection time, the axial, radial, and volumetric strains of coal show a stage‐wise expansion characteristic at different temperatures of steam injection, except for the radial strains at 151.11°C. A two‐phase flow theory of gas–liquid is adopted to elucidate the mechanism of pulsating seepage of steam. Moreover, the influencing mechanism of inward and outward thermal expansion on the permeability of coal is interpreted. The results presented in this paper provide new insight into the feasibility of thermal gas recovery by steam injection.

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Experimental Ivestigation of the Temperature and Pore Pressure Effect on Permeability of Lignite Under the In Situ Condition

Cited by 73 publications

References 15 publications

Influence of High Pressure and Temperature on the Mechanical Behavior and Permeability of a Fractured Coal

Influence of High Pressure and Temperature on the Mechanical Behavior and Permeability of a Fractured Coal

The mechanism of inward and outward expansion of multiscale dynamic permeability of coalbed methane at different temperatures

Evolution law of pulsating seepage and thermal deformation by injecting high‐temperature steam into coal for thermal coalbed methane recovery

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