Modelling anisotropic adsorption-induced coal swelling and stress-dependent anisotropic permeability

Chen, Min; Masum, Shakil; Sadasivam, Sivachidambaram; Thomas, Hywel Rhys

doi:10.1016/j.ijrmms.2022.105107

Cited by 14 publications

(8 citation statements)

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“…Coal is a kind of special porous medium, which has good adsorption capacity for gases (Abouloifa et al, 2021;Chen et al, 2022). At the same time, the gas adsorption changes the internal pore structure, which has a non-negligible influence on the gas flow.…”

Section: Theoretical Methodsmentioning

confidence: 99%

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

Wang

Yang²,

Zhou³

et al. 2023

Front. Energy Res.

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Permeability is an important parameter in the process of coalbed methane exploitation. To improve the production efficiency of coalbed methane and explore the control mechanism of the gas flow law in coal, the permeability of helium and nitrogen in the same coal sample was tested under different effective stress (the difference between external stress and pore pressure of coal mass) and pressure by using the seepage device. Based on the gas flow theory, the interaction mechanism of effective stress, adsorption effect and Klinkenberg effect in controlling the permeability has been analyzed. Increasing the gas pressure will enhance the adsorption and deformation ability of coal, causing the reduction of pore size, while it will also cause the reduction of effective stress and stress deformation. There is a certain competition between them under the same external stress condition, which will lead to the change of pore and then affect the permeability of coal seam. The Klinkenberg effect will lead to more complex change factors of permeability, especially in laboratory experiments. Both adsorption deformation and stress deformation will affect the pore structure of coal body, which will also lead to changes in the influence degree of Klinkenberg effect on apparent permeability. Under the influence of adsorption effect, the Klinkenberg effect may be a variable. The experimental results in this work elaborate the microscopic control mechanism of gas permeability change in coal. It can not only provide important guidance for gas injection technology, but also enrich the theory of coal seam gas flow.

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Section: Theoretical Methodsmentioning

confidence: 99%

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

Wang

Yang²,

Zhou³

et al. 2023

Front. Energy Res.

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“…The source term Q s in this work is only considered from gas adsorption, and eqs 12 and 18 are applied for calculation of the source term during adsorption and desorption, respectively. where k is the fracture permeability, the stress-dependent permeability model by Chen, et al 54 is used for estimating permeability evolution, μ is the viscosity of the gas, p f is the gas pressure, which can be estimated using the real gas law p f = ZRTρ f /M, Z is the gas compressibility factor, which is calculated using the Peng−Robinson equation of state, R is the universal gas constant, T is the temperature, and M is the molar mass. The mass transfer term in eqs B1 and B2 depends on the mass exchange rate and the difference between the gas concentrations in the fracture continuum and matrix continuum, 45,55 given as (B4) where τ is the diffusion time.…”

Section: B1 Theorymentioning

confidence: 99%

Modeling Gas Adsorption–Desorption Hysteresis in Energetically Heterogeneous Coal and Shale

et al. 2023

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Adsorption of gases in porous adsorbents such as coal and shale generally exhibits the phenomenon of hysteresis. Most of the previous studies on desorption hysteresis were conducted via experimental tests. However, few theoretical models that represent adsorption−desorption hysteresis of gases in porous sorbents are available. To address this issue, this work develops a new adsorption−desorption model for describing adsorption and desorption isotherms of gases with hysteresis. Particularly, the energetically heterogeneous surfaces of an adsorbent are considered via the patchwise model. Based on the change in site energy distribution, a logarithmically pressure-dependent hysteresis index, which is used to measure the degree of hysteresis, is derived for quantitative assessment of the degree of hysteresis. Besides, the correlation between the desorption isotherm and initialized pressure for desorption is established. The accuracy of the proposed model to adequately describe the adsorption−desorption hysteresis of gas in coal and shale is demonstrated by validating the model against laboratory experiments obtained from the literature. The results indicate that the adsorption isotherm depends significantly on site energy distribution. By comparing the site energy distributions for adsorption and desorption isotherms, it is found that the desorption hysteresis can be attributed to the change in pore size distribution caused by adsorption-induced deformation. The analyses support that the proposed model can be used as an effective tool to quantitatively predict the amount of released gas during desorption, which is significant for designing coalbed methane or shale gas production and assessing long-term CO 2 storage behavior.

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“…Although coal-seam CO 2 storage capacity increases with the reservoir depth, gas injection operations at a deeper subsurface suffer from technical challenges and limitations which question the viability of exploiting such coal seams. For example, swelling-induced coal permeability and gas injectivity loss, driven by CO 2 adsorption in coal under elevated confining pressures, are often reported in field tests and laboratory experiments. − This results in under-utilization of coal resources and requires stimulation or fracturing of coal deposits for facilitating gas injection and storage. In addition, coal seams at greater depths are usually found to be intact and of high methane content.…”

Section: Introductionmentioning

confidence: 99%

“…For example, swelling-induced coal permeability and gas injectivity loss, driven by CO 2 adsorption in coal under elevated confining pressures, are often reported in field tests and laboratory experiments. 1 − 3 This results in under-utilization of coal resources and requires stimulation or fracturing of coal deposits for facilitating gas injection and storage. In addition, coal seams at greater depths are usually found to be intact and of high methane content.…”

Section: Introductionmentioning

confidence: 99%

Low Subcritical CO₂ Adsorption–Desorption Behavior of Intact Bituminous Coal Cores Extracted from a Shallow Coal Seam

et al. 2023

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This study focuses on improving fundamental understanding of low, subcritical CO2 adsorption–desorption behavior of bituminous coals with the aim to evaluate the utility of shallow-depth coal seams for safe and effective CO2 storage. Comprehensive data and a detailed description of coal–CO2 interactions, e.g., adsorption, desorption, and hysteresis behavior of intact bituminous coals at CO2 pressures <0.5 MPa, are limited. Manometric sorption experiments were performed on coal cores (50 mm dia. and 30- or 60-mm length) obtained from a 30 m deep coal seam located at the Upper Silesian Basin in Poland. Experimental results revealed that the adsorption capacities were correlated to void volume and equilibrium time under low-pressure injection (0.5 MPa). The positive deviation, observed in the hysteresis of adsorption–desorption isotherm patterns, and the increased sample mass at the end of the tests suggested CO2 pore diffusion and condensation. This behavior is vital for assessing low-pressure CO2 injection and storage capabilities of shallow coal seams where confining pressure is much lower than that of the deeper seams. Overall, CO2 adsorption depicts a type II adsorption isotherm and a type H3 hysteresis pattern of the IUPAC classification. Experimental results fitted better to the Brunauer–Emmett–Teller model than the Langmuir isotherm model. CO2 adsorption behavior of intact cores was also evaluated by characteristic curves. It was found that Curve I favored physical forces, i.e., the presence of van der Waals/London dispersion forces to describe the coal–CO2 interactions. However, analysis of Curve II indicated that the changing pressure-volume behavior of CO2 in the adsorbed phase, under low equilibrium pressures, cannot be ignored.

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Modelling anisotropic adsorption-induced coal swelling and stress-dependent anisotropic permeability

Cited by 14 publications

References 50 publications

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

Modeling Gas Adsorption–Desorption Hysteresis in Energetically Heterogeneous Coal and Shale

Low Subcritical CO₂ Adsorption–Desorption Behavior of Intact Bituminous Coal Cores Extracted from a Shallow Coal Seam

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Modelling anisotropic adsorption-induced coal swelling and stress-dependent anisotropic permeability

Cited by 14 publications

References 50 publications

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

The influence mechanism of effective stress, adsorption effect and Klinkenberg effect on coal seam permeability

Modeling Gas Adsorption–Desorption Hysteresis in Energetically Heterogeneous Coal and Shale

Low Subcritical CO2 Adsorption–Desorption Behavior of Intact Bituminous Coal Cores Extracted from a Shallow Coal Seam

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Product

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About

Low Subcritical CO₂ Adsorption–Desorption Behavior of Intact Bituminous Coal Cores Extracted from a Shallow Coal Seam