Modeling Adsorption and Transport behavior of Gases in Moist Coal Matrix

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

doi:10.1021/acs.energyfuels.1c01334

Cited by 9 publications

(7 citation statements)

References 63 publications

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“…Based on the principle of mass conservation, the mass balance equation for a free gas in porous matrices can be expressed as (Chen et al, 2020b(Chen et al, , 2021Cui et al, 2022): where…”

Section: Free Gas Diffusion In Coal Matricesmentioning

confidence: 99%

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Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Chen¹,

Masum²,

Thomas³

2023

Gas Science and Engineering

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“…Based on the principle of mass conservation, the mass balance equation for a free gas in porous matrices can be expressed as (Chen et al, 2020b(Chen et al, , 2021Cui et al, 2022): where…”

Section: Free Gas Diffusion In Coal Matricesmentioning

confidence: 99%

“…where τ is tortuosity of the porous medium, d f is the fractal dimension of the pore surface accounting for the effect of pore-surface roughness. Following the work by Chen et al (2021), the viscous flow-induced diffusivity D v can be expressed as:…”

Section: Free Gas Diffusion In Coal Matricesmentioning

confidence: 99%

Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Chen¹,

Masum²,

Thomas³

2023

Gas Science and Engineering

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“…Day and Ozdemir showed that moisture can change the heat of adsorption. Based on the exponential decay equation, Chen further proposed a relationship between the Langmuir pressure and the moisture content P normalL = P Lg + P normalL normalw .25em exp ( − ξ ω ) where P Lg is the pressure constant unaffected by moisture, P Lw is the fraction that can be affected by moisture adsorption, and ξ is a weighting factor representing the role of moisture in gas adsorption.…”

Section: Apparent Permeability Model For Gas Transport In Moisture-po...mentioning

confidence: 99%

“…Wang reported that the presence of moisture occupies a portion of the pore space and diminishes the gas adsorption sites of coal, which lowers the amount of gas adsorption. Recent studies − have shown that the Langmuir volume drops with increasing intrinsic moisture content, and the exponential equation may be used to describe the relationship between the amount of methane adsorption and intrinsic moisture content.…”

Section: Introductionmentioning

confidence: 99%

Apparent Permeability Model of Coalbed Methane in Moist Coal: Coupling Gas Adsorption and Moisture Adsorption

et al. 2023

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Under specific conditions, moisture in natural coal seams can be adsorbed in the pores of the coal matrix, reducing the amount of methane adsorption sites and the effective area of the transport channels. This makes the prediction and evaluation of permeability in CBM exploitation more challenging. In this paper, we developed an apparent permeability model of coalbed methane coupling viscous flow, Knudsen diffusion, and surface diffusion which considers the effects of adsorbed gas and moisture in the pores of the coal matrix on the permeability evolution. The predicted data of the present model are compared with those of other models, and the results show good agreement, verifying the accuracy of the model. The model was employed to study the apparent permeability evolution characteristics of coalbed methane under different pressure and pore size distribution conditions. The main findings are as follows: (1) moisture content increases with saturation, with a slower increase for smaller porosities and an accelerated non-linear increase for porosities greater than 0.1. (2) Gas adsorption in pores decreases permeability, further weakened by moisture adsorption under high pressure but negligible at pressures below 1 MPa. (3) Higher water saturation weakens gas transport capacity, especially with pore sizes smaller than 10 nm. (4) The non-Darcy effect weakens with higher initial porosity, and neglecting moisture adsorption may significantly deviate from actual values in modeling methane transport in coal seams. The present permeability model can capture the transport characteristics of CBM in moist coal seams more realistically and is more applicable for predicting and evaluating the gas transport performance under dynamic variations of pressure, pore size, and moisture. The results in this paper can explain the transport behavior of gas in moist, tight, porous media and also provide a foundation for coalbed methane permeability evaluation.

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“…It is well-known that gas adsorption in the internal pores of rock matrices is one of the important gas storage mechanisms in coal or shale reservoirs, and the adsorption capacity influences the gas content of these reservoirs. , The amount of adsorbed gas in coal or shale can be influenced by several controlling factors, such as coal type, pressure, temperature, and moisture content. − However, gas adsorption, generally, is not a fully reversible process. Experimentally measured adsorption isotherms do not coincide with corresponding desorption isotherms determined over the same pressure range on the same samples.…”

Section: Introductionmentioning

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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Modeling Adsorption and Transport behavior of Gases in Moist Coal Matrix

Cited by 9 publications

References 63 publications

Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Apparent Permeability Model of Coalbed Methane in Moist Coal: Coupling Gas Adsorption and Moisture Adsorption

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

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