Numerical Modelling of Methane Gas Migration in Dry Coal Seams

Valliappan, S.; Zhang, Wohua

doi:10.1002/(sici)1096-9853(199608)20:8<571::aid-nag840>3.0.co;2-0

Cited by 79 publications

(17 citation statements)

References 9 publications

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“…At present, the main methods for calculating the effective extraction radius are theoretical calculation, 28,29 field measurement 14,27 and numerical simulation. 30,31 Zhang et al 32 concluded that the extraction radius increased nonlinearly with the borehole radius, while Kong et al 33 found that the relationship between the extraction radius and the borehole radius was linear.…”

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confidence: 99%

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Wang

Chang

et al. 2019

Energy Science & Engineering

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The effective extraction radius of borehole is the main parameter for determining the design and layout for coalbed methane extraction. This paper is aimed at the problem that the criteria and calculation methods for the effective extraction radius of coal seams are not comprehensive. With Wudong Coal Mine in China taken as an example, the critical gas pressure (0.441 MPa) for the calculation of effective extraction radius is first defined. Next, the gas seepage unit model around the borehole is developed, and the theoretical mathematical expression to calculate the effective extraction radius is derived. Then, the numerical simulation of gas extraction is carried out through a computational fluid dynamics program, and the effective extraction radius is obtained numerically. Furthermore, the influence of original gas pressure, borehole diameter, and negative pressure of gas extraction on gas extraction is analyzed. Finally, the results from the theoretical calculation and numerical simulation are validated by the field engineering measurement and the average relative error is small (less than 10%). The results indicate that the effective extraction radius has a linear relationship with the extraction time. Moreover, it is found that the original gas pressure is the main factor affecting the effective extraction radius and the effective extraction radius is proportional to the borehole diameter and negative pressure through analysis. Therefore, the above findings can provide a theoretical basis for determining parameters such as borehole spacing and extraction time of gas extraction in coal mines.

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confidence: 99%

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Wang

Chang

et al. 2019

Energy Science & Engineering

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“…The anisotropic damage characters can be expressed by the principal damage values (V 1 , V 2 , V 3 ) of the anisotropic damage state or by the three values (f 1 , f 2 , f 3 ) of area deduction rate along the anisotropic principal directions. According to this equivalence we have (Valliappan and Zhang, 1996):…”

Section: Relationship Between Damage and Porositymentioning

confidence: 99%

Study on constitutive model of coupled damage-permeability of porous media

Xue

Zhang²,

Yang³

2014

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose -The paper aims to clarify the relationship between the micro-structures of porous media and the coefficient of permeability. Most materials involve different types of defects like caves, pores and cracks, which are important characters of porous media and have a great influence on the physical properties of materials. To study the seepage mechanical characteristics of damaged porous media, the constitutive model of porous media dealing with coupled modeling of pores damage and its impact on permeability property of a deforming media was studied in this paper. Design/methodology/approach -The paper opted for an exploratory study using the approach of continuum damage mechanics (CDM). Findings -The paper provides some new insights on the fluid dynamics of porous media. The dynamic evolution model of permeability coefficient established in this paper can be used to model the fluid flow problems in damaged porous media. Moreover, the modified Darcy's law developed in this paper is considered to be an extension of the Darcy's law for fluid flow and seepage in a porous medium. Research limitations/implications -Owing to the limitations of time, conditions, funds, etc., the research results should be subject to multifaceted experiments before their innovative significance can be fully verified. Practical implications -The paper includes implications for the development of fluid dynamics of porous media. Originality/value -This paper fulfils an identified need to study the relationship between the micro-structures of porous media and the coefficient of permeability.

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“…This means that the influence of interaction between fluid and solid matrix must be added in the process of various simulation studies. After recognizing this problem, most scholars have fully considered the influence of fluidsolid coupling on the seepage of CBM and other fluids and have achieved certain research results [15][16][17][18]. Majewska et al [19] found that coal experienced a contraction trend after the initial expansion of adsorption, which was attributed to the compression effect of injection pressure.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation on Mesoscale Mechanism of Seepage in Coal Fractures by Fluid-Sloid Coupling Method

Peng

Zhao

et al. 2021

Geofluids

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Trying to reveal the mechanism of gas seepage in coal is of significance to both safe mining and methane exploitation. A series of FEM numerical models were built up and studied so as to explore the mesoscale mechanism of seepage in coal fractures. The proposed mesoscale FEM model is a cube with micron fractures along three orthogonal directions. The distribution of velocity and pressure under fluid-solid coupling was obtained, and furthermore, the seepage flow flux and an equivalent permeability of the whole model were calculated. The influences of fracture width, outlet velocity, and in situ stress level on seepage were investigated. The numerical results show that nonlinear Darcy seepage occurs during low velocity zone. The permeability is increased linearly with the increasing of facture width and outlet velocity. A certain change of lateral coefficient of in situ stress also affects seepage. The permeability is increased sharply once deviating the isotropic spherical stress state, but it is no longer changed obviously after the lateral coefficient has been increased or decreased more than 20%. The mesoscale seepage mechanism in coal fractures has been preliminarily revealed by considering fluid-solid coupling effect, and the key factors influencing fluid seepage in coal fractures were demonstrated. The proposed methods and results will be helpful to the further study of seepage behaviour in coal with more complex structures.

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Numerical Modelling of Methane Gas Migration in Dry Coal Seams

Cited by 79 publications

References 9 publications

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Study on constitutive model of coupled damage-permeability of porous media

Numerical Simulation on Mesoscale Mechanism of Seepage in Coal Fractures by Fluid-Sloid Coupling Method

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