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>3.3.co;2-s

Cited by 10 publications

(14 citation statements)

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

Section: Introductionmentioning

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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Section: Introductionmentioning

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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“…is means that gas desorption can be regarded as an Shock and Vibration 3 isothermal process. Once the dynamic phenomenon occurs, with the flooding of gas and the crushing and throwing of coal, the compensated heat will be reduced [22]. Because a coal and gas outburst occurs instantaneously and the entire gas expansion process is very short, it can be considered an approximately adiabatic process.…”

Section: Energy Condition Of a Coal And Gas Outburstmentioning

confidence: 99%

A Study on the Energy Condition and Quantitative Analysis of the Occurrence of a Coal and Gas Outburst

Dai

Liu

Cao

et al. 2019

Shock and Vibration

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With mining depths increasing, coal and gas outburst disasters are becoming more and more serious and complicated, which directly restricts the production efficiency of coal mines. In order to study the rules of energy dissipation during the occurrence of a coal and gas outburst based on the occurrence mechanisms, a simulation experiment of a coal and gas outburst with a ground stress of 16 MPa and a gas pressure of 0.5 MPa was carried out using a self-developed large-scale coal and gas outburst simulation experimental system. A quantitative analysis was given based on the energy model. The results showed the following: (1) In the process of the coal and gas outburst, the main energy source originated from the elastic potential energy of the coal body and the gas internal energy. The main energy loss was used for coal crushing and throwing. (2) The outburst coal sample in this experiment had a mass of 18.094 kg, and the relative outburst intensity was 1.21%. Additionally, the farthest throwing distance of the outburst coal samples was 3.3 m away from the outburst hole wall. The distribution of the outburst coal sample decreased along the roadway, and the proportion of the coal sample grain size in each area first decreased and then increased with the decrease of the grain size. The coal samples with a grain size less than 0.2 mm after the outburst accounted for 6.34% of the mass of the total coal samples. (3) The elastic potential energy of the coal body accounted for 0.34% of the total outburst energy, while the gas internal energy accounted for 99.66%. It was verified that gas internal energy was the key energy source for the coal and gas outburst, and this internal energy was two orders of magnitude more than the elastic potential energy, playing a leading role in the outburst process. After the outburst initiation, most of the energy was consumed in coal crushing, which was in the same order of magnitude as the gas internal energy. Moreover, the energy losses due to friction, vibration, and sound during the outburst process comprised no more than 10% of the total energy. The research results can provide certain guidance for clarifying the mechanism of a coal and gas outburst and the quantitative analysis of outburst energy.

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“…The numerical simulation of the effects of stress and gas pressure coupling on coal and gas outburst has provided various results. Valliappan et al proposed a solid-gas coupling model of coal and gas outbursts and numerically analysed coal-bed gas flow on the basis of the theories of coal layer mechanics and seepage mechanics [18,19]. Sobczyk, who also numerically analysed solidgas instability in coal and gas outbursts, concluded that stresses or gas pressures have crucial roles in outburst disasters.…”

Section: State Of the Artmentioning

confidence: 99%

An Experimental Study on the Interaction Law of the Pore Gas Pressure and Stress in Gassy Coals

Hu¹,

Sun²,

Tang³

2018

Teh. vjesn.

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Understanding the principle underlying the coupling between coal seam stress and gas pressure will help prevent the occurrence of dynamic coal and gas disasters. However, previous studies have mainly focused on the macroscopic qualitative analyses of the coupling between coal seam stress and gas pressure. In fact, laboratory quantitative tests, which investigate gas pressure in sealed sample tanks, fail to represent the essential relationship between stress and gas pressure in real time. In this study, a model of the stress-porosity-gas pressure relationship was established based on the pore characteristics of gassy coals and gas adsorption theory to quantify the coupling between coal seam stress and gas pressure. In addition, a method for determining the law governing stress and gas pressure coupling was proposed based on stress-strain curves obtained through triaxial loading tests. Results show that the porosity and gas pressure of gassy coals first decrease and then increase as loading stress increases. Under various confining pressures and initial gas pressures, porosity declines at a lower rate with the increase in the initial gas pressure. Specifically, gas pressure increases with stress before the value of stress reaches that of the compressive strength of the coal. This behaviour demonstrates that gas pressure and stress are positively correlated. High initial gas pressures are associated with small increments (i.e., from 136% to 30%) in pore gas pressure under stress. When stress exceeds the compressive strength of the coal, gas pressure begins to decrease with stress. Thus, stress and gas pressure are negatively correlated. Finally, the validity of the research method was verified through afield experiment. The proposed method provides new concepts for the study of the mechanism, prevention, and control technology of dynamic coal and gas disasters.

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Numerical Modelling of Methane Gas Migration in Dry Coal Seams

Cited by 10 publications

References 0 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

A Study on the Energy Condition and Quantitative Analysis of the Occurrence of a Coal and Gas Outburst

An Experimental Study on the Interaction Law of the Pore Gas Pressure and Stress in Gassy Coals

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