Study on gas seepage from coal seams in the distance between boreholes for gas extraction

Zhao, Dan; Liu, Jian; Jingtao, Pan

doi:10.1016/j.jlp.2018.04.013

Cited by 34 publications

(31 citation statements)

References 9 publications

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“…According to the Specification of Coal and Gas Outburst Prevention, mining operations should not be performed in coal seams where outburst hazards have not yet been eliminated, and a gas pressure criterion of 0.74 MPa or a gas content criterion of 8 m 3 /t is used to determine whether there are outburst hazards. The relationship between gas pressure and gas content can be expressed by the modified Langmuir equations as follows:

W = \frac{a b c ρ_{n} P}{(1 + b P)} + \frac{n ρ_{n} P}{P_{n}}

where W is the gas content of coal seam, m 3 /t; P is the gas pressure of coal seam, MPa; a is the maximum value of adsorbed gas, m 3 /t; b is the constant amount of adsorbed gas, MPa −1 ; c is mass parameter of coal, and c = 1 − A d − M ad , in which A d is the ash content, M ad is the water content, %; n is the coal porosity, %; P n is the standard atmospheric pressure, MPa; ρ n is the gas density at the gas pressure P n , kg/m.…”

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

“…The Coal Mine Safety Regulations specifies that the gas predrainage efficiency ŋ must be greater than 30%, that is, the residual gas content after predrainage must be less than 70% of the original gas content . This can be expressed as:

X_{normalc} < 70 % X

where X c is the residual gas content in coal seams and X is the original gas content in coal seams.…”

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

“…Figure shows the critical gas pressure for these two criteria. The red line represents the first criterion, which was used in some literatures, while the blue line represents the second criterion, which was adopted in other literatures . The two lines intersect where the original gas pressure P 0 is 1.08 MPa.…”

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

“…It is undeniable that numerical simulation has become an important method to study the effective extraction radius. Researchers have established mathematical models to describe the laws of gas flow in coal seams around boreholes and have used the CFD software for numerical simulation to obtain the effective extraction radius of boreholes along coal seams …”

Section: Introductionmentioning

confidence: 99%

“…Among the gas extraction test methods, the gas pressure method, gas content method, and gas tracer method are three common methods for measuring the effective extraction radius. The gas tracer method has low reliability, and thus, it cannot be used to analyze the degree of influence and obtain the effective extraction radius accurately .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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.

show abstract

W = \frac{a b c ρ_{n} P}{(1 + b P)} + \frac{n ρ_{n} P}{P_{n}}

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

X_{normalc} < 70 % X

where X c is the residual gas content in coal seams and X is the original gas content in coal seams.…”

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

Section: Definition Of Effective Gas Extraction Radiusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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show abstract

Optimal submerged waterjet for gas recovery based on Arbitrary Lagrange‐Euler

Wang

Hai

et al. 2019

Energy Science & Engineering

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This paper proposes a coupled model of waterjet cutting coal containing gas with the Arbitrary Lagrange‐Euler algorithm assistance. The dynamic evolution of coal damage and the cutting performance under different jet conditions, including jet pattern (submerged/nonsubmerged state), jet velocity, nozzle diameter, and the initial standoff distance, are investigated by tracing the number of failure elements and the stress distribution. Afterward, the gas flow model is built to study interactions of the discharged coal amount and the effective drainage radius at different periods with COMSOL software. The numerical results show the coal cutting performance of nonsubmerged jets is much better than that of submerged jets. Under submerged conditions, the penetration length increases with jet velocity and nozzle diameter, but decreases with the initial standoff distance. Moreover, the effective drainage radius of nonsubmerged waterjet is substantially greater than that of submerged jet. The increasing trend of the effective drainage radius slows down after 3 months with gas flow attenuation. Under the special submerged circumstances, the difference of coal cutting performance caused by the two jet patterns should be fully considered in order to reasonably arrange the spacing of boreholes.

show abstract

Tree-Type Boreholes in Coal Mines for Enhancing Permeability and Methane Drainage: Theory and an Industrial-Scale Field Trial

Zhang

et al. 2020

Nat Resour Res

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Study on gas seepage from coal seams in the distance between boreholes for gas extraction

Cited by 34 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

Optimal submerged waterjet for gas recovery based on Arbitrary Lagrange‐Euler

Tree-Type Boreholes in Coal Mines for Enhancing Permeability and Methane Drainage: Theory and an Industrial-Scale Field Trial

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