Coal permeability maps under the influence of multiple coupled processes

Zhang, Shouwen; Liu, Jishan; Wei, Mingyao; Elsworth, Derek

doi:10.1016/j.coal.2018.01.005

Cited by 75 publications

(47 citation statements)

References 31 publications

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“…Process of a gas filtration through a rock mass is highly nonlinear because its permeability depends on several factors (Zhang et al, 2018;Konečný and Kožušníková, 2016). It is widely acknowledged (Baiquan and Yang, 2017) that permeability of the coal mass increases due to degassing of methane as zones was conversely proportional to gas pressure gradient expected.…”

Section: Methodology Of Simulationmentioning

confidence: 99%

A method for measuring coalbd methane content in coal strata without the loss of the gas

Nazimko¹

2018

Acta Geodynamica Et Geomaterialia

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This paper describes an invented method for direct measurement of coalbed methane content in situ. In contrast to known procedures, this method does not need to place a rock or drilling cuts into an airtight canister, and does not involve sealing of the hole. Moreover, the new method is monitoring methane content in situ continuously and synchronously during drilling the hole not losing any portion of the gas. These positive features are a sequel of new approach based on injection of known portion of neutral gas into the hole. Methane content was determined from concentration of the mixture 'methane-neutral gas´ at the hole´s mouth. New method is applicable for commercial recovery application of coalbed methane and forecast of dangerous gas and coal bursts. FLAC3D computer simulation helped to investigate dynamics of methane outflow from the hole to account for the effect of drilling speed on the rate of gas emanation. ARTICLE INFOCite this article as: Nazimko V: A method for measuring coalbed methane content in coal strata without the loss of the gas.

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Section: Methodology Of Simulationmentioning

confidence: 99%

A method for measuring coalbd methane content in coal strata without the loss of the gas

Nazimko¹

2018

Acta Geodynamica Et Geomaterialia

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“…In addition, 80% of the gas is adsorbed in the coal, [38][39][40] and it takes a certain time for the gas in the adsorbed state to resolve into the free state. 41,42 Therefore, before the coal rock mass complete failure, the gas concentration changes little and is in the normal level. When the coal and rock mass outside the gas protective layer is completely unstable and destroyed, the AE parameters increase to the maximum value, and then begin to decrease until they reach the normal value.…”

Section: Relationship Between the Ae Parameters And The Gas Concentmentioning

confidence: 99%

Acoustic emission monitoring technology for coal and gas outburst

et al. 2019

Energy Science & Engineering

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In recent years, with the increase in mining depth and strength, coal‐rock gas dynamic disasters, such as coal and gas outburst, have shown an increasing trend. Acoustic emission (AE) technology has been viewed as a promising method that can effectively forecast coal and gas dynamic disasters. This paper first tests the AE characteristics of coal and rock samples during loading. Then, self‐developed AE continuous monitoring and early warning equipment is used to monitor and predict the coal and gas outburst dynamic disasters on the working face. And it is found that the coal samples primarily show ductile failure, and the AE exhibits the evolutionary characteristics of “rise‐peak‐fall”. The rock samples primarily exhibit brittle failure, and the AE evolution mode is almost no falling stage. Coal and gas outbursts occur after the stress peak. Before coal and gas outbursts occur, there is a clear increasing trend in the AE ahead of the gas concentration variation. When the gas‐bearing coal is damaged by the load, the coal body first breaks due to the stress, and the AE value increases. Then, due to the fracture of the coal body, the crack penetrates, gas rushes out, and the gas concentration increases. The research results can provide an advanced technical method for the monitoring and early warning of coal–rock gas dynamic disasters, and improve the prediction accuracy for dynamic disasters.

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“…Given that a dual porosity coal contains porous matrix and fractures, we apply the overlapping continuum approach to characterize the interactions between the matrix and the fracture [48]. The following assumptions are derived: (a) bulk coal containing matrix and fractures are homogeneous, isotropic, and elastic; (b) solid strain is infinitesimal; (c) injected helium is ideal gas; (d) gas flow is followed by Darcy's law.…”

Section: Numerical Analysismentioning

confidence: 99%

“…Based on the poroelastic theory [49], the constitutive relation for matrix and fracture can be defined as the following, respectively [10,48,50]:…”

Section: Governing Equations Of Cleat and Matrix Deformationmentioning

confidence: 99%

Interaction of Cleat-Matrix on Coal Permeability from Experimental Observations and Numerical Analysis

et al. 2019

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Gas transport through porous coal contains gas laminar flow in the cleat network and gas adsorption/diffusion in the matrix block. Since permeable capacity of the cleat is greater than that of the matrix, change of the matrix pressure readily lags behind change in the cleat pressure. Such unsynchronized pressure changes can result in a complex compatible deformation of a cleat-matrix system, significantly affecting the coal permeability. In this paper, we investigated the cleat-matrix interaction on coal permeability by using a modified pressure pulse decay method integrated with numerical analysis. The experimental results indicate that the bulk volume of the coal sample rapidly expanded at the beginning of gas injection, and then the volume expansion rate of the coal sample slowed down as the downstream pressure of the coal sample gradually equilibrated with the upstream pressure. During this process, the coal permeability was observed to gradually decrease with time. Numerical analysis results indicate that gas transport from the cleat to the matrix can attenuate the differential pressure between the cleat and the matrix. A smaller ratio of initial matrix permeability to initial cleat permeability can prolong decay duration of the differential pressure inside the cleat-matrix system. Although the coal sample is subjected to a stress-controlled condition, the coal permeability response to gas diffusion is closer to the case using a constant volume boundary. The dynamic change of coal permeability is significantly affected by the cleat-matrix interaction, in cases where the short-term change is mainly attributable to the cleat network and the long-term change is controlled by matrix swelling/shrinkage.

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Coal permeability maps under the influence of multiple coupled processes

Cited by 75 publications

References 31 publications

A method for measuring coalbd methane content in coal strata without the loss of the gas

A method for measuring coalbd methane content in coal strata without the loss of the gas

Acoustic emission monitoring technology for coal and gas outburst

Interaction of Cleat-Matrix on Coal Permeability from Experimental Observations and Numerical Analysis

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