In-situ testing method of the permeability coefficient in a coal seam based on the finite volume method and its application

Lin, Minghua; Lin, Baiquan; Yang, Wei; Zhao, Yang; Zheng, Wang

doi:10.1016/j.jngse.2021.104370

Cited by 19 publications

(8 citation statements)

References 33 publications

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“…), constructing the system of discrete equations, and solving the system of discrete equations. For the specific solution process, refer to the authors’ previous paper …”

Section: Theoretical Modelsmentioning

confidence: 99%

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Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

Lin

Liu

et al. 2023

Energy Fuels

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Gas transport within the coal matrix is key to realizing mass exchange between the fracture and matrix systems. However, considerable controversy remains regarding gas transport within the coal matrix system. In this study, the applicability of several typical models was evaluated based on the proposed criteria, mainly through gas emission under pressure experiments, and it is found that the Darcy seepage model describes gas transport behavior within the coal matrix more scientifically. Subsequently, the validity of the seepage model was re-evaluated through pore structure analysis, and the gas transport patterns and underlying mechanisms of the dual-porosity and dualpermeability models were discussed. The results suggest that gas transport within the matrix is dominated by the Fick diffusion flow only when methane molecules within the coal matrix are located in the micropore filling section. When the pore size is located in the outer pore section, gas within the matrix will be transported outward in a free state driven by pressure. In addition, the proposed gas transport model and field data were used to validate the analysis. It is concluded that in view of the low efficiency of gas transport in the micropore filling section, the dual-porosity and doublepermeability models can be used to simplify gas transport in coal seams.

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“…), constructing the system of discrete equations, and solving the system of discrete equations. For the specific solution process, refer to the authors’ previous paper …”

Section: Theoretical Modelsmentioning

confidence: 99%

“…For the specific solution process, refer to the authors' previous paper. 22 Once the pressure distribution in the coal matrix at any time is known, the cumulative gas emission at that time can be calculated according to eq 2.…”

Section: Ds Modelmentioning

confidence: 99%

Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

Lin

Liu

et al. 2023

Energy Fuels

Self Cite

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“…In recent years, numerical modelling has been used as an approach to investigate the effect of BRF's assumptions and operational parameters on the accuracy of the method [25][26][27]. Liu et al [25] assessed two assumptions of the BRF method, i.e., the single porosity model and the parabolic expression of gas content and gas pressure, by comparing the gas pressure distribution and borehole gas flow rate.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Evaluation of Coal Seam Permeability Derived from Borehole Gas Flow Rate

Shi

2022

Energies

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Coal seam permeability is a critical factor in coal seam gas extraction and gas outburst control. In Australian coal mines, coal seam permeability is normally estimated using a packer test or drill stem test. In contrast, Chinese coal mines generally estimate a parameter called the “gas conductivity coefficient” by measuring natural gas flow rates from an underground borehole drilled through a coal seam. With this method, it has been frequently reported that the permeability of many Chinese coal seams is between 0.0001 mD and 0.01 mD, which is extremely low compared to that of Australian coal seams (1–100 mD). It is therefore natural to wonder how closely the Chinese method measures permeability. Resolving this question will allow knowledge and experience in outburst management to be shared between Australian and Chinese coal mines. This question is investigated by the numerical modelling of gas desorption and flow through a seam of known permeability and by using the model’s borehole gas flow rate to estimate the permeability using the Chinese method. A total of 126 simulations were run with various input reservoir parameters. The results suggest that the Chinese method estimates permeability at an accuracy of 85% to 100%, which is adequate for mine pre-drainage design and outburst control. For the high diffusion rate (e.g., high gas content and short desorption time) and low Darcy flow rates (e.g., low permeability), these errors are reduced.

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“… 4 , 15 , 16 In addition, the permeability of coal and the gas flow are the key factors affecting the recovery effect of the extraction borehole. 17 , 18 Because underground gas extraction engineering usually lasts for a long time, and the physical fields of coal seams, such as geological stress, permeability, gas flow, and temperature, affect each other and change continuously, 19 , 20 hence, the discovery of the dynamic evolution law of permeability and gas flow is critical for CBM recovery and GHG emission reduction.…”

Section: Introductionmentioning

confidence: 99%

“…Gas pre-extraction technology and its derivative technology are widely used because of its engineering effectiveness. , Relevant studies show that it can effectively control greenhouse gas emissions and recover CBM in coal mining engineering. ,, In addition, the permeability of coal and the gas flow are the key factors affecting the recovery effect of the extraction borehole. , Because underground gas extraction engineering usually lasts for a long time, and the physical fields of coal seams, such as geological stress, permeability, gas flow, and temperature, affect each other and change continuously, , hence, the discovery of the dynamic evolution law of permeability and gas flow is critical for CBM recovery and GHG emission reduction.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Evolution of Gas Flow during Coalbed Methane Recovery to Reduce Greenhouse Gas Emission: A Case Study

et al. 2022

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Gas pre-extraction technology in a coal reservoir can not only reduce greenhouse gas (GHG) emissions but also effectively recover coalbed methane (CBM). In this work, we use a geomechanical-coupled gas flow (GCF) model to simulate and analyze the pre-extraction effect of a mining-disturbed coal seam. First, the simulation results of the GCF model are compared with field test data to verify the correctness and reliability of our model. Then, the evolution law of the stress field, permeability field, and gas flow field in the extraction process is analyzed through a case study. The results show that the first principal stress of coal in a mining area increases first and then decreases slowly and reaches the peak value at 5 m. The third principal stress increases gradually at first and becomes stable after 10 m. As the distance from the mining face increases, the permeability and gas pressure of the coal seam show continuous and asymmetric “U”-shaped and “n”-shaped distribution characteristics, respectively. In addition, the recovery effect and abnormal emission factors of CBM are discussed. This study can provide theoretical guidance for optimizing the CBM recovery effect and reducing GHG emissions during mining.

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In-situ testing method of the permeability coefficient in a coal seam based on the finite volume method and its application

Cited by 19 publications

References 33 publications

Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

A Numerical Evaluation of Coal Seam Permeability Derived from Borehole Gas Flow Rate

Dynamic Evolution of Gas Flow during Coalbed Methane Recovery to Reduce Greenhouse Gas Emission: A Case Study

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