Study on the influence of stress constraint conditions on multi-scale gas emission characteristics in in-situ coal

Shi, Yu; Lin, Baiquan; Liu, Ting; Liu, Tong; Zhang, Xiangliang; Yang, Wei

doi:10.1016/j.energy.2023.130160

Cited by 8 publications

(5 citation statements)

References 57 publications

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“…According to previous studies, the gas diffusion coefficient in the coal is controlled by the temperature and gas partial pressure in matrix pores. Therefore, Fick’s diffusion coefficient for multicomponent gases in the coal, which considers corrections for effective porosity and tortuosity, can be expressed by eq , D normalf i = 2 3 τ ϕ normalm 1 − ϕ f μ g i p normalm normalg i R T M g i where τ is the tortuosity; and μ g i is the kinematic viscosity of the gas component i .…”

Section: Modelingmentioning

confidence: 99%

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Dynamic Response of Gas Recovery Enhancement Efficiency in Coalbed Methane Displacement by Hot Flue Gas: From the Perspective of Thermo–Hydro–Mechanical–Chemical Coupling

Liu,

Shi,

Liu

et al. 2024

Energy Fuels

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The displacement of coalbed methane (CBM) by hot flue gas is an effective method to enhance gas recovery, but the dynamic response mechanism of gas recovery enhancement efficiency under the influence of the main engineering control parameters (pressure, components, and temperature) of hot flue gas remains unclear. In this study, a thermo−hydro−mechanical− chemical (THMC) coupling model that takes into account the interaction between gas−liquid two-phase fluids, chemical reactions of minerals (dissolution and precipitation), and temperature variations of the reservoir in CBM displacement by hot flue gas was established first. Besides, the mechanism of gas recovery enhancement by hot flue gas was analyzed based on the validated parameters in the THMC coupling model, including gas−liquid two-phase effective pressure in fractures, gas concentration, gas content, calcite content, H + concentration, and spatiotemporal evolution laws of temperature. Furthermore, the variations of the effective breakthrough radius, gas recovery amount, and recovery enhancement efficiency under the influence of different pressures, components, and temperatures of the flue gas were analyzed. Finally, the dynamic response relationship between the main engineering control parameters and the recovery enhancement efficiency in CBM displacement by hot flue gas was further investigated. This study can provide theoretical guidance for the engineering control of recovery enhancement efficiency in CBM displacement by hot flue gas.

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Section: Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic Response of Gas Recovery Enhancement Efficiency in Coalbed Methane Displacement by Hot Flue Gas: From the Perspective of Thermo–Hydro–Mechanical–Chemical Coupling

Liu,

Shi,

Liu

et al. 2024

Energy Fuels

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“…In summary of the current research status, implementing stress relief measures is essential for extracting gas from deep coal seams. These measures aim to enhance coal seam permeability by improving the coal pore–fracture structure, thereby facilitating the gas flow . In practical engineering, the degree of stress relief induced by flushing is commonly quantified by the borehole coal output.…”

Section: Introductionmentioning

confidence: 99%

“…These measures aim to enhance coal seam permeability by improving the coal pore–fracture structure, thereby facilitating the gas flow. 29 In practical engineering, the degree of stress relief induced by flushing is commonly quantified by the borehole coal output. A higher borehole coal output typically signifies a more substantial level of stress relief achieved through flushing.…”

Section: Introductionmentioning

confidence: 99%

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Zhao,

Zhang,

Liu

et al. 2024

ACS Omega

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Stress relief-induced enhanced permeability is one of the crucial measures for promoting gas desorption flow and strengthening gas extraction. In order to examine the impact of stress relief and its magnitude on gas migration, this article explores the gas desorption flow during the stress relief process and elucidates the influence of stress relief degree on gas extraction. The results indicate that considering the analysis of the pore structure effect on gas seepage, the four coal samples' permeability is ranked as PDS > CSL > JZS > GHS. Throughout the stress relief process, the gas desorption rates of different coal samples under various stress paths exhibit varying degrees of increase. As an illustration, following 3600 s of stress alterations, the gas desorption rate of CSL1# experiences a notable increase, surging by 2.57 times; PDS2# shows 55.93 times increase after 4200 s, and JZS3# exhibits 3.13 times increase after 5400 s. A stress relief degree model is established to investigate the variation of horizontal stress and stress relief degrees under different borehole spacings, vertical stresses, cohesion, and internal friction angles for various borehole diameters (coal output). Optimal stress relief is achieved with a borehole diameter greater than 1.52 m with a borehole spacing set at 4 m. When the stress relief degree exceeds 30%, the corresponding borehole diameter ranges for different vertical stresses are 1.49−1.6 m. Similarly, for cohesion, the ranges are 1.25−1.68 m, and for internal friction angles, the ranges are 1.39−1.53 m. The research results can provide valuable insights for determining parameters in the on-site construction of stress relief boreholes.

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“…Coal is a heterogeneous porous material containing a large number of randomly distributed natural fractures and defects. , During underground coal mining and roadway excavation, coal ahead of the working face typically undergoes complex loading–unloading processes. Under the action of mining-induced stress, the generation of new fractures and propagation of initial fractures will lead to the deformation and destabilization of coal, greatly increasing the risk of accidents such as coal and gas outbursts and the unstable deformation of roadways. − The macroscopic instability of any coal or rock mass is caused by fracture initiation, propagation, and coalescence at the microscale. , Therefore, it is of great significance to study the dynamic evolution of fractures in coal and rock during the loading and progressive processes and their influence on the seepage process. The results will contribute to the analyses of the gas migration and occurrence in coal and the control of deep coal and rock dynamic disasters.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Coal Fractures and Its Influence on Permeability during Progressive Failure Based on In Situ CT Scanning

Liu,

Li,

Lin

et al. 2024

Energy Fuels

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In the process of deep coal resource extraction, a large number of cracks will be generated in the coal body in front of the working face under mining stress, causing large-scale instability and damage to the coal seam. However, due to limitations in experimental conditions, there is little research on the specific process of crack propagation under mining-induced stress. In response to this situation, this article adopts in situ CT scanning technology to extract the dynamic development process of coal sample fractures under the mining stress path and the traditional triaxial loading path. The damage stages of the coal samples were characterized by analyzing the corresponding stress− strain curves. The reconstruction results of coal sample fractures were quantitatively characterized from four perspectives�fractal dimension, equivalent fracture opening, porosity, and crack volume�and the PNM model. This analysis also elucidated the changes of the internal flow field and permeability during the damage process. Furthermore, the digital volume correlation (DVC) method was utilized to study the evolution of the displacement and strain fields in middling coal samples throughout the loading process. Finally, this study explored the mechanisms of crack propagation by examining the distinct behaviors observed under the two stress paths. The research results of this article have certain reference significance for the study of the coal damage destruction mechanism and fluid transport law under mining stress.

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Study on the influence of stress constraint conditions on multi-scale gas emission characteristics in in-situ coal

Cited by 8 publications

References 57 publications

Dynamic Response of Gas Recovery Enhancement Efficiency in Coalbed Methane Displacement by Hot Flue Gas: From the Perspective of Thermo–Hydro–Mechanical–Chemical Coupling

Dynamic Response of Gas Recovery Enhancement Efficiency in Coalbed Methane Displacement by Hot Flue Gas: From the Perspective of Thermo–Hydro–Mechanical–Chemical Coupling

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Evolution of Coal Fractures and Its Influence on Permeability during Progressive Failure Based on In Situ CT Scanning

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