An explanation of large-scale coal and gas outbursts in  underground coal mines: the effect of low-permeability zones on abnormally abundant gas

An, Fenghua; Wang, Chenghao

doi:10.5194/nhess-14-2125-2014

Cited by 39 publications

(24 citation statements)

References 26 publications

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“…There are the front abutment zone, crushed zone, stress-relief zone and the recompaction zone (Durucan and Edwards 1986). Similarly, based on the distribution of pore pressure, the coal seam is divided into a zone of coal gas abundance zone, a low permeability zone and a pristine zone (An and Cheng 2014). As shown in Fig.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Gas adsorption/desorption, as a factor for the generation of gas outbursts, was initially studied by Russian investigators in the 1950s (Lama and Saghafi 2002). Recently, the sorptive behavior of coal has been extensively investigated both theoretically and experimentally, as related to the impact of sorption-induced swelling/shrinkage resulting from CO 2 sequestration, enhanced coalbed methane (CBM) production and the prevention of outbursts (An and Cheng 2014;Hol et al 2011Hol et al , 2012Wu et al 2011). However, few studies relate the contribution of the rapid stress-driven desorption with the redistribution of pore pressure in coal seams during excavation (Wang et al 2013a).…”

Section: Introductionmentioning

confidence: 99%

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The role of gas desorption on gas outbursts in underground mining of coal

Zhi

Elsworth

2016

Geomech. Geophys. Geo-energ. Geo-resour.

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Violent gas outbursts are one of the most severe hazards in underground mining. When outbursts occur, a large amount of coal and gas is suddenly and violently ejected into the roadway and working area with the possibility of serious hazard and injury. Recent studies have shown that the physical behavior responsible for the energetic failure of coal is entirely consistent with coal viewed as a dual porosity-dual permeability-dual stiffness continuum where strength is proportional to effective stresses, and where effective stresses are controlled by both the pore pressure and varying stress field. Gas desorption driven by overstress is highlighted in this study as the key factor responsible for the increase in pore pressure close to the working face, and implicated together with elevated stress level, permeability evolution and drainage conditions in the triggering of outbursts. In this work, we incorporate the likely mass rates of desorption driven by an increase in abutment stress and mediated by permeability evolution to define the rates and distributions of gas pressure changes. The changing pattern of pressure redistribution is identified, and parametric studies are then performed to investigate all the key factors that influence the redistribution of pore pressure with respect to the deformation of the coal seam. Permeability evolution in the overstressed zone is determined by the evolution of porosity, which is attributed to both the change in effective stresses in the abutment and sorptioninduced strain. Considering the weakening effects of desorption-induced pressure increase, energetic failure may be triggered from the pillar as defined by the Mohr-Coulomb failure criterion. According to this analysis, the pore pressure adjacent to the working face may be lowered by drainage in a measurable way to reduce the likelihood of an outburst. This model is capable of predicting the potential risk ahead of the working face during mining and can be adapted to different conditions in terms of varying mechanical factors, coal properties and mining methods.

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Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of gas desorption on gas outbursts in underground mining of coal

Zhi

Elsworth

2016

Geomech. Geophys. Geo-energ. Geo-resour.

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“…1,3,4 Therefore, controlling methane emissions in coal mines becomes very important for controlling the greenhouse emission in coal industry. [7][8][9][10][11][12] When the concentration of methane is in the explosive range between 5% and 15% in underground roadways, the CMM can be easily ignited resulting in methane explosions. 2 Potential usage of the CMM exists in the following areas such as fuel in boilers, steel furnace, and turbines for power generation, injection gas to natural gas pipelines, and vehicle fuel.…”

Section: Introductionmentioning

confidence: 99%

“…A proper CMM control system can not only enhance coal productions because of less frequent mining downtime and production slowdown caused by a higher methane concentration in underground entries and working face but also improve the mining safety by eliminating the coal and gas outburst risk of coal seam from a lower CMM content (pressure) in coal seams. [7][8][9][10][11][12] When the concentration of methane is in the explosive range between 5% and 15% in underground roadways, the CMM can be easily ignited resulting in methane explosions. 6 Collectively, the CMM control in underground coal mines is an important step to meet the challenge of climate change, diverse energy supplies and enhance the safety performance and mining management.…”

Section: Introductionmentioning

confidence: 99%

Influence radius of gas extraction borehole in an anisotropic coal seam: Underground in‐situ measurement and modeling

Yue

Hui

Yue

et al. 2019

Energy Science & Engineering

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Coal seam degasification by in‐seam drilling borehole is one of the popular techniques for coal mine methane (CMM) control. How to address the conflict between borehole numbers and drainage durations always arouses researchers’ interests. Furthermore, since coal has anisotropy structures, how the anisotropy feature of coal associated with bedding and cleat structure affects the influence radius of the drainage borehole has rarely been considered. In order to address the above‐mentioned issues, this work not only conducted underground in‐situ measurement of the borehole influence radius within 200 days in an anisotropy coal seam at Jiulishan coal mine in China, but also modeled the influence radius evolvement around borehole in an anisotropy coal seam using finite‐element based COMSOL package. The underground in‐situ measurement revealed an anisotropy feature of borehole influence radius associated with coal bedding and cleat structures. The influence radius of borehole parallel to the bedding plane in butt cleat direction is much larger than that perpendicular to the bedding plane. Ten permeability measurements of coal show that the permeability of coal parallel to the bedding plane in butt cleat direction is higher than that perpendicular to the bedding plane. Simulation results of the gas transport model in coal are consistent with underground in‐situ measurement in determining the influence radius of drainage borehole in the anisotropy coal seam. Based on modeling results, the ellipse influence area of borehole in an anisotropy coal seam is proposed, and the relationship between the influence radius of borehole and drainage time is obtained. On the basis of these findings, the proper in‐seam borehole arrangements for a specific mining panel at different drainage durations are determined. The finding of this work will be fundamental for addressing the conflict between minimizing the cost of borehole arrangement and increasing coal mining productions by adjusting CMM drainage durations.

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“…This leads to the formation of CBM-rich coals; thus, tectonic coals have huge CBM exploitation potential. However, a CBM extraction well drilled in an area hosting significant tectonic coal may seriously restrict CBM production because the tectonic coal's low permeability restricts gas desorption and migration [29,30]. Therefore, in such an area, CO 2 -ECBM is likely to be the technique implemented to solve this problem.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Study on Changes in the Pore Structures and Gas Desorption Properties of Intact and Tectonic Coals after Supercritical CO2 Treatment: Implications for Coalbed Methane Recovery

Zou

et al. 2018

Energies

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Tectonic coals in coal seams may affect the process of enhanced coalbed methane recovery with CO2 sequestration (CO2-ECBM). The main objective of this study was to investigate the differences between supercritical CO2 (ScCO2) and intact and tectonic coals to determine how the ScCO2 changes the coal’s properties. More specifically, the changes in the tectonic coal’s pore structures and its gas desorption behavior were of particular interest. In this work, mercury intrusion porosimetry, N2 (77 K) adsorption, and methane desorption experiments were used to identify the difference in pore structures and gas desorption properties between and intact and tectonic coals after ScCO2 treatment. The experimental results indicate that the total pore volume, specific surface area, and pore connectivity of tectonic coal increased more than intact coal after ScCO2 treatment, indicating that ScCO2 had the greatest influence on the pore structure of the tectonic coal. Additionally, ScCO2 treatment enhanced the diffusivity of tectonic coal more than that of intact coal. This verified the pore structure experimental results. A simplified illustration of the methane migration before and after ScCO2 treatment was proposed to analyze the influence of ScCO2 on the tectonic coal reservoir’s CBM. Hence, the results of this study may provide new insights into CO2-ECBM in tectonic coal reservoirs.

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An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Cited by 39 publications

References 26 publications

The role of gas desorption on gas outbursts in underground mining of coal

The role of gas desorption on gas outbursts in underground mining of coal

Influence radius of gas extraction borehole in an anisotropic coal seam: Underground in‐situ measurement and modeling

Laboratory Study on Changes in the Pore Structures and Gas Desorption Properties of Intact and Tectonic Coals after Supercritical CO2 Treatment: Implications for Coalbed Methane Recovery

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