Failure analysis of borehole liners in soft coal seam for gas drainage

Liu, Chun; Zhou, Fang; Yang, Kangkang; Xiang, Xiao

doi:10.1016/j.engfailanal.2014.04.010

Cited by 35 publications

(18 citation statements)

References 11 publications

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“…where f c is the compressional safety factor of the borehole. [24]). induced failure, and thus it can be roughly represented by sine function as [11]…”

Section: Deformation and Failure Form Of Boreholementioning

confidence: 99%

Spatial and Temporal Distribution Law and Influencing Factors of the Mining‐Induced Deformation and Failure of Gas Boreholes

Xue

Feng

2018

Advances in Materials Science and Engineering

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Because gas boreholes are easy to damage by integrated coal mining and gas exploration, based on the practice of relieving pressure in deep thin coal seams in the Huainan mining area, a multidimensional coupling numerical simulation method was used to reveal the space-time evolution characteristics and influence factors of fracture deformation of gob-side gas boreholes. Results indicate that the danger zone for borehole fractures is primarily between 5 and 12 m above the roof of the roadway. The final-hole position has little effect on the stability of boreholes, and migrating the open-hole position to the entity coal side and roadway roof side can improve the stability of the borehole. The initial failure of the borehole occurs at a distance of 10 m behind the coal face. The failure of the borehole is largely stable at a distance of 100 to 120 m behind the coal face. With the increase in mining height, which leads to an increase in the movement of strata and an increase in pressure relief range, the shear stability of the borehole is reduced, and the extrusion stability of the borehole is improved. A hard roof condition promotes borehole shear stability, while a weak roof condition promotes borehole extrusion stability. This change can decrease the maintenance difficulty associated with “minor supports” in boreholes to a certain extent by reinforcing the support strength of “primary supports” in roadway retaining walls. The simulation results are consistent with observed results for the 11 test boreholes, and the accuracy of the numerical simulation is verified.

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“…where f c is the compressional safety factor of the borehole. [24]). induced failure, and thus it can be roughly represented by sine function as [11]…”

Section: Deformation and Failure Form Of Boreholementioning

confidence: 99%

Spatial and Temporal Distribution Law and Influencing Factors of the Mining‐Induced Deformation and Failure of Gas Boreholes

Xue

Feng

2018

Advances in Materials Science and Engineering

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“…The-ejection of coal and gas from a borehole is such a process that coal collapses in a quasi-equilibrium state and high speed mixture of coal and gas is ejected out between the drill pipe and borehole wall (Ji, 2014;Liu et al, 2014a). It is normally caused by the disturbances, e.g.…”

Section: Coal-water-gas Separation Techniquementioning

confidence: 99%

Novel integrated techniques of drilling–slotting–separation-sealing for enhanced coal bed methane recovery in underground coal mines

Zou

Lin

Zheng

et al. 2015

Journal of Natural Gas Science and Engineering

163

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Coal bed Methane (CBM), a primary component of natural gas, is a relatively clean source of energy.Nevertheless, the impact of considerable coal mine methane emission on climate change in China has gained an increasing attention as coal production has powered the country's economic development. It is well-known that coal bed methane is a typical greenhouse gas, the greenhouse effect index of which is 30 times larger than that of carbon dioxide. Besides, gas disasters such as gas explosive and outburst, etc. pose a great threat to the safety of miners. Therefore, measures must be taken to capture coal mine methane before mining. This helps to enhance safety during mining and extract an environmentally friendly gas as well. However, as a majority of coal seams in China have low-permeability, it is difficult to achieve efficient methane drainage. Enhancing coal permeability is a good choice for high-efficiency drainage of coal mine methane. In this paper, a modified coal-methane co-exploitation model was established and a combination of drilling-slotting-separation-sealing was proposed to enhance coal permeability and CBM recovery. Firstly, rapid drilling assisted by water-jet and significant permeability enhancement via pressure relief were investigated, guiding the fracture network formation around borehole for high efficient gas flow. Secondly, based on the principle of swirl separation, the coal-water-gas separation instrument was developed to eliminate the risk of gas accumulation during slotting and reduce the gas emission from the ventilation air. Thirdly, to improve the performance of sealing material, we developed a novel cement-based composite sealing material based on the microcapsule technique. Additionally, a novel sealing-isolation combination technique was also proposed. Results of field test indicate that gas concentration in slotted boreholes is 1.05-1.91 times higher than that in conventional boreholes. Thus, the proposed novel integrated techniques achieve the goal of high-efficiency coal bed methane recovery.

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“…Most coal seams in Qinshui Basin exceed 6 m in thickness and the CBM geological reserves amount reaches 6.85 × 10 12 m 3 , with an extremely high content greater than 20 m 3 /t in some areas. [13][14][15] To address the high gas content of coal seam, the most useful methods are mining the protective seam and gas pre-extraction in coal mines. 7 The strong gas adsorption of coal seam deteriorates this condition.…”

Section: Introductionmentioning

confidence: 99%

“…These complicated CMM occurrence conditions (high methane content, low permeability, strong adsorption) give Qinshui Basin great gas pressures, and great difficulties in pre-drainage in the virgin coal seam, thus leading to highly potential hazard of gas accident. [13][14][15] To address the high gas content of coal seam, the most useful methods are mining the protective seam and gas pre-extraction in coal mines. 16 However, mining protective seam demands highly strict conditions, and especially works poorly in single coal seam.…”

Section: Introductionmentioning

confidence: 99%

A new pattern of underground space‐time tridimensional gas drainage: A case study in Yuwu coal mine, China

Nie

et al. 2019

Energy Science & Engineering

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With the increase of mining depth, the high gassy coal mine confronts with a variety of gas problems, such as gas concentration exceeding the limit in the working face, gas outburst and gas explosion. According to the situation of gas drainage in Qinshui Basin (South of Shanxi Province, China) and enlightened by horizontal directional drillings (HDD) and multi‐branched horizontal wells, a new gas drainage pattern that inverted π‐shape km borehole layout was proposed. Verified in Yuwu Coal Mine, the gas drainage data were standardized via the unified theory of standardization. It could dropped the coal seam gas content to 7.71 m3/t, and increased the gas drainage rate to 34.2%, which conformed to the Chinese regulation (<8 m3/t, >30%, respectively). This pattern has a significant effect on coal mines with a single seam, where protective seam mining technology was unsuitable to prevent gas outburst and gas explosion.

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Failure analysis of borehole liners in soft coal seam for gas drainage

Cited by 35 publications

References 11 publications

Spatial and Temporal Distribution Law and Influencing Factors of the Mining‐Induced Deformation and Failure of Gas Boreholes

Spatial and Temporal Distribution Law and Influencing Factors of the Mining‐Induced Deformation and Failure of Gas Boreholes

Novel integrated techniques of drilling–slotting–separation-sealing for enhanced coal bed methane recovery in underground coal mines

A new pattern of underground space‐time tridimensional gas drainage: A case study in Yuwu coal mine, China

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