Numerical simulation of sectional hydraulic reaming for methane extraction from coal seams

Fan, Yu; Shu, Longyong; Huo, Zhonggang; Hao, Jing; Li, Yang

doi:10.1016/j.jngse.2021.104180

Cited by 22 publications

(22 citation statements)

References 25 publications

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“…According to the permeability curve after hydraulic flushing and the stress state of coal around the hole, the area around hydraulic flushing can be divided into three zones (Hao et al, 2014;Fan et al, 2021). The first is the increased permeability zone; that is, the stress decreased zone, which is 0-2.1 m away from the hole.…”

Section: Permeability Evolution Of the Long Axis Of The Equivalent El...mentioning

confidence: 99%

Morphological characteristics and permeability evolution of deep mine gas drainage boreholes

et al. 2022

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Structural coal has low permeability and high gas content. The increase of mining depth seriously restricts the safe mining of deep mines. Hydraulic flushing is the main means of gas extraction. The shape of the hydraulic flushing hole is an important basis to determine the pumping radius, which is widely regarded as a cylinder. However, due to the differences in the stress level, water force, friction and external moisture, the pore morphology, and permeability evolution need to be further studied. At present, the hole shape for hydraulic punching is equivalent to a cylinder in drilling design and evaluation, which is one of the important bases to determine the effective extraction radius. However, the hole shape is affected by many factors, so the scientific equivalent to a cylinder remains to be discussed. The BR-PKN equation describing the hole shape is established by introducing and combining the Bergmark–Roos equation and PKN model, and the hole’s shape is shown by MATLAB. To verify its accuracy, YZD18.5 is used as an onsite logging tool for data acquisition and analysis, and the hole section is drawn. The BR-PKN equation and permeability evolution model are simulated by COMSOL Multiphysics, and the permeability evolution law of conventional cylinder with hydraulic flushing is compared and analyzed. The results show that 1) the shape of the hydraulic punch hole is ellipsoid with three different axes, and its horizontal section is approximately an ellipse; 2) within the influence range of quasi-ellipsoid holes, the permeability changes in the long and short axis of quasi-ellipsoid holes are similar. The permeability evolution curve of the coal first increases, then decreases, and finally, flattens with the increase of distance from borehole, and the permeability of the coal body increases with the extension of extraction time); 3) the permeability of the equivalent ellipsoid pore decreases with the increase in coal water content. The effective radius in the long and short axes of the minimum cross section of the quasi-ellipsoid hole is 0.89 and 0.95 times the effective extraction radius of the equivalent cylinder, which provides a basis for a drilling layout.

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Section: Permeability Evolution Of the Long Axis Of The Equivalent El...mentioning

confidence: 99%

Morphological characteristics and permeability evolution of deep mine gas drainage boreholes

et al. 2022

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“…In recent years, researchers are interested in the deformation and failure of coal in the process of hydraulic transformation, and some modern equipment including electromagnetic radiation signal, acoustic emission monitoring, and DC resistance experiment is used to monitor this process. Numerical simulation software is also widely used to simulate and predict the effect of hydraulic transformation measures because of its convenient and high efficiency. − …”

Section: Introductionmentioning

confidence: 99%

“…Numerical simulation software is also widely used to simulate and predict the effect of hydraulic transformation measures because of its convenient and high efficiency. 49 − 52 …”

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of the Drainage Effect Based on Improved Hydraulic Flushing Technology

Zhang

Liu

et al. 2022

ACS Omega

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The composite structure coal seam composed of coal seams with strong and weak deformation is widely developed in the coalfields in Southwest and North China. The implementation of hydraulic flushing in soft coal stratification can effectively relieve the pressure and increase the permeability of coal seams, so it can improve the effect of underground gas drainage. Taking Xin'an Coal Mine, West Henan province, China, as an example, this paper discussed the influence of hydraulic flushing on the gas drainage effect in soft coal seam by means of field investigation, numerical simulation analysis, similar simulation, and field verification. As the same time, a fluid−solid coupling model of gas drainage based on layered hydraulic flushing technology is established, and the differences and reasons of the gas drainage effect after layered hydraulic flushing in soft and hard composite coal seams are discussed. The results show that (1) the gas concentration change of layered flushing boreholes intermittently rises rapidly, and there is no obvious law, while that of conventional flushing boreholes shows a regular attenuation trend. (2) According to the numerical simulation results, after 30 days of drainage, the effective drainage range of layered hydraulic flushing is 8.33 m 3 higher than that of conventional hydraulic flushing. (3) There are not a few points where the single borehole concentration data of each row of layered flushing boreholes are in the high level. Meanwhile, the maximum concentration of all conventional flushing boreholes is less than 40%, except that one borehole can reach 70% at the beginning. (4) All of the average gas drainage concentration of single-row boreholes using layered flushing technology is greater than 20% in the vast majority of days, while that of the conventional flushing boreholes is only higher than 20% in row 5 and has only lasted for 2 days. The difference of the drainage effect is obvious.

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“…For coal seams with high permeability, a reasonable gas drainage system, reasonable drainage negative pressure, drilling and sealing methods, etc., can significantly improve the coal seam gas recovery rate. , However, due to the influence of coal seam sedimentary environment, geological structure, and other factors, the permeability of coal seams in most mining areas in China is generally low, only 10 –4 –10 –3 mD, which is not conducive to gas drainage. , To achieve the purpose of high-efficiency drainage, some artificial strengthening and antireflection measures must be taken to improve the permeability of coal seam. Among these measures, hydraulic punching, hydraulic slotting, hydraulic fracturing, and other hydraulic measures are commonly used. − These mainly use the impact, disturbance, and jet of high-pressure water to locally relieve the stress of the coal body around the borehole so as to improve the permeability and gas flow conditions of the coal seam. − …”

Section: Introductionmentioning

confidence: 99%

New Technology of Mechanical Cavitation in a Coal Seam to Promote Gas Extraction

et al. 2022

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Realizing efficient gas drainage in low permeability coal seams has always been a difficult problem for coal miners. Based on this, this paper proposes a new technology of large-diameter mechanical cave-making to promote gas extraction in a coal seam. This technology mainly uses the pressure of a water injection pump to control the automatic opening and closing of a mechanical reaming device to realize mechanical cavitation, and the hole diameter can reach up to 500 mm. The gas drainage effect of mechanical cavitation drilling is analyzed by a numerical simulation, which shows that under the condition of the same drainage time, the larger the cavitation radius is, the larger the effective influence radius of gas drainage is. According to the field test results, the time of single cave-making is about 5 min, and the speed of cave-making is fast. The coal output of a single cave is 0.42 t/m, and the pressure relief effect is obvious. Compared with ordinary drilling, the gas drainage concentration of mechanical cavitation drilling is increased by 2 times and the net amount of drainage is increased by 1.8 times. Large-diameter mechanical cavitation technology can better improve the gas drainage effect of outburst coal seams with low permeability and has a good application prospect.

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Numerical simulation of sectional hydraulic reaming for methane extraction from coal seams

Cited by 22 publications

References 25 publications

Morphological characteristics and permeability evolution of deep mine gas drainage boreholes

Morphological characteristics and permeability evolution of deep mine gas drainage boreholes

Comparative Analysis of the Drainage Effect Based on Improved Hydraulic Flushing Technology

New Technology of Mechanical Cavitation in a Coal Seam to Promote Gas Extraction

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