scholarly journals Study on the Radial Displacement Law and Permeability Enhancement Effect of Coal Body around Hydraulic Flushing Drilling

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
He Yang ◽  
Dejun Miao ◽  
Zhen Liu ◽  
Dawei Zhao ◽  
Mingrui Zhang
Keyword(s):  
Coalbed Methane ◽  
Radial Strain ◽  
Interaction Mechanism ◽  
Borehole Diameter ◽  
Equivalent Diameter ◽  
Enhancement Effect ◽  
Application Process ◽  
Radial Line ◽  
Pressure Relief ◽  
Permeability Enhancement

Hydraulic flushing drilling technology can not only improve the efficiency of high-pressure and low-permeability geological reservoir coalbed methane drainage but also effectively reduce the probability of coal and gas outburst disasters through pressure relief. The main mechanism of this technology is to expand the borehole diameter through hydraulic flushing measures, increase the strain of the coal around the borehole, and increase the development of cracked pores, to improve the permeability of the coal seam and realize the dual reduction of ground and gas pressure. However, in the actual application process, the interaction mechanism among the stress field, the structure field, and the seepage field is still not clear, and there is no clear method to accurately determine the pressure relief range based on the pressure relief mechanism in order to carry out reasonable drilling arrangements. Therefore, this article comprehensively uses laboratory experiments, numerical simulations, and field practices to fully explain the hydraulic flushing pressure relief mechanism and proposes a method to accurately determine the pressure relief range based on the radial line strain law. The results based on radial line strain showed that the effective relief radius expands to 0.86 m once adopting the Φ579 mm hydraulic flushing borehole compared to Φ160 mm; the borehole’s equivalent diameter of drilling field #11 is 2 to 3 times than that of #10 and 1.2 times the average CBM extraction amount. Therefore, as the borehole diameter increases, the permeability and radial line strain of the coal around the borehole increase significantly, but the tendency of the increase in permeability decreases with increasing vertical stress. The findings of this study can help for a better understanding of the pressure relief and permeability enhancement mechanism of hydraulic flushing, and the method of determining the pressure relief range based on radial strain can also provide a new way for other mines to practice ideas.

scholarly journals Permeability Enhancement and Gas Drainage Effect in Deep High Gassy Coal Seams via Long-Distance Pressure Relief Mining: A Case Study

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiang He ◽  
Ke Yang ◽  
Penghua Han ◽  
Wenjie Liu ◽  
Zhonghao Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Protective Layer ◽  
Enhancement Effect ◽  
Yield Model ◽  
Long Distance ◽  
Pressure Relief ◽  
Gas Drainage ◽  
Permeability Enhancement ◽  
Seam Mining

Coal 3 in group A is employed as a protective layer to release long-distance coal 4 in group B in Paner colliery (approximately 80 m vertical interval) as the mining depth extends downward, which is the first engineering test in the Huainan coal mining area. To evaluate the validity of the scheme, the permeability distribution, and evolution law, gas pressure distribution characteristics, swelling deformation, pressure relief range, and gas drainage volume of the protected coal seam are analyzed using a FLAC3D numerical simulation and field measurements. Therefore, different stress-permeability models are adopted for caved, fractured, and continuous deformation zones, and a double-yield model is applied in the goaf based on compaction theory to improve the accuracy of the numerical simulation. The results indicate that the extraction of coal 3 has a positive effect on permeability enhancement and pressure relief gas drainage. However, the dip angle of coal measurements causes asymmetric strata movement, which leads to the pressure relief and permeability enhancement area shifting to the downhill side, where the permeability enhancement effect of the downhill side is better than that of the uphill side. The permeability enhancement zone is an inverted trapezoid, but the effective pressure relief range is a positive trapezoid. The permeability of the protected coal seam in the pressure relief zone is significantly higher than that in the compressive failure zone. The permeability in the pressure relief zone will decrease again due to the recompaction of the coal seam with an advancement of the longwall face. Thus, pressure relief gas drainage is suggested during long-distance protective coal seam mining to eliminate gas hazards.

Applicability of The Equivalent Diameter Approach to Estimate Vortex Shedding Frequency and Acoustic Resonance Excitation From Different Finned Cylinders In Cross-Flow

2021 ◽  
Author(s):  
Mohammed Alziadeh ◽  
Atef Mohany
Keyword(s):  
Strouhal Number ◽  
Vortex Shedding ◽  
Interaction Mechanism ◽  
Acoustic Resonance ◽  
Resonance Excitation ◽  
Equivalent Diameter ◽  
Effective Diameter ◽  
Finned Tubes ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Abstract This article explores the applicability of utilizing different equivalent diameter (Deq) equations to estimate the vortex shedding frequency and onset of self-excited acoustic resonance for various types of finned cylinders. The focus is on three finned cylinder types that are commonly used in industrial heat exchangers: straight, twist-serrated, and crimped spirally finned cylinders. Within each type of fins, at least three different finned cylinders are investigated. The results indicate that at off-resonance conditions, utilizing the appropriate equivalent diameter collapses the Strouhal number data within the typical Strouhal number variations of an equivalent diameter circular, bare cylinder. However, when acoustic resonance is initiated, the onset and the peak of resonance excitation in all of the finned cylinder cases generally occurred at a reduced flow velocity earlier than that observed from their equivalent diameter bare cylinders. This suggests that although utilizing the appropriate equivalent diameter can reasonably estimate the vortex shedding frequency away from acoustic resonance excitation, it cannot be used to predict the onset of acoustic resonance in finned tubes. The findings of this study indicate that the effective diameter approach is not sufficient to capture the intrinsic changes in the flow-sound interaction mechanism as a result of adding fins to a bare cylinder. Thus, a revision of the acoustic Strouhal number charts is required for finned tubes of different types and arrangements.

scholarly journals Effects of Supercritical CO2 Treatment Temperature on Functional Groups and Pore Structure of Coals

2019 ◽  
Vol 11 (24) ◽  
pp. 7180
Author(s):  
Zhaolong Ge ◽  
Mengru Zeng ◽  
Yugang Cheng ◽  
Haoming Wang ◽  
Xianfeng Liu
Keyword(s):  
Pore Structure ◽  
Functional Groups ◽  
Coalbed Methane ◽  
Co2 Sequestration ◽  
Structural Changes ◽  
Fractal Theory ◽  
Treatment Temperature ◽  
Attenuated Total Reflection ◽  
Enhancement Effect ◽  
Methane Recovery

The buried depth of a coal seam determines the temperature at which CO2 and coal interact. To better understand CO2 sequestration, the pore structure and organic functional groups of coal treated with different ScCO2 temperatures were studied. In this study, three different rank coals were treated with ScCO2 at different temperatures under 8 MPa for 96 h in a geochemical reactor. The changes in pore structure and chemical structure of coal after ScCO2 treatment were analyzed using mercury intrusion porosimetry, attenuated total reflection Fourier transform infra-red spectroscopy, fractal theory, and curve fitting. The results show that the enhancement effect of ScCO2 on pore structure of coal becomes less significant as the increase of buried depth. In most of the treated coal samples, the variation proportion of mesopores decreased and the variation proportion of macropores increased. In the relatively higher rank coals, the degree of condensation (DOC) of aromatic rings decreased after treatment with ScCO2. The DOC values showed a U-shape relationship with temperature, and the aromaticity showed a downward trend with increasing temperature. The chemical structural changes in the relatively lower rank coal sample were complex. These findings will provide an understanding of mechanisms relevant to CO2 sequestration with enhanced coalbed methane recovery under different geothermal gradients and for different ranks of coal.

Numerical Simulation Analysis of the Permeability Enhancement and Pressure Relief of Auger Mining

2019 ◽  
Vol 29 (2) ◽  
pp. 931-948 ◽  
Author(s):  
Yong Yuan ◽  
Zhongshun Chen ◽  
Chaofeng Yuan ◽  
Cheng Zhu ◽  
Hongmin Wei ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Pressure Relief ◽  
Permeability Enhancement

Magnetic permeability enhancement effect in the Fe86-xNbxB14 (x = 5, 6) amorphous alloys

2005 ◽  
Vol 202 (13) ◽  
pp. 2574-2581 ◽  
Author(s):  
G. Haneczok ◽  
J. E. Frąckowiak ◽  
A. Chrobak ◽  
P. Kwapuliński ◽  
J. Rasek
Keyword(s):  
Magnetic Permeability ◽  
Amorphous Alloys ◽  
Enhancement Effect ◽  
Permeability Enhancement

The Mössbauer Study of Magnetic-permeability-enhancement Effect in the Fe86-xNbxB14(x=5, 6) Amorphous Alloys

2004 ◽  
Vol 54 (S4) ◽  
pp. 109-112 ◽  
Author(s):  
J.E. Frackowiak ◽  
G. Haneczok ◽  
P. Kwapuliński ◽  
J. Rasek ◽  
A. Chrobak
Keyword(s):  
Magnetic Permeability ◽  
Amorphous Alloys ◽  
Enhancement Effect ◽  
Mössbauer Study ◽  
Permeability Enhancement

scholarly journals Study on Pressure Relief Effect and Rock Failure Characteristics with Different Borehole Diameters

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Shiwei Liang ◽  
Long Zhang ◽  
Di Ge ◽  
Qiong Wang
Keyword(s):  
Acoustic Emission ◽  
Research Result ◽  
Borehole Diameter ◽  
Tunnel Construction ◽  
Emission Characteristics ◽  
Pressure Relief ◽  
Failure Characteristics ◽  
Damage And Failure ◽  
Acoustic Emission Count ◽  
Relief Effect

Rock burst is a common tunnel and mine dynamic disaster, especially for deep buried tunnels, which often leads to tunnel construction delay and even induces tunnel collapse and subsidence of strata. Rock drilling is one of the effective pressure relief methods to prevent these disasters. In order to study the influence of borehole diameter on rock mass pressure relief effect, indoor acoustic emission characteristics and numerical simulation of rock samples with different borehole diameter were studied. The research result shows that with the increase in borehole diameter, the effect of borehole pressure relief is better. Different borehole diameters do not change the overall trend of acoustic emission evolution, but it will lead to different acoustic emission count characteristics of rock damage and failure, especially the maximum acoustic emission count characteristics and corresponding strain values. The existence of drilling will lead to the failure stress of rock in advance. Moreover, the existence of drilling causes a great change in the failure mode of the specimen.

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