Influence factors analysis of a flexible gel sealing material for coal-bed methane drainage boreholes

Zhai, Cheng; Xiang, Xianwei; Zou, Quanle; Yu, Xu; Xu, Yanming

doi:10.1007/s12665-016-5286-1

Cited by 30 publications

(18 citation statements)

References 24 publications

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“…The calculation parameters in Equation (21) are determined according to the actual situation of the #43 coal seam in the 5004301 working face of Wudong Coal Mine, as shown in Table 2. The parameters in Table 2 are substituted into Equation (21), and the corresponding curves are calculated and plotted by the software Mathematica. These curves are used to analyze the variation of the gas pressure (P) with the extraction time (t) and the distance from the borehole center (r), and also used to find the effective extraction radius of boreholes, as shown in Figure 7.…”

Section: Theoretical Calculation Resultsmentioning

confidence: 99%

“…[13][14][15][16] Several unconventional gas resources located in coal deposits have been studied as systems. [17][18][19] At present, gas predrainage along coal seam boreholes is mainly used in China, which is also an effective method for coal seam gas recovery and gas disaster prevention and control in coal mines, [20][21][22] as shown in Figure 2. The effective extraction radius of borehole is an important parameter for this method, which is used for the determination of borehole spacing in gas extraction.…”

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confidence: 99%

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Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Wang

Chang

et al. 2019

Energy Science & Engineering

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The effective extraction radius of borehole is the main parameter for determining the design and layout for coalbed methane extraction. This paper is aimed at the problem that the criteria and calculation methods for the effective extraction radius of coal seams are not comprehensive. With Wudong Coal Mine in China taken as an example, the critical gas pressure (0.441 MPa) for the calculation of effective extraction radius is first defined. Next, the gas seepage unit model around the borehole is developed, and the theoretical mathematical expression to calculate the effective extraction radius is derived. Then, the numerical simulation of gas extraction is carried out through a computational fluid dynamics program, and the effective extraction radius is obtained numerically. Furthermore, the influence of original gas pressure, borehole diameter, and negative pressure of gas extraction on gas extraction is analyzed. Finally, the results from the theoretical calculation and numerical simulation are validated by the field engineering measurement and the average relative error is small (less than 10%). The results indicate that the effective extraction radius has a linear relationship with the extraction time. Moreover, it is found that the original gas pressure is the main factor affecting the effective extraction radius and the effective extraction radius is proportional to the borehole diameter and negative pressure through analysis. Therefore, the above findings can provide a theoretical basis for determining parameters such as borehole spacing and extraction time of gas extraction in coal mines.

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Section: Theoretical Calculation Resultsmentioning

confidence: 99%

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confidence: 99%

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Wang

Chang

et al. 2019

Energy Science & Engineering

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“…To solve the problem of difficulty in sealing fractures in coal and rock masses around the borehole [16][17][18][19][20], a new grouting solidification method is proposed in this study to seal fractures in coal and rock masses around the boreholes using an expandable material with high water content (as shown in Figure 1). The expandable material with high water content used in this method is a novel material formed by adding expander to high water content material [21].…”

Section: Introductionmentioning

confidence: 99%

Sealing Behavior and Flow Mechanism of Expandable Material Slurry with High Water Content for Sealing Gas Drainage Boreholes

Lan

2018

Geofluids

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Predrainage of coalbed gas by underground drilling is one of the main approaches for eliminating gas disasters in coal mines. Owing to the unsatisfactory sealing effect of conventional sealing materials, coalbed gas drainage boreholes face serious air leakage, resulting in a relatively low concentration of the drained gas. This study presents a new grouting solidification method for sealing boreholes using expandable materials with high water content. An experimental test method was used to study the groutability, compression resistance, and gas permeability of the expandable materials with high water content, as well as their binding properties with coal mass at different water-cement ratios. On this basis, the governing equation for slurry permeation considering the viscosity time-varying characteristics of the expandable material with high water content was established and numerically calculated. The slurry permeation patterns of the expandable material with high water content under different grouting pressures and water-cement ratios were obtained. The results show the following: (1) the expandable material with high water content was better than cement to bind with coal mass; (2) the slurry of expandable material with high water content, with a water-cement ratio above 6 : 1, is groutable, and as the water-cement ratio increases, the groutability and penetrability of the expandable material with high water content increase; (3) the optimal grouting pressure for expandable slurry with high water content is 2-3 MPa; and (4) the higher the water-cement ratio, the greater the permeation range of expandable slurry with high water content, but the increase in the permeation range is relatively small, and the optimal water-cement ratio for expandable slurry with high water content is 7 : 1. Therefore, featuring strong groutability, good sealability, high compressive strength, microexpansion, and tight binding with coal mass, expandable materials with high water content are ideal for sealing coalbed gas drainage boreholes because of their efficiency in sealing fractures in coal and rock masses around the borehole.

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“…e fractures are subsequently blocked by the particles after several days, presenting a barrier to air entering the seam. Zhai and Xiang et al [11,16] proposed a flexible gel (FG) sealing material with good compactness and stability and utilized an active sealing method to inject the FG material into the fractures around the borehole. Liu et al [17] tested the shrinkage rate and uniaxial compression strength of a sealing material composed of ordinary Portland cement (OPC) and an expansion agent and found that the best material had a water-cement ratio of 0.8 : 1.…”

Section: Introductionmentioning

confidence: 99%

Swelling Pressure of Double‐Expansive Material and Its Active Support Effect for Coal Seam Gas Drainage Borehole

Wang

Sun

2018

Advances in Materials Science and Engineering

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To improve coal seam gas drainage performance, we developed a double-expansive (DE) material to seal the borehole. The swelling process of this material includes an initial swelling stage and a secondary swelling stage. We studied the swelling pressure properties of the DE material under four constraint conditions using a self-made swelling test device. Further, the active support effect of the DE material on the borehole was analyzed by simulating borehole stability with COMSOL Multiphysics software. The results exhibit the following: (1) The swelling pressure of the DE material exhibits time-dependent behavior, and the mathematical relationship between the swelling pressure and time can be obtained by nonlinear fitting. (2) The radial swelling potential is principally formed during the secondary swelling stage, providing the main active support on the radial constraint. (3) The active support imposed on the hole wall can prevent the extension of plastic and damage regions around the borehole, for improved stability of the gas drainage borehole. Finally, field tests demonstrate improved gas drainage performance of the borehole sealed by the DE material compared to a conventional sealing material.

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Influence factors analysis of a flexible gel sealing material for coal-bed methane drainage boreholes

Cited by 30 publications

References 24 publications

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Theoretical, numerical, and experimental analysis of effective extraction radius of coalbed methane boreholes by a gas seepage model based on defined criteria

Sealing Behavior and Flow Mechanism of Expandable Material Slurry with High Water Content for Sealing Gas Drainage Boreholes

Swelling Pressure of Double‐Expansive Material and Its Active Support Effect for Coal Seam Gas Drainage Borehole

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