A method for improving the methane extraction concentrations of in-seam boreholes

Hu, Shengyong; Hao, Guocai; Feng, Guorui; Guo, Huabo; Wu, Dengyu

doi:10.1016/j.fuel.2020.117006

Cited by 16 publications

(9 citation statements)

References 29 publications

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“…17,18 To achieve efficient gas drainage from boreholes, Hu et al proposed a particular bag-type borehole sealing device. 19 Fu et al developed a material with dual expansion sources to seal boreholes via bag grouting sealing, which improved gas drainage efficiency in boreholes. 20 Liu et al established a full-force composite flow model to reveal the air leakage mechanism around the borehole, which they combined with cement grouting and gel injection to optimize borehole sealing and effectively improve the quality of borehole gas extraction.…”

Section: Introductionmentioning

confidence: 99%

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Air Leakage Characteristics of Gas Boreholes in Deep Coal Seams and Application of Short-Hole Grouting and Plugging

Wu,

Wang,

Fan

et al. 2024

ACS Omega

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Drilling for gas extraction is widely used as the main approach to manage gas in mines. However, gas leakage during borehole extraction reduces the root cause of the effectiveness of gas extraction. Given that forming a normal hole in the prominent coal seam of the Qingdong Coal Mine is impossible and that air leakage leads to difficulties in prepumping gas in the coal seam, we selected coal seam 3# as the object of this study. First, qualitative analysis determined that the air leakage channel restricted effective gas extraction. Second, short-hole grouting and plugging were proposed to increase the concentration and efficiency of gas extraction from the coal wall, forming a barrier by blocking the fissure network in the plastic zone of the surrounding rock of the coal roadway and preventing the air inside the roadway from penetrating into the coal seam and gas extraction drill holes. Finally, evaluation of the gas extraction efficiency between the grouting test and comparison areas indicated that the initial gas extraction concentration of a single hole could reach 89% when the depth of the selected blocking hole was 15 m. Grouting slowly decreased the gas extraction concentration from 72 to 25%, which effectively improved the speed at which the gas content was reduced in the coal body. The study findings provide a field basis for similar mines to improve their gas extraction efficiency and extend their extraction time.

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Section: Introductionmentioning

confidence: 99%

“…To achieve efficient gas drainage from boreholes, Hu et al proposed a particular bag-type borehole sealing device . Fu et al developed a material with dual expansion sources to seal boreholes via bag grouting sealing, which improved gas drainage efficiency in boreholes .…”

Section: Introductionmentioning

confidence: 99%

Air Leakage Characteristics of Gas Boreholes in Deep Coal Seams and Application of Short-Hole Grouting and Plugging

Wu,

Wang,

Fan

et al. 2024

ACS Omega

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“…After comparing multiple methods of gas recovery in the unloading zone of the extraction area, Li et al believed that oversized diameter top directional boreholes have a better gas extraction effect [19]. Considering the rapid decrease in gas extraction concentration, a bag-type borehole sealing device was developed by Hu et al to enhance the methane drainage concentration by cutting off the air leakage loop [20]. The injection of other gases is also an effective way to improve the efficiency of gas extraction.…”

Section: Introductionmentioning

confidence: 99%

Effects of Borehole Arrangement on Methane Migration and Implications for High Efficiency Extraction in Intact and Tectonic Combined Coal Seams

Chang

Dong

2022

Geofluids

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Gas extraction by bedding boreholes is a key means to realize safe mining of coal mine and protect the environment. The traditional bedding boreholes are usually constructed in the center of the coal seam, which may not obtain a high methane extraction rate because of the existence of tectonic coal sublayer with low permeability. In this paper, the gas migration characteristics of combined coal seams composed of tectonic and intact coal sublayers are investigated, and the efficient gas extraction method is further explored. The results indicate that only 2.676 kg/m3 of gas can be extracted under the traditional bedding borehole arrangement in 300 days. The tectonic coal sublayer with low permeability restricts the gas in the intact coal sublayers to flow to the extraction boreholes, which is the main reason for the low gas extraction rate. By arranging boreholes up and down alternately with a vertical spacing of 2.74 m, the maximum gas amount of 3.526 kg/m3 can be extracted, showing an increased rate of 31.8%. The optimal vertical spacing between adjacent boreholes (VSAB) raises with the relatively increasing thickness or decreasing permeability of the tectonic coal sublayer. The optimal VSAB has a linear relationship with the thickness ratio of the tectonic coal sublayer to the combined coal seams. The optimal VSAB can be obtained referring to the numerical relationship, and then, the extraction boreholes can be dilled to achieve efficient gas extraction of combined coal seams. In engineering, the dislocation arrangement of borehole can greatly improve the gas extraction efficiency and coal mine safety.

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“…Hao et al (2018) studied the anti-seepage effect of silica sol and conducted an experiment to show its effectiveness in improving borehole sealing. Hu et al (2020) analyzed the effect of surrounding rock creep on borehole sealing and proposed the method of filling the remaining voids by repeated grouting to block new fractures during CMM drainage. Based on the distribution of air-leakage fractures around boreholes, some new technologies using fine expansive particles to plug such fractures were proposed (Zhang et al 2020a(Zhang et al 2019Xia et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Method for designing the optimal sealing depth in methane drainage boreholes to realize efficient drainage

Wang

Chen

et al. 2021

Int J Coal Sci Technol

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The purpose of underground methane drainage technology is to prevent methane disasters and enable the efficient use of coal mine methane (CMM), and the sealing depth is a key factor that affects the performance of underground methane drainage. In this work, the layouts of in-seam and crossing boreholes are considered to analyze the stress distribution and failure characteristics of roadway surrounding rock through a numerical simulation and field stress investigation to determine a reasonable sealing depth. The results show that the depths of the plastic and elastic zones in two experimental coal mines are 16 and 20 m respectively. Borehole sealing minimizes the air leakage through the fractures around the roadway when the sealing material covers the failure and plastic zones, and the field test results for CMM drainage at different sealing depths indicate that the CMM drainage efficiency increases with increasing sealing depth but does not change once the sealing depth exceeds the plastic zone. Moreover, sealing in the high-permeability roadway surrounding rock does not have a strong influence on the borehole sealing performance. Considering these findings, a new CMM drainage system for key sealing in the low-permeability zone was developed that is effective for improving the CMM drainage efficiency and prolonging the high-concentration CMM drainage period. The proposed approach offers a valuable quantitative analysis method for selecting the optimum sealing parameters for underground methane drainage, thereby improving considerably the drainage and utilization rates of CMM.

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A method for improving the methane extraction concentrations of in-seam boreholes

Cited by 16 publications

References 29 publications

Air Leakage Characteristics of Gas Boreholes in Deep Coal Seams and Application of Short-Hole Grouting and Plugging

Air Leakage Characteristics of Gas Boreholes in Deep Coal Seams and Application of Short-Hole Grouting and Plugging

Effects of Borehole Arrangement on Methane Migration and Implications for High Efficiency Extraction in Intact and Tectonic Combined Coal Seams

Method for designing the optimal sealing depth in methane drainage boreholes to realize efficient drainage

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