Coal bed methane drainage with long directional boreholes

Ruban, A. D.; Zaburdyaev, V. S.; Харченко, А. В.

doi:10.1134/s1062739148030057

Cited by 8 publications

(2 citation statements)

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“…Thus, the optimization of layout layer of the LHB in overlying strata is the key to efficient gas extraction. However, currently, the layout layer of the LHB is mostly based on engineering experience and physical or numerical simulation results (Ruban et al 2012;Wang et al 2018). Theoretical analysis and determination of the layout layer of the LHB based on the above-mentioned three parameters have rarely been studied.…”

Section: Introductionmentioning

confidence: 99%

RETRACTED: A new method for layout layer optimization of long horizontal borehole for gas extraction in overlying strata: a case study in Guhanshan coalmine, China

Guo

Yuan

et al. 2021

Preprint

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The large emission of pressure-relief gas in coal mining will cause atmospheric greenhouse effect. Arranging long horizontal borehole (LHB) to extract the gas is an effective solution. However, the determination of LHB layout layer in strata has a decisive effect on efficient gas extraction. A "zone-block" theoretical method for determining the LHB layout layer, in present study, was proposed by combining physical simulation test, theoretical analysis and engineering application. Three processes of the method were presented. Firstly, stable fractured subzone (SFSZ) was the optimum zone of the LHB layout based on the analysis of mining-induced fractures distribution and the borehole stability, and spatial location boundaries of the SFSZ in overlying strata were defined. Secondly, the SFSZ was divided into nine-grid blocks, the LHB layout suitability rate of each block were determined according to borehole stability rate, fracture permeability rate and gas accumulation rate. Finally, the LHB drilling could be conducted sequentially according to the layout suitability rate of each block in SFSZ. Field application results show that: the maximum and average amount of pure gas extracted through single borehole arranged in block I can reach up to 5.52 and 2.43 m3·min-1, respectively; and the pure amount in the entire extraction stage of the borehole is 2.53 and 6.69 times of boreholes arranged in blocks II and III, respectively. The proposed method can effectively determine the LHB layout layer in strata, so as to improve the gas extraction efficiency and ensure safe and green mining.

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Section: Introductionmentioning

confidence: 99%

RETRACTED: A new method for layout layer optimization of long horizontal borehole for gas extraction in overlying strata: a case study in Guhanshan coalmine, China

Guo

Yuan

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Previous studies have identified four methods for extracting pressure-relief gas from the gob during underground mining: constructing entries above the target panel, drilling boreholes from the surface to the underground, creating high-level boreholes, and drilling long horizontal boreholes (LHB) from underground entries into the overlying strata. [12][13][14][15][16] Presently, coal mines in China predominantly employ the LHB technique due to its cost-effectiveness and high construction efficiency (Figure 1). 17,18 As depicted in Figure 1, LHBs are drilled at an inclined angle toward the targeted strata layers, extending horizontally before panel excavation.…”

Section: Introductionmentioning

confidence: 99%

A new method for layout layer optimization of long horizontal boreholes for gas extraction in overlying strata: A case study in Guhanshan coal mine, China

Guo,

Zhao

et al. 2024

Energy Science & Engineering

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The gases released by underground coal mining pose a threat to mine safety, lead to resource wastage, and contribute to environmental pollution. Employing long horizontal boreholes (LHB) for gas extraction proves to be an effective solution. However, accurately determining the LHB's position within the overlying rock strata is challenging due to complex mining and geological conditions. This study introduces a novel “zone‐position” method for identifying the optimal LHB placement, utilizing both physical simulation tests and theoretical analysis. The approach comprises two steps. Initially, it identifies the appropriate LHB layout zone within the overlying strata. It delineates four subzones within the fractured zone, among which the stable fractured subzone (SFSZ) is identified as the most favorable for LHB placement. The boundaries of the SFSZ are also defined. Subsequently, the method focuses on pinpointing the LHB's precise location within the SFSZ, proposing a criterion that considers gas accumulation, strata permeability, and LHB stability. Application of this method in engineering projects demonstrates that the gas extracted by LHBs accounts for about 60% of the total gas emission. Furthermore, the volume of gas extracted at the optimal LHB location reaches up to 5.52 m3 min−1, triple that of other locations.

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Study on the effective drainage range of long horizontal borehole for goaf gas drainage

Guo,

Yuan

et al. 2024

Energy Science & Engineering

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Laying long horizontal borehole (LHB) in mining‐induced strata fractures for coal‐bed gas drainage in the goaf is a pivotal method for eliminating safety hazards, preventing atmospheric pollution, and realizing gas utilization. A crucial premise of this method is to determine the effective drainage range of the borehole, a key parameter directly affecting boreholes spacing and drainage efficiency. In this study, a model of gas seepage during LHB drainage within a circular equipotential boundary was presented, and the complex variable function theory and the mirror principle were adopted for deriving the complex potential function of gas flow under the condition of LHB drainage and the drainage volume function of a single center borehole. Besides, the main indicator to determinate the effective drainage range of LHB was given. Specifically, the indicator refers to the distance between the turning point (the point at which the change rate of the gas flow velocity is −0.002 around the borehole) and the center of the borehole. Subsequently, numerical simulation was conducted to obtain the effective drainage range of LHB within mining‐induced fractures of overlying strata, that is, 4 m < r < 7 m. Furthermore, discussion of the effective drainage range of LHB was carried out by analyzing gas flow velocity distributions and LHB drainage volumes. A case study demonstrates that a double‐borehole layout with a 10 m spacing can effectively control pressure‐relief gas in the goaf. Meanwhile, such a layout can achieve well‐balanced drainage efficiency of each borehole with a minimal difference of 0.31 m3 min−1, which is only about 7.9% of the average drainage volume of the two boreholes. The above results verify that the determined effective drainage range of LHB is reasonable. The research results can provide references for determining the drainage range of LHB in multi‐borehole layout of coal mines, and then determining the spacing of LHBs arrangement, thereby improving the efficiency of gas extraction.

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Coal bed methane drainage with long directional boreholes

Cited by 8 publications

References 0 publications

RETRACTED: A new method for layout layer optimization of long horizontal borehole for gas extraction in overlying strata: a case study in Guhanshan coalmine, China

RETRACTED: A new method for layout layer optimization of long horizontal borehole for gas extraction in overlying strata: a case study in Guhanshan coalmine, China

A new method for layout layer optimization of long horizontal boreholes for gas extraction in overlying strata: A case study in Guhanshan coal mine, China

Study on the effective drainage range of long horizontal borehole for goaf gas drainage

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