Control of directional long borehole on gas drainage and optimal design: Case study

Zhang, Qiming; Wang, Enyuan; Li, Zhonghui; Wang, Hao; Xue, Zhaozhao

doi:10.1016/j.jngse.2022.104766

Cited by 11 publications

(4 citation statements)

References 40 publications

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“…However, there are still many problems with the technology and process of gas extraction in Chinese mines at present. The average gas extraction rate in mines is still less than 30% and the level of gas extraction and utilization is still relatively low [9][10][11][12]. One important reason is that there are many and widely distributed soft coal seam mines in China, and the low strength and poor stability of soft coal seams have led to the problem of difficult sealing of gas extraction boreholes in soft coal seams, which has directly led to the current situation of poor gas extraction efficiency in soft coal seams.…”

Section: Introductionmentioning

confidence: 99%

Expansion Characteristics and Creep Test of New Curing Expansion Material for Gas Extraction Boreholes

Jiang,

Bao,

Lei

2024

Processes

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In order to find the optimal expansion effect of a new curing expansion material so that it can better meet the requirements of the efficient sealing of drilled holes, the expansion and creep characteristics of the new curing expansion material were studied. Based on the creep results of graded loading, the Kelvin–Volgt model was selected to analyze its mechanical parameters, and a new “concentric ring” reinforcement sealing method was proposed. Numerical simulation was employed to analyze and discuss the reinforcement radius and depth of the “protective wall rock hole ring” in the “concentric ring” model, and on-site application experiments were carried out in a soft coal seam. The results show that the “concentric ring” reinforcement sealing method can effectively solve the problems of easy collapse and stress concentration instability in the sealing section of soft coal seams, ensuring long-term and efficient sealing of gas extraction boreholes in soft coal seams. When the diameter of the extraction drilling hole is 100 mm, the optimal reinforcement radius for the “protective wall rock hole ring” is 0.16–0.18 m. A reasonable reinforcement depth of the “protective wall rock hole ring” for drilling in soft coal seams is about 0.8–1 times the width of the roadway. In the on-site application process, experimental boreholes using “concentric ring” reinforcement sealing technology did not show any collapse phenomena, and the volume fraction of extracted gas remained above 30% for the first 30 days. Moreover, the gas volume fraction on the 30th and 60th days was 2.5 times and more than 3 times that of bag sealing boreholes using expanded cement, further proving that the sealing quality of boreholes using “concentric ring” reinforcement sealing is higher.

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Section: Introductionmentioning

confidence: 99%

Expansion Characteristics and Creep Test of New Curing Expansion Material for Gas Extraction Boreholes

Jiang,

Bao,

Lei

2024

Processes

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“…One of the most debatable areas is the prediction of zones with different parameters of the filtration channels "methane drainage zone" [23][24][25], which provide a decaying metastable solid gas-coal solution and the boundaries (angles of complete displacement) [26][27][28][29] for real conditions of reserve development. For this purpose, a commercial software, which implements numerical simulation methods, such as the finite element method (FEM) in COSFLOW [30,31], CFD gas flow in ANSYS [32,33], CMG-GEM [34], PFC2D [35], finite differential method (FDM) in FLAC3D [36], discrete models [37] (such as UDEC [38,39]), and physical simulation with equivalent materials [40], is widely used. At the same time, valid estimation methodologies are still lacking to fully understand the processes under study.…”

Section: Introductionmentioning

confidence: 99%

Substantiation of Drilling Parameters for Undermined Drainage Boreholes for Increasing Methane Production from Unconventional Coal-Gas Collectors

et al. 2023

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Decarbonization of the mining industry on the basis of closing the energy generation, on the basis of cogeneration of coal mine methane, and on the internal consumption of the mine is a promising direction in ensuring sustainable development. Known problems of deep underground mining do not allow for realizing the potential of man-made gas reservoirs due to the deterioration of the conditions of development of reserves of georesources. The aim of the work was to improve recommendations for the substantiation of drilling parameters for undermined drainage boreholes for increasing methane production from unconventional coal-gas collectors. The authors’ approach innovation lies in the possibility of using the established patterns of better natural stability of undermined boreholes to optimize them as spatial orientation parameters in an existing drilling passport for the improvement of methane extraction productivity. For this purpose, smoothing (LOESS) of the experimental data of two similar types of wells was used; then deterministic interpolation methods in combination with a three-dimensional representation of the response function in “gnuplot” were used. As a result, it was found that the increase in the inclination angle from 40° to 60° leads to a significant transformation of the model of the studied process, accompanied by a decline in the dynamics of methane emission and a decrease in the distance of the productive work zone of this type of well from 13 to 5 m before the roof landing, which then is replaced by a sharp increase in the productive work zone up to 35 m ahead of the longwall face. This allows under specific conditions for recommending increasing the productivity of methane capex from technogenic disturbed coal-gas reservoir replacement of wells with a smaller angle of rise to the transition to a more frequent grid of clusters from wells #4.

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“…An innovative mine design for safe and efficient mining of low permeability and high gas-containing coal seams was also advanced 17 . Zhang et al 18 investigated the relationship between the migration of gas and its enrichment in fissures caused by mining, and proposed a zoning model of gas migration channels. Ni et al 19 establishment of mathematical model for crack length, construction of mathematical model for productivity using stage-fractured horizontal wells.…”

Section: Introductionmentioning

confidence: 99%

Evolution of fissures and pressure discharge of gas caused by mining of the upper protective layer of a coal seam

Xie

Cai

et al. 2023

Sci Rep

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The evolution of fissures and permeability associated with mining of the upper protective layer of the coal seam is crucial for pressure relief gas drainage of the underlying seam. To understand the influence of mining the upper protective layer on gas drainage within the underlying coal seam, this study utilized the M16 and M18 seams in the Qinglong Coal Mine in Guizhou. Theoretical analysis, discrete element numerical simulation, and field tests were used to characterize the evolution of fractures associated with mining of the upper protective layer and the effects of pressure relief gas drainage within the protected coal seam. The results show that mining-related stress changes controlled the development of fractures, altering the permeability values of coals. An analysis of the crack development in the coal mass caused by mining of the upper protective layer shows that during the initial stage of mining, the produced cracks exhibited a butterfly shape network. Yet, with further development of the mining, these cracks and the stress changes gradually produced an inverted butterfly shape network. According to simulations, the areas of maximum deformation via expansion in the protected coal seam were located near the open cut and the mining end line of the working face. The maximum deformation values were 29.06 and 26.68 mm, respectively, and the corresponding deformation rates were 9.37‰ and 8.61‰, which are greater than the required 3‰. The findings of this study provide a new reference for gas control in pressure relief coal seams under similar working conditions.

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Control of directional long borehole on gas drainage and optimal design: Case study

Cited by 11 publications

References 40 publications

Expansion Characteristics and Creep Test of New Curing Expansion Material for Gas Extraction Boreholes

Expansion Characteristics and Creep Test of New Curing Expansion Material for Gas Extraction Boreholes

Substantiation of Drilling Parameters for Undermined Drainage Boreholes for Increasing Methane Production from Unconventional Coal-Gas Collectors

Evolution of fissures and pressure discharge of gas caused by mining of the upper protective layer of a coal seam

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