A new method of monitoring the stability of boreholes for methane drainage from coal seams

Niu, Yue; Xin, Zhang; Wang, Enyuan; Li, Zhonghui; Cheng, Zhen‐Qiang; Xian-jun, Duan; Li, Hao; Wei, Yanwei; Qian, Jiansheng; Cai, Guannan; Lin, Song; Li, Bing

doi:10.1016/j.measurement.2020.107521

Cited by 15 publications

(4 citation statements)

References 34 publications

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“…The temperature profile of the production string is important for ensuring wellbore sustainability, which, with a lack of control, can lead to packer sealing failure [85]. Besides, we should admit the growth of the stability problem (borehole collapse and shrinkage) [86][87][88] for wells N • 3 and N • 4 by the mechanism described in [89,90]. Some cases of productivity loss in the operation of the degassing network at a mine site are caused by imperfect drilling techniques [91,92] or the limitation of methods of resource extraction by surface boreholes [93][94][95].…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…In the process of gas extraction, the air outside the coal body is constantly mixed into the extracted gas flow through the fissure channel of the surrounding rock in the coal roadway, which reduces the gas concentration. The fissures in the coal wall of the roadway, secondary fissures in drilled holes, incompact voids in the sealing section, and fissures in the coal seam caused by mining constitute the main air leakage channel in extraction drilling are the main reasons for reduced gas extraction efficiency. − …”

Section: Analysis Of the Attenuation Pattern Of Wind Leakage From Dri...mentioning

confidence: 99%

“…The fissures in the coal wall of the roadway, secondary fissures in drilled holes, incompact voids in the sealing section, and fissures in the coal seam caused by mining constitute the main air leakage channel in extraction drilling are the main reasons for reduced gas extraction efficiency. 25 − 27 …”

Section: Analysis Of the Attenuation Pattern Of Wind Leakage From Dri...mentioning

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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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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“…Qu et al [23] found that the stability of coal seam borehole was affected by the time lag effect based on field tests and numerical simulation; they found that the change of pore pressure was the main factor affecting the time lag effect, and the rich cleat was the internal factor. Niu et al [24,25] studied the monitoring and evaluation of borehole stability through experiments and simulations, proposed an index to calculate the degree of borehole damage based on the residual area, and fitted the functional equation between the relative pressure of the sensor (the difference between the real-time pressure of the sensor and the coupling pressure of the borehole wall) and the degree of borehole damage. Combined with the amount of gas extracted, it was verified that the borehole deformation first increased and then became stable with time, and then increased and then decreased with depth.…”

Section: Introductionmentioning

confidence: 99%

Study on Instability Characteristics of the Directional Borehole on the Coal-Seam Roof: A Case Study of the Tingnan Coal Mine

et al. 2023

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Directional long drilling on the roof is an effective gas control measure in the goaf, but there is little research on the stability of the surrounding rock. In this study, the geological conditions of the #4 coal seam in the Tingnan Coal Mine, Shaanxi Province, China taken as the application background, and the deformation characteristics of boreholes under four typical coal and rock conditions were first analyzed based on the Universal Distinct Element Code (UDEC) numerical simulation. Secondly, the stress, strain, and plastic deformation of the rock surrounding the borehole with different diameters were carried out using the Fast Lagrangian Analysis of Continua 3D (FLAC 3D). The effect of the casing on the stability of the borehole was also simulated. The results showed that the borehole stability of coal and mudstone was lower than that of fine-grained sandstone and coarse-grained sandstone. The larger the borehole diameter, the lower the stability. The borehole tended to be unstable, especially when the diameter was 160 mm and 200 mm. Traditional pipes can provide some protection, but for large boreholes, the protection is poor. Based on the above research, uniaxial compression tests were carried out on various internal support tubes, such as ‘line-shaped’, ‘Y-shaped’, and ‘cross-shaped’. The results showed that the cross-shaped pipe had the highest compressive strength, which was 4–5 times that of the other types of protective pipe and had a good protective effect. The research results can provide reliable technical support for the protection of directional boreholes on roofs through strata and have important implications for the popularization and application of the directional long borehole technique.

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A new method of monitoring the stability of boreholes for methane drainage from coal seams

Cited by 15 publications

References 34 publications

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

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

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

Study on Instability Characteristics of the Directional Borehole on the Coal-Seam Roof: A Case Study of the Tingnan Coal Mine

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