Deviation Principles of Gas Drainage Drilling in Three-Soft Outburst Coal Seams

Zhang, Qi; Liu, Qinzhi; Lou, Yahui; Kong, Dezhong

doi:10.1007/s10706-022-02084-y

Cited by 2 publications

(1 citation statement)

References 16 publications

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“…And on this basis, methods such as hydraulic fracturing coalbed water injection were improved so as to improve the extraction efficiency of coalbed methane. ,,− The first method has been widely used, with the increasing depth of coal mining, the underground environment is more and more complex, the performance of the commonly used sealing materials can not meet the needs of the project site. Especially for the “three soft” coal seams and other special coal seams, the long condensation time and the insufficient strength of the material are easy to cause problems such as collapse in the extraction process. − Finding a way to enhance the rapid solidification properties of the hole sealing material has emerged as a pressing issue. − Fly ash and poly(vinyl alcohol) (PVA) fibers are commonly employed in cementitious materials. Fly ash is a byproduct of thermal power generation, and excessive accumulation of fly ash can have detrimental effects on the environment.…”

Section: Introductionmentioning

confidence: 99%

Research on the Performance of Cement-Based Composite Borehole Sealing Material Based on Orthogonal Test

Xu,

Wei,

Xie

et al. 2024

ACS Omega

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In order to achieve better sealing of boreholes, the performance of sealing materials is modified to improve the efficiency of coalbed methane extraction. In this paper, a new type of cement-based hole sealing material was prepared by using silicate cement (PC) and cement sulfoaluminate (SAC) as raw materials, supplemented with various additives, such as fly ash, Na 2 SO 4 , Ca(OH) 2 , and poly(vinyl alcohol) (PVA) fiber. The effects of these additives on the fluidity, setting time, and compressive strength of the PC-SAC compounded cementitious pore sealing material were investigated by orthogonal tests, and the hydration process and hydration products were analyzed by X-ray diffraction (XRD), thermogravimetry-differential thermogravimetry (TG-DTG), and scanning electron microscopy (SEM). The results show that the water−cement ratio has the most significant influence on the various properties of the material; the two additives of Na 2 SO 4 and Ca(OH) 2 play a key role in the setting time of the material; the optimal group, i.e., water−cement ratio of 0.5, fly ash of 5%, Na 2 SO 4 of 1%, Ca(OH) 2 of 0.75%, and PVA fibers of 0.8%, is obtained by the orthogonal test method, which is the closest to the actual needs of the project. The hydration products of the optimized materials have obvious changes, and the needle-like AFt and C−S−H increase so that the performance of the materials has been significantly improved.

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Section: Introductionmentioning

confidence: 99%

Research on the Performance of Cement-Based Composite Borehole Sealing Material Based on Orthogonal Test

Xu,

Wei,

Xie

et al. 2024

ACS Omega

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Characteristics of Stress-Displacement-Fracture Multi-Field Evolution around Gas Extraction Borehole

et al. 2023

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To ensure the effectiveness of the gas extraction borehole, it is necessary to investigate the stress-displacement-fracture evolution of the coal around the borehole. In this study, by constructing a numerical model of a gas extraction borehole, the burial depth and side pressure coefficient are used to characterize the overall stress level of the borehole and the difference in stress distribution caused by complex stress conditions. First, the stress time-varying pattern and force chain distribution of coal around the borehole were revealed. Then, the displacement time-varying pattern and displacement distribution of coal around the borehole were elucidated. Then, the microfracture distribution of coal around the borehole, which characterizes the microfractures, was analyzed. Finally, the validity of the numerical results was verified. The results showed that, after the stress field of the coal around the borehole was adjusted, the force chain of the borehole was unevenly distributed and the stress concentration phenomenon appeared. With the increase in burial depth, the stress around the borehole gradually increased, while the range of stress concentration zone in the borehole kept increasing, and the borehole changed from unilateral instability to bilateral instability. Moreover, the displacement field around the borehole was distributed in the shape of a ”disk leaf”. With the increase in burial depth, the deformation of coal around the borehole increased. With the increase in the side pressure coefficient, the vertical and horizontal displacement also increased gradually. Furthermore, there was a certain correspondence between the development of fracture and the deformation around the coal. With the increase in burial depth, the development of fractures was gradually obvious, and the distribution characteristics were concentrated in the middle and dispersed around. This study provides a theoretical reference for the stability of gas extraction boreholes, aiming to improve the gas extraction effect.

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Deviation Principles of Gas Drainage Drilling in Three-Soft Outburst Coal Seams

Cited by 2 publications

References 16 publications

Research on the Performance of Cement-Based Composite Borehole Sealing Material Based on Orthogonal Test

Research on the Performance of Cement-Based Composite Borehole Sealing Material Based on Orthogonal Test

Characteristics of Stress-Displacement-Fracture Multi-Field Evolution around Gas Extraction Borehole

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