The correlation between dynamic phenomena of boreholes for outburst prediction and outburst risks during coal roadways driving

Coal and gas outburst accidents occur most frequently during coal uncovering operation, and uncovering-induced outburst accidents have caused great economic losses and casualties. In order to quickly and safely uncover the outburst coal seam at the air intake shaft in panel 2, Zhaozhuang Coal Mine has come up with the technology of multibranch radial borehole hydraulic fracturing (MRBHF) coal uncovering technology in the surface coalbed methane (CBM) well. By conducting fracturing of constructed radial boreholes in the CBM well, the technology increases fractures, enhancing coal permeability and raising gas drainage volume in the uncovering area. It brings the following three major benefits: (1) uncovering coal efficiently, rapidly, and safely; (2) greatly reducing engineering quantity, coal uncovering period, and construction cost, i.e., significantly improving the economic benefits; and (3) efficiently reusing the CBM well. Compared with conventional uncovering measures, the proposed technology shortens the uncovering period by 118 d, enhances the coal seam permeability by 3.55 times, raises the gas drainage rate by 22%, increases the gas drainage volume by 1.93 times, and reduces the engineering volume of drilling by 12,000 m. The safe, rapid, economical, and applicable technology provides scientific guidance and reference for domestic and foreign shaft coal uncovering engineering and possesses important economic and social values and application prospect for safe and efficient production of coal mines.

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“…If the fall/caving causes the sudden exposure of the outburst coal seam, then delayed outburst will occur. 27 , 28…”

Section: Outburst Prevention During Coal Uncoveringmentioning

confidence: 99%

A Method of Quick and Safe Coal Uncovering by Hydraulic Fracturing in a Multibranch Radial Hole with a Coalbed Methane Well

Liu

Wei

et al. 2020

ACS Omega

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“…Second, the airflow mixes with the coal slag at the bottom to make them suspended. Finally, under the agitation of the rib drill pipe blade, the coal slag is transported outward from the annular channel formed between the outer surface of the drill pipe and the hole wall [24]. In the process of slag discharge, the rotating motion of blade can prevent the coal slag from being deposited at the below place of the drill hole, so that the coal slag and the high-speed airflow can always be fully mixed.…”

Section: Slag Discharge Mechanism Of Rib Drill Pipementioning

confidence: 99%

Structure Optimization of Rib Drill Pipe Based on Gas-Solid Coupling and Orthogonal Experiment

Zhong

et al. 2020

Shock and Vibration

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At present, drilling rig is a common equipment for controlling gas outburst generated in underground coal mine, and rib drill pipe is an important component of drilling rig. Due to the insufficiency of slag discharge capacity, pipe-sticking accidents often occur during the drilling process, which greatly reduces the effect of gas control. In order to improve the capacity of slag discharge of rib drill pipe, the mechanism of slag removal was analyzed, and the process of slag discharge was simulated as a gas-solid two-phase flow coupling process. Utilizing the computational fluid dynamics method, the process of slag discharge was simulated on the Edem-Fluent cosimulation platform. The structural parameters of the drill pipe affecting the capacity of slag discharge were derived. Based on the analysis results, the structural parameters of rib drill pipe were optimized by orthogonal experiment method. The global optimal results were obtained as follows: its pitch, blade height, and blade width are 120 mm, 3 mm, and 15 mm, respectively. Therefore, the results of slag discharge experiment on the optimum structure of rig drill pipe show that the slag discharge efficiency is increased by 11.38%, which effectively resolves the pipe-sticking problem.

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“…High gas mines in the low-rank coal mining area caused a lot of gas emission accidents and have been the main serious natural disaster during underground coal mining. 3 As an energy source, coal-bed methane (CBM) has many advantages, exploring the adsorption mechanism of methane is significant because it plays a crucial role in the CBM utilization and the prevention and prediction of gas accidents. 4 …”

Section: Introductionmentioning

confidence: 99%

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

et al. 2021

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With the increase in high gas mines in the low coal rank mining area in the northwestern part of China, high gas mines in the low-rank coal mining area have caused many gas emission accidents. Coal is a porous material, containing a large number of micropores (<2 nm), which can absorb large amounts of methane, so it is necessary to explore methane adsorption in micropores of low-rank coal. In this work, FTIR, HRTEM, and 13 C-NMR were used to test the macromolecular structural parameters of Buertai coal, which was a kind of low-rank Jurassic coal in northwestern China. The results showed that the aromatic structural units in the Buertai coal structure mainly consist of naphthalene, anthracene, and phenanthrene. The fat structure mainly occurs in the form of aliphatic side chains, cycloalkanes, and other compounds. The oxygen atoms are present in the form of carbonyl groups, ether bonds, and phenol groups with a ratio of about 6:4:9. The nitrogen atoms are present in the form of pyrrole and pyridine compounds. Finally, the macromolecular structure model of Buertai coal was built, and the calculated NMR spectrum from the model was very consistent with the experimental NMR spectrum of Buertai coal. The relationship between the macromolecular density and energy of Buertai coal was explored using the Amorphous Cell module in the simulation software, Materials Studios 8.0 (MS 8.0), and the density value at the lowest energy was determined to be about 1.23 g/cm 3 . The pore structure parameters of Buertai coal were also calculated. It was found that both pore volume and void fraction decreased evenly as the diameter of the probe molecule increased, but the surface area decreased rapidly when the diameter of the probe molecule was 3.46 Å. All pore sizes were found to be smaller than 10 Å from the pore size distribution (PSD) curve of Buertai coal, which provided a lot of adsorption sites for methane (CH 4 ). The results of the CH 4 adsorption simulation from Grand Canonical Monte Carlo (GCMC) showed that CH 4 is adsorbed inside the micropores of coal, and the adsorption capacity of CH 4 depends on the diameters of micropores when the micropores are less than 8.5 Å. There are many micropores where CH 4 did not appear because these micropores are closed and did not provide a channel for CH 4 to enter. The results of experimental methane adsorption indicate that the excess adsorption capacity from the GCMC simulation was very close to the experimental results of Buertai coal. This work provides a new perspective to study the methane adsorption behavior in micropores of coal.

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The correlation between dynamic phenomena of boreholes for outburst prediction and outburst risks during coal roadways driving

Cited by 41 publications

References 32 publications

A Method of Quick and Safe Coal Uncovering by Hydraulic Fracturing in a Multibranch Radial Hole with a Coalbed Methane Well

A Method of Quick and Safe Coal Uncovering by Hydraulic Fracturing in a Multibranch Radial Hole with a Coalbed Methane Well

Structure Optimization of Rib Drill Pipe Based on Gas-Solid Coupling and Orthogonal Experiment

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

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