scholarly journals Characterisation of mechanics and flow fields around in-seam methane gas drainage borehole for preventing ventilation air leakage: A case study

2016 ◽  
Vol 162 ◽  
pp. 123-138 ◽  
Author(s):  
Chunshan Zheng ◽  
Zhongwei Chen ◽  
Mehmet Kizil ◽  
Saiied Aminossadati ◽  
Quanle Zou ◽  
...  
Keyword(s):  
Flow Fields ◽  
Air Leakage ◽  
Gas Drainage ◽  
Methane Gas ◽  
Drainage Borehole

scholarly journals Improvement of Gas Drainage Efficiency via Optimization of Sealing Depth of Cross-Measure Boreholes

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Pu Li ◽  
Zhiheng Cheng ◽  
Liang Chen ◽  
Hongbing Wang ◽  
Jialin Cao
Keyword(s):  
Stress Concentration ◽  
Drainage System ◽  
Stress Concentration Zone ◽  
Concentration Zone ◽  
Air Leakage ◽  
In Situ Tests ◽  
Gas Drainage ◽  
Drainage Borehole

The sealing depth of a gas-drainage borehole is critically important as it directly affects the efficiency of the whole drainage system. In order to determine the shortest reasonable sealing depth, in this paper, a theoretical drainage model using different sealing depths was proposed. Based on theoretical analysis presented, two parts of the fractures system surrounding the drainage borehole were proposed, i.e. the fractures induced by roadway excavation and the fractures induced by borehole drilling. A series of geological in-situ tests and simulations research were conducted to determine the stress and fracture distributions in the surrounding rock of the borehole. The depths of crushing zones, plastic zones and stress concentration zones were determined as 5 m, 2 m and 12 m, respectively. Meanwhile, stress simulation shows that the depth of the stress concentration zone was 12 m from the roadway wall and the stress peak was located at the depth of 8 m, which can be verified by the results of drilling penetration velocity analysis. To determine the optimum sealing depth, gas drainage holes with different sealing depths were drilled in the field. The field results revealed that the crushing zones were the main area for air leakage, and the stress concentration induced by roadway excavation assisted in the reduction of air leakage. Therefore, the optimized sealing depth should both cover the plastic zone and the stress concentration zone. The research achievements can provide a quantitative method for the determination of optimum sealing depth in cross-measure drainage boreholes.

scholarly journals Research on Optimization of Key Areas of Drainage Borehole Sealing in Ultrathick Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xin Guo ◽  
Sheng Xue ◽  
Yaobin Li ◽  
Chunshan Zheng ◽  
Linfang Xie
Keyword(s):  
Test Scheme ◽  
Actual Situation ◽  
Air Leakage ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Gas Leakage ◽  
Important Means ◽  
M 12 ◽  
Drainage Effect ◽  
Drainage Borehole

Gas drainage is an important means of gas control. The influence of the key position of the sealing hole on gas drainage was studied by theoretical and numerical simulation combined with field measurement to solve low gas concentration in gas predrainage boreholes in coal mines of China. By analyzing the distribution of cracks around the boreholes and the law of air leakage and simulating the drainage effect of different sealing areas (8 m, 12 m, and 16 m), it was proposed that the key position of the sealing hole should be in the prepeak stress concentration area. According to the actual situation of Baode Mine, the sealing test scheme of different sealing areas was put forward, and the field test was carried out to obtain the key sealing area of gas predrainage boreholes in Baode Mine. Research shows that when the sealing area is 8–16 m, the average gas concentration is 63.57%, and the average pure gas flux is 0.408 m3/min. The sealing effect of this area is better, with fewer cracks, than that of the existing sealing area, effectively preventing gas leakage and increasing the gas concentration and gas scalar.

scholarly journals Instability-negative pressure loss model of gas drainage borehole and prevention technique: A case study

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242719
Author(s):  
Qingjie Qi ◽  
Xinlei Jia ◽  
Xinhua Zhou ◽  
Youxin Zhao
Keyword(s):  
Negative Pressure ◽  
Pressure Loss ◽  
Gas Flow ◽  
Technical Problem ◽  
Complex Stress ◽  
Creep Model ◽  
Gas Drainage ◽  
Methane Gas ◽  
Screen Mesh ◽  
Drainage Borehole

The internal collapse of deep seam drainage borehole and negative pressure loss represents a serious technical problem affecting gas drainage. To address this problem a creep model of coal around borehole was established based on the plastic softening characteristics of coal. The final collapse time of the borehole was determined and used to derive the three stages of the borehole collapse process. The model of negative pressure loss in drainage borehole was established according to the theory of fluid dynamics, the model of methane gas flow and the creep model of the coal around the borehole. The relationship between the negative pressure loss of drainage and the change of borehole aperture was derived, thereby revealing the main influencing factors of the negative pressure loss in the borehole. A drainage technique named “Full-hole deep screen mesh pipe” was introduced and tested to prevent the collapse of borehole and reduce the negative pressure loss. The result shows that after the borehole was drilled, the borehole wall was affected by the complex stress of the deep coal seam, the coal surrounding the borehole collapsed or presented the characteristics of creep extrusion towards the borehole. The “Full-hole deep screen mesh pipe drainage technology” could effectively control the collapse as well as the deformation of the borehole and reduced the negative pressure loss. Compared with the traditional drainage technology, the methane gas drainage concentration was increased by 101% and the gas flow was increased by 97% when the methane gas was drained for 90 days, the gas drainage efficiency increased significantly.

scholarly journals Problems of Mechanized Tunneling In Gassy Ground Conditions a Case Study: Nousoud Water Transmission Tunnel

2014 ◽  
Vol 3 (8) ◽  
pp. 101-113
Author(s):  
Naser Tali ◽  
Gholam Reza Lashkaripour ◽  
Mohamad Ghafoori ◽  
Naser Hafezimoghadas
Keyword(s):  
Hydrogen Sulfide ◽  
Dissolved Gas ◽  
Loss Of Life ◽  
Methane Gas ◽  
Project Costs ◽  
Ground Conditions ◽  
Water Transmission ◽  
Working Efficiency ◽  
Geotechnical Studies

Current advances in science, followed by development of excavation equipments technology resulted in growth of tunnelling projects for different purposes. In spite of conducting exploratory studies prior to these projects, in some cases due to of impassable paths, the studies are limited to certain areas. Hence, during geotechnical studies, it is possible that all problems facing tunnelling not be detected. Therefore, lack of awareness of these conditions can result in a lack of proper planning and consequently lead to problems during the projects. Due to the lack of knowledge and consequently not predicting and planning the projects, drilling of the second sector of Nousoud water transmission tunnel, -26 km long- has been faced with many problems including emission of hydrogen sulfide and methane gas and drainage of high volumes of water containing dissolved gas into the tunnel, which has led to the loss of life, loss of working efficiency, as well as increased project costs. In this study, problems occurred in this project, reasons behind them will be addressed; and the solutions to these problems will be mentioned. The results of the study have shown that oil-bearing formations of the region and the immigration of gases coming from these formations have let the gas entered into the tunnel. In addition, due to the high solubility of hydrogen sulfide and methane gas in water on one hand, and hydrated formations with high permeability on the other hand, caused the influx of large quantities of water and therefore the concentration of these gases in the tunnel.

Stability of Gas Drainage Borehole Analysis on Rock Mechanics Parameters with Roadway of Complex Stress

2015 ◽  
Vol 723 ◽  
pp. 330-335 ◽  
Author(s):  
Tian Jun Zhang ◽  
Lei Zhang ◽  
Hong Yu Pan ◽  
Chao Zhang
Keyword(s):  
Numerical Simulation ◽  
Internal Friction ◽  
Rock Mechanics ◽  
Vertical Direction ◽  
Friction Angle ◽  
Complex Stress ◽  
Stress Redistribution ◽  
Horizontal Direction ◽  
Gas Drainage ◽  
Drainage Borehole

The pattern of stress redistribution in the effect of circular roadway is analyzed and numerical simulation on stability of gas drainage borehole which is in the area of the stress redistribution was done with FLAC3D. The model of that circular roadway and gas drainage borehole are perpendicularly crossed is established and compute with the Coulomb Mohr criterion. It can be found that the stress of gas drainage borehole decreases with decreasing of internal friction angle and the cohesion value. The stress of gas drainage borehole steep rises where the distances of away from roadway is two times of the diameter and the stress of horizontal direction are larger than the stress of vertical direction.

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