Influence Factors of Gas Extraction Effect and Residual Gas Content Distribution on Working Face

To study the behavior of gas extraction from the protected layer by surface drilling, the common characteristics of gas extraction concentration and gas extraction quantity are summarized through the collection of key parameters of surface drilling and a combination of data and figures, with the background of 11−2 coal protection 13−1 coal in the Huainan mining area. The research results show that the flow of pressure relief gas extraction of the protected layer by surface drilling has three stages: a rising period, stable period, and decay period. When the extraction processes of multiple surface wells on the same working face are coordinated, the extraction flow is superimposed, and the extraction volume of surface drilling shows an increasing trend and fluctuates with the location of the drilling. The extraction flow rate before ground drilling is relatively small, and the extraction flow rate increases after ground drilling. This behavior is further confirmed by field observation of mining changes in the protective layer and the expansion and deformation of the protected layer. The periodic variation in the surface drilling and extraction quantity is affected primarily by the mining movement of the working face of the protective layer. Specifically, it is affected by factors such as the mining progress of the working face of the protective layer, mining height, degree of compacted goaf, degree of pressure relief of the protected layer, original gas content, and other measures taken to extract the protected layer.

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A method to remove gas hazard around underground thrust faults: Kilometre directional feathery drilling

Thermal Science ◽

10.2298/tsci180607262x ◽

2019 ◽

Vol 23 (6 Part B) ◽

pp. 3767-3774

Author(s):

Tong-Qiang Xia ◽

Hong-Yun Ren ◽

Hong Li ◽

Chang-Kang Du

Keyword(s):

Gas Content ◽

Shanxi Province ◽

Engineering Practice ◽

Gas Extraction ◽

Thrust Faults ◽

Coal Gas ◽

Mining Areas ◽

Working Face ◽

Gas Hazard ◽

Occurrence Regularity

In this paper, we take the W2303 working face in Sihe mine, Shanxi Province, China as a project case, where it has been met with three thrust faults. The occurrence regularity of coal gas near the faults are studied, and the gas content around the faults are measured. The comprehensive measures of gas extraction are carried out, including the wear layer and in-seam kilometer directional feathery drilling combined with multi-branch technique. The gas threat around underground thrust faults is effectively eliminated. This technical engineering practice has a good guiding significance to other similar mining areas.

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residual gas content

Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik ◽

10.1007/978-3-642-41714-6_181755 ◽

2014 ◽

pp. 1108-1108

Keyword(s):

Gas Content ◽

Residual Gas

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Determination of Optimal Extrication Location of High Extraction Roadway of Large-Mining-Height Fully Mechanized Face

Advances in Civil Engineering ◽

10.1155/2018/5145746 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7

Author(s):

Xue-bo Zhang ◽

Ming Yang

Keyword(s):

Gas Extraction ◽

Horizontal Distance ◽

High Position ◽

Working Face ◽

Extraction Site ◽

Large Mining Height ◽

Porosity And Permeability ◽

Permeability Distribution ◽

Mining Height

Determining the optimal extrication location of the high extraction roadway can improve the gas extrication effect of highly gassy mine and solve the problem of gas concentration overrun at the upper corner, which is of great significance to safety and efficient mine production. According to the actual situation of mine, the gas gushing amount in the goaf, pressure difference at both ends of the working face, the 3D porosity, and permeability distribution of the caving zone and fissure zone were obtained by field measurement and numerical calculation. Through theoretical calculation, the proper extraction site of a high-position alley was determined. On this basis, the optimal extraction site of a high-position alley was determined by numerical analysis of the gas extraction effect at different sites. The results show that as the perpendicular distance between high-position alley and goaf floor increases, the gas extraction amount increases first and then decreases. The concentration of extraction gas gradually increases, and the increasing trend is gradually diminished. With the increase of the horizontal distance between the air return way and the high-position alley, the gas extraction amount and gas extraction concentration increase first and then decrease. The optimal extraction site of a high-position alley should be 39 m vertically away from the goaf floor and 30 m horizontally away from the air return way.

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Experimental Study on Deep Borehole Pre-Cracking Blasting of Drilling through Strata at Low Permeability Seam

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.868.339 ◽

2013 ◽

Vol 868 ◽

pp. 339-342

Author(s):

Jian Liu ◽

Qian Le

Keyword(s):

Coal Seam ◽

Control Area ◽

Low Permeability ◽

Gas Extraction ◽

Test Results ◽

Deep Borehole ◽

Coal Seam Gas ◽

Gas Concentration ◽

Working Face ◽

Outburst Coal Seam

In the process of roadway excavation in the low permeability outburst coal seam, with drilling through strata in the bottom drainage roadway extracting coal seam gas of control area. In order to improve extraction effect, the method that deep borehole pre-cracking blasting is used to increase the permeability of coal in the drilling through strata seam segment is proposed. The calculation formula on crushing circle and crack circle radius of deep borehole pre-cracking blasting are derived, and the effective loosening radius of blasting is calculated in theory, the research achievements are applied to field test, the test results show that deep borehole pre-cracking blasting permeability improvement technology is carried out in the drilling through strata of the low permeability outburst coal seam, the permeability of coal seam is improved by 180 times, the gas extraction scalar is raised by 8-10 tomes, during the process of roadway excavation, gas concentration of the working face is 0.2%-0.3%, and tunneling footage is increased by 2 times.

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Investigation of Large-Diameter Borehole for Enhancing Permeability and Gas Extraction in Soft Coal Seam

Geofluids ◽

10.1155/2020/6618590 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Yongwen Wang ◽

Wanjun Yan ◽

Zhongjiu Ren ◽

Zhiqiang Yan ◽

Ziwen Liu ◽

...

Keyword(s):

Coal Seam ◽

Shear Failure ◽

Large Diameter ◽

Gas Content ◽

Gas Extraction ◽

Extraction Area ◽

Damage Area ◽

Soft Coal ◽

Coal Deformation ◽

Soft Coal Seam

The efficiency of gas extraction from the soft coal seam with ultralow permeability is low. Gas extraction with large-diameter borehole is proposed to deplete gas content for preventing gas outburst disaster in this study. The fractures around the large borehole will enhance the permeability in the damage area to promote gas extraction. We established a damage-stress-seepage coupling model for large-diameter borehole gas extraction in soft coal seam. This mathematical model contains governing equations of gases sorption and transport, coal deformation, and damage, reflecting the coupling responses between gas and coal seam. The model is solved by the finite element method to simulate the gas drainage large-diameter borehole through roadway. Distributions of elastic modulus, damage area, and maximum principal stress in soft coal seam with different borehole diameters including 94 mm, 133 mm, 200 mm, and 300 mm are analyzed. The gas pressure, gas content, and effective extraction area in soft coal seam are discussed. Results show that the shear failure zone appears around the large-diameter borehole, and its permeability rises sharply. This opens up the gas transport channel and is conducive to the rapid extraction. It is confirmed that gas extraction using large-diameter borehole (300 mm) can greatly improve the efficiency of the gas preextraction in soft coal seam by increasing gas extraction rate. These provide a foundation for guiding the operation of gas extraction with large borehole from the soft coal seam in the field.

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Reasonable Layout of High Drainage Roadways for Jiaojiazhai Mine

10.21203/rs.3.rs-1152634/v1 ◽

2022 ◽

Author(s):

Dongjie Hu ◽

Zongxiang Li

Keyword(s):

Control Program ◽

Simulation Software ◽

Fluid Simulation ◽

Gas Extraction ◽

Tracer Gas ◽

Element Analysis ◽

Gas Concentration ◽

Working Face ◽

Deformation Law ◽

Better Than

Abstract To ensure that the gas concentration at the top corner does not exceed the limit, a reasonable level of the high drainage roadway layout in Jiaojiazhai Mine should be determined. In this work, based on the actual conditions of the working face, an SF6 tracer gas was used to test the connectivity between the high drainage roadway and the working face. A discrete element analysis program was used to simulate the deformation law of the overlying strata in the goaf, and a corresponding caving control program for the surrounding rock was written based on the obtained parameters and “O” ring theory. A fluid simulation software was used to simulate and analyze five goaf models with different high drainage roadway layouts (10, 15, 20, 25, and 30 m). The gas drainage data for two layers (10 m and 20 m) of the high drainage roadway were measured. The results showed that the height of the caving zone in the goaf is approximately 20 m, and when the high drainage roadway is arranged along the roof (when the layout layer height is 10 m), the roadway will be directly connected to the working face, thus pumping fresh air to the working face. The gas extraction effect of the 20 m stratum was better than those of the other strata. The simulation results of the gas extraction were consistent with the measured data. The proposed scheme was practically applied, and its effect was found to be evident, thus solving the problem of high gas concentration at the top corner and increasing the mine output.

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The gas content distribution of coal reservoir at the Changzhi block, south-central Qinshui Basin, North China: Influences of geologic structure and hydrogeology

Energy Exploration & Exploitation ◽

10.1177/0144598718784037 ◽

2018 ◽

Vol 37 (1) ◽

pp. 144-165 ◽

Cited By ~ 3

Author(s):

Zhigang Du ◽

Xiaodong Zhang ◽

Qiang Huang ◽

Shuo Zhang ◽

Chenlin Wang

Keyword(s):

Coalbed Methane ◽

Content Distribution ◽

Gas Content ◽

Exploration And Exploitation ◽

Geologic Structure ◽

Stagnation Region ◽

Qinshui Basin ◽

Himalayan Orogeny ◽

South Central ◽

Coal Reservoir

Coalbed methane is now large-scalely explorated and exploitated in the world. The Changzhi coalbed methane block, south-central Qinshui Basin, is a new resource target zone for coalbed methane exploration and exploitation in China. However, the gas content distribution of this block and its influential factors have not yet studied. Based on the recent coalbed methane exploration and exploitation activities, the gas content distribution of coal reservoir in this block was studied. The results show that the gas content hold by the coal reservoir is 7.0 − 21.7 m3/t, which was determined by a combining control effect from geologic structure and hydrogeology. The Changzhi coalbed methane block has experienced multiple-stages geologic structure evolution, especially a tectonic-thermal event during the middle Yanshanian Orogeny improved the coal to the current R o,max 1.9 − 2.7% and meanwhile the coalbed methane was greatly generated. Subsequently, the widespreadly developed normal fault structures during the Himalayan Orogeny accelerated the coalbed methane escape through the “gas escape windows”, particularly where the location within the distance of about 1300 m to the “gas escape window” the gas content decreases significantly. Moreover, due to the action of the later Himalayan Orogeny, the slope areas of most Yanshanian fold structures were structurally cross-cut by the Himalayan normal faults, and thus an “open” syncline folds were formed. The coal reservoir was depressurized surrounding this “open” syncline structure and consequently the hydrodynamic losing effect has resulted in a comparatively lower gas content therein. By the control of geologic structure and hydrogeology, this block can be generally, compartmentalized into three hydrodynamic systems including the western groundwater stagnation region, the middle runoff region, and the north-eastern recharge region, where the hydrodynamic sealing effect at the groundwater stagnation region has made a comparatively higher gas content for the coal reservoir, but the hydrodynamic losing effect at the recharge region and runoff region has made a comparatively lower gas content of the coal reservoir.

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