Gas Migration Patterns with Different Borehole Sizes in Underground Coal Seams: Numerical Simulations and Field Observations

Gas flow in a coal seam is a complex process due to the complicated coal structure and the sorption characteristics of coal to adsorbable gas (such as carbon dioxide and methane). It is essential to understand the gas migration patterns for different fields of engineering, such as CBM exploitation, underground coal mine gas drainage, and CO2 geo-sequestration. Many factors influence gas migration patterns. From the surface production wells, the in-seam patterns of gas content cannot be quantified, and it is difficult to predict the total gas production time. In order to understand the gas flow patterns during gas recovery and the gas content variations with respect to production time, a solid-fluid coupled gas migration model is proposed to illustrate the gas flow in a coal seam. Field data was collected and simulation parameters were obtained. Based on this model, different scenarios with different borehole sizes were simulated for both directional boreholes and normal parallel boreholes in coal seams. Specifically, the borehole sizes for the directional boreholes were 10 m, 15 m, and 20 m. The borehole sizes for the normal parallel boreholes were 2 m, 4 m, and 6 m. Under different gas drainage leading times, the total gas recovery and residual gas contents were quantified. In Longwall Panel 909 of the Wuhushan coal mine, one gas drainage borehole and five 4 m monitoring boreholes were drilled. After six months of monitoring, the residual gas content was obtained and compared with the simulation results. Of the total gas, 61.36% was drained out from the first 4 m borehole. In this field study, the effective drainage diameter of the drainage borehole was less than 8 m after six months of drainage. The gas drainage performance was tightly affected by the borehole size and the gas drainage time. It was determined that the field observations were in line with the simulation results. The findings of this study can provide field data for similar conditions.

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Research on the Effective Influence Radius of Hydraulic Reaming in Mining Seam

The Open Fuels & Energy Science Journal ◽

10.2174/1876973x01508010161 ◽

2015 ◽

Vol 8 (1) ◽

pp. 161-167

Author(s):

Li Peng ◽

Wang Kai ◽

Li Bo ◽

Jiang Yifeng ◽

Gou Jianqiang

Keyword(s):

Gas Flow ◽

Coupling Model ◽

Field Investigation ◽

Coal Mass ◽

Gas Content ◽

Coal Seams ◽

Gas Drainage ◽

Permeability Increase ◽

Influence Radius ◽

Drainage Effect

In Accordance with the present situations suggesting that the construction of the gas drainage boreholes in mining seam is sufficient and the gas drainage effect in low permeability coal seams does not yield perfectly, the hydraulic reaming technology in mining seam was proposed to increase the gas drainage efficiency. Through the gas flow method, the effective influence radius of hydraulic reaming was determined and the fluid-solid coupling model of gas drainage along boreholes after hydraulic reaming was established theoretically. Following this, the changes in the laws of gas content around the boreholes in the coal seam were simulated and analyzed. The results indicated that hydraulic reaming can effectively promote the stress-relief and permeability-increase of the coal mass around the boreholes, and the coal mass around the reaming boreholes can be divided into gas flow increase zone, gas flow delay attenuation zone and fast decay zone. The effective influence radius of hydraulic reaming was 5.5~6 m. The obtained simulation results were basically in accordance with the field investigation.

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Nitrogen Injection To Flush Coal Seam Gas Out Of Coal: An Experimental Study

Archives of Mining Sciences ◽

10.1515/amsc-2015-0067 ◽

2015 ◽

Vol 60 (4) ◽

pp. 1013-1028 ◽

Cited By ~ 7

Author(s):

Lei Zhang ◽

Naj Aziz ◽

Ting Ren ◽

Jan Nemcik ◽

Shihao Tu

Keyword(s):

Coal Seam ◽

Clean Energy ◽

Gas Content ◽

Coal Seams ◽

Coal Seam Gas ◽

Gas Recovery ◽

Nitrogen Injection ◽

Gas Desorption ◽

Effective Role ◽

Study Laboratory

Abstract Several mines operating in the Bulli seam of the Sydney Basin in NSW, Australia are experiencing difficulties in reducing gas content within the available drainage lead time in various sections of the coal deposit. Increased density of drainage boreholes has proven to be ineffective, particularly in sections of the coal seam rich in CO2. Plus with the increasing worldwide concern on green house gas reduction and clean energy utilisation, significant attention is paid to develop a more practical and economical method of enhancing the gas recovery from coal seams. A technology based on N2 injection was proposed to flush the Coal Seam Gas (CSG) out of coal and enhance the gas drainage process. In this study, laboratory tests on CO2 and CH4 gas recovery from coal by N2 injection are described and results show that N2 flushing has a significant impact on the CO2 and CH4 desorption and removal from coal. During the flushing stage, it was found that N2 flushing plays a more effective role in reducing adsorbed CH4 than CO2. Comparatively, during the desorption stage, the study shows gas desorption after N2 flushing plays a more effective role in reducing adsorbed CO2 than CH4.

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Undesorbable residual gas in coal seams and its influence on gas drainage

International Journal of Mining Science and Technology ◽

10.1016/j.ijmst.2017.07.019 ◽

2017 ◽

Vol 27 (5) ◽

pp. 763-769 ◽

Cited By ~ 4

Author(s):

Gongda Wang ◽

Ting Ren ◽

Lang Zhang ◽

Longyong Shu

Keyword(s):

Coal Seams ◽

Gas Drainage ◽

Residual Gas

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The Effect Evaluation of Removing Outburst through Bedding and Layer-through Boreholes Combined Gas Drainage

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.366 ◽

2012 ◽

Vol 256-259 ◽

pp. 366-371

Author(s):

Zhong Ming Zhao ◽

Lei Wang ◽

Jian Bang Wu

Keyword(s):

Gas Pressure ◽

Gas Content ◽

Effect Evaluation ◽

Prevention Measures ◽

Gas Drainage ◽

Residual Gas ◽

Favorable Conditions

In order to test the validity of regional outburst prevention measures that combined the bedding boreholes and layer-through boreholes in 3104 coalface, according to the relevant provisions, used drilling index, pre-pumping index and gas index to evaluate the effect of removing outburst in 3104 coalface. The evaluation results shown that through the pre-pumping gas, the rate of pre-pumping gas was 53.7%, more than 30%; residual gas content was 2.85～5.07m3/t, less than 8m3/t; residual gas pressure was 0.01～0.02MPa, less than 0.74 MPa. Therefore, the coalface has eliminated the danger of outburst and created favorable conditions for safety mining.

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STUDY OF RESIDUAL GAS CONTENT OF COAL SEAMS IN ERUNAKOVSKY DEPOSIT OF KUZBASS

Vestnik of Kuzbass State Technical University ◽

10.26730/1999-4125-2020-2-5-11 ◽

2020 ◽

pp. 5-11

Author(s):

Sergej N. Shirjaev ◽

Oleg V. Tailakov ◽

Denis N. Zastrelov ◽

Artem V. Gerasimov

Keyword(s):

Gas Content ◽

Coal Seams ◽

Residual Gas

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Speculum Observation and Trajectory Measurement in Gas Extraction Drilling: A Case Study of Changling Coal Mine

Geofluids ◽

10.1155/2021/5545067 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Enbiao Zhao ◽

Kangnan Li ◽

Xin Yang ◽

Nan Deng

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Efficient Production ◽

Drilling Process ◽

Coal Seams ◽

Adjacent Layer ◽

Gas Drainage ◽

High Level ◽

Trajectory Measurement ◽

Drainage Borehole

Coal will still be China’s basic energy for quite a long time. With the increase of mining depth, gas content and pressure also increase. The problems of gas emission and overrun affect the safety and efficient production of coal resource to a certain extent. In this work, the field test of gas drainage borehole peeping and trajectory measurement in coal seam of Changling coal mine are carried out. These coal seams include C5b coal seam, upper adjacent C5a coal seam, C6a coal seams, C6c in lower adjacent strata, and C5b coal seam in high-level borehole. The view of gas drainage borehole peeping and trajectory measurement in the working seam, upper adjacent layer, lower adjacent layer, and high position are obtained. It is found that the hole collapses at the position of about 20 m in both adjacent strata and high-level boreholes, and there are a lot of cracks in the high-level boreholes before 12 m. The deviation distance of high-level borehole is large, and the actual vertical deviation of upper adjacent layer is small. Finally, the strategies to prevent the deviation of drilling construction are put forward. It includes four aspects: ensuring the reliability of drilling equipment, reasonably controlling the drilling length, standardizing the drilling, and reasonably selecting the drilling process parameters.

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Analysis of the Natural Methane Content of Boldyrevsky Seam at S.M. Kirov Mine of JSC SUEK-Kuzbass

Occupational Safety in Industry ◽

10.24000/0409-2961-2021-3-61-66 ◽

2021 ◽

pp. 61-66

Author(s):

E.V. Fedorov ◽

◽

S.B. Kulibaba ◽

A.A. Meshkov ◽

◽

...

Keyword(s):

Methane Content ◽

Actual Data ◽

Gas Content ◽

Coal Seams ◽

Actual Distribution ◽

Coal Gas ◽

Residual Gas ◽

Mine Workings ◽

Host Rocks

S.M. Kirov mine of JSC SUEK-Kuzbass develops Boldyrevsky and Polenovsky seams and is classified as a super-category for methane. Under these conditions, the development of seams requires a set of measures for their degassing. Methods and parameters for degassing the main sources of methane release in the coal mines are selected considering the faces gas content. It is calculated based on the natural methane content of the coal seams and host rocks determined at the stage of geologic exploration activity. The aim of the work conducted by the authors is to establish the actual distribution of natural methane seam Boldyrevsky based on the analysis of research results of the coal-gas samples and experimental evaluation of the residual gas content in the mine workings. Natural gas content of the mine field of S.M. Kirov JSC SUEK-Kuzbass mine was determined based on the analysis of 538 coal-gas samples on 30 seams. All the coal and gas samples taken from Boldyrevsky seam were analyzed. Distribution of the actual values of natural methane content from the hypsometric depths of the seam was plotted. Distribution was plotted concerning the actual values of natural methane from hypsometric depths of the formation. The obtained data were compared with the results of experimental determination of the residual gas content of Boldyrevsky seam from the mine workings. Based on the results obtained, CH4 isogases were constructed based on the actual and maximum values of the natural methane content in Boldyrevsky seam. It is established that the natural methane content of Boldyrevsky seam, that was determined at the stage of geological exploration for the entire field of S.V. Kirov mine, has overestimated values — by 35–40 % compared to the actual data, and by 25–30% in relation to the maximum actual data.

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DETERMINATION OF METHANE DESORPTION ZONE FOR THE DESIGN OF A DRAINAGE BOREHOLE PATTERN (CASE STUDY: E4 PANEL OF THE TABAS MECHANIZED COAL MINE, IRAN)

Rudarsko-geološko-naftni zbornik ◽

10.17794/rgn.2021.1.6 ◽

2021 ◽

Vol 36 (1) ◽

pp. 61-75

Author(s):

Ali Hosseini ◽

Mehdi Najafi

Keyword(s):

Coal Seam ◽

Coal Mining ◽

Coal Mine ◽

Methane Emissions ◽

Gas Content ◽

Coal Seams ◽

Mining Operations ◽

Methane Drainage ◽

Tabas Coal Mine ◽

Drainage Borehole

Underground coal mining is known as one of the major sources of methane emissions which mainly occurs after underground coal extraction. Rock strata in-situ methane can potentially be the most significant hazard in coal mining operations. To prevent or minimize the risks of methane emissions, methane drainage approaches have been adopted by coal mines. Rock mass methane drainage is the most efficient and effective approach toward controlling methane hazards as it prevents and reduces the frequency of methane emissions, outflows into the working area and sudden outbursts of methane and rocks. The method includes drilling boreholes from the tailgate side to the unstressed zone in the roof and floor strata above and below a working coal seam. The coal seam gas content in Tabas Parvadeh I is estimated to be about 16 m3 /t, which is relatively high. Based on exploration data, five distinct coal seams have been identified (B1, B2, C1, C2 and D) at the coal deposit and currently C1 is being worked. Considering the high value of C1 gas content and surrounding rocks, the Methane Drainage System (MDS) has been utilized for gas drainage. This paper tries to determine the desorption area which is essential and helpful for the selection of an effective drilling pattern into the adjacent coal seams. In this study, the methane drainage zone in the E4 panel of the Tabas coal mine was calculated using experimental equations and a drainage borehole pattern was determined.

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Study on gas drainage effect of hydraulic fracturing in soft coal seam

E3S Web of Conferences ◽

10.1051/e3sconf/202018501004 ◽

2020 ◽

Vol 185 ◽

pp. 01004

Author(s):

Liangwei Li

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Gas Flow ◽

Water Injection ◽

Fracture Initiation ◽

Gas Content ◽

Gas Drainage ◽

Soft Coal ◽

Drainage Effect ◽

Soft Coal Seam

Aiming at the difficulty of gas drainage by drilling along the seam in soft coal seam, the permeability of coal seam was increased by hydraulic fracturing test in the field, and the permeability and gas drainage parameters of coal seam before and after fracturing were studied. The results show that: ① The fracture initiation pressure of 3# coal seam in Guojiahe coal mine is 15~20MPa. When the water injection is 30~40m3, the fracturing radius is 15m, when the water injection is 50 ~ 60m3, the fracturing radius can reach 20m, when the water injection reaches 70m3, the fracturing radius can reach 30m; ② Driven by high pressure water, the gas in the fractured area migrates to the unfractured area, and the gas content in the fractured area decreases; ③ The attenuation coefficient of natural gas flow after fracturing is reduced by 50% compared with that before fracturing, and the permeability coefficient of coal seam after fracturing is increased by 50 times compared with that of original area; ④ The recovery concentration after fracturing is much higher than that before fracturing.

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