scholarly journals An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

2013 ◽  
Vol 1 (5) ◽  
pp. 4751-4775 ◽  
Author(s):  
F. H. An ◽  
Y. P. Cheng
Keyword(s):  
Coal Seam ◽  
Large Scale ◽  
Gas Pressure ◽  
Underground Mines ◽  
Low Permeability ◽  
Gas Distribution ◽  
Coal Gas ◽  
Annular Zone ◽  
Wall Deformation ◽  
Coal And Gas Outbursts

Abstract. Large-scale coal and gas outbursts post a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution. A steep gradient of gas pressure in the low-permeability zone and the high gas pressure in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

scholarly journals An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

2014 ◽  
Vol 14 (8) ◽  
pp. 2125-2132 ◽  
Author(s):  
F. H. An ◽  
Y. P. Cheng
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Large Scale ◽  
Underground Mines ◽  
Low Permeability ◽  
Gas Distribution ◽  
Coal Gas ◽  
Annular Zone ◽  
Wall Deformation ◽  
Coal And Gas Outbursts

Abstract. Large-scale coal and gas outbursts pose a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution, and the permeability is required to be several orders of magnitude less than that of normal coal and enough length is also in demand. A steep gradient of gas pressure in the low-permeability zone and the high-pressure gas in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high-pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

scholarly journals The Relationship between Mining-Induced Stress and Coal Gas under an Optimized Support Scheme: A Case Study in the Guanyinshan Coal Mine, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Tianjun Zhang ◽  
Jiaokun Wu ◽  
Yong Chen ◽  
Hong Ding ◽  
Hongyu Ma ◽  
...  
Keyword(s):  
Gas Pressure ◽  
Gas Content ◽  
Rock Support ◽  
Drill Cuttings ◽  
Coal Gas ◽  
Gas Desorption ◽  
Induced Stress ◽  
Coal And Gas Outbursts ◽  
Residual Gas ◽  
The Relationship

Stress is one of the main factors influencing coal and gas outbursts. The apparent effects of the crustal stress, the structural stress, and the mining-induced stress increase as the depth of mining increases. At present, there have been few studies of the relationship between the comprehensive analyses of the crustal stress, mining-induced stress, and coal gas. The in situ measurement of the relationship between stress-related behaviors and coal gas under the influence of mining was conducted through experimental analysis of surrounding rock support and coal and gas outburst control and optimization of surrounding rock support materials and system construction. The results showed that the mining-induced stress first increased to a peak value, then gradually decreased, and tended to stabilize as the footage progresses. Stress appears at 96 m ahead due to mining; after 57 m of advancing, there is a large increase until it passes through this area. The stress in front of the working face increases linearly, and the increase range is obviously larger than that of the coal body in a certain range on both sides. The support anchoring force gradually decreased and tended to be stable after rapidly increasing to a maximum value. The deep displacement of the roof increased linearly and tended to be stable after reaching an accumulated displacement which can reach 16-28 mm. The residual gas pressure in front of mining operations decreased rapidly, and beyond 15 m on each side of the roadway, it decreased significantly. The residual gas pressure and gas content were consistent with the gas desorption index of drill cuttings due to the influences of gas predrainage and mining. The stress along the direction of the roadway and the residual gas content, the residual gas pressure, and the gas desorption index of drill cuttings conform to the logarithmic functional relationship. The research results provide a basis for the comprehensive prevention and control of coal and gas outbursts from multiple angles considering stress, coal, and gas.

scholarly journals Numerical Investigation of Complex Thermal Coal-Gas Interactions in Coal-Gas Migration

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xiaoyan Ni ◽  
Peng Gong ◽  
Yi Xue
Keyword(s):  
Coal Seam ◽  
Variable Temperature ◽  
Gas Pressure ◽  
Gas Migration ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Coal Gas ◽  
Thermal Coal ◽  
Gas Seepage ◽  
Gas Interactions

Understanding the influence of temperature on the gas seepage of coal seams is helpful to achieve the efficient extraction of underground coal seam gas. Thermal coal-gas interactions involve a series of complex interactions between gas and solid coal. Although the interactions between coal and gas have been studied thoroughly, few studies have considered the temperature evolution characteristics of coal seam gas extraction under the condition of variable temperature because of the complexity of the temperature effect on gas drainage. In this study, the fully coupled transient model combines the relationship of gas flow, heat transfer, coal mass deformation, and gas migration under variable temperature conditions and represents an important nonlinear response to gas migration caused by the change of effective stress. Then, this complex model is implemented into a finite element (FE) model and solved through the numerical method. Its reliability was verified by comparing with historical data. Finally, the effect of temperature on coal permeability and gas pressure is studied. The results reveal that the gas pressure in coal fracture is generally higher than that in the matrix blocks. The higher temperature of the coal seam induces the faster increase of the gas pressure. Temperature has a great effect on the gas seepage behavior in the coal seams.

Numerical Study on Shocking Coal Seam of Multi-Points Explosion with High-Pressure Gas

2012 ◽  
Vol 524-527 ◽  
pp. 450-454
Author(s):  
Kun Gao ◽  
Ji Ren Wang ◽  
Bao Shan Jia
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Percolation Theory ◽  
Gas Permeability ◽  
Numerical Study ◽  
Pressure Change ◽  
Gas Pressure ◽  
Low Permeability ◽  
Gas Extraction ◽  
Coal Seams

The permeability of coal seam is an important parameter for the gas extraction and gas outburst control. However, most of the coal seams are low-permeability with outstanding characteristic in China. Therefore，it is a good technology to provide the theoretical basis for increasing the permeability of low-gas- permeability coal seam by shocking with high-pressure air. Based on the percolation theory of porous media and combining the gas pressure change after shocking the coal seam with high-pressure air, the solid-gas coupled mathematical model is presented for the flow in the coal seam. By applying the software, the numerical simulation is computed and analyzed for the gas pressure evolution owing to the multi-spot continuous shocking the coal seam by the high-pressure air under the different pressure values and strata pressure.

ASSESSMENT OF OIL WELL PRODUCTIVITY IN LOW-PERMEABILITY RESERVOIRS IN THE FIELDS OF EASTERN SIBERIA

2017 ◽  
pp. 30-36
Author(s):  
R. V. Urvantsev ◽  
S. E. Cheban
Keyword(s):  
Oil Recovery ◽  
Large Scale ◽  
Oil And Gas ◽  
Oil Extraction ◽  
Low Permeability ◽  
Oil Well ◽  
Eastern Siberia ◽  
Development Costs ◽  
Traditional Fields ◽  
Low Permeability Reservoirs

The 21st century witnessed the development of the oil extraction industry in Russia due to the intensifica- tion of its production at the existing traditional fields of Western Siberia, the Volga region and other oil-extracting regions, and due discovering new oil and gas provinces. At that time the path to the development of fields in Eastern Siberia was already paved. The large-scale discoveries of a number of fields made here in the 70s-80s of the 20th century are only being developed now. The process of development itself is rather slow in view of a number of reasons. Create a problem of high cost value of oil extraction in the region. One of the major tasks is obtaining the maximum oil recovery factor while reducing the development costs. The carbonate layer lying within the Katangsky suite is low-permeability, and its inventories are categorised as hard to recover. Now, the object is at a stage of trial development,which foregrounds researches on selecting the effective methods of oil extraction.

scholarly journals Permeability Enhancement Properties of High-Pressure Abrasive Water Jet Flushing and Its Application in a Soft Coal Seam

2021 ◽  
Vol 9 ◽  
Author(s):  
Xinzhe Zhang ◽  
Piotr Wiśniewski ◽  
Sławomir Dykas ◽  
Guojie Zhang
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Water Jet ◽  
Gas Pressure ◽  
Theory And Practice ◽  
Abrasive Water Jet ◽  
Gas Drainage ◽  
Permeability Enhancement ◽  
Soft Coal ◽  
Soft Coal Seam

High-pressure abrasive water jet flushing (HPAWJF) is an effective method used to improve coal seam permeability. In this study, based on the theories of gas flow and coal deformation, a coupled gas-rock model is established to investigate realistic failure processes by introducing equations for the evolution of mesoscopic element damage along with coal mass deformation. Numerical simulation of the failure and pressure relief processes is carried out under different coal seam permeability and flushing length conditions. Distributions of the seepage and gas pressure fields of the realistic failure process are analyzed. The effects of flushing permeability enhancement in a soft coal seam on the gas drainage from boreholes are revealed by conducting a field experiment. Conclusions can be extracted that the gas pressure of the slotted soft coal seam is reduced and that the gas drainage volume is three times higher than that of a conventional borehole. Field tests demonstrate that the gas drainage effect of the soft coal seam is significantly improved and that tunneling speed is nearly doubled. The results obtained from this study can provide guidance to gas drainage in soft coal seams regarding the theory and practice application of the HPAWJF method.

scholarly journals Brown Coal in Victoria, Australia and Maddingley Brown Coal Open Cut Mine Batter Stability

2020 ◽  
Vol 9 (3) ◽  
pp. 109-118
Author(s):  
Lei Zhao ◽  
Greg You
Keyword(s):  
Coal Seam ◽  
Brown Coal ◽  
Large Scale ◽  
Low Cost ◽  
Three Dimensional ◽  
Open Pit ◽  
Open Pit Mining ◽  
Mining Operations ◽  
Power Generators ◽  
Three Dimensional Finite Element

Brown coal is young, shallowly deposited, and widely distributed in the world. It is a fuel commonly used to generate electricity. This paper first reviews the resources and characteristics of brown coal in Victoria, Australia, and its exploitation and contribution to the economy or power supply in Victoria. Due to the shallow depth of the brown coal seam, e.g. very favorable stripping ratio, open pit mining is the only mining method used to extract the coal at low cost for power generators. With the large-scale mining operations, cases of batter failure were not rare in the area. From the comprehensive review of past failures, overburden batter tends to fail by circular sliding, coal batter tends to fail by block sliding after the overburden is stripped due to a weak water-bearing layer underneath the coal seam and tension cracks developed at the rear of the batter, and batter failure is typically coincided with peak raining seasons. Secondly, the paper reviews the case study of Maddingley Brown Coal (MBC) Open Cut Mine batter stability, including geology, hydrogeology, and hydro-mechanically coupled numerical modelling. The modelling employs three-dimensional finite element method to simulate the MBC northern batter where cracks were observed in November 2013. The comprehensive simulation covers an overburden batter, a brown coal batter, two rainfall models, and a buttressed batter. The simulated results agree well with observed data, and it is found that the rainfall at the intensity of 21mm substantially lowered the factor of safety of the coal batter.

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