scholarly journals Prediction of gas pressure in thin coal seams in the Qinglong Coal Mine in Guizhou Province, China

2021 ◽  
Vol 11 (11) ◽  
pp. 4075-4086
Author(s):  
Jian Zhang ◽  
Yongqiang Zhang ◽  
Jilin Wang ◽  
Xiaobin Wen
Keyword(s):  
Coal Seam ◽  
Large Deviation ◽  
Gas Pressure ◽  
Guizhou Province ◽  
Burial Depth ◽  
Coal Seams ◽  
Measuring Point ◽  
Coal Structure ◽  
Deviation Rate ◽  
Structure Index

AbstractThin coal seams in mines usually lack gas data. Thus, preventing and controlling gas outbursts of thin coal seams are difficult. In this study, a coal structure index, which is used to express the damage degree of coal, was estimated by logging curve. In accordance with the contour line of the floor of the coal seam, structural curvature was calculated to express the complexity of the coal seam structure quantitatively. Subsequently, relationships among the burial depth, thickness, coal structure index, structural curvature were analyzed on the basis of the gas pressure of coal seam. The gas pressure values of the coal seams of Nos. 22, 24, and 27 in the study area were predicted by multiple linear regression (MLR) and were then verified and analyzed. The deviation rate of the MLR method was 6.5%–19.7%, with an average of 13.0%. The average deviation rate between the predicted value and the measured value was 11.6%, except for the measuring point of No. 2, which had a large deviation. Results show that the prediction accuracy of the aforementioned method is acceptable and has practical value in the prediction of gas pressure in thin coal seams without measured data. The results in the gas pressure prediction provide a basis for evaluating the risk of gas outbursts in thin coal seams.

scholarly journals Prediction of Gas Pressure in Thin Coal Seams in the Qinglong Coal Mine in Guizhou Province, China

2021 ◽  
Author(s):  
Jian Zhang ◽  
Yongqiang Zhang ◽  
Jilin Wang ◽  
Xiaobin Wen
Keyword(s):  
Coal Seam ◽  
Large Deviation ◽  
Gas Pressure ◽  
Guizhou Province ◽  
Burial Depth ◽  
Coal Seams ◽  
Measuring Point ◽  
Coal Structure ◽  
Deviation Rate ◽  
Structure Index

Abstract Thin coal seams in mines lack gas data; thus, gas outbursts of thin coal seams are difficult to prevent and control. In this study, a coal structure index, which is used to express the damage degree of coal, was estimated by logging curve. In accordance with the contour line of the floor of the coal seam, structural curvature was calculated to quantitatively express the complexity of the coal seam structure. Then, the relationships among the burial depth, thickness, coal structure index, structural curvature, with gas pressure of coal seam were analyzed. The gas pressure of coal seam of Nos. 22, 24, and 27 in the study area was predicted by multiple linear regression (MLR) and then was verified and analyzed. The deviation rate of the MLR method was 6.5%–19.7%, with an average of 13.0%. The average deviation rate between the predicted value and the measured value was 11.6%, except for measuring point of No. 2, which had a large deviation. Results show that the prediction accuracy of the above method is acceptable, and it has practical value in the prediction of gas pressure in thin coal seams without measured data. Results of the gas pressure prediction provide a basis for evaluating the risk of gas outbursts in thin coal seams.

scholarly journals Study on Reservoir Properties and Critical Depth in Deep Coal Seams in Qinshui Basin, China

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Guiqiang Zheng ◽  
Bin Sun ◽  
Dawei Lv ◽  
Zhejun Pan ◽  
Huiqing Lian
Keyword(s):  
Coal Seam ◽  
Step Change ◽  
Gas Content ◽  
Burial Depth ◽  
Critical Depth ◽  
Coal Seams ◽  
Reservoir Properties ◽  
Qinshui Basin ◽  
Geological Conditions ◽  
Change Characteristics

Coalbed methane (CBM) reservoir properties and relationship of properties with burial depth were studied based on the data derived from 204 deep CBM production wells in Qinshui Basin, China. Through the study, it is found that permeability and porosity decrease with the increase of burial depth and the decreasing trend shows step-change characteristics at a critical burial depth. They also show divisional characteristics at certain burial depth. Gas content, geostress, and geotemperature increase with the increase of burial depth, and the increasing trend shows step-change characteristics and also have divisional characteristics at certain burial depth. Based on the previous study on the reservoir property changes with burial depth, three series of critical depth using different parameters are obtained through simulating the critical depth using the BP neural network method. It is found that the critical depth is different when using different parameters. Combined the previous study with the normalization of three different parameter types, the critical depth in Qinshui Basin was defined as shallow coal seam is lower than 650 m and transition band is 650–1000 m, while deep coal seam is deeper than 1000 m. In deep coal seams, the geological conditions and recovery becomes poor, so it can be defined as unfavorable zones. Therefore, other development means, for example, CO2 injection, need to be used to accelerate the deep coal methane development.

scholarly journals Investigation of Hydraulic Fracturing Crack Propagation Behavior in Multi-Layered Coal Seams

2020 ◽  
Vol 10 (3) ◽  
pp. 1153 ◽  
Author(s):  
Shirong Cao ◽  
Xiyuan Li ◽  
Zhe Zhou ◽  
Yingwei Wang ◽  
Hong Ding
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Crack Propagation ◽  
Principal Stress ◽  
Fracture Propagation ◽  
Clean Energy ◽  
Burial Depth ◽  
Coal Seams ◽  
Initiation Pressure ◽  
Dip Angle

Coalbed methane is not only a clean energy source, but also a major problem affecting the efficient production of coal mines. Hydraulic fracturing is an effective technology for enhancing the coal seam permeability to achieve the efficient extraction of methane. This study investigated the effect of a coal seam reservoir’s geological factors on the initiation pressure and fracture propagation. Through theoretical analysis, a multi-layered coal seam initiation pressure calculation model was established based on the broken failure criterion of maximum tensile stress theory. Laboratory experiments were carried out to investigate the effects of the coal seam stress and coal seam dip angle on the crack initiation pressure and fracture propagation. The results reveal that the multi-layered coal seam hydraulic fracturing initiation pressure did not change with the coal seam inclination when the burial depth was the same. When the dip angle was the same, the initiation pressure linearly increased with the reservoir depth. A three-dimensional model was established to simulate the actual hydraulic fracturing crack propagation in multi-layered coal seams. The results reveal that the hydraulic crack propagated along the direction of the maximum principal stress and opened in the direction of the minimum principal stress. As the burial depth of the reservoir increased, the width of the hydraulic crack also increased. This study can provide the theoretical foundation for the effective implementation of hydraulic fracturing in multi-layered coal seams.

scholarly journals A New Method for the Measurement of Gas Pressure in Water-Bearing Coal Seams and Its Application

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiao Cui ◽  
Jiayong Zhang ◽  
Liwen Guo ◽  
Xuemin Gong
Keyword(s):  
Coal Seam ◽  
Field Experiments ◽  
Water Pressure ◽  
Direct Methods ◽  
Gas Pressure ◽  
New Method ◽  
Well Testing ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Gas Disaster

Coal seam gas pressure is one of the fundamental parameters used to assess coal seam gas occurrence and is an important index in assessing the risk of gas disaster. However, the geological characteristics of coal seams become increasingly complex with increasing mining degree, thus decreasing the accuracy and success rate of direct methods for measuring gas pressure. To address such issues, we have developed a new method for direct measurement of gas pressure in water-bearing coal seams. In particular, we developed a pressure measurement device based on theoretical analysis and quantified the basic parameters of the device based on well testing. Then, we verified the applicability of our method based on comparative analysis of the results of field experiments and indirect measurements. Our results demonstrate that this new method can resolve the effects of water pressure, coal slime, and other factors on the estimation of gas pressure. The performance of this new method is considerably better than that of traditional methods. In particular, field test results demonstrate that our method can accurately and efficiently measure gas pressure in water-bearing coal seams. These results will be of great significance in the prevention and control of coal seam gas disaster.

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.

scholarly journals The channel and characteristics of the stope supplied by atmospheric precipitation in the karst landform mining area

2021 ◽  
Author(s):  
Xianzhi Shi ◽  
Weiqiang Zhang ◽  
Yongjin Tang ◽  
Ting Jiang ◽  
Shaojie Zhang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Mine Water ◽  
Time Lag ◽  
Atmospheric Precipitation ◽  
Lag Time ◽  
Water Inflow ◽  
Guizhou Province ◽  
Burial Depth ◽  
Self Healing ◽  
Pipeline Flow

Abstract Atmospheric precipitation causes some mining faces, mining areas or mines to be flooded every year. In order to explore the relationship between atmospheric precipitation and mine water inflow under Karst geomorphic conditions in Guizhou Province, some typical mine related data were collected systematically. It was found that atmospheric precipitation can supply mine goaf through weathered zone cracks, mining fissures, water conducting faults, water flowing subsided columns and karst channels. These channels are in the form of surface infiltration, pipeline flow and layered recharge Replenish the goaf. The results show that the mine water inflow is significantly affected by rainfall under all kinds of recharge modes, the correlation between them is significant under layered recharge mode，the correlation coefficient R reaches 0.88. The recharge channel is filled by loess and other materials on the surface, and has the self-healing characteristics of gradual plugging; the recharge amount is affected by the burial depth of coal seam and the rock combination characteristics of the upper roof. The deeper the coal seam is, the worse the recharge effect is to the mine. The results show that the atmospheric precipitation is the main water filling source of coal mine stope water inflow in the study area, and its recharge has seasonal characteristics. The mine water inflow in rainy season is 1.2-12 times of that in dry season, with an average of 1.9 times; the recharge of mine water by atmospheric precipitation has hysteresis, the lag time of surface infiltration recharge mine is generally 1-4 days, and the lag time of pipeline flow replenishing mine is generally 24 hours In general, the time lag of laminar flow recharge to mine is more than 2 days.

Geological Characteristics of Coalbed Methane Reservoir in Southern Shizhuang Block, Southeastern Qinshui Basin

2013 ◽  
Vol 295-298 ◽  
pp. 3209-3212
Author(s):  
Li Ren Xing ◽  
Yan Bin Yao ◽  
Da Meng Liu ◽  
Jun Gang Liu ◽  
Lu Lu Zhou ◽  
...  
Keyword(s):  
Coal Seam ◽  
Local Structure ◽  
Coalbed Methane ◽  
Simple Structure ◽  
Gas Content ◽  
Burial Depth ◽  
Coal Seams ◽  
Structure Characteristics ◽  
Geological Characteristics ◽  
Coalbed Methane Reservoir

Southern Shizhuang Block has simple structure characteristics, relatively thick coal seams (3.1-10.5 m, 6 m in average), and favorable burial depth (450-900 m). The gas content of the No.3 coal seam in the Shanxi formation ranges from 6-20 m3/t, and it increases from the southeast to northwest area in the southern Shizhuang Block. Gas content is high in the structural low in the area, which means the gas accumulation is controlled by the geological characteristics of local structure and hydrogeologic conditions.

Comprehensive Prediction about Water Abundance of NO.5 Coal Seam Roof’ Sand in Yili NO.1 Coal Mine

2013 ◽  
Vol 706-708 ◽  
pp. 483-487
Author(s):  
Dao Lei Xie ◽  
Jiu Chuan Wei ◽  
Hui Yong Yin ◽  
Jian Bin Guo ◽  
Song Zhou ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Coal Seams ◽  
Water Abundance ◽  
Hydrogeological Characteristics ◽  
Structure Index ◽  
Hydrogeological Data

Collect geological and hydrogeological data of Yili NO.1 coal mine and analyze Hydrogeological Characteristics of sandstone aquifers in the roof of No5 coal seams; predict the water abundance and classify sandstone aquifers’ water abundance with considering the sandstone’s thickness, content and lithology structure index, and provide the basis for controlling the sandstone water of NO.5 coal seam’s roof.

scholarly journals Gas Expansion Energy Model and Numerical Simulation of Outburst Coal Seam under Multifield Coupling

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jie Cao ◽  
Qianting Hu ◽  
Yanan Gao ◽  
Minghui Li ◽  
Dongling Sun
Keyword(s):  
Diffusion Coefficient ◽  
Coal Seam ◽  
Volumetric Strain ◽  
Gas Pressure ◽  
Coal Seams ◽  
Distribution Law ◽  
Free Gas ◽  
Working Face ◽  
Expansion Energy ◽  
Gas Expansion

Due to the insufficient understanding of the outburst mechanism, the coal and gas outburst disasters in China are more serious. Gas expansion energy is the main source of energy that causes outburst. In order to explore the distribution law of gas expansion energy in outburst coal seams, a gas-solid coupling equation of outburst coal seams was established. The distribution law of coal stress field, deformation field, gas flow field, and gas expansion energy were simulated and analyzed by using COMSOL Multiphysics. The results showed that from the excavation face to the deep part of coal seam, the stress presented unloading zone, stress concentration zone, and original stress zone. The volumetric strain and permeability reached the minimum, while the gas pressure reached the maximum at the peak value of vertical stress. As time goes on, the gas pressure in the fracture near the working face gradually decreased and was less than the pressure in coal matrix. The total gas expansion energy consists of free gas and desorption gas expansion energy. Affected by the excavation, free gas expansion energy maintained a constant value in the original coal seam and gradually decreased in the area close to the working face. The expansion energy provided by desorption gas was zero in the original coal seam. And it first increased and then decreased rapidly near the working face. Compared with stress and coal seam thickness, gas pressure and initial diffusion coefficient had significant influence on gas expansion energy of coal seam. When the diffusion coefficient was greater than 1e-9 m2/s, the gas expansion energy of the coal seam near the working face was significantly higher than that of the original coal seam, which had the risk of inducing outburst.

The Application of Crossing and Grid Drainage Boreholes in Floor Tunnel for Coal Roadway Safety Tunneling

2014 ◽  
Vol 962-965 ◽  
pp. 1169-1174
Author(s):  
Hong Qing Zhu ◽  
Bei Fang Gu ◽  
Min Bo Zhang ◽  
Chao Yu ◽  
Zhen Zhang
Keyword(s):  
Coal Seam ◽  
Gas Pressure ◽  
Gas Content ◽  
Dynamic Phenomenon ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Technical Parameters ◽  
Coal Roadway ◽  
Roadway Safety ◽  
The Relationship

In order to reduce the danger of single coal seams outburst during the tunneling in coal roadway and ensure the tunneling of coal seams, this text analyzed the mechanism of crossing drilling against outburst; studied the area measures of floor tunnel crossing and grid drainage boreholes in coal roadway, Designed and optimized the drilling technical parameters; Analyzed the relationship between the drainage concentration and scalar; Calculated the maximum overlying coal seam gas to spare scalar quantity is 224300 m3 ;Used a variety of indicators to investigate the effect of outburst prevention. It shows that Gas content and gas pressure have significant lower than drainage. After the drainage up to standard, all the sensitive indexes is not overrun, during the coal roadway tunneling, it does not appears dynamic phenomenon. Solve the problem of mining imbalances, guaranteed the safety driving of roadway.

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