Experimental Study of the Raw Coal Desorption Method On the Corresponding Relation between Coal Seam Gas Pressure and Content

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.

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

Advances in Civil Engineering ◽

10.1155/2018/9020872 ◽

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.

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Influence of Ground Stress on Coal Seam Gas Pressure and Gas Content

Fluid Dynamics & Materials Processing ◽

10.32604/fdmp.2019.04779 ◽

2019 ◽

Vol 15 (1) ◽

pp. 53-61

Author(s):

Xuebo Zhang ◽

Zhiwei Jia

Keyword(s):

Coal Seam ◽

Gas Pressure ◽

Gas Content ◽

Coal Seam Gas ◽

Ground Stress

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Stable Dispersion of Coal Fines during Hydraulic Fracturing Flowback in Coal Seam Gas Reservoirs—An Experimental Study

Energy & Fuels ◽

10.1021/acs.energyfuels.0c00045 ◽

2020 ◽

Vol 34 (5) ◽

pp. 5566-5577 ◽

Cited By ~ 7

Author(s):

Faisal Ur Rahman Awan ◽

Alireza Keshavarz ◽

Hamed Akhondzadeh ◽

Sarmad Al-Anssari ◽

Ahmed Al-Yaseri ◽

...

Keyword(s):

Experimental Study ◽

Coal Seam ◽

Hydraulic Fracturing ◽

Coal Seam Gas ◽

Gas Reservoirs ◽

Stable Dispersion ◽

Coal Fines

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Numerical Simulation on the Influence of Mining-Induced Fractures Field on Gas Drainage and its Application

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.477 ◽

2011 ◽

Vol 90-93 ◽

pp. 477-484

Author(s):

Shu Jing Zhang ◽

Yong Wei Peng ◽

Yong Jiang Yu

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Gas Flow ◽

Underground Mining ◽

High Strength ◽

Gas Pressure ◽

Comsol Multiphysics ◽

Coal Seam Gas ◽

Gas Drainage ◽

Induced Fractures

In order to study the influence of mining-induced fractures field on gas drainage,the paper adopts software of numerical simulation COMSOL Multiphysics to simulate gas drainage of coal seam under the condition of high-strength underground mining. The main aspects can be seen as the following: (1) In the case without considering the fractures, gas drainage in single hole, the gas pressure distribution showed a funnel-type distribution in space along the drainage holes around. (2) The orientation and direction of fractures play a major role on the flow field of gas. In the region that exits fractures, the distribution of gas pressure has a clear fluctuation and adjustment.(3) The numerical simulation of coal seam gas drainage that considered the fracture of coal mining, was closer to the true gas flow.

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Research on Permeability of Coal Samples with and without the Effect of Supercritical CO2

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.455-456.168 ◽

2012 ◽

Vol 455-456 ◽

pp. 168-173

Author(s):

Tao Yang ◽

Bai Sheng Nie ◽

Dong Yang ◽

Ru Ming Zhang

Keyword(s):

Experimental Study ◽

Coal Seam ◽

Low Permeability ◽

Coal Seam Gas ◽

Gas Drainage ◽

Laboratory Conditions ◽

Before And After ◽

Order Of Magnitude ◽

Volume Stress

To improve the low-permeability coal seam gas drainage and gas prevention and to seek the methods to improve the permeability of low-permeability coal, the experimental study on supercritical CO2 on coal was conducted in the laboratory conditions, and the experiment on pseudo-triaxial permeability testing for coal samples, with and without supercritical CO2, was conducted. The results show that due to the effect of supercritical CO2 on coal like physi-chemistry, the porosity of coal was changed, which markedly varied the permeability of coal samples before and after the effect of supercritical CO2; the permeability of the experimented coal samples was significantly higher than before, and average permeability increased by nearly an order of magnitude under the same volume-stress.

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Study of Sealing Technology of Downward & Permeable Borehole

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.351 ◽

2012 ◽

Vol 524-527 ◽

pp. 351-354 ◽

Cited By ~ 1

Author(s):

Zu Xiang Hu

Keyword(s):

Coal Seam ◽

Wall Rock ◽

Gas Pressure ◽

Good Effect ◽

Time Sharing ◽

Coal Seam Gas ◽

Local Practice ◽

Prediction And Prevention ◽

Geological Conditions ◽

Pressure Measure

In gas prediction and prevention , it is important for the Mine-managers to know coal-seam gas-pressure. Because of the limitation of geological conditions,some seam can not use upward bore to measure gas pressure,so using downward bore is essential, but coal-seam gas-pressure measure is difficult on the this condition(QixiangYu. 1992) . In order to resolve this problem, the way of “subsection and time-sharing hole sealing” is propounded in this paper.by using this method, the crevice water of wall rock is blockaded effectively and the influence of measure gas pressure by crevice water is avoided. It can provide guarantee to measure gas pressure under the complicated condition.By the local practice,good effect is achieved.

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Research and Optimization of Gas Extraction by Crossing-Seam Boreholes from Floor Roadway

Geofluids ◽

10.1155/2021/7499012 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Gang Li ◽

Jiafei Teng

Keyword(s):

Coal Seam ◽

Gas Permeability ◽

Gas Pressure ◽

Gas Content ◽

Gas Extraction ◽

Gas Migration ◽

Governing Equations ◽

Coal Seam Gas ◽

Gas Seepage ◽

Gas Disaster

Deep coal seams are characterized by large stress, high gas pressure, and low permeability. The gas disaster threatens the safe production of coal mine seriously. Gas extraction by crossing-seam boreholes from floor roadway (GECMBFR) can reduce the pressure and content of coal seam gas, which is the main measure to prevent gas disaster. Considering the Klinkenberg effect, governing equations of gas adsorption/desorption-diffusion, gas seepage, and stress fields within the coal seam are established to form the seepage-stress coupling model. The governing equations are embodied into a finite element driven software to numerically simulate gas migration and fluid-solid coupling law in coal seam. On this basis, the process of gas extraction under different borehole spacings and diameters is simulated. The effects of these two key parameters on coal seam gas pressure, gas content, and gas permeability were analyzed. The borehole spacing and diameter were determined to be 5 m and 0.09 m, respectively. Combined with the actual situation of a mine, the process of gas extraction from floor roadway with different cross-sectional schemes, ordinary drilling boreholes and punching combined drilling boreholes, is comparatively analyzed. The results show that the gas extraction effect by ordinary drilling boreholes is lower than that of the punching combined drilling boreholes, and the extraction is uneven and makes it difficult to meet the standard. Hydraulic punching was carried out, and coal was washed out of the borehole, which expanded the contact area between the borehole wall and coal seam. The coal seam around the punching borehole is unloaded, which improves coal permeability and accelerates gas migration towards the borehole, thus promoting the efficiency of gas extraction. It is more reasonable to use punching combined drilling borehole scheme when implementing the GECMBFR technology.

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