Investigation into the Gas-Dynamic State of a Coal Seam under Degassing and Moistening

The paper represents the results of monitoring and evaluation of the efficiency of hydroimpulsive disintegration of outburst-prone coal seams in the stopes of development mine workings using a system of sound detecting facilities. Methods of acoustic emission control have been considered as well as the monitoring tasks to evaluate rock mass conditions before the procedure and after it inclusive of the results of sound accompaniment of hydraulic disintegration of the coal seam. It has been determined that the higher concentration of stresses within the rock mass is, the more efficient action of high frequency self-oscillations of cavitation transmitter is on both the fissuring and changes in gas-dynamic state of the coal seam. It has been recommended to apply a mode of impulsive fluid pumping under the conditions where coal seam is in the stress-strain state.

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INFLUENCE OF TECTONIC DISTURBANCES OF COAL LAYER ON HIS GAS DYNAMIC STATE

Odesa National University Herald Geography and Geology ◽

10.18524/2303-9914.2021.1(38).234711 ◽

2021 ◽

Vol 26 (1(38)) ◽

pp. 192-204

Author(s):

V. V. Zberovskyi ◽

P. S. Pashenko ◽

A. V. Pazynich ◽

S. V. Stefanko

Keyword(s):

Coal Seam ◽

Strength Properties ◽

Dynamic State ◽

Gas Dynamic ◽

Disturbed Zone ◽

Tectonic Disturbances ◽

Sudden Release ◽

High Degree ◽

Outburst Hazard

Problem Statement and Purpose. At one of the coal mines of the Donetsk basin, there was a sudden release of coal and gas. The peculiarity of this case is that the accident happened in the place of the alleged development of a geological disturbance, but without any visible signs of this. Inspection of the ejection site and adjacent horizons made it possible to conclude that the emergency site is located in the place of the plicative disturbance development. Thus, it is necessary to study in more detail the influence of disturbed zones hidden nature on the gas-dynamic state of the reservoir, as well as to develop and implement methods for determining such zones. Data & Methods. To achieve this goal, a new method was tested, based on the property of structureless substances to form crystal-like units. This phenomenon has been studied for decades; therefore, such new formations have long been given the name quasicrystals. It was noted that the increase in the concentration of such forms is associated with the presence of geological disturbances. Consequently, the increase in quasicrystals in the rock is an indicator of its disturbance due to the influence of tectonic pressure. Thus, in order to test the technique and reveal the hidden geological disturbance of the coal seam, coal samples were taken, microstructural features were studied, and the strength of the coal seam was measured at 56 points. Result. As a result the values of the concentration of quasicrystals, data on the strength of the formation were obtained, a schematic map of the development of the disturbance in this area was built, its contours were determined, the center of the disturbed zone was identified and the role of such disturbances in the outburst hazard of the formation was substantiated. It has been established that geological disturbances, even of plicative nature, have a high degree of fracturing. Such pores and cracks in coal reduce the strength properties and are able to concentrate sufficient volumes of gas for manifestation of GDP.

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Adsorbed moisture as a complex indicator of the gas-dynamic state of a coal seam (in Russian)

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/0148-9062(84)91672-3 ◽

1984 ◽

Vol 21 (3) ◽

pp. A95

Keyword(s):

Coal Seam ◽

Dynamic State ◽

Gas Dynamic ◽

Adsorbed Moisture

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Labor safety and control of the working area state in the penals while mining steep coal seams by shield aggregates

Geo-Technical mechanics ◽

10.15407/geotm2020.152.047 ◽

2020 ◽

pp. 47-64

Author(s):

V.V. Zberovskyi ◽

◽

R.А. Ahaiev ◽

K.K. Sofiiskyi ◽

B.М. Dehlin ◽

...

Keyword(s):

Coal Seam ◽

Physical And Mechanical Properties ◽

Dynamic State ◽

Coal Seams ◽

Gas Dynamic ◽

Geological Conditions ◽

Labor Safety ◽

Sudden Outburst ◽

District Change ◽

And Control

In this article, circumstances and factors which can lead to a degraded labour protection and occurrence of emergency in a district are reviewed and analyzed on the example of an accident occurred at sudden coal-and-gas outburst in the panel face № 42-1146 m of the Tovstyi-Zakhid seam m3 in the Central Mine of the Toretsvukhillia Mining Company. In this article, state of equipment and its location in the district in accordance with the requirements of the safety rules, records of devices which monitor gas-dynamic state of the coal seam and operation of the shield aggregate are considered. Mining and geological conditions of the seam bedding and technological conditions of the district location within the working horizon; methane content in the air of the roadways in the district; change of coal physical and mechanical properties in the area of possible geological disturbance; results of control of the coal seam gas-dynamic state analyzed by acoustic emission parameters; and other risk factors that led to emergencies were studied. The decisions made for controlling possible area with geological disturbance impact which was detected in the horizons of 916 m and 1026 m on the basis of mining-graphic materials and data of geological study in the mining roadways adjacent to the panel No. 14 in the district 42-1146 m were analyzed. The order and sequence of the works established for eliminating consequences of the coal and gas sudden outburst and detecting zone with disturbed coal and outburst cavity were considered. On the basis of the results obtained, conclusions were made and actions were elaborated on preventing accidents at mining steep prone-to-outburst coal seams by the shield aggregates. It is recommended to continue the scientific research for the purpose of detecting zone with possible impact of discontinuous geological disturbance and plicate disturbed zones in the coal seams by the changed hardness of coal in the adjacent panel, and developing certain local measures on preventing gas-dynamic phenomena at mining steep prone-to-outburst seams by the shield aggregates. The objective of this work was to analyze state of the working area and labor protection and to study the conditions and factors which had led to the accident with serious consequences and emergency condition of the panel.

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A COAL SEAM GAS DYNAMIC ACTIVITYAND ITS DEGASING APPLICATION NECESSITY

Bulletin of Research Center for Safety in Coal Industry (Industial Safety) ◽

10.26631/arc1-2018-8-13 ◽

2018 ◽

pp. 8-13

Author(s):

Ye. N. Kozyreva ◽

◽

A. A. Riabtsev ◽

Keyword(s):

Coal Seam ◽

Coal Seam Gas ◽

Gas Dynamic

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Method of characteristics for the problems of stages of the serviceability check of elementary section of a gas pipeline for operation

Journal of Physics Conference Series ◽

10.1088/1742-6596/2131/3/032117 ◽

2021 ◽

Vol 2131 (3) ◽

pp. 032117

Author(s):

I K Khujaev ◽

Kh Aminov ◽

S Akhmadjonov ◽

A Ismailov

Keyword(s):

Analytical Solution ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Method Of Characteristics ◽

Gas Injection ◽

Gas Pipeline ◽

Dynamic State ◽

Gas Dynamic ◽

Elementary Section

Abstract The article is devoted to modeling the gas-dynamic state of an elementary section of a gas pipeline during gas injection and its outflow through the choke in the final section of the pipe and to solving these problems using the method of characteristics. The subject of the study is the gas-dynamic state of an elementary horizontal section of a gas pipeline in the process of checking its serviceability for operation. The processes of gas injection into the section and gas outflow from it, considered in the article, were modeled using the N.E. Zhukovsky formula on gas outflow into unbounded space in a framework of the short pipeline approach. The original equations are linearized by introducing the mass flow rate of gas and waves traveling in two directions. When solving the problem, the method of characteristics was applied; numerical results were obtained and analyzed using an analytical solution to the problem. The research methods are based on the laws of conservation of momentum and gas mass, the d’Alembert method for solving a system of hyperbolic equations and the methods of conducting a computational experiment. An analytical solution to the problem with a rupture caused by an instantaneous change in the gas pressure at the end of the section is obtained. It is shown that the process proceeds with the formation of compression and rarefaction waves, and their multiple reflections at the ends of the section. The gas in the section tends to a state of rest with time, and the changes in the mass flow rate and gas pressure are of exponential nature.

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A Fully Coupled Hydromechanical Model for CO2 Sequestration in Coal Seam: the Roles of Multiphase Flow and Gas Dynamic Diffusion on Fluid Transfer and Coal Behavior

Geofluids ◽

10.1155/2020/8871614 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Rui Yang ◽

Weiqun Liu ◽

Tianran Ma ◽

Junhe Xie ◽

Yang Hu ◽

...

Keyword(s):

Coal Seam ◽

Multiphase Flow ◽

Coupled Model ◽

Gas Dynamic ◽

Fluid Transfer ◽

The Impact ◽

Fully Coupled ◽

Dynamic Diffusion ◽

Hydromechanical Model

CO2 sequestration in coal seam has proved to be an effective way for reducing air pollution caused by greenhouse gases. A study on the rules of fluid transfer and reliability of CO2 storage during gas injection is necessary for the engineering application. However, the clarification of multifield coupling in long-term CO2 sequestration is the difficulty to solve the aforementioned problem. Previous investigations on the coupled model for CO2 storage in coal seam were not exactly comprehensive; for example, the multiphase flow in the fracture and the nonlinear behavior of gas diffusion were generally neglected. In this paper, a new multistage pore model of the coal matrix and the corresponding dynamic diffusion model were adopted. Meanwhile, the CO2-induced coal softening and the CO2-water two-phase flow in coal fracture were also taken into account. Subsequently, all the mentioned mechanisms and interactions were embedded into the coupled hydromechanical model, and this new fully coupled model was well verified by a set of experimental data. Additionally, through the model application for long-term CO2 sequestration, we found that the stored CO2 molecules are mainly in an adsorbed state at the early injection stage, while with the continuous injection of gas, the stored CO2 molecules are mainly in a free state. Finally, the roles of multiphase flow and gas dynamic diffusion on fluid transfer and coal behavior were analyzed. The results showed that the impact of multiphase flow is principally embodied in the area adjacent to the injection well and the coal seam with lower initial water saturation is more reliable for CO2 sequestration, while the impact of gas dynamic diffusion is principally embodied in the area far away from the injection well, and it is safer for CO2 sequestration in coal seam with greater attenuation coefficient of CO2 diffusion.

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