In this paper,breaking through the traditional research path of flow theory from macroscopic view to macroscopic view,the complex flow process of mash gas desorption,diffusion and seepage in coal seam is studied by using Monte Carlo simulation and molecular simulation.The process of mash gas adsorption and desorpton is discussed based on Monte Carlo simulation,and the process of mash gas diffusion and seepage is discussed based on molecular simulation.The emphases and difficulties in studying the flow law of mash gas in coal seam by molecular simulation are pointed out.The general procedures how to apply molecular simulation to study the flow law of mash gas in coal seam are expounded,it lays the foundation for further study.
The evolution of fissures and permeability associated with mining of the upper protective layer of the coal seam is crucial for pressure relief gas drainage of the underlying seam. To understand the influence of mining the upper protective layer on gas drainage within the underlying coal seam, this study utilized the M16 and M18 seams in the Qinglong Coal Mine in Guizhou. Theoretical analysis, discrete element numerical simulation, and field tests were used to characterize the evolution of fractures associated with mining of the upper protective layer and the effects of pressure relief gas drainage within the protected coal seam. The results show that mining-related stress changes controlled the development of fractures, altering the permeability values of coals. An analysis of the crack development in the coal mass caused by mining of the upper protective layer shows that during the initial stage of mining, the produced cracks exhibited a butterfly shape network. Yet, with further development of the mining, these cracks and the stress changes gradually produced an inverted butterfly shape network. According to simulations, the areas of maximum deformation via expansion in the protected coal seam were located near the open cut and the mining end line of the working face. The maximum deformation values were 29.06 and 26.68 mm, respectively, and the corresponding deformation rates were 9.37‰ and 8.61‰, which are greater than the required 3‰. The findings of this study provide a new reference for gas control in pressure relief coal seams under similar working conditions.
The gas content and permeability of coal reservoirs are the main factors affecting the productivity of coalbed methane. To explore the law of gas content and permeability of coal reservoirs in the Zhijin area of Guizhou, taking No.16, No.27 and No.30 coal seams in Wenjiaba mining area of Guizhou as the engineering background, based on the relevant data of coalbed methane exploration in Wenjiaba block, the geological structure, coal seam thickness, coal quality characteristics,coal seam gas content and permeability of the area were studied utilizing geological exploration, analysis of coal components and methane adsorption test. The results show that the average thickness of coal seams in this area is between 1.32 and 1.85 m; the average buried depth of the coal seam is in the range of 301.3-384.2 m; the gas content of No.16 and No.27 coal seams is higher in the syncline core. The gas content of the No.30 coal seam forms a gas-rich center in the south of the mining area. The buried depth and gas content of coal seams in the study area show a strong positive correlation. Under the same pressure conditions, the adsorption capacity of dry ash-free basis is significantly higher than that of air-dried coal. The permeability decreases exponentially with the horizontal maximum principal stress and the horizontal minimum principal stress. The horizontal maximum primary stress and the flat minimum prominent stress increase with the increase of the buried depth of the coal seam. The permeability and coal seam burial depth decrease exponentially. This work can provide engineering reference and theoretical support for selecting high-yield target areas for CBM enrichment in the block.
Methane adsorption/desorption and permeability measurements are critical for evaluating reserves and production potential in coalbed methane (CBM) extraction. The varying temperature and stress in CBM wells have an impact on these characteristics. To understand these effects, take the Wenjiaba mining area and the Qinglong mining area in Guizhou, China, as the research objects, which are called WJB and QL for short. Characterizing the coal's surface area and pore structure using low-field nuclear magnetic resonance and low-temperature nitrogen adsorption is essential for methane flow and storage. The coal's adsorptive capacity under in situ conditions was revealed by isothermal methane adsorption tests conducted at pressures ranging from 0 to 18 MPa at different temperatures. Triaxial stress-controlled adsorption experiments simulated the impact of effective stress on methane adsorption. Stress-permeability tests evaluated the stress sensitivity and its effect on the coal's methane transmission ability, a key factor in CBM well producibility. The results showed that increased temperature reduced adsorption capacity for WJB and QL coals by 14.2% and 16.3%, respectively, while desorption rates and diffusion coefficients increased, suggesting that higher temperatures enhance desorption and diffusion. However, higher coal ranks can hinder desorption. Effective stress application led to over a 90% decrease in both adsorption capacity and permeability, emphasizing the need for stress management in CBM extraction. These insights provide a theoretical framework for the interplay between coal's pore structure, adsorption/desorption properties, and permeability under different stress and temperature conditions, guiding the optimization of CBM extraction strategies for efficient and sustainable methane recovery.
This paper is based on the theory of coal mine fan performance test.It is accomplished by the language Visual Basic 6.0.The author designed and developed the computer deal system of coal mine fan performance text. The system has advantages of simple operation,advanced calculation way,highly precision,etc.It has a popularized value in certain coalfield.
Poverty caused by disasters poses a great challenge to consolidate the achievements of poverty alleviation. Livelihood resilience is the key factor for farmers to resist risks and get rid of poverty. Therefore, this study used the China Family Panel Studies (CFPS) database. Firstly, we examined the impact of natural disasters on the poverty vulnerability of farmers. Secondly, taking livelihood resilience and its decomposition dimensions as threshold variables, we examined the mechanism of livelihood resilience between natural disasters and poverty. The results show that natural disaster shocks, natural disaster intensity, and natural disaster frequency all had a significant positive effect on farm households’ vulnerability to poverty. The threshold test shows that natural disasters had larger effects on the poverty vulnerability of the farmers with lower buffer capacity, self-organizing capacity, and learning capacity. When the livelihood resilience value exceeded the third threshold, the impact of natural disasters on the poverty vulnerability of farmers turned from positive to negative. When the buffer capacity exceeded the third threshold, the impact of natural disasters on poverty vulnerability turned from positive to negative; when the self-organizing capacity exceeded the first threshold, the impact of natural disasters on poverty vulnerability turned from positive to negative; when the learning capacity exceeded the third threshold, the impact of natural disasters on poverty vulnerability turned from positive to negative. Therefore, it is suggested that appropriate policies should be needed to support farmers’ livelihood resilience and address disaster-induced poverty by improving farmers’ buffer capacity, self-organizing capacity, and learning capacity. Focusing on farmers’ livelihood resilience, government should establish a policy support system aimed at improving farmers’ buffer capacity, self-organizing capacity, and learning capacity, that will help farmers to escape from disaster-induced poverty.
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