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- Title
N<sub>2</sub>/CO<sub>2</sub> 注入压力对含瓦斯煤岩中甲烷解吸的影响.
- Authors
李树刚; 白 杨; 林海飞; 严 敏; 龙 航; 郭豆豆
- Abstract
Gas injection can increase the drainage efficiency of low permeability coal beds. So far, however, the interaction mechanism between the molecule of injected gas and the gas-bearing coal rock in the process of gas injection has not been clarified. Based on the coal model containing adsorbed methane, this paper studies the desorption behavior of CH4 in the gas-bearing coal structure after the injection of N2 and CO2 at different pressures using the grand canonical Monte Carlo (GCMC) method. On this basis, the mechanism of CO2/N2 injection to promote CH4 desorption in coal beds was clarified. And the following research results were obtained. First, compared with N2 injection, there are more free CH4 molecules, the total energy of the CH4-CO2 system is overall lower than that of the CH4-N2 system and the CH4-CO2 system is more stable after CO2 injection into gas-bearing coal. Second, under the same injection pressure conditions, CH4 mean square displacement, CH4 molecular activity and CH4 diffusion coefficient of the CH4-CO2 system are higher than those of the CH4-N2 system, indicating that CO2 has a better effect in promoting CH4 desorption. Third, after CO2/N2 is injected into the gas-bearing coal structure, with the increase of the injection pressure, the relative concentration of CO2, N2 and CH4 in the vacuum layer all rise. On the whole, the relative concentration of CH4 is the highest in the CH4-CO2 system and moderate in the CH4-N2 system, the relative concentration of CO2 is moderate in the CH4-CO2 system, and the relative concentration of N2 is the lowest in the CH4-N2 system. Fourth, the reasonable N2 and CO2 injection pressure to promote CH4 desorption are in the range of 2-4 MPa and 3-4 MPa, respectively. In conclusion, the research results can provide theoretical support for the studies on the coal bed stimulation technology by gas injection.
- Subjects
GAS injection; METHANE; DESORPTION kinetics; COAL gas; DIFFUSION coefficients; GEOLOGICAL carbon sequestration; DRAINAGE; COAL combustion
- Publication
Natural Gas Industry, 2021, Vol 41, Issue 3, p80
- ISSN
1000-0976
- Publication type
Article
- DOI
10.3787/j.issn.1000-0976.2021.03.009