Modeling and experiment for effective diffusion coefficient of gas in water-saturated coal

被引:116
作者
Si, Leilei [1 ,2 ,3 ]
Zhang, Hongtu [1 ,2 ,3 ]
Wei, Jianping [1 ,2 ,3 ]
Li, Bo [1 ,2 ,3 ]
Han, Hongkai [1 ,2 ,3 ]
机构
[1] Henan Polytech Univ, Sch Safety Sci & Engn, Jiaozuo 454003, Henan, Peoples R China
[2] Henan Polytech Univ, State Key Lab Cultivat Base Gas Geol & Gas Contro, Jiaozuo 454003, Henan, Peoples R China
[3] State Collaborat Innovat Ctr Coal Work Safety & C, Jiaozuo 454003, Henan, Peoples R China
基金
中国国家自然科学基金;
关键词
Effective diffusion coefficient; Water-saturated coal; Pore structure; Adsorption; Radial diffusion; PORE STRUCTURE; METHANE ADSORPTION; LIQUID-NITROGEN; MOISTURE; EVOLUTION; TRANSPORT; PRESSURE; STORAGE; SEAM;
D O I
10.1016/j.fuel.2020.118887
中图分类号
TE [石油、天然气工业]; TK [能源与动力工程];
学科分类号
0807 ; 0820 ;
摘要
The diffusion of gas in water-saturated porous media plays a significant role in CO2 geological sequestration and mine gas prevention and control. However, it is lack of an accurate model to calculate the effective diffusion coefficient of gas in a water-saturated coal core. In this work, an improved model was constructed to calculate the effective diffusion coefficient of gas in a water-saturated coal core by considering both the gas adsorption in residual pore and the gas dissolution in pore water. By using a PVT (Pressure-Volume-Temperature) test method, the calculation results of improved model are in the range of 1.03 x 10(-12) similar to 30.40 x 10(-12)m(2)/s, which are 5 similar to 6 orders of magnitude lower than those calculated by traditional model, because the traditional model only considers the gas dissolution in pore water. Therefore, the results of improved model are more in line with the actual situation. Furthermore, the saturated moisture, equilibrium moisture and NMR experiments were carried out. Results shows that, the saturated moisture and equilibrium moisture decreases with the rising coal rank. The pore size changes from micropore/mesopore-dominated to micropores-dominated as the coal rank rise. In addition, the proportion of open porosity gradually reduces with the rising coal rank, while the closed porosity increases, indicating that the pore connectivity decreases with the growing coal rank. Finally, the influences of adsorbability, pore structure, pressure and liquid properties on the effective diffusion coefficient were analyzed.
引用
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页数:9
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