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为了研究粒径对页岩吸附甲烷的作用机理,分别制成粒径范围为1700~3 350μm、850~1000μm、180~250μm和106~131μm的4种样品,开展了高温高压等温吸附实验,根据Langmuir吸附理论并拟合实验结果获得了不同粒径下的吸附参数,分析基于粒径作用下的孔隙连通性、比表面积和粗糙度对吸附能力的影响,并探讨页岩吸附的粒径敏感性。结果表明:随页岩粒径减小,甲烷吸附量增加,Langmuir体积呈现出先急剧增大后减小再增大的趋势;粒径从1700~3350μm减小至180~250μm,中孔体积增加了72.46倍,直径小于5nm孔隙的孔容贡献率从57.94%增至80.36%,比表面积贡献率从74.34%增至92.85%。结论认为:①粒径随颗粒碾碎减小,改善了孔隙连通性,减少了吸附阻碍,优化了甲烷分子的传质吸附路径,提高了吸附速率;②粒径越小,被包裹的闭孔暴露出来,2~5nm的中孔数量增加,孔隙体积和比表面积得到了较大的提高,为甲烷分子提供了更大的吸附空间;③粒径减小增强了孔隙表面的粗糙程度,贡献了比表面积的同时也使得颗粒中的有机质和黏土矿物一定程度地暴露出来,增加了更多的高能吸附位。
In order to study the action mechanism of particle size on the adsorption of methane by shale, four kinds of samples with particle sizes in the range of 1700-3 350μm, 850-1000μm, 180-250μm and 106-131μm were prepared respectively. The isothermal adsorption experiments were carried out according to Langmuir adsorption theory and fitting the experimental results obtained under different particle size adsorption parameters, based on particle size under the influence of pore connectivity, specific surface area and roughness of the adsorption capacity, and to explore the particle size of shale adsorption sensitivity . The results show that with the decrease of shale particle size, the adsorption amount of methane increases and the volume of Langmuir increases sharply and then increases and then increases. The particle size decreases from 1700 ~ 3350μm to 180 ~ 250μm, and the mesopore volume increases 72.46 times the pore volume of less than 5nm pore volume contribution rate increased from 57.94% to 80.36%, the specific surface area contribution increased from 74.34% to 92.85%. The conclusions are as follows: (1) The particle size decreases as the particles are crushed, the pore connectivity is improved, the adsorption inhibition is reduced, the mass transfer path of methane molecules is optimized, and the adsorption rate is increased. The smaller the particle size is, Exposed, the number of mesopores increased from 2 nm to 5 nm, the pore volume and specific surface area increased greatly, which provided more adsorption space for methane molecules. (3) The decrease of particle size enhanced the roughness of pore surface, contributing to The specific surface area also exposes the organic matter and clay minerals in the grain to some extent, adding more high-energy adsorption sites.