高压条件下CO2对页岩微观孔隙结构影响及其在页岩中的吸附特征

为了解高压条件下二氧化碳（CO₂）对页岩微观孔隙结构改造及吸附行为，以四川盆地焦页6井页岩为研究对象，通过低温N₂吸附和重量法等温吸附实验，研究了不同温压条件下CO₂处理前后的页岩微观结构特征及CO₂在页岩中的吸附行为.研究表明随处理温度升高，CO₂作用后的页岩比表面积呈下降趋势，平均孔径和孔体积呈上升趋势，微孔、中孔比例减少，宏孔比例增大.CO₂会改变页岩孔隙结构，改变程度与温度呈正相关关系.研究同时表明页岩对CO₂的过剩吸附量随压力增大而增加直至达到最大值，后随压力增大而减小；绝对吸附量随压力增大而增加，在40 MPa之后，吸附量趋于稳定.页岩对CO₂的吸附行为与温度压力有关，在高压条件下，Langmuir模型依然能较好地拟合CO₂在页岩中的吸附. 

Impact on Microscopic Pore Structure and Adsorption Behavior of Carbon Dioxide on Shale under High Pressure Condition

In order to understand the transformation of microscopic pore structure and adsorption behavior of carbon dioxide (CO₂) on shale under high pressure condition, using low-pressure N₂ adsorption analysis and isothermal adsorption instrument based on gravimetric method, the microstructural characteristics before and after CO₂ treatment, and the adsorption behavior of CO₂ in Jiaoye 6 shale from Jiaoshiba area of Sichuan basin were studied. The results show that the shale specific surface area decreased, and the average pore size and pore volume increased with increasing CO₂ treatment temperature. Besides, the proportions of micropore and mesopore decreased, and the proportion of macropore increased with increasing temperature. CO₂ could change the pore structure of shale, and the degree of change is positively correlated with temperature. The results also show that the excess adsorption amount of CO₂ increased with increasing pressure, reached a maximum value, and then decreased. The absolute adsorption amount of CO₂ increased with increasing pressure, and then tended to be stable after 40 MPa. The adsorption behavior of CO₂ on shale is related to temperature and pressure. Langmuir model can still fit CO₂ adsorption on shale well under high pressure.