CO₂ cyclic injection is a promising method for enhanced shale oil recovery. However, the enhanced shale oil recovery mechanism is unclear, especially the adsorption and dissolution of CO₂ and oil in kerogen. Therefore, it is of great importance to study the adsorption and dissolution mechanisms of CO₂ and oil mixtures in shale. In this study, a new experimental apparatus was designed to test the change in the mole fractions of CO₂ and oil before and after adsorption and dissolution at equilibrium conditions. For simplicity, n-dodecane (n-C₁₂) was used as the oil. The adsorption and dissolution amounts of CO₂ and n-C₁₂ were obtained using a mathematical method. Moreover, the adsorption and dissolution characteristics of the CO₂ and n-C₁₂ mixtures in shale and the effect of pressure on the adsorption and dissolution amounts were studied. Finally, the swelling factor of the shale, which was caused by the dissolution of the mixtures, was calculated from the experimental results. The results show that dissolved n-C₁₂ in shale could be replaced by CO₂ when the mole fraction of CO₂ in the free phase was larger than a threshold. The adsorption and dissolution amounts of CO₂ and n-C₁₂ increased with pressure. The lower pressure and larger mole fraction of CO₂ enabled a lower swelling factor of shale. This study provides a straightforward method to experimentally determine the adsorption and dissolution properties of shale, which can be used to evaluate enhanced shale oil recovery by CO₂ injection and the geological storage of CO₂.

中文翻译：

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页岩中二氧化碳和正十二烷混合物的吸附和溶解行为

CO ₂循环注入是提高页岩油采收率的有前途的方法。然而，尚不清楚增强的页岩油采收机理，尤其是干酪根中CO ₂和油的吸附和溶解。因此，研究页岩中CO ₂和油混合物的吸附和溶解机理具有重要意义。在这项研究中，设计了一种新的实验设备，以测试在平衡条件下吸附和溶解前后，CO ₂和油的摩尔分数的变化。为了简单起见，使用正十二烷（n -C ₁₂）作为油。CO ₂和n的吸附和溶解量-C ₁₂使用数学方法获得。此外，研究了页岩中CO ₂和n -C ₁₂混合物的吸附和溶解特性以及压力对吸附和溶解量的影响。最后，根据实验结果计算出了页岩的溶胀系数，该溶胀系数是由混合物的溶解引起的。结果表明，溶解Ñ -C ₁₂在页岩可以通过CO代替₂时CO的摩尔分数₂在免费的相为大于阈值。CO ₂和n -C ₁₂的吸附和溶解量随着压力增加。较低的压力和较大的CO ₂摩尔分数使页岩的溶胀系数较低。本研究提供了一个简单的方法通过实验来确定页岩的吸附和溶解性质，其可用于评估由CO增强页岩油采收₂注射和CO的地质储存₂。