Carbon dioxide injection in shale reservoirs can be beneficial for enhanced oil recovery and CO₂ storage scenarios. CO₂ mass transfer can be influenced strongly by the in-situ liberation of light oil components from live oil forming a distinct gas phase. This mechanism has been overlooked in the past for studying CO₂ and oil interactions in tight formations. In this work, a series of analytical solutions and numerical simulations were developed to identify the effect on EOR by CO₂ due to the liberation of a light hydrocarbon gas phase from live oil in shales. The analytical model demonstrated faster diffusion of CO₂ in the two-phase system due to the presence of this gas phase. Using numerical approaches, laboratory-scale simulations indicated that in-situ gas formation can increase oil recovery by 35%. At the field-scale, an additional oil recovery of 9.8% could be attained. Also, the CO₂ storage capacity of shale formations could be significantly enhanced due to capillary trapping of CO₂ in the liberated gas. The results of this study could potentially be used to improve evaluations of the potential of CO₂ EOR in shale reservoirs.

在页岩油藏中注入二氧化碳对于提高采油率和CO ₂储存方案可能是有益的。轻油成分从形成独特气相的活油中原位释放会严重影响CO _2的传质。过去在研究致密地层中的CO ₂和油的相互作用时，已经忽略了这种机理。在这项工作中，开发了一系列分析解决方案和数值模拟以识别由于页岩中的活油释放出轻质烃类气相而导致的CO ₂对EOR的影响。分析模型表明，CO ₂扩散更快由于存在该气相，因此在两相系统中处于不平衡状态。使用数值方法，实验室规模的模拟表明，原位气体形成可以使石油采收率提高35％。在油田规模上，可以实现9.8％的额外采收率。而且，由于释放出的气体中CO _2的毛细管捕集，可以显着提高页岩地层的CO ₂储存能力。这项研究的结果可潜在地用于改善对页岩储层中CO ₂ EOR潜力的评估。