Abstract CO2 injection is a promising method to rejuvenate the shale oil reservoirs after the primary production. In this work, we comprehensively reviewed the CO2 injection enhanced oil recovery (EOR) and carbon storage related literature in shales over the past decade. The aspects reviewed include description of major shale reservoirs producing oil and the necessity to perform EOR, selection of injection scheme, models applied to simulate gas injection, oil recovery mechanisms for different types of gas, molecular diffusion and its laboratory measurement, nanopore effect, adsorption effect on carbon storage and transport, laboratory work of gas injection in shale cores, pilot tests, and economic evaluation. Advanced models in recent years applied to simulate these processes were introduced in details, such as the traditional dual continuum model, the embedded discrete fracture model (EDFM). Heterogeneity effect and upscaling algorithm on the shale oil recovery performance were discussed. Molecular diffusion, as an important flow and oil recovery mechanism, was described regarding its definition, empirical correlation and laboratory measurement with consideration of the porous media effect which is crucial for accurate modeling result. Recovery mechanisms by carbon dioxide, methane and nitrogen were compared at the molecule and pore levels. Pros and cons of different types of gas were evaluated as well. Pore confinement caused by the extremely tiny pores in the organic matter, along with the capillary and adsorption effects were discussed, and approaches to take them into account of the model were addressed. Core-scale gas injection experiments on shales from various institutions were described, and the results were compared. Outcomes of recent pilot tests in the Eagle Ford, and the Bakken formations were summarized, and finally, economic considerations were provided for the feasibility of gas injection in shale oil reservoirs.

中文翻译：

---

页岩油藏 CO2 注入 EOR 储碳研究进展综述

摘要 CO2 注入是页岩油初级生产后恢复活力的一种有前景的方法。在这项工作中，我们全面回顾了过去十年页岩中 CO2 注入提高石油采收率 (EOR) 和碳储存的相关文献。回顾的方面包括主要产油页岩油藏的描述和进行 EOR 的必要性、注入方案的选择、用于模拟注气的模型、不同类型气体的采油机制、分子扩散及其实验室测量、纳米孔效应、吸附对碳储运的影响、页岩岩心注气实验室工作、中试和经济评价。详细介绍了近年来应用于模拟这些过程的先进模型，如传统的双连续体模型、嵌入式离散断裂模型 (EDFM)。讨论了对页岩油采收率性能的非均质性影响和升级算法。分子扩散作为一种重要的流动和采油机制，从其定义、经验相关性和实验室测量方面进行了描述，并考虑了对精确建模结果至关重要的多孔介质效应。在分子和孔隙水平上比较了二氧化碳、甲烷和氮气的回收机制。还评估了不同类型气体的优缺点。讨论了由有机质中极细孔引起的孔隙限制，以及毛细管和吸附效应，并讨论了将它们纳入模型的方法。描述了来自不同机构的页岩岩心规模注气实验，并对结果进行了比较。总结了近期在 Eagle Ford 和 Bakken 地层中试的结果，最后为页岩油储层注气的可行性提供了经济考虑。