Abstract CO2 injection is a promising technique that not only enhances shale gas recovery but also achieves geological storage of CO2. This paper reviewed the performance of CO2 injection techniques based on simulations and field test studies. We observed that CO2 injection can be practical and successful in a hydraulically fractured shale. The techniques can lead up to 26% more methane production after primary recovery, and sequester more than 60% of the injected CO2 for continuous CO2 injection, while for huff-n-puff higher amount of CO2 is reproduced. Reservoir pressure gradient, competitive adsorption, flow dynamics, and shale properties were found as essential factors controlling CH4 recovery and CO2 storage. Despite the flow dynamics of gases being important for predicting gas production and storage, most simulations described it based on models suitable for well connected fractures and homogenous shale. Moreover, these models are incapable of analyzing fluid flow in stimulated fractures. Future studies on CO2 injection should address the issue of higher CO2 reproduction during the huff-n-puff, the effects of moisture content, induced effects on shale matrix properties by CO2 injection, the kinetics of CO2–CH4 competitive adsorption, flow dynamics of multicomponent gas, and consider the complex pore system of a heterogeneous shale.

中文翻译：

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提高页岩气采收率的 CO2 注入技术回顾：前景与挑战

摘要 CO2 注入是一种很有前景的技术，不仅可以提高页岩气采收率，而且可以实现 CO2 的地质封存。本文根据模拟和现场试验研究回顾了 CO2 注入技术的性能。我们观察到，在水力压裂页岩中注入 CO2 是实用且成功的。这些技术可以在一次采收后使甲烷产量增加 26%，并且可以隔离超过 60% 的注入 CO2 以进行连续 CO2 注入，而对于 huff-n-puff，则可以再生产更多的 CO2。发现储层压力梯度、竞争吸附、流动动力学和页岩特性是控制 CH4 回收和 CO2 储存的重要因素。尽管气体的流动动力学对于预测气体生产和储存很重要，大多数模拟都基于适用于连接良好的裂缝和均质页岩的模型来描述它。此外，这些模型无法分析增产裂缝中的流体流动。未来对 CO2 注入的研究应解决在吞吐过程中 CO2 再生较高的问题、含水量的影响、CO2 注入对页岩基质性质的诱导影响、CO2-CH4 竞争吸附动力学、多组分流动动力学气，并考虑非均质页岩的复杂孔隙系统。