Abstract Foam has been applied in enhanced oil recovery (EOR) for more than sixty years. The surfactant-stabilized N2/CO2 foams are two of the most widely used foams in foam EOR processes, and numerous oil reservoirs could potentially benefit from them. This paper comprehensively reviews the development of these foams over the past decade. We focused on the promising surfactant formulas and their corresponding mechanisms under different reservoir conditions, especially harsh conditions. The most recent studies have shown that low interfacial tension foaming surfactants are efficient in fractured/tight reservoirs, while CO2-switchable surfactants are well suited to CO2 foam in carbonate reservoirs with high temperatures. Pure surfactants and mixed surfactants that combine anions and cations contain superior foam properties. The surfactant aggregates, such as vesicles and wormlike micelles, could distinctly enhance the foam stability. However, the adsorption of the mixed surfactants on reservoir rocks and the temperature sensitivity of the complex structures should be given particular consideration. The phase behaviors involved in foam EOR processes are vital and much more complicated than those in other EOR processes. Thus, a better knowledge of the phase behaviors could further improve foam EOR performance. The results of this paper provide clues to N2/CO2 foam EOR design and also promote the development of harsh reservoirs.

中文翻译：

---

表面活性剂稳定的 N2/CO2 泡沫在提高石油采收率中的新进展

摘要 泡沫在提高采收率（EOR）中的应用已有六十多年。表面活性剂稳定的 N2/CO2 泡沫是泡沫 EOR 过程中使用最广泛的两种泡沫，许多油藏都可能从中受益。本文全面回顾了这些泡沫在过去十年中的发展。我们重点研究了在不同储层条件下，特别是恶劣条件下有前景的表面活性剂配方及其相应的机制。最近的研究表明，低界面张力发泡表面活性剂在裂缝/致密储层中是有效的，而 CO2 可转换表面活性剂非常适用于高温碳酸盐岩储层中的 CO2 泡沫。结合阴离子和阳离子的纯表面活性剂和混合表面活性剂具有优异的泡沫特性。表面活性剂聚集体，如囊泡和蠕虫状胶束，可以明显提高泡沫稳定性。然而，混合表面活性剂在储集岩上的吸附和复杂结构的温度敏感性应特别考虑。泡沫 EOR 过程中涉及的相行为至关重要，而且比其他 EOR 过程中的相行为要复杂得多。因此，更好地了解相行为可以进一步提高泡沫 EOR 性能。本文的结果为 N2/CO2 泡沫 EOR 设计提供了线索，也促进了恶劣储层的开发。应特别考虑混合表面活性剂在储集岩上的吸附和复杂结构的温度敏感性。泡沫 EOR 过程中涉及的相行为至关重要，而且比其他 EOR 过程中的相行为要复杂得多。因此，更好地了解相行为可以进一步提高泡沫 EOR 性能。本文的结果为 N2/CO2 泡沫 EOR 设计提供了线索，也促进了恶劣储层的开发。应特别考虑混合表面活性剂在储集岩上的吸附和复杂结构的温度敏感性。泡沫 EOR 过程中涉及的相行为至关重要，而且比其他 EOR 过程中的相行为要复杂得多。因此，更好地了解相行为可以进一步提高泡沫 EOR 性能。本文的结果为 N2/CO2 泡沫 EOR 设计提供了线索，也促进了恶劣储层的开发。