Emulsions, including oil-in-water (O/W) and water-in-oil (W/O) emulsions, can play important roles in both controlling reservoir conformance and displacing residual oil for enhanced oil recovery (EOR) projects. However, current methods, like high-shear mixing, high-pressure homogenizing, sonicators and others, often use lots of extra energy to prepare the emulsions with high costs but very low energy efficiency. In recent decades, spontaneous emulsification methods, which allow one to create micro- and nano-droplets with very low or even no mechanical energy input, have been launched as an overall less expensive and more efficient alternatives to current high extra energy methods. Herein, we primarily review the basic concepts on spontaneous emulsification, including mechanisms, methods and influenced parameters, which are relevant for fundamental applications for industrials. The spontaneity of the emulsification process is influenced by the following variables: surfactant structure, concentration and initial location, oil phase composition, addition of co-surfactant and non-aqueous solvent, as well as salinity and temperature. Then, we focus on the description of importance for emulsions in EOR processes from advances and categories to improving oil recovery mechanisms, including both sweep efficiency and displacement efficiency aspects. Finally, we systematically address the applications and outlooks based on the use of spontaneous emulsification in the practical oil reservoirs for EOR processes, in which conventional, heavy, high-temperature, high-salinity and low-permeability oil reservoirs, as well as wastewater treatments after EOR processes are involved.

中文翻译：

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自发乳化的进展及其在提高采油率中的重要应用。

乳化液，包括水包油（O / W）和油包水（W / O）乳液，在控制储层一致性和置换残油以提高采油率（EOR）项目中都可以发挥重要作用。然而，当前的方法，例如高剪切混合，高压均质，超声仪和其他方法，通常使用大量额外的能量来制备乳液，成本高但能量效率非常低。在最近的几十年中，自发乳化方法作为一种可以替代目前高附加能量方法的更便宜，更有效的替代方法，使人们能够以非常低的甚至没有机械能输入的方式产生微滴和纳米滴。在这里，我们主要回顾一下自发乳化的基本概念，包括机理，方法和受影响的参数，与工业的基本应用有关。乳化过程的自发性受以下变量影响：表面活性剂的结构，浓度和初始位置，油相组成，助表面活性剂和非水溶剂的添加以及盐度和温度。然后，我们将重点介绍乳液在EOR工艺中的重要性，从进步和类别到改善采油机理，包括扫油效率和驱油效率方面。最后，我们基于自发乳化在EOR工艺的实际油藏中的应用，系统地探讨了其应用和前景，在这些油藏中，常规，重，高温，高盐度和低渗透率的油藏，