A pH‐responsive amphiphilic surfactant stearic amide 3‐(N,N‐dimethylamino)propylamide (SAA) was synthesized and served as a thickener in aqueous solution to construct a switchable viscoelastic surfactant fluid (VES fluid). The structure of SAA was studied by ¹H NMR, and the viscoelastic behavior of VES fluid was studied in detail by rheological measurements. The viscosity of this VES fluid can be switched reversibly from low to high immediately by adjusting system pH value. Even at high shear rate (170 s⁻¹) and high temperature (90 °C), excellent viscoelastic behavior of this VES fluid can be observed, which is a key performance for fracturing applications. Meanwhile, the recycled VES fluid can still maintain good pH‐responsive behavior even after more than three cycles. These unique performances of this VES fluid not only enhanced our understanding of the transformation of wormlike micelles at high temperature, but also enriched a large potential of VES fracturing fluid in the development of oil and gas reservoirs.

中文翻译：

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pH响应型粘弹性表面活性剂在高温下作为可循环流体的应用

合成了具有pH响应的两亲表面活性剂硬脂酰胺3-（N，N-二甲基氨基）丙基酰胺（SAA），并在水溶液中用作增稠剂，以构建可转换的粘弹性表面活性剂流体（VES流体）。通过¹ H NMR研究了SAA的结构，并通过流变学方法详细研究了VES流体的粘弹性。通过调节系统的pH值，可以立即将VES流体的粘度从低到高可逆地切换。即使在高剪切速率（170 s ^-1）和高温（90°C）下，可以观察到该VES流体具有出色的粘弹性，这是压裂应用的关键性能。同时，即使经过三个以上的循环，循环使用的VES流体仍可以保持良好的pH响应性能。这种VES流体的独特性能不仅增强了我们对高温下蠕虫状胶束的转化的了解，而且丰富了VES压裂液在油气藏开发中的巨大潜力。