In this work, the interfacial tensions (IFTs) of a series of alkyl ether carboxylates containing different ethylene oxide (EO) and propylene oxide (PO) groups (C₁₂PO₁₅EO₅C, C₁₂PO₁₅EO₁₀C and C₁₂PO₁₅EO₁₅C) against n-alkanes were investigated. Based on the experimental and theoretic results, we find that for adsorbed extended surfactant molecules with both PO and EO groups, the PO group stretches towards the oil phase in a helical winding manner, which improves the size of hydrophobic part and decreases IFT. On the other hand, the whole EO group arranges in an “L” pattern with 4 EO flat at the interface and the others stretching into the water. The “dumbbell” type with the large size of the ionic head and PO group at both ends and the linear EO chain in the middle results in the high IFT values. Therefore, a sufficient PO number and few EO number are prerequisites for obtaining ultralow IFT. The addition of NaCl can decrease the size of anionic head and C₁₂PO₁₅EO₅C solution can produce ultralow IFT against hydrocarbons at optimized salinity. However, electrolyte shows little effect on the IFTs of extended surfactants with “dumbbell” conformation at the interface because the size of linear EO group plays the crucial role. Our research has important implications for the in-depth understanding of extended surfactants and their application in high-salt reservoirs.

在这项工作中，一系列含有不同环氧乙烷 (EO) 和环氧丙烷 (PO) 基团的烷基醚羧酸盐 (C ₁₂ PO ₁₅ EO ₅ C、C ₁₂ PO ₁₅ EO ₁₀ C 和 C ₁₂采购订单₁₅ EO ₁₅C) 对正构烷烃进行了研究。基于实验和理论结果，我们发现对于吸附的同时具有PO和EO基团的扩展表面活性剂分子，PO基团以螺旋缠绕的方式向油相伸展，从而提高了疏水部分的尺寸并降低了IFT。另一方面，整个EO组呈“L”形排列，4个EO平面在界面处，其他的延伸到水中。两端离子头和PO基团较大，中间为线性EO链的“哑铃”型导致IFT值较高。因此，足够的 PO 号和少量的 EO 号是获得超低 IFT 的先决条件。添加NaCl可以减小阴离子头和C ₁₂ PO ₁₅ EO _5的尺寸C 溶液可以在优化的盐度下对碳氢化合物产生超低的 IFT。然而，电解质对界面处具有“哑铃”构象的扩展表面活性剂的 IFT 几乎没有影响，因为线性 EO 基团的大小起着至关重要的作用。我们的研究对于深入理解扩展型表面活性剂及其在高盐储层中的应用具有重要意义。