The design of surfactants for CO₂-in-water (C/W) foams in carbonate reservoirs above 100 °C has been limited by thermal instability of surfactants, surfactant adsorption to mineral surfaces, and challenges in generating and stabilizing the foams. Here, we have identified a diamine surfactant, C_12–14N(CH₃)C₃N(CH₃)₂ (Duomeen CTM), with good thermal stability (>1 month at 135 °C), that stabilizes viscous C/W foam with an apparent viscosity of up to ∼35 cP at 120 °C in 22% total dissolved solid (TDS) brine. Strong foams with excessively high viscosity were reported to be generated with longer-tailed C_16–18N(CH₃)C₃N(CH₃)₂ (Duomeen TTM) that formed a viscoelastic aqueous phase. Here, the tail length was shorter for C_12–14N(CH₃)C₃N(CH₃)₂ and thus a viscoelastic aqueous phase was not formed, resulting in a weaker CO₂ foam with a more appropriate viscosity for the proposed applications. Moreover, at the lowest superficial velocity studied (4 ft/day), the apparent viscosity for C_12–14N(CH₃)C₃N(CH₃)₂ was ∼20 fold lower than that of C_16–18N(CH₃)C₃N(CH₃)₂, consistent with the lower viscosity for the aqueous phase. Not only the foam viscosity with C_12–14N(CH₃)C₃N(CH₃)₂ was high enough for CO₂ mobility control in enhanced oil recovery (EOR) but also it was low enough to be more favorable with regard to the injection pressure than the excessive high flow resistance associated with C_16–18N(CH₃)C₃N(CH₃)₂. In addition, viscous C/W foam was maintained at low fractions of dodecane (model oil) and broke in the presence of large fractions of dodecane, both of which are beneficial to EOR. The oil/water (O/W) emulsions formed with C_12–14N(CH₃)C₃N(CH₃)₂ were unstable and broke in 30 min, and the O/W partition coefficient depended greatly on pH at 120 °C in 22% TDS brine. All of these factors suggest that the surfactant C_12–14N(CH₃)C₃N(CH₃)₂ is a good candidate for further evaluation and scale up for CO₂ EOR, CO₂ sequestration, and hydraulic fracturing at high salinities and temperatures.

中文翻译：

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高盐度卤水中可转换胺表面活性剂稳定的CO ₂水包泡沫的设计及油的影响

在高于100°C的碳酸盐储层中，用于CO ₂水包（C / W）泡沫的表面活性剂的设计受到表面活性剂的热不稳定性，表面活性剂吸附在矿物表面的局限性以及产生和稳定泡沫的挑战。在这里，我们确定了一种二胺表面活性剂C _12–14 N（CH ₃）C ₃ N（CH ₃）₂（Duomeen CTM），具有良好的热稳定性（在135°C时> 1个月），可以稳定粘性C /。 W泡沫在120°C下在22％的总溶解固体（TDS）盐水中的表观粘度高达〜35 cP。据报道，长尾C _16-18 N（CH ₃）C ₃会产生粘度过高的强泡沫。形成粘弹性水相的N（CH ₃）₂（Duomeen TTM）。在此，C _12–14 N（CH ₃）C ₃ N（CH ₃）₂的尾巴长度较短，因此未形成粘弹性水相，从而导致较弱的CO ₂泡沫，其粘度更适合所建议的应用程序。此外，在研究的最低表观速度（4 ft /天）下，C _12–14 N（CH ₃）C ₃ N（CH ₃）₂的表观粘度比C _16–18 N（表观）低约20倍。CH ₃）C ₃N（CH ₃）₂，与水相的较低粘度一致。C _12–14 N（CH ₃）C ₃ N（CH ₃）₂的泡沫粘度不仅足够高以控制CO ₂迁移率以提高采油率（EOR），而且还足够低以至于在使用时更有利比与C _16-18 N（CH ₃）C ₃ N（CH ₃）₂相关的过高流动阻力。另外，粘性C / W泡沫保持在低馏分的十二烷（模型油）下，并在存在大量馏分的十二烷的情况下破裂，这两者均对EOR有利。由C _12–14 N（CH ₃）C ₃ N（CH ₃）₂形成的油/水（O / W）乳状液不稳定并在30分钟内破裂，并且O / W分配系数在120°C下很大程度上取决于pH值在22％TDS盐水中的温度为°C。所有这些因素表明，表面活性剂C _12–14 N（CH ₃）C ₃ N（CH ₃）₂是进一步评估和扩大CO ₂ EOR，CO _{2的良好选择。} 盐分和高温下的固溶和水力压裂。