Although CO₂ geological storage (CGS) is thought to be one of the most promising technologies to sequester the anthropogenic CO₂ to mitigate the climate change, implementation of the method is still challenging due to lack of fundamental understanding of controls of wettability, which is responsible for residual trapping of the gas and its flow dynamics. One of the key parameters that controls the wetting state is the zeta potential, ζ, at rock-water and CO₂-water interfaces. ζ in systems comprising rocks, carbonated aqueous solutions and immiscible supercritical CO₂ have not been measured prior to this study, where we detail the experimental protocol that enables measuring ζ in such systems, and report novel experimental data on the multi-phase ζ. We also demonstrate for the first time that ζ of supercritical CO₂-water interface is negative with a magnitude greater that 14 mV. Moreover, our experimental results suggest that presence of multi-valent cations in tested solutions causes a shift of wettability toward intermediate-wet state. We introduce a new parameter that combines multi-phase ζ and relative permeability endpoints to characterize the wetting state and residual supercritical CO₂ saturation. Based on these results, we demonstrate that ζ measurements could serve as a powerful experimental method for predicting CGS efficiency and/or for designing injection of aqueous solutions with bespoke composition prior to implementing CGS to improve the residual CO₂ trapping in sandstone formations.

中文翻译：

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超临界 CO2-水-砂岩系统的 Zeta 电位及其与 CO2 润湿性和残余地下捕获的相关性


尽管 CO₂ 地质封存 （CGS） 被认为是最有前途的技术之一，可以封存人为的 CO₂ 以缓解气候变化，但由于缺乏对润湿性控制的基本理解，该方法的实施仍然具有挑战性，润湿性是导致气体残余捕获及其流动动力学的原因。控制润湿状态的关键参数之一是岩石-水和 CO₂-水界面的 zeta 电位 ζ。在本研究之前，尚未测量过由岩石、碳酸水溶液和不混溶的超临界 CO₂ 组成的系统中的ζ，我们详细介绍了能够在此类系统中测量ζ的实验方案，并报告了有关多相ζ的新实验数据。我们还首次证明了超临界 CO₂-水界面的ζ是负的，幅度大于 14 mV。此外，我们的实验结果表明，测试溶液中存在多价阳离子会导致润湿性向中等湿状态转变。我们引入了一个新参数，该参数结合了多相ζ和相对渗透率终点，以表征润湿状态和残余超临界 CO₂ 饱和度。基于这些结果，我们证明ζ测量可以作为一种强大的实验方法，用于预测 CGS 效率和/或在实施 CGS 之前设计具有定制成分的水溶液的注入，以改善砂岩地层中残留的 CO₂ 捕获。