Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology , Dalian 116024, China.
Research Institute of Innovative Technology for the Earth , Kizugawa City, Kyoto 619-0292, Japan.
Langmuir. 2017 Apr 11;33(14):3358-3366. doi: 10.1021/acs.langmuir.6b04533. Epub 2017 Mar 29.
The wettability of porous media is of major interest in a broad range of natural and engineering applications. The wettability of a fluid on a solid surface is usually evaluated by the contact angle between them. While in situ local contact angle measurements are complicated by the topology of porous media, which can make it difficult to use traditional methods, recent advances in microfocused X-ray computed tomography (micro-CT) and image processing techniques have made it possible to measure contact angles on the scale of the pore sizes in such media. However, the effects of ionic strength, CO phase, and flow pattern (drainage or imbibition) on pore-scale contact angle distribution are still not clear and have not been reported in detail in previous studies. In this study, we employed a micro-CT scanner for in situ investigation of local contact angles in a CO-brine-sand system under various conditions. The effects of ionic strength, CO phase, and flow pattern on the local contact-angle distribution were examined in detail. The results showed that the local contact angles vary over a wide range as a result of the interaction of surface contaminants, roughness, pore topology, and capillarity. The wettability of a porous surface could thus slowly weaken with increasing ionic strength, and the average contact angle could significantly increase when gaseous CO (gCO) turns into supercritical CO (scCO). Contact angle hysteresis also occurred between drainage and imbibition procedures, and the hysteresis was more significant under gCO condition.
多孔介质的润湿性在广泛的自然和工程应用中具有重要意义。流体在固体表面的润湿性通常通过它们之间的接触角来评估。然而，由于多孔介质的拓扑结构使得传统方法难以应用，原位局部接触角测量变得复杂，最近微焦点 X 射线计算机断层扫描（micro-CT）和图像处理技术的进步使得在这种介质的孔径范围内测量接触角成为可能。然而，离子强度、CO 相和流动模式（排驱或吸吮）对孔径范围内接触角分布的影响仍不清楚，在以前的研究中也没有详细报道。在这项研究中，我们采用微 CT 扫描仪在不同条件下原位研究 CO-盐水-砂系统中的局部接触角。详细研究了离子强度、CO 相和流动模式对局部接触角分布的影响。结果表明，由于表面污染物、粗糙度、孔隙拓扑和毛细作用的相互作用，局部接触角在很大范围内变化。因此，多孔表面的润湿性可能会随着离子强度的增加而逐渐减弱，当气态 CO（gCO）转变为超临界 CO（scCO）时，平均接触角会显著增加。排驱和吸吮过程之间也会发生接触角滞后，而在 gCO 条件下滞后更为明显。
