Wettability in unconventional reservoirs is poorly understood. However, it plays a fundamental role in fluid-rock interactions, and an understanding of wetting behavior is essential for capillary seal assessments and hydrocarbon reserve estimation and recovery in clay-rich reservoirs. In this study, the wetting behavior of transitional Shanxi-Taiyuan shale from the southern North China basin was examined via the contact angle (CA) and spontaneous imbibition (SI) measurement methods. Under water-air-shale conditions, water-wet and neutral-wet behaviors were observed, whereas neutral-wet and oil-wet behaviors were observed under water-oil-shale conditions (Young’s equation was used to convert the water-air-shale system to the water-oil-shale system). When the CA method was used, the shale was shown to be hydrophobic, whereas when the SI test was used, the shale was observed to be hydrophilic. The water-air CAs are negatively correlated with the total organic content (TOC), carbonate and clay mineral contents (excluding those of illite). Furthermore, iron-containing compounds, such as pyrite and siderite, were shown to decrease the water wetness. A linear negative correlation was found between the surface roughness and the CA value. The relationship between these parameters can be used to predict the CAs at different surface roughness values for a given sample. The contradictory wetting behaviors between the results of SI and CA methods can be explained by: (i) differences between the CAs formed under water-air-shale conditions and those formed under hydrocarbon-brine-shale conditions; (ii) differences in the surface roughness, which is dependent on the texture and mineralogy of the shale sample; and (iii) clay swelling after water sorption and the formation of microfractures due to water–rock interactions.

对非常规水库的润湿性了解甚少。但是，它在流体与岩石的相互作用中起着根本性的作用，对润湿行为的理解对于富粘土储层中的毛细管密封评估，油气储量估算和采收至关重要。在这项研究中，通过接触角（CA）和自发吸收（SI）测量方法研究了华北盆地南部过渡山西—太原页岩的润湿行为。在水-油页岩条件下，观察到水-湿和中性-湿行为，而在水-油-页岩条件下观察到中-湿和油-湿行为（使用杨氏方程式转换水-油-页岩）。系统到水-油页岩系统）。使用CA方法时，页岩显示为疏水性，相反，当使用SI测试时，观察到页岩是亲水的。水-空气CAs与总有机物含量（TOC），碳酸盐和粘土矿物含量（伊利石含量除外）呈负相关。此外，含铁化合物（如黄铁矿和菱铁矿）已显示出可降低水的润湿性。在表面粗糙度和CA值之间发现线性负相关。这些参数之间的关系可用于预测给定样品在不同表面粗糙度值下的CA。SI和CA方法结果之间矛盾的润湿行为可以通过以下方式解释：（i）在水-气页岩条件下形成的CA与在烃-盐水页岩条件下形成的CA之间的差异；（ii）表面粗糙度的差异，这取决于页岩样品的质地和矿物学；（iii）吸水后粘土膨胀，并且由于水-岩石相互作用而形成微裂缝。