Surface wettability is one of the major factors that regulate immiscible fluid displacement in porous media. However, the role of pore-scale wettability heterogeneity on dynamic immiscible displacement is rarely investigated. This study investigated the impact of pore-scale wettability heterogeneity on immiscible two-fluid displacement and the resulting macroscopic constitutive relations, including the capillary pressure-water saturation (P_c-S_w) and relative permeability curves. A digital Bentheimer sandstone model was obtained from X-ray micro-computed tomography (micro-CT) scanning and the rock surface wettability fields were generated based on in-situ measurements of contact angles. A graphics processing unit-accelerated lattice Boltzmann model was employed to simulate the immiscible displacement processes through the primary drainage, imbibition, and second drainage stages in a CO₂-water-rock system. We found that pore-scale surface wettability heterogeneity caused noticeable local supercritical CO₂ (scCO₂) and water redistribution under less water-wet conditions. At the continuum scale, the P_c-S_w curves under the heterogeneous wetting condition were overall similar to those under the homogeneous wetting condition. This is because the impact of local wettability heterogeneity on the large-scale capillary pressure-water saturation curve was statistically averaged out at the entire-sample scale. The only difference was that heterogeneous wettability led to a negative entry pressure at the primary drainage stage under the intermediate-wet condition, which was caused by local, scCO₂-wet surfaces. The impact of pore-scale wettability heterogeneity was more noticeable on the relative permeability curves. Particularly, the variation of the scCO₂ relative permeability curve in the heterogeneous wettability scenario was more significant than that in the homogenous wettability scenario. This suggests that pore-scale wettability heterogeneity enhances the coalescence and snap-off behaviors of scCO₂ blobs. This is the first study that systematically investigated the role of pore-scale contact angle heterogeneity on dynamic immiscible displacement and associated P_c-S_w curves in complicated, three-dimensional porous media.

表面润湿性是调节多孔介质中不混溶流体驱替的主要因素之一。然而，很少研究孔隙尺度润湿性非均质性对动态不混溶驱替的作用。本研究研究了孔隙尺度润湿性非均质性对非混相二流体驱替的影响以及由此产生的宏观本构关系，包括毛细管压力-水饱和度（P _c -S _w) 和相对渗透率曲线。通过 X 射线微计算机断层扫描 (micro-CT) 扫描获得数字 Bentheimer 砂岩模型，并基于接触角的原位测量生成岩石表面润湿性场。采用图形处理单元加速的格子Boltzmann 模型来模拟CO ₂ -水-岩系统中通过初级排水、自吸和二级排水阶段的不混溶驱替过程。我们发现，孔隙尺度的表面润湿性异质性导致明显的局部超临界 CO ₂ (scCO ₂ ) 和在较少水润湿条件下的水重新分布。在连续尺度上，P _c -S _w非均匀润湿条件下的曲线总体上与均匀润湿条件下的曲线相似。这是因为局部润湿性非均质性对大尺度毛细管压力-水饱和度曲线的影响在整个样本尺度上被统计平均了。唯一的区别是不均匀的润湿性导致在中间润湿条件下初级排水阶段的负入口压力，这是由局部的scCO ₂润湿表面引起的。孔隙尺度润湿性非均质性对相对渗透率曲线的影响更为明显。特别是，scCO _2的变化非均质润湿性情景中的相对渗透率曲线比均质润湿性情景中的相对渗透率曲线更显着。这表明孔隙尺度的润湿性异质性增强了scCO ₂团块的聚结和断裂行为。这是第一项系统研究孔隙尺度接触角不均匀性对复杂三维多孔介质中动态不混溶位移和相关 P _c -S _{w曲线的作用的研究。}