ABSTRACT Information on menisci dynamics and equilibrium contact angles, θe, is needed for modeling multiphase flow of fluids in geologic formations. The wettability of fracture faces is relevant to applications such as waterflooding in enhanced oil recovery and evaluation of caprock integrity for geologic carbon sequestration. We investigated the vertical capillary rise of air-water menisci on exposed fracture faces for a sandstone, a shale, and three granites. The experimental design approximated that employed in the Wilhelmy plate method. Replicate fracture faces were prepared by fracturing cylindrical rock cores using the Brazilian method and splitting the fractured cores apart along their fracture planes. Meniscus onset was imaged from a cross-sectional perspective using dynamic neutron radiography, and quantified with change point analysis. An existing model for meniscus onset fitted the experimental data very well (median R2 = 0.96). Capillary rise was typified by t 2 3 scaling (where t is time), followed by a constant equilibrium height, ze. The average time taken for the menisci to reach ze was 0.39 s, with no differences between rock types. The menisci achieved a greater vertical extent on the fracture faces of the sedimentary rocks as compared to those of the granites. Apparent θe values were calculated from the best fit estimates of ze using the Wilhelmy plate equation for a smooth and planar vertical surface. Despite the fractal roughness of some of the fracture faces, there was a significant linear relationship (R2 = 0.80) between the apparent θe values and intrinsic θe values measured on polished surfaces of the same rocks using the sessile drop method. The regression equation indicated the apparent θe values were consistently greater than the intrinsic values. This overestimation may be due to averaging of pixels at the air-water-solid interface, a required step in the image analysis. Further exploration of the range of applicability and measurement accuracy of this proposed new technique would be valuable.

中文翻译：

---

岩石断裂面上空气-水弯液面的起始动力学

摘要 流体在地质地层中的多相流动建模需要有关弯液面动力学和平衡接触角 θe 的信息。裂缝面的润湿性与诸如水驱提高石油采收率和评估地质碳封存盖层完整性等应用有关。我们研究了砂岩、页岩和三块花岗岩的暴露裂缝面上空气-水弯月板的垂直毛细管上升。实验设计近似于 Wilhelmy 板法中采用的设计。通过使用巴西方法压裂圆柱形岩心并沿其断裂面将裂开的岩心分开来制备复制断裂面。使用动态中子射线照相术从横截面角度对半月板开始进行成像，并通过变化点分析进行量化。现有的弯月面起始模型与实验数据非常吻合（中值 R2 = 0.96）。毛细管上升的典型代表是 t 2 3 缩放（其中 t 是时间），然后是恒定的平衡高度 ze。半月板到达 ze 所需的平均时间为 0.39 s，岩石类型之间没有差异。与花岗岩相比，半月板在沉积岩的断裂面上实现了更大的垂直延伸。使用 Wilhelmy 板方程从 ze 的最佳拟合估计值计算出表观 θe 值，用于平滑和平坦的垂直表面。尽管某些断裂面具有分形粗糙度，但使用固滴法在相同岩石的抛光表面上测量的表观 θe 值和固有 θe 值之间存在显着的线性关系（R2 = 0.80）。回归方程表明表观 θe 值始终大于内在值。这种高估可能是由于对空气-水-固体界面处的像素进行了平均，这是图像分析中的一个必需步骤。进一步探索这项提议的新技术的适用范围和测量精度将是有价值的。