During fluid displacement, e.g. in aquifers or other fluid reservoirs such as CO or H storage sites or hydrocarbon reservoirs, water films are expected to form along the internal pore surface due to its wetting properties and capillarity. Near connate water saturation, these water films would dominate the macroscopic multiphase flow behaviour when e.g. water penetrates the porous medium. We use Atomic Force Microscopy (AFM) to study the sub-pore scale configuration of microscale water films on the rough pore surface of Ketton and Estaillades rocks, after drainage of the medium with decane. Then, we compare the results with a numerical simulation and use a film flow model to estimate the relative permeability through these films, which can be potentially used to link the water film configuration to pore- and core-scale responses. We find that the surface coverage and connectivity of the water films varies substantially with capillary pressure. This can affect the permeability of the films up to several orders of magnitude and thus potentially dictate the displacement efficiency at the onset of imbibition, when the brine phase re-enters the pore space. The novel experimental workflow proposed in this study may help future digital assessment of multiphase flow behaviour near connate saturation.

中文翻译：

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多孔岩石天然颗粒表面水膜的原位 3D 测量


在流体置换过程中，例如在含水层或其他流体储层（例如二氧化碳或氢气储存地点或碳氢化合物储层）中，由于其润湿特性和毛细管作用，预计会沿着内部孔隙表面形成水膜。接近原生水饱和度时，这些水膜将主导宏观多相流行为。水渗透多孔介质。我们使用原子力显微镜（AFM）研究了用癸烷排水介质后，Ketton 和 Estaillades 岩石粗糙孔隙表面上微尺度水膜的亚孔隙尺度构型。然后，我们将结果与数值模拟进行比较，并使用膜流模型来估计通过这些膜的相对渗透率，这可以潜在地用于将水膜配置与孔隙和岩心尺度响应联系起来。我们发现水膜的表面覆盖度和连通性随毛细管压力的变化而变化很大。这可能会影响薄膜的渗透率高达几个数量级，因此当盐水相重新进入孔隙空间时，可能会决定自吸开始时的驱替效率。本研究提出的新颖的实验工作流程可能有助于未来对原生饱和附近的多相流行为进行数字评估。