The overall benefits of geological carbon storage (GCS) depend primarily on CO storability and injectability, expressed as saturation and relative permeability, respectively. The effects of GCS schemes on these two properties, the macroscopic response indicators of a two-phase seepage system, are closely related to pore-scale two-phase behaviors. However, the comprehensive effects of capillary number () and wettability () on saturation and relative permeability are poorly understood. Here we proposed a digital rock physics (DRP) technique workflow for the phase field method and systematically investigated how these effects control two-phase seepage at pore scale through the high-resolution visualization results obtained. We created a phase diagram identified by four pore-scale displacement mechanisms, including finger-like invasion, burst, cooperative filling and coexistence of concave and convex interfaces, to illustrate the comprehensive effects of and . We found that the relative permeability of the defending phase (water in this work) is determined by the net effect of the direct driving and viscous coupling effects. We organized comprehensive diagrams and revealed the favorable conditions for CO injectability and storability. Our results demonstrate that GCS schemes, mainly about capillary number and wettability, can significantly influence CO storage performance via the two-phase flow at pore scale, which should be considered carefully. This work provides valuable insights into the selection of an optimal GCS scheme and contributes to an in-depth understanding of multiphase seepage at pore scale.

中文翻译：

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二氧化碳-水两相流的孔隙尺度洞察及其对地质碳储存效益的影响


地质碳储存（GCS）的总体效益主要取决于二氧化碳的可储存性和可注入性，分别表示为饱和度和相对渗透率。 GCS方案对这两个性质（两相渗流系统的宏观响应指标）的影响与孔隙尺度两相行为密切相关。然而，毛细管数 () 和润湿性 () 对饱和度和相对渗透率的综合影响却知之甚少。在这里，我们提出了相场方法的数字岩石物理（DRP）技术工作流程，并通过获得的高分辨率可视化结果系统地研究了这些效应如何控制孔隙尺度的两相渗流。我们创建了由指状侵入、破裂、协同充填和凹凸界面共存等四种孔隙尺度驱替机制识别的相图，以说明 和 的综合效应。我们发现防御相（本研究中为水）的相对渗透率由直接驱动和粘性耦合效应的净效应决定。我们整理了综合图表，揭示了二氧化碳注入和储存的有利条件。我们的结果表明，GCS 方案（主要涉及毛细管数和润湿性）可以通过孔隙尺度的两相流显着影响 CO 储存性能，应仔细考虑。这项工作为选择最佳 GCS 方案提供了宝贵的见解，并有助于深入了解孔隙尺度的多相渗流。