Depleted oil fields in the Gulf of Suez (Egypt) can serve as geothermal reservoirs for power generation using a CO${}_2$-Plume Geothermal (CPG) system, while geologically sequestering CO${}_2$. This entails the injection of a substantial amount of CO${}_2$ into the highly permeable brine-saturated Nubian Sandstone. Numerical models of two-phase flow processes are indispensable for predicting the CO${}_2$-plume migration at a representative geological scale. Such models require reliable constitutive relationships, including relative permeability and capillary pressure curves. In this study, quasi-static pore-network modelling has been used to simulate the equilibrium positions of fluid–fluid interfaces, and thus determine the capillary pressure and relative permeability curves.

Three-dimensional images with a voxel size of 0.65 $\mu {\mathrm{m}}^3$ of a Nubian Sandstone rock sample have been obtained using Synchrotron Radiation X-ray Tomographic Microscopy. From the images, topological properties of pores/throats were constructed. Using a pore-network model, we performed a sequential primary drainage, main imbibition cycle of quasi-static invasion in order to quantify (1) the CO${}_2$ and brine relative permeability curves, (2) the effect of initial wetting-phase saturation (i.e. the saturation at the point of reversal from drainage to imbibition) on the residual-trapping potential, and (3) study the relative permeability-saturation hysteresis. The results improve our understanding of the potential magnitude of capillary trapping in Nubian Sandstone, essential for future field-scale simulations.

苏伊士湾（埃及）的枯竭油田可作为地热储层，利用二氧化碳发电${}_2$-羽状地热（CPG）系统，同时地质隔离CO${}_2$。这需要注入大量的CO${}_2$进入高渗透性饱和盐水的努比亚砂岩。两相流过程的数值模型对于预测CO必不可少${}_2$-有代表性的地质规模的泥质迁移。这种模型需要可靠的本构关系，包括相对渗透率和毛细管压力曲线。在这项研究中，准静态孔隙网络模型已用于模拟流体-流体界面的平衡位置，从而确定毛细管压力和相对渗透率曲线。

三维图像尺寸为0.65的三维图像 $\mu {\mathrm{米}}^3$使用同步辐射X射线断层扫描显微镜已经获得了努比亚砂岩岩石样品的一部分。从图像中，构造出孔/喉的拓扑特性。使用孔隙网络模型，我们进行了准静态入侵的顺序主要排水，主要吸水周期，以量化（1）CO${}_2$和盐水相对渗透率曲线，（2）初始润湿相饱和度（即从排水到吸水的反转点处的饱和度）对剩余捕集势的影响，以及（3）研究相对渗透率-饱和滞后。结果提高了我们对努比亚砂岩中毛细血管捕集潜力的认识，这对于将来的现场规模模拟至关重要。