Synchrotron-based pore-network modeling of two-phase flow in Nubian Sandstone and implications for capillary trapping of carbon dioxide. (December 2020)

• Record Type: Journal Article
• Authors: Hefny, Mahmoud; Qin, ChaoZhong; Saar, Martin O.; Ebigbo, Anozie
• Is Part Of: International journal of greenhouse gas control. Volume 103(2020)
• Publication Date: 2020-12
• Subjects: Pore-network modelling -- Carbon capture and storage -- CO2-plume geothermal -- Nubian Sandstone (Egypt) -- Residual trapping; Greenhouse gases -- Environmental aspects -- Periodicals; Air -- Purification -- Technological innovations -- Periodicals; Gaz à effet de serre -- Périodiques; Gaz à effet de serre -- Réduction -- Périodiques; Air -- Purification -- Technological innovations; Greenhouse gases -- Environmental aspects; Periodicals; 363.73874605
• DOI: 10.1016/j.ijggc.2020.103164
• Languages: English
• ISSNs: 1750-5836

Abstract

Highlights: 3D images of a Nubian Sandstone rock have been obtained using Synchrotron Radiation X-ray Tomographic Microscopy. Lab experiments and image analyses provide a pore-size distribution and P c − S w relationship for the CO 2 -brine system. Relative permeability curves have been obtained for Nubian sandstone using quasi-static pore-network modelling. The Land trapping coefficient for CO 2 in the Nubian Sandstone sample has been quantified as 1.2. The sensitivity study reflects the importance of the wettability and aspect ratio on the residual CO 2 trapping. Abstract: 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 μ 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.