Title: Synchrotron-based pore-network modeling of two-phase flow in Nubian Sandstone and implications for capillary trapping of carbon dioxide
Authors: Hefny, Mahmoud
Qin, Chao Zhong
Saar, Martin O.
Ebigbo, Anozie  
Language: eng
Keywords: Carbon capture and storage;CO₂-plume geothermal;Nubian Sandstone (Egypt);Pore-network modelling;Residual trapping;Physics - Geophysics
Subject (DDC): DDC::500 Naturwissenschaften und Mathematik::550 Geowissenschaften, Geologie
Issue Date: 1-Dec-2020
Document Type: Article
Journal / Series / Working Paper (HSU): International Journal of Greenhouse Gas Control
Volume: 30
Pages: 21
Abstract: 
Depleted oil fields in the Gulf of Suez (Egypt) can serve as geothermal reservoirs for power generation using a CO₂-Plume Geothermal (CPG) system, while geologically sequestering CO₂. This entails the injection of a substantial amount of CO₂ into the highly permeable brine-saturated Nubian Sandstone. Numerical models of two-phase flow processes are indispensable for predicting the CO₂-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 μm3 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 CO₂ 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.
Organization Units (connected with the publication): Hydromechanik 
URL: http://arxiv.org/abs/2004.06792v1
ISSN: 17505836
Publisher DOI: 10.1016/j.ijggc.2020.103164
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