The Liujiagou formation is an important CO 2 aquifer storage unit in the Ordos Basin in central China. Thus far, it has stored over 90% of the total injected CO 2 from the Shenhua carbon capture and storage (CCS) project, which is the fi rst full-chain CCS project in China. Understanding the basic properties of CO 2 fl ooding is critical for site characterization and evaluation. A core-scale characterization and CO 2 fl ooding study of Liujiagou sandstone is the fi rst step to understanding the fl ooding properties in a CO 2 aquifer storage project. The pore geometry of a sample was characterized using medical, industrial, and micro X-ray computed tomography (X-CT) scanners, as well as mercury intrusion porosity and thin section petrography. To study the fl ooding process, a CO 2 core fl ooding experiment using medical X-CT scanning was conducted with a Liujiagou sandstone sample. Based on the CT data, experimental data, simplifi ed models and COMSOL software, a three-dimensional sub-core scale numerical model that considered porosity, permeability, and capillary pressure heterogeneity was constructed for numerical simulation of CO 2 fl ooding under different scenarios. Laboratory experiments and numerical simulations on a Liujiagou sample revealed the following. The Liujiagou sandstone is a low-porosity and low-permeability sandstone with very high heterogeneity. The sub-core porosity heterogeneity signifi cantly affects CO 2 migration. The relative permeability and saturation distribution are signifi cantly affected by the injection velocity of CO 2 and are different from those of other sandstones, such as Berea. The analyzed Liujiagou sandstone sample has a very low storage effi ciency factor at the core scale. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifi cations or adaptations are made.Modeling and Analysis: CO 2 fl ooding properties of Liujiagou sandstone: infl uence of sub-core scale structure heterogeneity N Wei et al. 401

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