Effect of CO₂ Injection on the Multiphase Flow Properties of Reservoir Rock

Geologic carbon storage (GCS) has recently been drawing attention as an effective and sustainable method to reduce CO₂ emissions to the atmosphere. The injection of CO₂ is mainly conducted into brine-saturated reservoir formations, and assessment of the multiphase flow properties becomes essential to evaluate the injectivity and storage capacity for carbon storage. Characterization of the CO₂/water flow system requires comprehensive knowledge of host rock’s relative permeability, capillary pressure, and wettability that are related to each other. Moreover, chemical reactions between the mineral grains and acidic mixture of CO₂ and water may significantly affect the flow properties. In this study, a comprehensive experimental approach to characterize the chemical effect on the multiphase flow of CO₂ in water-saturated reservoir rock is presented. One silica-rich formation—Berea sandstone, and two calcite-rich formations—Apulian and Indiana limestones, are selected to represent the reservoir materials. Robust experimental techniques for measurements of the relative permeability and degree of saturation based on the changes in poroelastic response are introduced. The relative permeability curves are determined, as it is shown that the curvatures and maximum degree of CO₂ saturation change after CO₂ treatment, especially for the limestones. In addition, the apparent contact angle increases and surface roughness decreases due to the chemical effect of CO₂ injection on limestones. Finally, the advantages and limitations of the presented measurements are discussed and reported flow properties are compared to those predicted from the pore-scale analyses.