The effect of CO₂ solubility on supercritical CO₂ injection into low permeable rocks

As CO₂ is injected to deep underground, it tends to flow upward due to its own buoyancy while flowing laterally driven by differential pressure. When CO₂ flowing, it will also dissolve into brine that resides rock formations and this may affect its migration and generated pore pressure. In this paper, we developed numerical simulation to investigate the effect of CO2 dissolution in the saturated water on supercritical CO₂ injection into low permeable rocks. The numerical simulation, based on the mathematical model of two phases flow in porous media with solubility effect considered using Henry's Law, was employed to interpret the experimental results of supercritical CO₂ injection to a cored Ainoura sandstone saturated with water using new developed flow pump permeability test. The saturation of supercritical CO₂ in the sandstone was predicted, and subsequently compared to the CO₂ saturation calculated using numerical analysis without solubility effect including the theoretical analysis of flow pump permeability test. It is observed that the saturation of supercritical CO ₂ in the cored sandstone is larger as the solubility effect considered. It is also found that the increase of CO₂ dissolution in the saturated water will increase the pore pressure of the sandstone yielded by CO₂ injection. These results suggested that the solubility of CO ₂ would become positive factor to drive more CO₂ injected, whereas its effect on increasing pore pressure must be taken into account in designing better CO₂ sequestration in low permeable rocks.