Modeling rock-fluid interactions due to CO2 injection into sandstone and carbonate aquifer considering salt precipitation and chemical reactions

Abstract

Carbon dioxide is a greenhouse gas that has the most effect on the phenomenon of global warming. Saline aquifers have higher potential compared to other storage options to store carbon dioxide. Sandstone and carbonate aquifers have good reservoir characteristics and can be appropriate choices for CO2 storage. The modeling of the process has been performed combining salt precipitation, solubility, region specification and pressure drop models to study the effect of CO2 injection on gas saturation and pressure distribution profile, skin factor over time, the amount of salt precipitation, porosity and permeability. Sensitivity analysis has been done for temperature, pressure, permeability, porosity, salinity, critical gas saturation and CO2 injection rate. In order to study chemical reactions, long time simulation of rock-fluid interaction in carbonate and sandstone aquifer is also performed.The permeability reduction is in the range of 0.69–0.86 in all cases of salt precipitation simulation which is consistent with experimental results. The proposed salt precipitation model with an average relative deviation of about 5% for rock-fluid interaction parameters is able to predict the aquifer properties accurately during CO2 gas injection. The advantage of the model presented in this study compared to Zeidouni's model (2009) is that the proposed model predicts the pressure distribution after injection and estimates mole fraction of components in equilibrium with higher accuracy. The results of this study are shown that CO2 storage needs an aquifer with lower temperature, higher pressure and lower salinity compared to other options as the solubility trapping of carbon dioxide increases in this case. Permeability change does not influence on determining equilibrium regions and the only effect of the permeability is on the injectivity. Simulation of mineral reactions shows that chemical equilibrium is established after long time (more than 100 years) in sandstone aquifer and it is established in less than one day in carbonate aquifer. It should be noted that mineral trapping capacity of carbonate aquifer is less than sandstone aquifer in the CO2 storage process.