Investigating the Potential of Saline Aquifers for CO2 Mineral Storage - PHREEQC Batch −1D Diffusion-reaction Simulations

Due to increase in CO2 concentration in the atmosphere and its consequent problems, finding a solution for reducing CO2 concentration in the atmosphere is very important. One promising method that has been proposed for reducing the substantial amount of CO2, released to atmosphere, is sequestration of CO2 in saline aquifers. Having injected CO2 into a saline aquifer, it starts dissolving into the brine and it forms a weak carbonic acid. Over a long time, however, this weak acid can react with the minerals in the surrounding rock to form solid minerals. This process is one of the safest mechanisms for CO2 storage in saline aquifers; however, it can be rapid or very slow.

In this study based on the XRD results of a reservoir core, we assess the potential of that reservoir for CO2 mineral storage by tracking the precipitation and dissolution of each mineral over 100 years. We simulated the aquifer system at reservoir pressure by using PHREEQC. For this purpose, we used a closed-system batch simulation at constant CO2 pressure of 454 atm with sensitivity studies of temperature. Next, we estimated the change in porosity caused by mineral reactions.