Pore-scale insights into the dynamics of salt precipitation during CO۲ injection in saline

Underground gas storage, including carbon dioxide (CO۲) capture and storage (CCS), involves storing large volumes of gas in geological formations such as saline aquifers. CCS is a key technology in combating climate change by capturing and storing CO۲, thus reducing emissions. However, one of the significant challenges in the CCS is salt precipitation, which occurs due to water evaporation during CO۲ injection into saline aquifers. This process could significantly reduce porosity and permeability of geological formations, thus limiting CO۲ injection rates. This study aims to investigate the impact of CO۲ injection on the salt precipitation under constant injection rate and salinity in a heterogeneous glass micromodel at ambient conditions. Also, salt precipitation induced by nitrogen (N۲) injection was considered for comparison purposes. It was found that CO۲ injection resulted in rapid, uniform salt precipitation, reaching a final salt saturation of ۳۸.۹۹ %, which led to severe pore blockage and a significant permeability reduction to as much as ۰.۶۳ times of the initial value. As to the pore-scale observation, the formation of dendritic crystals amplified such permeability impairment. In contrast, N۲ injection led to slower salt precipitation, with a final salt saturation of ۴۲.۰۹ % and an asymmetric salt distribution. The permeability reduction in the N۲-injected model was about ۰.۸۲ times of its initial value. The pore-scale insights of this study shed light on the effect gas type and also its composition on the salt precipitation in saline aquifers, helping develop appropriate strategies to reduce operational risks and enhance CCS sustainability.

کلیدواژه ها:

CO۲ storage ، Saline aquifer ، Salt precipitation ، Micromodel study