Preventing Salt Precipitation in CO2 Storage Processes in Saline Aquifers: Dissolved-Water CO2 Injection Method.

Abstract

CO₂ storage in geological formations, particularly deep saline aquifers, is a critical component of carbon capture and storage technology, offering significant potential for mitigating greenhouse gas emissions. However, high salinity of these aquifers poses the risk of salt precipitation, leading to pressurization and injectivity reduction. Developing a method to prevent salt precipitation remains a challenge, and this is an area that this study is focused on. Dissolved-water CO₂ injection (dwCO₂ injection) is proposed here as a novel method to prevent salt precipitation where water is dissolved in CO₂ before injection into an aquifer. Presence of water in the CO₂ stream prevents more dissolution of water into CO₂ (evaporation) and, hence, prevents salt precipitation. Before presenting this method and in order to provide a good mechanistic understanding of the interactions involved in a CO₂ storage process, six different scenarios are examined using the CMG-GEM simulator within a carbonate aquifer. The results showed that saturating CO₂ with water reduced the precipitation nearly to zero, and dissolving 2000 ppmv water decreased the salt precipitation to one-third. It should be noted that injection of humid CO₂ requires special methods to tackle the potential challenges, including corrosion and hydrate formation risks, and the paper also discusses them.