Study of mineral trapping of CO₂ and seal leakage mitigation

Mineral trapping of carbon dioxide is the safest and the most permanent sequestration mechanism. Brine composition, brine pH, system temperature and pressure have been reported to have significant effects on mineral trapping of CO₂ in brines. It has also been reported that iron cation in brine could cause pH instability that may lead to lower carbonation conversion rate. This study aims to investigate whether ferric or ferrous iron caused this pH instability. pH stability studies and high temperature/high pressure carbonation experiments (150°C,100bar) with the addition of 1.0M KOH were conducted using different synthetic brines with Fe³⁺, Fe²⁺, and without Fe. It can be concluded from this study that ferrous iron causes pH instability. However, ferrous iron might promote carbonate precipitation in non-pure CO₂ streams in iron oxyhydroxide-containing saline aquifers as seal leakage mitigation.