Fig. 5: Normalized Storage Efficiency Caused by Impurities (NSEI) at different pressures and temperatures.

a 95% CO2; b 90% CO2; c 80% CO2; d 70% CO2; e 60% CO2; f 50% CO2. The white dash line represents inaccessible temperature-pressure boundaries. Pressure and temperature are impractical out of these boundaries. Blue area (low NSEI area) expands as the CO2 concentration decreases. The six reference CCS projects exhibit different NSEI values, owing to their distinct pressure and temperature conditions.