Accelerating CO2 Mineralization in Wollastonite-Rich Saline Aquifers: The Role of Post Water Injection in CCUS

Abstract This study aims to investigate the effects of water injection after CO2 injection on mineralization efficiency in wollastonite-rich saline aquifers. By enhancing the carbonation process, it seeks to provide a viable strategy to mitigate long-term CO2 leakage risks from cap rocks, which often occurs due to their low permeability. Long-term simulations were conducted to analyse the impact of varying water injection rates following CO2 injection. The model included key parameters such as wollastonite concentration and initial CO2 levels. Sensitivity analyses determined the relationship between water injection rates and mineralization kinetics, assessing both the speed of mineralization and the total amount of mineralization at the end of the simulation. Water injection significantly accelerated the dissolution of wollastonite, enhancing the carbonation process. Results indicated that the speed of mineralization was directly proportional to the water injection rate. However, despite varying the injection rates, the total amount of mineralization remained constant over the long-term simulation period, suggesting a fixed capacity for mineral trapping in the saline aquifers. This finding highlights the importance of understanding the long-term behaviour of mineralization processes. One significant benefit of accelerated mineralization is the reduction of risks associated with possible cap rock leakage. To address this challenge, large volumes of water are proposed for injection post-CO2 injection to rapidly capture CO2 and enhance mineralization trapping, providing a practical solution for improving CO2 sequestration efficiency in CCUS applications. This study introduces a practical approach to enhance CO2 mineralization by employing water injection to accelerate the dissolution of reactive minerals. It presents an effective perspective on addressing long-term leakage risks associated with infinite low-permeability cap rocks, positioning post water injections as a potential solution for improving the effectiveness of CCUS strategies.