Enhanced CO₂ Mineralization in Saline Aquifers Using Alkaline Earth Metals

Subsurface saline aquifer formations have emerged as a promising natural sink for mineral carbon dioxide (CO₂) storage. However, there is a disconnect between the speed and permanence of the different trapping mechanisms that come into play when CO₂ is injected into subsurface formations. This study aims to investigate the efficacy of chemical additives strontium chloride (SrCl₂) and barium hydroxide (Ba(OH)₂) in accelerating the two slowest CO₂ trapping mechanisms, dissolution and mineralization, their effect on the dissolution of the carbonate-bearing minerals, and the changes in the poroelastic properties of the host rock. High-pressure, high-temperature experiments were conducted on limestone core samples in the presence of supercritical CO₂ and synthetic brine at a temperature of 333.15 K and pressure of 2500 psi with and without the addition of SrCl₂ and Ba(OH)₂. Petrophysical, geochemical, and geomechanical analytical techniques were utilized to assess the influence of these additives on the poroelastic properties of the limestone core samples. The evolution of mineral-fluid reactions and changes in mineralogy and porosity over an extended period of approximately 75 days was analyzed, with the experimental results demonstrating that both additives significantly accelerated CO₂ mineralization rates compared to the control experiments. The additives promoted the formation of less dense stable carbonate minerals potentially ensuring formation integrity is maintained. Analysis of the core samples after treatment revealed changes in porosity and permeability due to mineral dissolution and precipitation, providing insights into the effectiveness of these additives on reservoir quality. The findings from this study will provide a better understanding of the complex interactions between the formation, brine, injected CO₂, and the chemical additives. This will lead to the development of more effective and sustainable carbon storage strategies in saline aquifers through the potential use of SrCl₂ and Ba(OH)₂ as chemical additives and provide a solution for the long-term stability and security of CO₂ storage in saline aquifers.