Integrated Geochemical and Reactive Transport Modeling of Long-Term Carbon Storage in Carbonate Formations: Leveraging Petrasim and Micro-Ct Imaging for Mineralization, Precipitation, and Dissolution Effects

The USA instigated new (2025) tax incentives to encourage CO 2 utilization and sequestration (CCUS). An objective of this study is to characterize and quantify geochemical reactions during the migration and storage phases of CCUS. Batch laboratory tests were calibrated to mimic specific storage scenarios. We contemporaneously developed hydrogeochemical models of those tests and then used those calibrated models to extrapolate results to long-term storage time scales. We compare the laboratory results to the long-term model results, including analysis of high-resolution micro-CT images and data on influent vs. effluent brine ion composition using inductively coupled plasma. From the micro-CT images of limestone reservoirs, we found significant changes in micro-porosity after one month of aging, rather than in macro-porosity. Using the reactive transport model, we track changes in porosity and permeability to examine the processes of mineral precipitation and dissolution over extended periods, such as 5, 10, 20 years, and even up to 10,000 years. This method is effective for modeling changes in the physical properties of the rocks. The main variables addressed with the reactive transport model include the types of rocks, the fluids involved, the injected CO₂, reaction rates, and the relationship between porosity and permeability. We analyzed and evaluated these factors based on the rock matrix, initial fluid (brine), the injected CO₂, and porosity and permeability. Our model includes the geochemical reactions that happen when CO₂ is injected into deep saline aquifers. It captures how scCO₂ interacts with brine and host minerals over long periods. This helps us understand changes in storage capacity, long-term security, and changes in rock and fluid properties over time. Important reactions include the dissolution of calcite in acidic conditions. When CO₂ dissolves in brine, it causes calcite to dissolve, releasing Ca²⁺ and bicarbonate ions, which increases porosity. To further enhance the model, we will also consider how temperature, salinity, and pressure affect different types of formations and reservoirs. This research supports the development of reliable CCS and CCUS and contributes to the safer and long-term storage of CO₂ in carbonate formations.