Enhanced CO₂ mineralization and geologic CO₂ storage have received increasing attention as two prominent approaches in combating climate change and fostering sustainable development of human society. This paper aims to explore three emerging areas of research within the realm of enhanced CO₂ mineralization and geologic CO₂ storage, including enhanced rock weathering, numerical modeling and validation of CO₂ storage accounting for the interplay of various trapping mechanisms, and the examination of how reservoir heterogeneity influences the migration of CO₂-brine multiphase flow. Discussions highlight the effectiveness of the spectrum induced polarization for monitoring changes in petrophysical and geochemical properties of rocks during enhanced rock weathering. Additionally, the multi-scale heterogeneity of geological formations needs to be carefully characterized, due to the fact that it plays a vital role in CO₂ migration. Further research is required to achieve accurate and reliable simulations of convective mixing for field-scale applications.

CO₂ geological utilization and storage is considered as an effective approach to deeply cut anthropogenic CO₂ emissions. It is vital to enhance the amount of CO₂ stored in the subsurface, at the same time to ensure safe and long-term subsurface storage of CO₂ without any CO₂ leakage. Science and engineering research in modeling concepts, experimental approaches, safety assurance and emerging CO₂ geological utilization and storage technologies have driven the advancement of CO₂ geological utilization and storage in recent years. In order to encourage communication and collaboration in CO₂ geological utilization and storage research worldwide, a Sino-German joint symposium titled “Opportunities and Challenges in CO₂ Geologic Utilization and Storage” was organized in Wuhan and Stuttgart from February 22 to 24, 2023, bringing together experts from China, Germany, and other countries. The symposium was jointly organized by Institute of Rock and Soil Mechanics, Chinese Academy of Sciences and Institute for Modelling Hydraulic and Environmental Systems, University of Stuttgart with financial support from the Sino-German Center for Research Promotion. A two-site hybrid meeting was held (participants in China met in Wuhan, participants in Germany met in Stuttgart, and other participants joined the meeting online), attracting more than 100 participants from around the world. The latest studies in the field of CO₂ geological utilization and storage were presented at the symposium.

A thorough understanding of the microscopic flow process in porous and fractured media is significant for oil and gas development, geothermal energy extraction and subsurface CO₂ storage etc. In CO₂ geological sequestration, the CO₂ is often injected at the supercritical state (scCO₂), which will displace the connate fluids in the pore spaces during the drainage process. However, when CO₂ injection stops, the connate brine or water flows back to displace the scCO₂. Therefore, the configuration of migration paths in a specific reservoir plays a significant role in affecting the connectivity and storage efficiency of scCO₂. In this paper, the two-phase (scCO₂ and water) boundary has been defined using the phase field method, and the COMSOL Multiphysics simulator is applied to study the migration of scCO₂ in porous/fractured media at the pore scale. The geological conditions of Shiqianfeng formation in the CO₂ capture and storage pilot site of the Ordos Basin in China is selected as the engineering background. Before using the actual microscopic geometry based on thin-section of Shiqianfeng sandstone, we get the general understanding on scCO₂ migration in fractured porous media that has the highly simplified configuration with circular particles, considering the impacts of wettability, geometry of formation mineral grains, interfacial tension, injection rates, and fracture geometry. Results show that the CO₂ preferential flow occurs at locations with high CO₂ flow rates and high CO₂ pore pressure. The preferential flow of scCO₂ occurs adjacent to the wall of grains while minimal or little flow takes place through the interior between the grains, considering the grains with irregular shapes. The interfacial tension of porous media plays a significant role in controlling the spatial distribution of the scCO₂. A much lower interfacial tension results in a much thinner scCO₂ flow band with a much higher saturation. The geometry of fractures in porous media increases the complexity of the scCO₂ flow paths at the pore scale.