The impact of brine salinity on CO2 capillary trapping efficiency in sandstone saline aquifers using a two-dimensional micromodel

What is it about?

CO₂ storage in deep saline aquifers is a key strategy for reducing atmospheric CO₂. Capillary trapping effectively immobilizes CO₂ in reservoir rocks, yet the role of brine salinity in this process remains underexplored. This study used a micromodel and brine-alternate-CO₂ (BAC) injection to assess salinity effects on capillary trapping. Lower salinity enhanced trapping by forming larger CO₂ clusters, while higher salinity reduced efficiency due to increased brine viscosity, interfacial tension, and a shift in wettability toward CO₂-wet conditions. Optimizing brine salinity is essential for effective CO₂ sequestration.

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Why is it important?

This study addresses a critical gap in understanding how brine salinity influences capillary trapping of supercritical CO₂ in deep saline aquifers, a key mechanism for secure long-term CO₂ storage, and by demonstrating that lower salinity enhances trapping efficiency through favorable interfacial and wettability conditions, the findings provide practical insights for optimizing injection strategies in carbon capture and storage (CCS) projects, thereby contributing to improving the safety and effectiveness of geological CO₂ sequestration and supporting global efforts to mitigate climate change.