Reactive transport modeling of CO2 trapping in carbonate saline aquifers: Coupled effects of wettability, temperature, and salinity on mineralization and storage efficiency

Abstract

Secure long-term storage of carbon dioxide (CO₂) in saline aquifers requires a clear understanding of how reservoir conditions and geochemical reactions influence rock properties and trapping mechanisms. While the individual effects of wettability, temperature, and salinity have been examined, their combined impact, particularly under varying wettability states where hysteresis controls phase behavior, remains insufficiently quantified. This study employs reactive transport modeling to assess the effects of temperature (50–90 °C), salinity (70,000–210,000  ppm NaCl), and wettability on CO₂ mineralization, dissolution, and capillary trapping in carbonate-rich formations. Geochemical reactions involving calcite, kaolinite, and anorthite are modeled using transition state theory, while water-wet and mixed-wet conditions are represented through relative permeability and capillary pressure curves that capture wettability-dependent flow behavior. Mineralization increases from ∼ 4.4 × 10⁶ to ∼ 1.3 × 10⁷ mol in mixed-wet systems from 50 °C to 90 °C, while capillary trapping decreases from ∼ 67 % to ∼ 54 % (water-wet) and ∼ 48 % to ∼ 36 % (mixed-wet), and dissolution rises to > 30 %. At 90 °C, increasing salinity shifts CO₂ plumes from vertically elongated, dissolution-dominant (∼36 %) in mixed-wet to laterally confined, capillary-dominant (∼82 %) in water-wet systems, governed by hysteresis (0.2 vs. 0.35). Calcite precipitation declines by ∼ 22 % (water-wet) with temperature and by ∼ 14 % with salinity, while kaolinite precipitation triples and anorthite dissolution varies from − 25 % to + 90 % depending on wettability. Over 60 years, porosity and permeability increase modestly by ∼ 0.36 % and ∼ 1.22 %. These findings clarify how wettability-driven interfacial dynamics influence mineralization and phase trapping, providing mechanistic guidance for optimizing CO₂ storage performance across diverse reservoir settings.