Field-scale investigation of CO2 plume dynamics under spatial wettability variations: Implications for geological CO2 storage

Subsurface formations typically exhibit heterogeneous wetting characteristics due to the complex pore system, mixed lithology, and prolonged contact with native fluids. This non-uniformity in spatial wettability distribution thus makes the subsurface formations exhibit more complex localized CO2/brine/rock interactions, introducing uncertainties in estimating trapping capacity and predicting CO2 plume migration. Field-scale investigation on the role of wettability in CO2 geo-storage has received limited attention, and previous studies typically assume an internal uniform wettability condition across the whole formation. However, the more realistic scenario of internal wettability spatial variations within a single formation is yet to be thoroughly examined. In this study, a range of experiment-derived wettability-dependent trapping coefficients were utilized to implement the internal wettability heterogeneity in a single formation model, and its impact on CO2 plume pattern and trapping efficiency was examined. Furthermore, mixed-wet systems with different CO2-wet fractions were also considered in this study. The results indicate that internal wettability variations result in changes in the local CO2 saturation pattern and thus impact the overall plume shape and migration. In addition, the internal heterogeneous wettability system exhibits an approximately 35% reduction and an approximately 20% increase in residual trapping capacity in comparison to internal uniform strongly water wet and uniform weakly water-wet systems, respectively. An increase in the fraction of CO2-wet regions in the mixed-wet system results in concentrated high-saturation clusters and reduced local CO2 residual saturation. This further results in reduced residual and dissolution trapping, followed by a linear correlation. Document Type: Original article Cited as: Zhang, H., Mahmoud, M., Iglauer, S., Arif, M. Field-scale investigation of CO2 plume dynamics under spatial wettability variations: Implications for geological CO2 storage. Advances in Geo-Energy Research, 2025, 15(3): 230-244. https://doi.org/10.46690/ager.2025.03.06