Effect of wettability heterogeneity and reservoir temperature on CO2 storage efficiency in deep saline aquifers

Abstract

Reservoir heterogeneity at various length scales is a well-established fact. This includes reservoir wettability − a key factor influencing CO2 geo-storage efficiency and containment security − which changes with depth, and is generally non-uniform due to different depositional environments and fluid flow paths over geological times. However, the effect of heterogeneous wettability distribution on CO2 storage efficiency is not understood. Moreover, there is a knowledge gap in terms of how temperature affects capillary and dissolution trapping, CO2 mobility and vertical CO2 migration distance, particularly when coupled with wettability heterogeneity effects. Thus, in this work we studied the effect of wettability heterogeneity and reservoir temperature on the vertical CO2 plume migration, and capillary and dissolution trapping capacities. Our results clearly show that both wettability heterogeneity and reservoir temperature have a significant effect on vertical CO2 migration, and the associated capillary and dissolution trapping mechanisms: both heterogeneously distributed wettability and higher temperature significantly accelerated the vertical CO2 migration, CO2 mobility and solubility trapping, while it reduced residual trapping. We thus conclude that wettability heterogeneity and reservoir temperature are important factors in the context of CO2 geo-storage, and that heterogeneous wettability and higher reservoir temperatures reduce storage capacity.