Effect of water films on salt precipitation in sandstone saline aquifers: A review of current understanding, potential improvements, and implications for CO2 injectivity

Abstract

Salt precipitation is one of the most significant factors contributing to injectivity impairment during geological carbon dioxide (CO₂) storage in saline aquifers. However, the role of water films in this process remains poorly quantified. This review evaluates current understanding of water-film properties and the potential influence on salt precipitation and CO₂ injectivity. Water-film behavior is controlled by coupled surface, pore-scale, fluid, and injection conditions and therefore cannot be represented by a single universal film thickness. Connected water films may sustain brine and dissolved ion transport towards drying regions, influencing supersaturation, salt growth, and spatial distribution. However, their relationship with injectivity is indirect and multiscale, as permeability impairment depends strongly on the amount, morphology, and location of precipitated salts, while other geochemical, geomechanical, and operational processes may concurrently alter injectivity. Available studies largely infer water-film behavior indirectly, with limited direct quantitative measurements under reservoir conditions. This review therefore proposes a hybrid multiscale framework integrating nanoscale characterization, pore-scale visualization, core-scale experiments, and reservoir modeling, with explicit consideration of uncertainty during upscaling.