Effects of geochemical reactions on flow properties during compressed air energy storage in aquifer

Abstract

Reservoir flow properties are crucial for sustaining the magnitude and effectiveness of compressed gas energy storage in aquifer. Although changes in flow properties due to CO₂ injection have received attention, the impact of compressed air injection-induced geochemical reactions on flow properties has been overlooked. This study presents a series of controlled experiments with different reaction conditions to reveal the effects of pore-scale mechanisms of geochemical reactions on pore structure and flow properties. Although air injection enhanced the oxidation potential of the brine, oxidation reactions were limited due to the absence of oxidation-sensitive minerals. Integrated analyses of fluid chemistry, mineralogical characterization, and kinetic reaction modeling indicated that albite dissolution was the primary process governing rock property alteration. Albite dissolution occurring in pores and throats drives pore structure evolution and interconnects isolated pores, thereby leading to a significant increase in the total and connected porosity. As a result, an increase in permeability was observed. The brine percolating through the larger pores initiates the albite dissolution, further widens the seepage pathways and enhances the fluid flow. Ultimately, a quantitative relationship between permeability and porosity influenced by geochemical reactions was established. This study highlights the significance of geochemical reactions in compressed air energy storage in aquifer and provides essential theoretical insights for future numerical simulations and commercial exploitation.