Coupled hydromechanical analysis of an underground compressed air energy storage facility in sandstone

The underground storage of compressed air is a favourable and low-cost option for balancing off-peak electricity demands. Large volumes of air can be compressed and stored in the ground during low-demand electricity periods, and this pressurised air can then be released to generate electricity during high-demand times. Excavated caverns (generally in salt rock), depleted gas fields and abandoned/excavated mines are the main options typically considered in the design of a compressed air energy storage (CAES) facility. The storage of compressed air in aquifers is a new alternative that has been studied recently. The natural formations around a CAES facility are subjected to significant perturbations in hydraulic and mechanical fields. This paper presents an analysis of a CAES project in an aquifer using a fully coupled hydromechanical framework with the ability to consider the main physical phenomena that control the behaviour of this kind of system. The case study is based on an actual planned CAES project in Iowa, USA. Particular attention was paid to changes in the hydraulic and mechanical fields induced by the operational phases anticipated in a CAES project and to the impact of porosity heterogeneities on system performance. The analysis confirmed that the site is not suitable for a CAES plant.