Geological controls for Compressed Air Energy Storage in porous media

In this work a novel and comprehensive review of the geological essentials that control subsurface Compressed Air Energy Storage in non-aquifer porous media (CAES-PM) is presented. CAES-PM is envisaged as a promising method for supporting sustainable energy transition as it allows the accumulation and utilisation of energy for long periods, while helping to reduce dependency from fossil fuels and to improve the management of electrical grids in a complex energy-mix future. This review builds on results from classical works, past CAES-PM experiments and recent scientific developments, in which a comprehensive analysis of the independent geological elements that comprise the geoenergy system are described using a Play Based Evaluation framework. Accordingly, a systematic description of the reservoir, the seal, the trap and the storage conditions is implemented. Each of the elements is scrutinised for their main components, to reveal how they can explain the feasibility of the process, and how they can contribute for the unbiased assessment of subsurface storage opportunities. Ultimately, a critical analysis of the major challenges and way forward paths that require scientific developments are discussed. These include the differences between storage in salt caverns and porous strata, the main associated geohazards, the technical problems linked with seal integrity, and an updated view on the aspects associated with fluid and rock interactions. This works elucidates on how CAES-PM can become a tangible reality, disentangling the geological complexities for wider understanding and acceptance by researchers, industry and authorities. • CAES-PM is envisaged as a fundamental tool for energy transition • Geological controls for CAES-PM are depth-dependent • Geoenergy system elements comprise the reservoir, seal, trap and storage conditions • Critical technological and scientific challenges are analyzed