Measuring Poromechanical Properties of Berea Sandstone Relevant to Underground Hydrogen Storage

Abstract

ABSTRACT Seasonal fluctuation in electricity generation is a major set-back for the integration of renewable energy sources such as solar and wind into a national grid. Temporary storage of ‘green’ hydrogen in underground porous reservoirs could be a cost-effective solution to balance renewable energy fluctuations to stabilize the energy grid. However, due to the novelty of Underground Hydrogen Storage (UHS) in deep porous reservoirs, our knowledge about the interaction between hydrogen and host reservoir rock is limited. It is crucial to develop the fundamental understanding of these interactions and their impact on the reservoir rock for successful deployment of UHS. In this study, we measure the poromechanical properties, such as bulk compressibility, in-situ porosity, Biot's effective stress coefficient, and P-wave velocity of Berea sandstone specimen at in-situ reservoir stress condition i.e., depth of ∼ 1.25 km. Results showed decrease in bulk compressibility, porosity, and Biot's coefficient due to increase in effective stress. Considered together, results from this study infer change in stress regime in UHS reservoir due to multiple injection/extraction cycles could alter the reservoir capacity and transport properties. In addition, P-wave velocity increased with the effective stress. However, it remained insensitive to different gas (i.e., air and Argon) saturated pores at same effective stress. INTRODUCTION Renewable energy is a focal point in our effort to achieve global net zero emission target by 2050. However, seasonal fluctuation in electricity generation is a major set-back for the integration of renewable energy sources such as solar and wind into national grid. As such, surplus energy produced from renewable sources during the period of low demand can be used to produce ‘green’ hydrogen, which can be stored for future consumption to stabilize the grid when the demand is higher. Hydrogen is an ideal energy storage option due to its low carbon footprint and versatility to be used in different sectors such as transportation, industry, residential, and others (e.g., IEA, 2019). Hydrogen has higher specific energy capacity compared to other gases such as methane but, due to its low density very large volume is required to store energy at the scale of GWhr to TWhr needed to balance seasonal fluctuations. Such large-scale volume is available in underground geological formation such as salt caverns, saline aquifer, and depleted oil and gas reservoir (e.g., Heinemann et al., 2021; Zivar et al., 2021; Chen et al., 2022).