Effect of Organics and Nanofluids on Capillary-Sealing Efficiency of Caprock for Hydrogen and Carbon-Dioxide Geological Storage

Abstract

Abstract Gas (hydrogen (H2) and carbon dioxide (CO2)) geo-storage is a prominent solution for a low-carbon global economy. Geo-storage formations are very complex in nature and their wetting characteristics are dependent on various parameters. The literature lacks analysis of caprock’s structural trapping capacities, sealing efficiency, and proposed solutions for enhanced trapping potential. This work investigates H2 and CO2 wettability (pressure up to 25 MPa and temperature up to 343K) of pure and organic-aged (lignoceric acid C24, stearic acid C18, lauric acid C12, and hexanoic acid C6) mica samples as a proxy of caprock. Alumina nanofluid priming was used on organic-aged mica samples as a solution for reversing the wettability to hydrophilic conditions. Furthermore, capillary entry pressure and gas column heights were calculated. The results depict that H2 and CO2 wettability turned from Intermediate to strong CO2-wet mainly due to the increase in organic surface concentration and pressure. The higher the alkyl chain length of organic acids, the higher the hydrophobic conditions for mica substrates. Alumina nanofluid has shown great potential to reverse the wettability, where 0.25 wt.% was the optimum concentration. In a nutshell, the present work provides a detailed theoretical workflow to assess the capacity of caprock for safe and secure geo-storage projects. Introduction Hydrogen emerges as a promising clean fuel to support the decarbonization process by converting energy from fossil fuels into a more environmental-friendly form and effectively storing clean energy from renewables to overcome their intermittent supply issue (Alanazi et al., 2022). Wide-scale implementation of H2-based economy requires a medium with a large storage capacity, which can be theoretically offered by geological formations such as deep saline aquifers, depleted oil and gas reservoirs, and salt caverns (Zivar et al., 2021).