Hydrogen Sustainability in Saline Aquifers: Impact of Dry-Out and Salt Precipitation on Storage Performance

Abstract Underground hydrogen storage (UHS) in saline aquifers is a critical enabler for large-scale renewable energy integration, but formation damage due to salt precipitation poses a major threat to injectivity, productivity, and long-term storage efficiency. The feasibility of underground hydrogen storage (UHS) in saline aquifers depends on the stability of the multiphase flow processes governing the hydrogen displacement, storage efficiency, and recovery rates. A key challenge is the formation of a dry-out zone near the wellbore due to brine displacement and evaporation, which impact both storage integrity and operational feasibility. This study provides a comprehensive experimental framework to assess dry-out and salt precipitation (DSP) effects, linking pore-scale dynamics to reservoir-scale performance. This study aims to characterize the development of dry and wet zones, evaluate the effects of salt precipitation effects, and assess their implications for long-term hydrogen injectivity and recovery. Laboratory core flood experiments were conducted under controlled reservoir conditions to analyze the hydrogen injectivity, brine displacement efficiency, and the extent of permeability impairment due to salt precipitation and dissolution. In addition, a combination of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and BET surface area analysis was employed to investigate pore-scale salt deposition, its morphology, distribution, and potential clogging effects. Results demonstrate that salt precipitation significantly reduces porosity and permeability, with lower flow rates exacerbating salt accumulation by enhancing evaporation. Elevated salinity and high initial water saturation further amplify the damage. SEM reveals micron- to nano-scale NaCl crystals clustered in the pore throats, drastically altering the pore structure. The experimental results demonstrate that low pressure, high temperature and elevated flow rates significantly accelerate dry-out and salt precipitation (DSP) near the wellbore. This study advances the fundamental understanding of hydrogen plume behavior and addresses critical storage challenges through experimental insights that directly inform operational best practices. The findings enable optimized reservoir management for cyclic hydrogen storage while demonstrating the viability of saline aquifers as sustainable storage reservoirs. These contributions elevate both scientific knowledge and practical frameworks for large-scale geological hydrogen storage."