Laboratory study of cyclic underground hydrogen storage in porous media with evidence of a dry near-well zone and evaporation induced salt precipitation

• Published in: International journal of hydrogen energy 2024-06, Vol.71 (C), p.515-527
• Main Authors: K C, Bijay, Frash, Luke P., Creasy, Neala M., Neil, Chelsea W., Purswani, Prakash, Li, Wenfeng, Meng, Meng, Iyare, Uwaila, Gross, Michael R.
• Format: Article
• Language: English
• Subjects: Grid stability; Hydrogen storage; Injectivity; Relative permeability; Saturation; Ultrasonic velocity
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2024.05.234

Large-scale storage of ‘green’ hydrogen is essential in our quest to transition to renewable energy sources and achieve the net-zero emission targets. As such, Underground Hydrogen Storage (UHS) in geological porous media, such as in depleted oil and gas fields or saline aquifers, provides a cost-effective solution to store such large volumes of hydrogen (H2) to buffer seasonal fluctuations in renewable energy supply and demand. Due to the novelty of the topic, many research gaps persist, but we focus on H2 transport characteristics in the subsurface, hydrogen recoverability during cyclic operations, chemical interactions, and acoustic velocity as an indicator of H2 saturation. In this study, we investigate UHS using a triaxial core-flooding experiment to address the above-mentioned research gaps by replicating field operations in the laboratory setup at representative subsurface conditions. Unstable displacement due to immiscible two-phase flow led to early H2 breakthrough at 18% of H2 saturation, ultimate H2 saturation of 36% and withdrawal efficiency of 78% during the first cycle. However, cyclic charging and discharging led to an eventual H2 withdrawal efficiency as high as 95%. Observed chemical interactions during our 3-day experiments were negligible, but our results also indicated a strong potential for evaporation-induced salt precipitation after injection of dry H2 gas, leading to decreased reservoir porosity and permeability over time. Our ultrasonic measurements confirmed the sensitivity of P-wave velocity to H2 saturation, which decreased by 3.5% when the H2 saturation increased to 36%. This indicates that H2 plume and leaks in UHS should be possible to monitor using 4D seismic surveys. Our results help to better understand H2 flow, storage, and transport during cyclic UHS. The results indicate that H2 withdrawal efficiency increases as the UHS reservoir matures and provides evidence of a dry near-well zone and evaporation induced salt precipitation in a UHS reservoir. [Display omitted] •Early breakthrough of H2 at 18% H2 saturation led to ultimate H2 saturation of 36% after injecting 1.2 pore volumes of H2.•H2 withdrawal efficiency increased from 78% in the first cycle to 95% in the fourth cycle.•H2 was produced at 90% purity with water vapor contamination indicating evaporation of liquid water into gaseous H2.•3.5% reduction in P-wave velocity when the H2 saturation inside the specimen increased to 36%.•Evidence obtained for a dry near-well