Evaluating long-term integrity of shale for safe hydrogen storage: A nanoscale analysis of hydrogen-shale interactions

This study provides an in-depth evaluation of the mechanical integrity of organic-rich shale samples subjected to prolonged hydrogen exposure. Utilizing nanoindentation techniques, the mechanical response of the shale samples was systematically analyzed both prior to and after exposure to hydrogen over extended periods. Scanning Electron Microscopy (SEM) was employed to visualize surface and morphological changes, complementing the mechanical assessment. The shale samples, with an average total organic carbon (TOC) content of 6.17%, were exposed to hydrogen for 7, 30, and 60 days to assess the effects of long-term hydrogen interaction. The results indicate a progressive weakening of the shale matrix with increasing hydrogen exposure. Nanoindentation data revealed an increase in the average indenter displacement under a fixed force, with a 4.3% increase after 7 days, 8.7% after 30 days, and 11.5% after 60 days, highlighting the impact of hydrogen on the mechanical properties of shales. These findings confirm that hydrogen exposure leads to a gradual reduction in the mechanical strength of shale samples over time. This research offers critical insights into the degradation mechanisms of shale under hydrogen conditions, providing valuable data for optimizing subsurface hydrogen storage and ensuring the long-term stability of geo-storage systems.