Researchers from the University of Cambridge, led by Hannah P. Menke, have conducted a groundbreaking study on natural hydrogen generation from ultramafic rocks, offering valuable insights for the energy industry. The team, which includes Zaid Z. Jangda, Max Webb, Jim Buckman, and Amy Gough, utilized advanced imaging techniques to observe and understand the processes involved in hydrogen production from these rocks.
The study, published in the journal Nature Communications, focuses on the pore-scale processes that control the initiation and early transport of a free gas phase in ultramafic rocks. The researchers conducted an in situ X-ray micro-tomography experiment, heating a granular pack of dunnite from West Papua, Indonesia, saturated with a potassium iodide-doped brine to 100°C. The experiment was conducted under specific pressure conditions, with a pore pressure of 4 bar and a confining pressure of 10 bar, all within a micro-CT scanner.
The time-resolved 4D imaging captured the transition from a fully liquid-saturated pore space to the appearance and growth of a distinct gas phase after an 8-hour induction period. Bubbles first nucleated near the top of the sample before becoming distributed throughout the imaged volume as a connected ganglia. The researchers suggest that the nucleating gas phase is most likely dominated by molecular hydrogen generated by low-temperature fluid-rock reactions, as indicated by independent hydrogen-presence detectors. However, they acknowledge that minor contributions from other gases cannot be fully excluded.
The study also employed Scanning Electron Microscope-Backscattered Electron (SEM-BEX) imaging to reveal textural alteration and local changes in elemental signals between reacted and unreacted material. These observations provide spatially and temporally resolved evidence for gas generation during low-temperature alteration of ultramafic grains. The research demonstrates that pore-scale imaging can directly link water-rock reaction kinetics, gas generation, and multiphase flow behavior in natural hydrogen systems.
For the energy industry, this research highlights the potential of ultramafic rocks as a source of natural hydrogen. Understanding the pore-scale processes involved in hydrogen generation and transport can help in the development of more efficient and effective methods for extracting this clean energy source. The insights gained from this study could contribute to the advancement of natural hydrogen as a viable and sustainable energy resource.
This article is based on research available at arXiv.