Time-Resolved Neutron Imaging for Hydrogen Uptake in Subsurface Lithologies

Area of Science:

• Geophysics
• Subsurface Energy Storage
• Materials Science

Background:

• Geologic hydrogen production and storage are vital for clean energy, but hydrogen's high diffusivity poses leakage risks.
• Evaluating hydrogen transport in subsurface materials is crucial for safe and efficient storage.
• Existing methods like X-ray microcomputed tomography (μCT) often require contrast agents or surrogate gases.

Purpose of the Study:

• To demonstrate the use of neutron transmission radiography/CT for real-time, in situ observation of hydrogen migration.
• To investigate hydrogen transport behavior in common reservoir and caprock lithologies.
• To establish neutron imaging as a viable tool for subsurface hydrogen research.

Main Methods:

• Real-time neutron radiography and computed tomography (CT) were used to image hydrogen migration.
• Cylindrical core samples of Indiana limestone, Amherst Gray sandstone, and Tumey shale were subjected to constant-pressure hydrogen charging.
• Image subtraction techniques were employed for quantitative analysis of hydrogen distribution in sandstone.

Main Results:

• Hydrogen rapidly infiltrated and distributed homogeneously within the pore structures of sandstone and limestone.
• Hydrogen was largely excluded from the fine-grained shale matrix, with presence detected only in a localized fracture zone.
• Distinct neutron imaging signatures of hydrogen were achieved even under low-pressure, single-phase conditions.

Conclusions:

• Neutron imaging provides a powerful, non-invasive method for visualizing in situ hydrogen migration in diverse subsurface lithologies.
• The findings highlight differential hydrogen transport behavior in reservoir rocks versus caprocks.
• This research validates neutron imaging as a promising technique for advancing the understanding of subsurface hydrogen behavior and storage.