Mechanical alteration of magnetite mineral after hydrothermal exposure: Implication for natural hydrogen generation and storage

Title : Mechanical alteration of magnetite mineral after hydrothermal exposure: Implication for natural hydrogen generation and storage

Abstract:

Magnetite-bearing geological formations may serve as natural, low-carbon hydrogen (H₂) sources through water–rock reactions under anoxic conditions. However, H₂ generation is expected to alter mineral surfaces and mechanical properties, potentially affecting reservoir integrity. This study investigated how long-term hydrothermal brine exposure changes the surface morphology and mechanical behaviour of magnetite. Polished natural magnetite slabs were exposed to anoxic brine at 100 °C and 100 bar for 60 days, and pre- and post-treatment samples were analyzed using nanoindentation to assess mechanical property changes. Results revealed significant mechanical stiffening following hydrothermal alteration. Mean Young's modulus increased threefold from 76.4 GPa (pre-treatment) to 218.5 GPa (post-treatment), with maximum values rising from 320.9 GPa to 483.3 GPa. Although these values differ from pure phase literature values, the systematic increase provides mechanical evidence for extensive magnetite-to-hematite transformation. These findings suggest that progressive mineral alteration during H? generation could substantially modify reservoir geomechanical properties, with implications for fracture development, permeability evolution, and long-term reservoir integrity in magnetite-hosted hydrogen systems.

Biography:

Kaveh Moghanirahimi is a PhD candidate at Edith Cowan University in Perth, Western Australia, funded by CSIRO. His research explores natural hydrogen generation and storage in iron-rich minerals and rocks, combining hydrothermal experiments with advanced characterisation (XRD, SEM, BET and wettability testing). With several years of experience in reservoir geology, mining and petroleum laboratories in Iran, he focuses on geochemical processes that support cleaner energy and carbon management, including CO₂ sequestration and mineral/fluid interactions.