Investigative research for occurrences of hydrogen, helium, methane and carbon dioxide in West Macedonia: linking geological reservoirs to subsurface gas generation and migration.

BACKGROUND

Exploration of subsurface gases such as hydrogen, helium, methane, and carbon dioxide can be achieved by integration of geological framework, hydrogeochemistry, and isotope analysis to understand generation, migration, and trapping mechanisms. A focused hydrogeochemical survey for the aforementioned gases was conducted in West Macedonia (Greece) to identify potentially suitable locations for geological reservoirs, gas sources and gas migration routes based on previous research. West Macedonia (Greece) is characterised by ophiolitic complexes, sedimentary basins, and active fault systems. This presents favourable geological conditions for investigating potential gas reservoirs and migration pathways.

METHODS

The investigation presented in this study deployed sequential spring and borehole water sampling for geochemical analysis of trace elements and gas analysis for hydrogen, helium, methane and carbon dioxide to identify and characterise gaseous geological reservoirs. The investigation extended into isotope studies for d 13C TDC, δ 13C CH 4 , δ 13D CH 4 , δD H 2O, δ 18O H 2O.

RESULTS

The analysis provided evidence for the existence of helium, biogenic methane, carbon dioxide and traces of hydrogen that need to be further investigated for validation and better understanding of the gas generation and migration routes. Variations in dissolved ions and gas composition largely reflect enrichment of resident groundwater by meteoric recharge and subsequent water-rock interaction. Fault-controlled pathways appear to facilitate multi-gas signatures in specific locations.

CONCLUSIONS

The data suggests the existence of helium, methane, carbon dioxide and validated trace concentrations of hydrogen from previous studies in the wider area. Isotopic analysis provides strong evidence for biotic generation of methane, whereas helium comes from a deeper source. Hydrogeochemical controls, structural features, and lithological variability collectively influence gas occurrence. This preliminary investigation indicates the existence of multiple gas generation and migration mechanisms and provides a scientific basis for further targeted exploration of natural hydrogen and associated gases.