Natural Hydrogen System: Some Facts and Biases

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Summary Natural hydrogen systems work somewhat like petroleum systems with sources, migration paths, reservoirs, seals, and traps. Natural hydrogen can be produced from source rocks but above all by other mechanisms such as radiolysis, serpentinization, oxidation of rocks rich in FeII. Once generated, hydrogen can migrate either in the vapor phase or dissolved in water. Dissolved hydrogen can outgas at shallow depths depending on pressure and temperature conditions and accumulate in reservoir rocks. Recent studies provide the physical and chemical properties of hydrogen thus allowing the comparison between the petroleum system and the hydrogen system. The efficiency of the hydrogen system (HSY) must be lower than the efficiency of the petroleum system (PSY). Therefore, the mass balance performed on the global hydrogen system shows some inconsistencies in considering natural hydrogen as a major source of sustainable energy. Considering published hydrogen flux values and hydrogen production values from major recognized sources, the resulting concentration factors (CF) are several orders of magnitude higher than those observed for hydrocarbons. Is this realistic or is there a bias in the interpretation of surface measurements or is there a missing source of natural hydrogen?