A PRELIMINARY MODEL OF GLOBAL SUBSURFACE NATURAL HYDROGEN RESOURCE POTENTIAL

Geologic hydrogen (H₂) has recently gained interest as a potential primary energy resource. To guide decision-making, policy makers, resource managers, exploration companies, and investors will need information as to the extent of the potential resource. However, the uncertainties associated with the generation, migration, accumulation, and preservation of H₂ in the subsurface make it impossible to precisely determine potential resource volumes at this time. Despite the uncertainties, the occurrence and behavior of H₂ in the subsurface is not completely unknown. Additional inferences on the occurrence of H₂ in the subsurface can be made by employing knowledge derived from studies of fluid migration, accumulation, and preservation related to other geologic resources (e.g., petroleum, geothermal energy, noble gases, etc.). These factors can be combined to provide some constraints on the possible magnitude of geologic H₂ resources in the subsurface.

A preliminary box model for the global geologic H₂ resource potential has been developed using a mass balance approach. The model inputs include surface flux, trapping efficiency, residence time in traps, and biotic and abiotic H₂ consumption (differentiated as shallow versus deep), which are constrained by knowledge of these factors for H₂ or other analogues. Earth is assumed to currently be at steady state with respect to H₂ flux from the subsurface to the atmosphere. Hydrogen consumption from future production of H₂ is modeled based on historical natural gas production. Stochastic model results indicate a greater than 98% probability of geologic H₂ production meeting at least 50% of the forecast green H₂ production by the year 2100 and beyond, with long-term renewable H₂ production potentially in the range of 100s of Mt per year. Moreover, the model indicates that the residence time of H₂ in reservoirs and the annual flux of H₂ to the atmosphere are the most influential factors affecting the resource potential, whereas variations in biotic and abiotic consumption of H₂ have relatively little effect. These results strongly suggest that additional investigation of the resource potential of natural H₂ is warranted. This model provides an initial framework for assessing global H₂ resource potential and can be an important tool for guiding future research initiatives.