Exploring Natural Hydrogen Hotspots: A Review and Soil-Gas Survey Design for Identifying Seepage

Exploration for natural hydrogen seepages has grown rapidly, with surface seepages being seen as a primary indication of an underlying resource. While soil gas sampling has proven successful in detecting hydrogen in the soil, current understanding of hydrogen in the subsurface remains incomplete, with various potential sources of origin. This paper presents a selected review of published hydrogen hotspots around the world, examining their distribution with respect to two main features commonly associated with natural seepages: sub-circular depressions (SCD) and fault zones. Based on the findings, the paper proposes a conceptual soil-gas survey design for efficiently identifying potential hydrogen hotspots. The proposed scheme is tested on a SCD and a fault zone located in Western Australia. The study findings near the Perth Basin and the Yilgarn Craton highlight the presence of anthropogenic artifacts in hydrogen measurement, necessitating further investigation to constrain the possible sources of hydrogen generation. The study of the SCD in the Perth Basin supports the development of a statistical understanding of hydrogen distribution around surface features associated with hydrogen hotspots. Such a framework can guide soil-gas surveys and target areas with a higher likelihood of detecting natural hydrogen seepage. By addressing these points, prospective areas for natural hydrogen seepage can be better identified and evaluated, ultimately contributing to the development of hydrogen as a sustainable energy resource. Thematic collection: This article is part of the Hydrogen as a future energy source collection available at: https://www.lyellcollection.org/topic/collections/hydrogen