Building a Picture of the Geological Hydrogen and Helium System in West Texas, USA

Geological hydrogen and helium exploration have increased substantially in recent years, driven by requirements for the energy transition and high-tech industries. These efforts have highlighted the need for fundamental understanding of the underlying geologic systems influencing the generation, migration, and storage of these gases. Since hydrogen (H₂) and helium (He) are naturally produced in the subsurface via chemical and nuclear reactions involving major igneous rock types that are common in crystalline basements (e.g., mafic/ultramafic for hydrogen and felsic for helium), predicting and mapping basement terranes and lithologies has become a key focus in these new exploration efforts. Further, historical data from oil and gas wells have suggested the presence He and H₂ at depth. While these findings offer promising leads, many of these measurements are outdated and require modern verification to assess their current relevance and potential for commercial accumulation.

Our research aims to generate regional-scale interpretations of the He and H₂ system across the state of Texas. To this end, we explore field and well data to complement and refine existing basement lithology interpretations previously derived from core and geophysical data. The main contribution of our work is the application of Bayesian analysis as the basis for joint inversion of gravity and aeromagnetic data to produce probabilistic estimates of basement lithologies throughout the state. Secondly, the extensive analysis of soil and well gas samples for determining He and H₂ generation and storage. Thirdly, improve well log analysis of basin scale lithological interpretations to increase the accuracy of the hydrogen and helium migration and storage potential across the system. These methods ultimately aim to significantly improve the predictive capability of He and H₂ plays based on a suite of geochemical and geophysical data.

The research is currently focusing on the Permian Basin and Ouachita Thrust Belt region in West Texas (USA) that have traditionally been targeted for oil and gas exploration. The Mesoproterozoic basement of the Permian Basin forms an intractonic sag and consists of a complex assemblage of igneous and metamorphic rocks, which are rock types known to generate He and H₂. Interestingly, the basin comprises a 300-1200 m thick Permian evaporite sequence, which may act as an effective seal for basement-sourced He and H₂. A soil gas survey was conducted to identify potential emission zones and to evaluate the sealing potential of the evaporite sequence. This survey was complemented by well data to investigate gas presence below any overburden. In the most favorable areas, long-term H₂ monitoring was implemented to assess possible cyclicity (e.g., diurnal, seasonal) in gas emissions. Basement rock sampling and well gas analyses provide insights into both past and potentially ongoing reactions beneath the overburden, helping to constrain the He and H₂ system and the geological controls.

In this presentation, we demonstrate this approach to generate Texas-wide basement lithology maps. We focus on specific compositions relevant to geologic He and H₂ exploration, and highlight the utility of these maps to help focus future exploration and development efforts for this rapidly growing field of study.