Helium and natural hydrogen in the Bohai Bay Basin, China: Occurrence, resources, and exploration prospects

Helium, a scarce strategic resource, and hydrogen, a zero‑carbon clean energy source, are abundantly stored in sedimentary basins and are essential components of underground energy systems. However, comprehensive studies on their occurrence, resources, and exploration prospects in tectonically active sedimentary basins remain limited. Herein, helium and natural hydrogen resources in the Bohai Bay Basin in China, a tectonically active sedimentary basin, were investigated through comparisons with tectonically stable basins such as the Hugoton–Panhandle gas field and Mali. An average helium content of 372 ppm and an average natural hydrogen content of 0.34 % were identified in the natural gas reservoirs of the Bohai Bay Basin. Radioactive element decay, water–rock interactions, and water radiolysis within Earth's crust, along with mantle-derived gas, contribute helium and natural hydrogen to the natural gas reservoirs of the Bohai Bay Basin. Our assessment revealed 2.46 × 109 m3 of helium and 22.4 × 109 m3 of natural hydrogen in the Bohai Bay Basin, of which the natural hydrogen resources are equivalent to 67.12 TWh. The Boxing subsag in the Bohai Bay Basin was identified as a promising exploration area for helium and natural hydrogen due to sufficient helium and natural hydrogen production and favorable reservoir–cap rock assemblages. Moreover, the Boxing subsag with developed iron-rich intrusive rocks can produce orange hydrogen through water injection, and this area is also considered as an ideal site for carbon capture and storage and underground hydrogen storage.