A comprehensive review of helium geology

Abstract

This study thoroughly examines helium-rich fields, investigating their origin and depositional hierarchy on a global scale. The development processes of helium include its generation, initial migration within minerals, secondary migration with carrier gases, subsurface conditions for economic accumulation, and the overlaying effective seals for entrapment. Helium generation primarily originates from mantle releases and the radioactive decay of Uranium (U) and Thorium (Th). The primary migration focuses on the diffusion-driven escape of helium from fine-grained minerals. The secondary migration of helium emphasizes the transportation through faults and fractures, facilitated by various carrier gases, including natural gas (CH4), Nitrogen (N2), and Carbon Dioxide (CO2). Moreover, N2 acts as a dissolving agent for helium, while CH4 and CO2 participate in a stripping process. The evolution of sedimentary unit structure significantly influences helium accumulation and distribution. Continental cratons allow for billion-year aggregation of helium, resulting in high helium concentrations within pore water. The associated CH4 and CO2 also promote degassing and accumulating processes that contribute helium into trapping structures. Shale and evaporite seals possess physical characteristics such as near-zero porosity and low hydraulic conductivity of halite and anhydrite, respectively, which satisfy requirements for the effective entrapment of helium. Eventually, the economic aspects of helium exploration and development are analyzed, and five critical factors influencing the economic extraction of helium are discussed. This comprehensive review will enhance the fundamental understanding, provide valuable insights for predicting helium exploration prospects, and highlight the irreplaceable resource's economic potential.