Interactions Between Gas Hydrate and Hydrogen in Nature: Laboratory Evidence of Hydrogen Incorporation

Natural hydrogen is generated via serpentinization, radiolysis and organic metagenesis in geological settings. After expulsion from the source, and along its upward migration path, the free gas may encounter hydratebearing sediments. To simulate this natural scenario, CH4 hydrate and CH4 + C3H8 hydrate were synthesized at 5.0 MPa and exposed to a hydrogen-containing gas mixture. In-situ Raman spectroscopic measurements demonstrated the incorporation of H2 molecules into the hydrate phase even at a partial pressure of 0.5 MPa. Exsitu Raman spectroscopic characterization of hydrates formed from a CH4 + H2 gas mixture at 5.0 MPa confirmed the H2 inclusion within the large cavities of structure I. The results show that the interactions between H2 and the natural gas hydrate phase range from the incorporation of H2 molecules into the hydrate phase to the rapid dissociation of the gas hydrate, depending on thermodynamic conditions and H2 concentration in the coexisting gas phase.