GUEST MOLECULAR AND ISOTOPIC COMPOSITIONS OF NATURAL GAS HYDRATES AND ITS GEOCHEMICAL APPLICATIONS

A global dataset of molecular and stable isotope compositions of hydrate-bound gases from 244 samples in 18 representative regions(including seas, inland seas and lakes, permafrost)is presented and discussed, during 1999-2011. The results indicate that Methane (C₁) is the most abundant hydrate-bound gas, while CO₂ and C₂ -C₆ hydrocarbon gases are frequently present in small amounts. Other gases, such as C₆⁺ and H₂S, are uncommon. The kinds of guest molecules in gas hydrates from seas, inland seas, lakes and permafrost were different, and the stable isotope composition (δ¹³C and δD) of hydrate-bound gases varies significantly. In addition to the diagnosis of origins and sources of hydrate-bound gases, molecular and isotopic data can help to better study the control factors of formation and decomposition, and provide valuable insights into the gas migration and accumulation process of gas hydrate.