Integrated signatures of secondary microbial gas within gas hydrate reservoirs: A case study in the Shenhu area, northern South China Sea

A series of highly saturated pore-filled gas hydrate deposits were recently discovered in the Shenhu area of northern South China Sea. However, the main hydrocarbon sources of the gas hydrates remain controversial. The main hypotheses include a shallowly buried microbial gas source or a deeply buried thermogenic hydrocarbon source. In this study, an integrated geochemical-microbial-geological analysis of gas hydrate and sediment samples from sites SC1 and SC2 in the Shenhu area was conducted to investigate the possible hydrocarbon sources, and to identify the signatures of the secondary microbial gases in the gas hydrate reservoirs. The results show that the gas hydrates from sites SC1 and SC2 exhibit the geochemical characteristics of secondary microbial gas (C1/(C2+C3) >100, −50.2‰