Paleo-environment and paleo-productivity of the hydrate reservoirs in the Shenhu area of northern South China Sea

The accumulation of natural gas hydrate requires a stable supply of organic gas. The Shenhu area of the northern part of the South China Sea has been proved a favorable area for natural gas hydrates generation. In the year of 2017, the trial case of hydrate production made a breakthrough there. To further understand the influence of the paleo-environment and paleo- productivity onto organic preservation, this paper is specially devoted to the interval of 180-215 meters below the sea floor at the station of SH3, especially the horizon of 190-200mbsf of the main hydrate storage in the Shenhu area. Studies on the Paleo-environment, redox environment and terrigenous detrital material input suggests that the input of terrigenous detrital material (TDM) increase in the hydrate-bearing horizons and the suboxic depositional environments. The two factors jointly created a favorable external condition for storage and preservation of organic matters. At the same time, the stronger hydrodynamic conditions are conducive to the production of algae, and the biogenic organic gas is relatively abundant. Together with the better conditions for the formation of thermogenic gas, there are enough gas sources for the formation of gas hydrate deposits in the Shenhu area.