The Characteristics of Gas Hydrates Recovered from Shenhu Area in the South China Sea

For the first time gas hydrate samples were recovered in the South China Sea during a drilling campaign implemented in Shenhu area in June 2007. Laboratory based studies for the characteristics of gas hydrate were carried out on two hydrate-bearing sediment samples. Observations found that gas hydrates occurred in the pores of fine grained sediments. The hydrates were structure I based on the Raman spectroscopic results. The guest gas molecules in hydrate cages were predominantly methane (> 99.3%) and trace amount of ethane (0.4%) and propane (0.04%) as determined with the method of gas chromatography. As estimated from the intensities of Raman peaks, the cage occupancy rates were more than 99% in large cage, and ~ 86% in small cage, respectively, corresponding to a hydration number of 5.9.

► The hydrates occurred in the pores of fine grained sediments. ► Both samples are structure I methane hydrate with hydration numbers around 5.9. ► The hydrates are mainly composed of methane and with trace amount of C2 and C3. ► Gas hydrate experienced stepwise dissociation in fine sediments.