Abstract
Gas hydrate model and free gas model are established, and two-phase theory (TPT) for numerical simulation of elastic wave velocity is adopted to investigate the unconsolidated deep-water sedimentary strata in Shenhu area, South China Sea. The relationships between compression wave (P wave) velocity and gas hydrate saturation, free gas saturation, and sediment porosity at site SH2 are studied, respectively, and gas hydrate saturation of research area is estimated by gas hydrate model. In depth of 50 to 245 m below seafloor (mbsf), as sediment porosity decreases, P wave velocity increases gradually; as gas hydrate saturation increases, P wave velocity increases gradually; as free gas saturation increases, P wave velocity decreases. This rule is almost consistent with the previous research result. In depth of 195 to 220 mbsf, the actual measurement of P wave velocity increases significantly relative to the P wave velocity of saturated water modeling, and this layer is determined to be rich in gas hydrate. The average value of gas hydrate saturation estimated from the TPT model is 23.2%, and the maximum saturation is 31.5%, which is basically in accordance with simplified three-phase equation (STPE), effective medium theory (EMT), resistivity log (Rt), and chloride anomaly method.
Highlights
Gas hydrate mainly exists in the seafloor and polar permafrost [1], and it owns the cage structure of solid crystal, which is formed by water molecules and natural gas
In order to research the characteristics of gas hydrate reservoir, gas hydrate model and free gas model have been established and based on these two models, the numerical simulation method and the two-phase theory (TPT) are used to study the dependence of the elastic wave velocity on sediment porosity, gas hydrate saturation and free gas saturation
When Sh = 0, we can get the P wave velocity of water saturated sediments forward stimulated by gas hydrate model based on the TPT
Summary
Gas hydrate mainly exists in the seafloor and polar permafrost [1], and it owns the cage structure of solid crystal, which is formed by water molecules and natural gas (usually dominated by methane). The accurate estimation of gas hydrate reserves is very difficult due to the lack of research on the determination of gas hydrate distribution and gas hydrate saturation. In May 2007, the gas hydrate samples and various log data of gas hydrate zone were firstly obtained in Shenhu area, South China Sea, which made a significant breakthrough in exploration of gas hydrate in China. It provided a great convenience for investigating the properties of the gas hydrate reservoir [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
