Characteristics of Sonic and Seismic Velocities of Gas Hydrate Bearing Sediments in the Shenhu Area, Northern South China Sea
详细信息
- 责任者：Liang Jin (Guangzhou Marine Geological Survey ; Guangzhou 510075 ; China) ; Wang Mingjun
- 刊名：Natural Gas Industry
- 出版年：2013
- 卷期：33(7)
- 关键词：天然气水合物 ; gas hydrates ; 储集层 ; reservoirs ; 南海 ; South China Sea
- 页码：p.29-35
- 图表：6 illus., 31 refs.
- 分类号：1003
- issnNo：ISSN1000-0976
- isbnNo：CN51-1179/TE
摘要
According to the drilling results of natural gas hydrate reservoirs in the Shenhu area,northern South China Sea,in 2007,both bottom simulating reflections(BSR) and blank reflections failed to reveal the storage of gas hydrate in sedimentary beds and were also incapable of accurately delineating the distribution area and reservoir thickness of gas hydrate.In view of this,we analyzed in detail the logging and seismic data from this study area,and studied the distribution characteristics and variations of sonic and seismic velocities in gas hydrate bearing formations.The following conclusions were obtained.(1) On the seismic reflection profile,the increases of gas hydrate saturation and reservoir thickness causes the increase of deposition rate of hydrate beds,thus a push-up structure is formed,below which a push-down structure occurs correspondingly due to the gas-bearing layers with a low deposition rate,which resulted in an augen-like amplitude anomaly.(2) The interval velocity of gas hydrate beds is closely related to the porosity and saturation of hydrate.The saturation of gas hydrate fluctuates with the increase of sonic velocity,but the overall trend is increasing with the increase of sonic velocity.(3) Within the gas hydrate bearing zone,the high velocity layers are featured by zonation distribution in parallel with the sea floor.The highest velocity occurs at the bottom of the gas hydrate bearing zone and the velocity decreases gradually upwards.(4) Based on the above characteristics,the interval velocity can be used to identify the existence of gas hydrate and to compute the saturation of gas hydrate.Combined with the other geological and geophysical data,the interval velocity can also be used to determine the thickness and distribution area of gas hydrate reservoirs,and to calculate the resource volume of natural gas hydrate.
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