Anomalous feature of elastic parameters in sediments with gas-hydrate and free gas and application in estimation of saturation
Feng Kai1,3, Li Min-feng2, Liu Jun-chuan4, Liu Xue-wei1
1. School of Geophysics and Technology Information, China University of Geosciences, Beijing City, 100083, China;
2. ConocoPhilips China, Inc., Beijing City, 100027, China;
3. BGP, CNPC, Zhuozhou City, Hebei Province, 072751, China
Abstract：Comparing with water-saturated sediments, such elastic parameters as velocity of seismic waves, Poisson ratio, elastic module and ratio of elastic module in sediments with gas-hydrate and free gas have clearly anomalous feature. For contact-cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are S-wave velocity and wave impedance; For non-contact cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and P-wave velocity; and for free gas layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and Poisson ratio. When contact cement of gas hydrate with rock frame, the show of gas hydrate layer on velocity and wave impedance sections is high-value anomalous zone near parallel to sea bottom and without clear anomaly on Poisson ratio section. Using elastic parameters sensitive to the change of saturation to estimate the saturation of gas-hydrate and free gas has higher precision. Based on the analysis and study of gas hydrate for seismic data from line USGS95-1 in Blake ridge, it discovered that the gas-hydrate in the region is contact cemented type, and the max saturation of gas hydrate can reach to 20 and content of free gas in underlying layer is less than 2.
冯凯, 李敏锋, 刘竣川, 刘学伟. 天然气水合物和游离气层的弹性参数异常特征及其在饱和度估算中的应用[J]. 石油地球物理勘探, 2008, 43(4): 430-436.
Feng Kai, Li Min-feng, Liu Jun-chuan, Liu Xue-wei. Anomalous feature of elastic parameters in sediments with gas-hydrate and free gas and application in estimation of saturation. OGP, 2008, 43(4): 430-436.
