5. Laboratory/Scaled Geophysics
A Study on the Seismic Characteristics of Gas Hydrate using Physical and Numerical Modeling
Sung-Ryul Shin, Eun-Min Yeo and Chan-Su Kim
Korea Maritime University, Korea.
Abstract
We have developed the seismic physical modeling system and carried out physical modeling experiments to analyze seismic properties on gas hydrate bearing zone in deep sea condition. Horizontal layered model and pinch-out structure model which is composed of polyethylene, acrylic, ABS(acrylonitrile butadiene styrene), and bakelite sheet material were set up for the geological model in this study. We have successfully acquired the seismic data to the various source-receiver geometries for multi-channel seismic survey at surface and deep tow method. In the horizontal layered model, the seismic p-wave velocity estimated from travel times of reflection events is in good agreement with the modeling materials velocity by direct measurement. We could confirm the high amplitude and the phase reversal of reflections at the interface between gas hydrate layer and a free gas layer called a BSR(Bottom Simulating Reflector) which is the evidence for existence of gas hydrate in seismic reflection data. We performed a numerical modeling, a 2-D staggered grid finite difference seismic method to generate synthetic elastic seismogram, to investigate seismic properties of gas hydrate bearing zone and to compare with physical modeling. We could easily observe the amplitude variation corresponding to offset distance in the reflection strength profile which is generated by seismic complex analysis for the physical modeling data at common shot gather. Also the relative amplitude acquired from the physical modeling was very well consistent with the reflection coefficients obtained by Shuey's equation for AVO analysis. AVO analysis of seismic data in deep sea environment should be carefully performed since the incidence angle is inherently limited and amplitude variation is very small.Key words
Last modified: Fri May 12 19:39:36 2006