Seismic Amplitude and Frequency Characteristics of Gas hydrate Bearing Geologic Model

가스 하이드레이트 지층 모델의 탄성파 진폭 및 주파수 특성

  • Shin, Sung-Ryul (Division of Ocean Development Engineering, Korea Maritime University) ;
  • Lee, Sang-Cheol (Division of Ocean Development Engineering, Korea Maritime University) ;
  • Park, Keun-Pil (Division of Petroleum and Marine Resources, Korean Institute of Geology and Mining) ;
  • Lee, Ho-Young (Division of Petroleum and Marine Resources, Korean Institute of Geology and Mining) ;
  • Yoo, Dong-Geun (Division of Petroleum and Marine Resources, Korean Institute of Geology and Mining) ;
  • Kim, Young-Jun (Division of Petroleum and Marine Resources, Korean Institute of Geology and Mining)
  • 신성렬 (한국해양대학교 해양개발공학부) ;
  • 이상철 (한국해양대학교 해양개발공학부) ;
  • 박근필 (한국지질자원연구원 석유해저자원연구부) ;
  • 이호영 (한국지질자원연구원 석유해저자원연구부) ;
  • 유동근 (한국지질자원연구원 석유해저자원연구부) ;
  • 김영준 (한국지질자원연구원 석유해저자원연구부)
  • Published : 2008.05.31

Abstract

In gas hydrate survey, seismic amplitude and frequency characteristics play a very important role in determining whether gas hydrate exists. According to the variation of source frequency and scatterer size, we study seismic amplitude characteristics using elastic modeling applied at staggered grids. Generally speaking, scattering occurs in proportion to the square of source frequency and the scatterer volume, which has an effect on seismic amplitude. The higher source frequency is, the more scattering occurs in gas hydrate bearing zone. Therefore, BSR is hardly observed in high frequencies. On the other side, amplitude blanking zone and BSR is clearly observed in lower frequencies although the resolution is poor as a whole. Seismic reflections traveling through free-gas layer below gas hydrate bearing zone decay so severely a high frequency component that a low frequency term is dominant. Amplitude anomaly of BSR result from high acoustic impedance contrast due to free-gas, which is a very crucial factor to estimate gas hydrate bearing zone. Seismic frequency analysis is carried out using wavelet transform method that frequency component could be decomposed with time variation. In application of wavelet transform to the seismic physical experiments data, we can observe that reflections traveling through air layer, which corresponds to the free-gas layer, decay a high frequency component.

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