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동해 울릉분지 북서지역 가스하이드레이트 부존 지시자의 탄성파 속성 분석

Seismic Attribute Analysis of the Indicators for the Occurrence of Gas Hydrate in the Northwestern Area of the Ulleung Basin, East Sea

  • 김경진 (과학기술연합대학원대학교 석유자원공학과) ;
  • 이보연 (한국지질자원연구원 석유해저연구본부) ;
  • 강년건 (한국지질자원연구원 석유해저연구본부) ;
  • 유동근 (한국지질자원연구원 석유해저연구본부) ;
  • 신국선 (한국석유공사 석유개발기술원) ;
  • 조영호 (한국석유공사 석유개발기술원)
  • Kim, Kyoung Jin (Department of Petroleum Resources Technology, Korea University of Science and Technology (UST)) ;
  • Yi, Bo Yeon (Petroleum and Marine Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Kang, Nyeon Keon (Petroleum and Marine Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Yoo, Dong Geun (Petroleum and Marine Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Shin, Kook Sun (Institute for Exploration and Production Technology, Korea National Oil Corporation (KNOC)) ;
  • Cho, Young Ho (Institute for Exploration and Production Technology, Korea National Oil Corporation (KNOC))
  • 투고 : 2014.10.07
  • 심사 : 2014.11.20
  • 발행 : 2014.11.30

초록

동해 울릉분지 북서 해역에서 취득한 3차원 탄성파 탐사자료의 해석에 의하면 연구해역 내 천부퇴적층은 광역반 사면에 의해 분리되는 5개의 탄성파 단위로 구분되며, 다수의 단층을 수반하는 배사구조가 발달한다. 가스하이드레이트 안정영역 내에는 높은 RMS 진폭을 보이는 해저모방반사면과 낮은 RMS 진폭을 보이는 음향공백대가 특징적으로 분포한다. 탄성파 속성 분석에 의하면 가스하이드레이트와 자유가스가 동시에 부존한 경우 그 경계를 따라 순간진폭이 높게 나타나며 하부에서 순간주파수가 급격히 감소한다. 반면 가스하이드레이트만 존재하는 경우에는 하부에서 순간진폭이 낮고 순간주파수가 감소하지 않는다. 해저모방반사면의 주파수 성분 분해 결과 특정 고주파수 영역에서 나타나는 강한 진폭은 하부 자유가스에 의한 튜닝효과를 지시한다. 가스하이드레이트, 자유가스 및 퇴적층의 경사를 고려한 네 가지 가스하이드레이트 부존모델을 제시하고 그 특징을 기술하였다.

Based on the interpretation of 3D seismic profiles acquired in the northwestern area of the Ulleung Basin, East Sea, the shallow sediments consist of five seismic units separated by regional reflectors. An anticline is present in the study area that documents activity of many faults. Bottom simulating reflectors are characterized by high RMS amplitude. Acoustic blanking with low RMS amplitude is distinctively recognized in the gas hydrate stability zone. Seismic attribute analysis shows that if gas hydrates are underlain by free gas, the high reflection strength and the low instantaneous frequency are displayed below the boundary between them. Whereas, if not, the reflection strength is low and instantaneous frequency is high continuously below the gas hydrate zone. Based on the spectral decomposition of the bottom simulating reflector, the high envelope at the specific high frequency range indicates the generation of the tuning effect due to the lower free gas content. Four models for the occurrence of the gas hydrate are suggested considering the slope of sedimentary layers as well as the presence of gas hydrate or free gas.

키워드

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