• Title, Summary, Keyword: 해저모방반사면

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Geophysical studies of gas hydrate in the Ulleung Basin, East Sea (동해 울릉분지 가스하이드레이트 지구물리탐사연구)

  • Yoo, Dong-G.;Kim, Gil-Y.;Park, Keun-P.;Lee, Ho-Y.;Ryu, Byong-J.
    • 한국신재생에너지학회:학술대회논문집
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    • pp.672-675
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    • 2009
  • 동해 울릉분지에서 취득된 다중채널 탄성파자료 해석에 의하면 이 지역에는 가스하이드레이트 부존가능성을 지시하는 해저모방반사면, 탄성파침니/칼럼, 음향공백대, 증폭반사면, 가스분출 구조 등을 포함하는 5가지 탄성파 지시자가 존재한다. 가장 대표적인 지시자인 해저모방반사면은 연구지역의 남쪽사면의 경우 연속성이 양호하고 강한 진폭을 갖는 반면, 북쪽 중앙분지에서는 상대적으로 진폭이 약하고 연속성이 불량하다. 반사도 감소 및 속도 풀업 특징을 갖는 탄성파 침니/칼럼구조는 중앙분지와 북동쪽해역에 주로 분포하며 가스하이드레이트 혹은 가스유체의 부존가능성을 시사해준다. 반사강도가 약화되어 나타나는 음향공백대는 저탁류/원양성 퇴적물이 분포하는 중앙분지에 부분적으로 발달하며, 칼럼과 연계된 음향공백대는 북동쪽 사면저부에 주로 분포한다. 해저모방반사면의 하부에 위치하는 증폭반사면은 연구지역의 서쪽 사면에 분포하며 강한 음의 진폭특성으로 보아 자유가스를 함유한 층으로 해석된다. 가스분출구조는 주로 쇄설성 퇴적물이 우세한 조사지역의 남쪽 대륙사면지역에 광범위하게 분포하며 돔구조 혹은 폭마크 등을 수반한다.

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Seismic Attribute Analysis of the Indicators for the Occurrence of Gas Hydrate in the Northwestern Area of the Ulleung Basin, East Sea (동해 울릉분지 북서지역 가스하이드레이트 부존 지시자의 탄성파 속성 분석)

  • Kim, Kyoung Jin;Yi, Bo Yeon;Kang, Nyeon Keon;Yoo, Dong Geun;Shin, Kook Sun;Cho, Young Ho
    • Geophysics and Geophysical Exploration
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    • v.17 no.4
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    • pp.216-230
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    • 2014
  • 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.

Geophysical study about gas hydrate formation in the Ulleung Basin, East Sea (동해 울릉분지 가스하이드레이트 형성에 관한 지구물리해석)

  • Kang, Dong-Hyo;Ryu, Byong-Jae;Yoo, Dong-Geun;Bahk, Jang-Jun;Koo, Nam-Hyung;Kim, Won-Sik
    • 한국신재생에너지학회:학술대회논문집
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    • pp.680-681
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    • 2009
  • On the basis of seismic interpretation, seismic indicators of gas hydrate and associated gas such as bottom simulating reflector (BSR), acoustic blanking, column structure, gas seepage, enhanced reflection were identified in the Ulleung Basin. Fractures, faults, sandy layer could be the migration pathways transporting fluid and gas to stability zone. The formation of gas hydrate in the Ulleung Basin include: (1) nodules, veins, layers in muddy sediments and disseminated forms in sandy layer within localized column structure, (2) disseminated forms in sandy layer, and (3) disseminated forms in sandy layer just above BSR.

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Sound Velocity Property of Sediment Containing Gas Hydrate in the Ulleung Basin, East Sea (동해 울릉분지 가스하이드레이트 함유 퇴적물의 음파전달속도 특성)

  • Kim, Gil-Young;Yoo, Dong-Geun;Ryu, Byong-Jae
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.5
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    • pp.424-431
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    • 2009
  • This study investigates the difference of sound velocity (compressional wave velocity) between gas hydrate-bearing sediments and nongas hydrate-bearing sediments in the Ulleung Basin, East Sea. We use a dataset measured from one site in the central part of the Ulleung Basin. Sound velocity for gas hydrate-bearing sediment shows the range from 1600 m/s to 2200 m/s. However, the value for nongas hydrate-bearing sediment is mostly around 1500 m/s, being less than 1400 m/s below 140 m subbottom depth. This trend is probably due to the presence of free gas below BSR (Bottom Simulating Reflector). Gas hydrate-bearing sediments show high value (maximum 150 Ohm-m) of resistivity. The physical properties between gas hydrate-bearing sediment and nongas hydrate-bearing sediment are characterized by the different patterns due to the presence of gas hydrate in comparison with those of marine unconsolidated sediments. Therefore, in order to investigate acoustic and physical properties for gas hydrate-bearing sediments, the study for the occurrence type and the amount of gas hydrates should be conducted simultaneously.