The Journal of the Acoustical Society of Korea

The Acoustical Society of Korea (한국음향학회)
권호 표지

Acoustic Properties of Gassy Sediments: Preliminary Result of Jinhae Bay, Korea

가스함유퇴적물의 음향특성: 한국 진해만의 예비결과

  • Kim, Gil-Young (Petroleum & Marine Resources Division, Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Kim, Dae-Choul (Department of Environmental Exploration Engineering, Pukyong National University) ;
  • Yeo, Jung-Yoon (Gematek Corporation) ;
  • Yoo, Dong-Geun (Petroleum & Marine Resources Division, Korea Institute of Geoscience and Mineral Resources (KIGAM))
  • Published : 2007.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

Compressional wave velocity and shear wave velocity were measured for gassy sediments collected from Jinhae Bay, Korea. To distinguish inhomogeneities of gassy sediments, Computed Tomography (CT) was carried out for gassy sediment using CT Scanner. The cored sediments are composed of homogeneous and soft mud (greater than $8{\Phi}$ in mean grain size) containing clay content more than 50%. In depth interval of gassy sediments, compressional wave velocity is significantly decreased from 1480m/s to 1360m/s, indicating that the gas greatly affects compressional wave velocity due to a gas and/or degassing cracks. Shear wave velocity shows a slight increasing pattern from ${\sim}55\;m/s$ in the upper part of the core to ${\sim}58\;m/s$ at 320 cm depth, and then decreases to ${\sim}54\;m/s$ in the lower part of the core containing a small amount of gas. But shear wave velocity in the gassy sediments is slightly greater than that of non-gassy sediments in the upper part of the core. Thus, the Vp/Vs ratio is decreased (from 30 to 25) in gas charged zone. The Vp/Vs ratio is well correlated with shear wave velocity, but no correlation with compressional wave velocity. This suggests that low concentrations of gas have little affects on shear wave velocity. By CT images, the gas in the sediments is mostly concentrated around inner edge of core liner due to a long duration after sediment collection.

Keywords

References

  1. E,L. Hamilton, 'The elastic properties of marine sediments' , Journal of Geophysical Research, 76, 579-604, 1971 https://doi.org/10.1029/JB076i002p00579
  2. R.H. Tatham and P .L, Stoffa, 'Vp;Vs-A potential hydrocarbon indicator' , Geophysics, 41, 837-849, 1976 https://doi.org/10.1190/1.1440668
  3. A,R, Gregory, 'Fluid saturation effects on dynamic elastic properties of sedimentary rocks', Geophysics, 41, 895-921, 1976 https://doi.org/10.1190/1.1440671
  4. M,D, Richardson and A.M, Davis, 'Modelling methane-rich sediments of Eckernforde Bay', Continental Shelf Research, 18, 1671-1688, 1998 https://doi.org/10.1016/S0278-4343(98)00074-0
  5. A,L, Anderson, F, Abbegg, J.A, Hawkins, M.E, Duncan, and A.P, Lyons, 'Bubble populations and acoustic interaction with the gassy floor of Eckernforde Bay' , Continental Shelf Research, 18, 1807-1838, 1998 https://doi.org/10.1016/S0278-4343(98)00059-4
  6. R.H, Wilkens and M,D, Richardson, 'The influence of gas bubbles on sediment acoustic properties: in situ, laboratory, and theoretical results from Eckernforde Bay, Baltic sea'. Continental Shelf Research, 18, 1859-1892, 1998 https://doi.org/10.1016/S0278-4343(98)00061-2
  7. G,G, Sills and S.J. Wheeler, 'The significance of gas for offshore operations', Continental Shelf Research, 12, 1239-1250
  8. B,P, Boudreau, C. Algar, B,D, Johnson, A.Reed, Y. Furukawa, K.M, Dorgan, P,A, Jumars, A,S. Grader, and B.S, Gardiner, 'Bubble growth and rise in soft sediments', Geological Society of America, 33, 517-520, 2005
  9. F, Birch, 'The velocity of compressional waves in rocks up to 10 kilobars' . Journal of Geophysical Research, 65, 1083-1102, 1960 https://doi.org/10.1029/JZ065i004p01083
  10. G.Y. Kim and D.C. Kim, Shear wave velocity in unconsolidated marine sediments of the western continental margin, the East Sea'. The Journal of the Acoustical Society of Korea, 22, 167-175, 2003
  11. G,Y, Kim, 'Acoustic and elastic properties of the southeastern Yellow Sea Mud, Korea' . The Journal of the Acoustical Society of Korea, 25, 49-55, 2006
  12. J.Y. Yoon, Seismic characteristics and physical properties of gas-bearing sediment in Jinhae Bay, the south sea of Korea, (MS. Thesis, Pukyong National University, 2005) PP. 92
  13. G. S. Lee, Sedimentary environment and acoustic characteristics of gas-bearing sediments in Jinhae Bay, the south sea of Korea, (M.S. Thesis, Pukyong National University, 2006) PP. 94
  14. S.C. Park, K.W. Lee, and Y.I, Song, 'Acoustic characters and distribution pattern of modern fine-grained deposits in a tide-dominated coastal bay: Jinhae Bay, Southeast Korea', Geo-marine Letters, 15, 77-84, 1995 https://doi.org/10.1007/BF01275410
  15. F. Yuan, J.D. Bennel, and A.M. Davis, 'Acoustic and physical characteristics of gassy sediments in the western Irish Sea', Continental Shelf Research, 12, 1121-1134, 1992 https://doi.org/10.1016/0278-4343(92)90073-S
  16. M.D, Richardson, E. Muzi, B, Miaschi and F. Turgutcan, 'Shear wave velocity gradient in near-surface marine sediment' In: Hovem, J,M., Richardson, M,D, and Stoll, R.D. (eds,), Shear wave in marine sediments. Kluwr Academic Pub' Netherlands, 1991 pp, 295-304
  17. F,J. McDonal, FA Angona, R.L, Mills, R,R, Sengbush, R.G. Van Norstrand and J.E. White, 'Attenuation of shear and compressional waves in Pierre Shale' , Geophysics, 23, 421-439, 1985 https://doi.org/10.1190/1.1438489
  18. J.E. White and R.L, Sengbush, 'Shear waves from explosive sources'. Geophysics, 28, 1001-1019, 1963 https://doi.org/10.1190/1.1439296
  19. R.L. Geyer and S,T. Martner, 'SH waves from explosive sources' . Geophysics, 34, 893-905, 1969 https://doi.org/10.1190/1.1440060
  20. E.L, Hamilton, 'VpNs and poisson' s ratios in marine sediments and rocks'. Journal of the Acoustical Society of America, 66, 1093-1101, 1976 https://doi.org/10.1121/1.383344
  21. Universal Systems, CT core analysis series, Web site: www.universal -systems.com, 1998