Marine Geophysical Researches

, Volume 28, Issue 3, pp 201–211 | Cite as

Velocity and AVO analysis for the investigation of gas hydrate along a profile in the western continental margin of India

Original Research


The occurrence of gas hydrate has been inferred from the presence of Bottom-Simulating Reflectors (BSRs) along the western continental margin of India. In this paper, we assess the spatial and vertical distribution of gas hydrates by analyzing the interval velocities and Amplitude Versus Offset (AVO) responses obtained from multi-channel seismics (MCSs). The hydrate cements the grains of the host sediment, thereby increasing its velocity, whereas the free gas below the base of hydrate stability zone decreases the interval velocity. Conventionally, velocities are obtained from the semblance analysis on the Common Mid-Point (CMP) gathers. Here, we used wave-equation datuming to remove the effect of the water column before the velocity analysis. We show that the interval velocities obtained in this fashion are more stable than those computed from the conventional semblance analysis. The initial velocity model thus obtained is updated using the tomographic velocity analysis to account for lateral heterogeneity. The resultant interval velocity model shows large lateral velocity variations in the hydrate layer and some low velocity zones associated with free gas at the location of structural traps. The reflection from the base of the gas layer is also visible in the stacked seismic data. Vertical variation in hydrate distribution is assessed by analyzing the AVO response at selected locations. AVO analysis is carried out after applying true amplitude processing. The average amplitudes of BSRs are almost constant with offset, suggesting a fluid expulsion model for hydrate formation. In such a model, the hydrate concentrations are gradational with maxima occurring at the base of hydrate stability zone.


Gas hydrates BSRs Velocity analysis AVO analysis Wave-equation datuming Error analysis Tomographic velocity analysis 



The authors wish to thank the Director, National Institute of Oceanography (NIO) for giving the permission to publish the paper. Our gratitude goes to the members of Gas Hydrate Team, NIO, for useful discussions. We would also like to thank Mr. Priyank Jaiswal, Rice University, for his comments/suggestions in implementing RayInvr code in NIO. We thank the anonymous reviewers and the associate editor for their invaluable comments and suggestions that has drastically improved the quality of the paper. The seismic data used in this paper was provided by Gas Authority of India Limited (GAIL) through National Gas Hydrate Program (NGHP) from Oil and Natural Gas Commission (ONGC). This is NIO contribution no. 4270.


  1. Al-Chalabi M (1979) Velocity determination from seismic reflection data. In: Fitch AA (ed) Developments in geophysical exploration methods, vol 1. Applied Science Publishers, London, pp 1–68Google Scholar
  2. Bangs NJB, Sawyer DS, Golovchenko X (1993) Free gas at the base of the gas hydrate zone in the vicinity of the Chile triple junction. Geology 21:905–908CrossRefGoogle Scholar
  3. Berryhill JR (1979) Wave equation datuming. Geophysics 44:1329–1344CrossRefGoogle Scholar
  4. Berryhill JR (1984) Wave equation datuming before stack (short note). Geophysics 49:2064–2067CrossRefGoogle Scholar
  5. Biswas SK (1987) Regional tectonic framework, structure and evolution of the western marginal basins of India. Tectonophysics 135:307–327CrossRefGoogle Scholar
  6. Chapman NR, Gettrust JF, Walia R, Hannay D, Spence GD, Wood TW, Hyndman RD (2002) High-resolution, deep-towed, multichannel seismic survey of deep-sea gas hydrates off western Canada. Geophysics 67:1038–1047CrossRefGoogle Scholar
  7. Dix CH (1955) Seismic velocities from surface measurements. Geophysics 20:68–86CrossRefGoogle Scholar
  8. Doherty SM, Claerbout JF (1976) Structure independent velocity estimation. Geophysics 41:850–881CrossRefGoogle Scholar
  9. Hamilton EL (1971) Prediction of in-situ acoustic and elastic properties of marine sediments. Geophysics 36:266–284CrossRefGoogle Scholar
  10. Haznal Z, Sereda IT (1981) Maximum uncertainty of interval velocity estimates. Geophysics 46:1543–1547CrossRefGoogle Scholar
  11. Holbrook WS, Hoskins H, Wood WT, Stephen RA, Lizarralde D, Leg 164 Science Party (1996) Methane hydrate and free gas on the blake ridge from vertical seismic profiling. Science 273:1840–1843Google Scholar
  12. Hyndmann RD, Spence GD (1992) A seismic study of methane hydrate marine bottom simulating reflectors. J Geophys Res 97:6683–6698Google Scholar
  13. Jaiswal P, Zelt CA, Pecher IA (2006) Seismic characterization of a gas hydrate system in the Gulf of Mexico using wide-aperture data. Geophys J Int 165:108–120CrossRefGoogle Scholar
  14. Karisiddaiah S, Veerayya M (1994) Methane bearing sediments in the eastern Arabian Sea: a probable source of greenhouse gas. Cont Shelf Res 14:1361–1370CrossRefGoogle Scholar
  15. Karisiddaiah S, Veerayya M (1996) Potential distribution of subsurface methane in the sediments of the eastern Arabian Sea and its possible implications. J Geophys Res 101:25887–25895CrossRefGoogle Scholar
  16. Kvenvolden KA (1988) Methane hydrate—a major reservoir of carbon in the shallow geosphere? Chem Geol 71:41–51CrossRefGoogle Scholar
  17. Lu S, McMechan GA (2002) Estimation of gas hydrate and free gas saturation, concentration, and distribution from seismic data. Geophysics 67:582–593CrossRefGoogle Scholar
  18. MacKay ME, Jarrard RD, Westbrook GK, Hyndman RD, Shipboard Scientific Party of ODP Leg 146 (1994) Origin of bottom-simulating reflector; Geophysical evidences from the Cascadia accretionary prism. Geology 22:459–462CrossRefGoogle Scholar
  19. Markl RG, Bryan GM, Ewing JI (1970) Structure of the Blake-Bahama outer ridge. J Geophys Res 75:4539–4555Google Scholar
  20. Mackenzie KV (1981) Nine-term equation for sound speed in the oceans. J Acoust Soc Am 70:807–812CrossRefGoogle Scholar
  21. McKenzie DP, Sclater J (1971) The evolution of Indian Ocean since the late Cretaceous. Geophys J R Astron Soc 25:437–528Google Scholar
  22. Neidell NS, Taner MT (1971) Semblance and other coherency measures for multichannel data. Geophysics 36:498–509CrossRefGoogle Scholar
  23. Rao YH, Subrahmanyam C, Rastogi A, Deka B (2001) Anomalous seismic reflections related to gas/gas hydrate occurrences along the western continental margin of India. Geo-Marine Lett 21:1–8CrossRefGoogle Scholar
  24. Satyavani N, Shankar U, Thakur NK, Reddi SI (2002) Probable gas hydrate/free gas model over western continental margin of India. Mar Geophys Res 23:423–430CrossRefGoogle Scholar
  25. Shankar U, Sinha B, Thakur NK, Khanna R (2005) Amplitude-versus-offset modeling of the bottom simulating reflection associated with submarine gas hydrates. Mar Geophys Res 26:29–35CrossRefGoogle Scholar
  26. Sheriff RE, Geldart LE (1982) Exploration seismology vol 1, history, theory, data acquisition. Cambridge University Press, New YorkGoogle Scholar
  27. Shipley TH, Houston MH, Buffler RT, Shaub FJ, McMillen KJ, Ladd JW, Worzel JL (1979) Seismic evidence for widespread possible gas hydrate horizons on continental slopes and rises. Am Assoc Petrol Geol Bull 63:2204–2213Google Scholar
  28. Singh SC, Minshull TA, Spence GD (1993) Velocity structure of a gas hydrate reflector. Science 260:204–207CrossRefGoogle Scholar
  29. Sloan ED (1998) Clathrate hydrates of natural gases. Marcel Dekker Inc, New YorkGoogle Scholar
  30. Stork C (1991) Reflection tomography in the post migrated domain. Geophysics 57:680–692CrossRefGoogle Scholar
  31. Subrahmanyam V, Ramana MV, Gopala Rao D (1993) Reactivation of Precambrian faults on the southwestern continental margin of India: evidence from gravity anomalies. Tectonophysics 219:327–339CrossRefGoogle Scholar
  32. Taner MT, Koehler F (1981) Surface consistent corrections. Geophysics 46:17–22CrossRefGoogle Scholar
  33. Veerayya M, Karisiddaiah SM, Vora KH, Wagle BG, Almeida F (1998) Detection of gas charged sediments and gas hydrate horizons along the western continental margin of India. In: Henriet JP, Mienert J (eds) Gas hydrates: relevance to world margin stability and climate change. Geol Soc London Spec Publ 137:239–253Google Scholar
  34. Yuan T, Hyndman RD, Spence GD, Desmons B (1996) Seismic velocity increase and deep-sea gas hydrate concentration above a bottom-simulating reflector on the northern Cascadia continental slope. J Geophys Res 101:13655–13671CrossRefGoogle Scholar
  35. Zelt CA (1999) Modeling strategies and model assessment for wide-angle seismic traveltime data. Geophys J Int 139:183–204CrossRefGoogle Scholar
  36. Zelt CA, Smith RB (1992) Seismic traveltime inversion for 2-D crustal velocity structure. Geophys J Int 108:16–34CrossRefGoogle Scholar
  37. Zoeppritz K (1919) On the reflection and propagation of seismic waves. Gottinger Nachrichten 1:66–84Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  1. 1.Geological OceanographyNational Institute of OceanographyDona PaulaIndia

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