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SUGAR Subproject A1 Objectives
The generation of gas hydrates requires the presence of free gas. Consequently, the presence of rising gas bubbles from the seafloor or gas flares in the water column is a strong indicator for the presence of gas hydrates in the subsurface. Gas bubbles in the water column can best be detected by hydro-acoustic methods.
Very efficient tools for that purpose are multibeam echosounder. Traditionally these systems were optimized for the precise detection of the seafloor which means that signals from the water column are suppressed or disregarded.
The aim of subproject A1 is to develop data processing methods and enhanced visualisation techniques to allow for a better and faster detection and localisation of gas flares in the water column using portable multibeam systems. The newest generation of echosounder of L-3 communications ELAC-Nautik GmbH allow for a precise determination of seafloor topography as well as for a complete recording of signals from the water column.
To enable these systems for a systematic and routine prospection of gas flares, however, the following objectives have to be achieved:
- Development of suitable algorithms to automatically select interesting parts in the data stream in space and / or time for a reasonable data reduction
- Development of algorithms and techniques to allow for a real-time detection of reflections from gas bubbles
- Development of algorithms for the discrimination between echoes from gas bubbles and other objects in the water column, such as fish swarms, plankton, or abrupt changes of the physical properties of the water
- Investigation of the geological environment of vent sites
- Transfer of the new methods to portable multibeam systems which enable a flexible use of ships of opportunity
The objectives of subproject A1 will allow for a substantially better detection and analysis of gas bubbles in the water column and thus enable an efficient exploration on gas hydrate deposits. Furthermore, these methods can also serve as a leakage-monitor-system during a prospective CO2-deposition in the sediments, as they are sensitive not just to gas bubbles but also to small droplets of fluid CO2 in the water column.
Literature
| Author | Title | Year | Journal/Proceedings | Reftype | DOI/URL |
|---|---|---|---|---|---|
| Artemov, Y.G. | Acoustic observations of gas bubble streams in the NW Black Sea as a method for estimation of gas flux from vent sites [Abstract] [BibTeX] | 2003 | Vol. 5(09421)Geophysical Research Abstracts | conference | URL |
| Best, A.I., Richardson, M.D., Boudreau, B.P., Judd, A.G., Leifer, I., Lyons, A.P., Martens, C.S., Orange, D.L. & Wheeler, S.J. | Shallow Seabed Methane Gas Could Pose Coastal Hazard [Abstract] [BibTeX] | 2006 | EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION Vol. 87(22) | article | DOI |
| Brewer, P.G., Chen, B., Warzinki, R., Baggeroer, A., Peltzer, E.T., Dunk, R.M. & Walz, P. | Three-dimensional acoustic monitoring and modeling of a deep-sea CO2 droplet cloud [Abstract] [BibTeX] | 2006 | Geophysical Research Letters Vol. 33(L23607) | article | DOI |
| Clarke, J.E.H. | Applications of Multibeam Water Column Imaging for Hydrographic Survey [Abstract] [BibTeX] | 2006 | The Hydrographic Journal Vol. 120, pp. 3-15 | article | URL |
| von Deimling, J.S., Brockhoff, J. & Greinert, J. | Flare imaging with multibeam systems: Data processing for bubble detection at seeps [Abstract] [BibTeX] | 2007 | Geochemistry Geophysics Geosystems Vol. 8, pp. 7 | article | DOI |
| Greinert, J., Artemov, Y., Egorov, V., De Batist, M. & McGinnis, D. | 1300-m-high rising bubbles from mud volcanoes at 2080m in the Black Sea: Hydroacoustic characteristics and temporal variability [Abstract] [BibTeX] | 2006 | Earth and Planetary Science Letters Vol. 244(1-2), pp. 1-15 | article | DOI |
| Greinert, J. & Nutzel, B. | Hydroacoustic experiments to establish a method for the determination of methane bubble fluxes at cold seeps [Abstract] [BibTeX] | 2004 | Geo-Marine Letters Vol. 24(2), pp. 75-85 | article | DOI |
| Haeckel, M., Suess, E., Wallmann, K. & Rickert, D. | Rising methane gas bubbles form massive hydrate layers at the seafloor [Abstract] [BibTeX] | 2004 | Geochimica Et Cosmochimica Acta Vol. 68(21), pp. 4335-4345 | article | DOI |
| Klaucke, I., Sahling, H., Weinrebe, W., Blinova, V., Burk, D., Lursmanashvili, N. & Bohrmann, G. | Acoustic investigation of cold seeps offshore Georgia, eastern Black Sea [Abstract] [BibTeX] | 2006 | Marine Geology Vol. 231(1-4), pp. 51-67 | article | DOI |
| Klaucke, I., Weinrebe, W., Sahling, H., Bohrmann, G. & Bürk, D. | Mapping deep-water gas emissions with sidescan sonar [Abstract] [BibTeX] | 2005 | EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION Vol. 86(83) | article | DOI |
| Milkov, A.V. | Global estimates of hydrate-bound gas in marine sediments: how much is really out there? [Abstract] [BibTeX] | 2004 | Earth-Science Reviews Vol. 66(3-4), pp. 183-197 | article | DOI |
| Pfannkuche, O. | Methane cycle at shallow gaseous sediments in the central North Sea [Abstract] [BibTeX] | 2005 | techreport | ||
| Rehder, G., Brewer, P.W., Peltzer, E.T. & Friederich, G. | Enhanced lifetime of methane bubble streams within the deep ocean [Abstract] [BibTeX] | 2002 | Geophysical Research Letters Vol. 29(15) | article | DOI |
| Weber, T., Bradley, D., Culver, R.L. & Lyons, A. | Inferring the vertical turbulent diffusion coefficient from backscatter measurements with a multibeam sonar [Abstract] [BibTeX] | 2003 | The Journal of the Acoustical Society of America Vol. 114(4), pp. 2300-2300 | article | URL |
