STRUCTURE AND DISTRIBUTION OF GAS HYDRATES IN MARINE SEDIMENTS

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STRUCTURE AND DISTRIBUTION OF GAS HYDRATES IN
MARINE SEDIMENTS

• Contribution 4, by
• F. Abegg, G. Bohrmann, GEOMAR
• J. Freitag S. Kipfstuhl, AWI

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Introduction

• Objectives, techniques, working areas
• Examples of different internal gas hydrate
  structures
• Quantification of gas hydrate, free gas and host
  sediment
• A frozen core from the Black Sea
• A pressurised core from Hydrate Ridge
• Conclusions

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Tool X-Ray CT scanner
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Frozen gas hydrate sample in a foam box
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Black Sea core location
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Hydrate Ridge core location
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Sample SO148-11
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Honeycomb structure
gas hydrate (light grey)
mud (dark grey)
carbonate (black spots)
20 mm
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Sample SO148-20
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Dense gas hydrate
40 mm
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Sample SO148-14
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Alternating layers
50 mm
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SO148-5 3-D using 227 slices
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SO148-5 3-D cutout
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Example of thresholding
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Quantification of components
Example from sample SO148-11
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Frozen core from the Black Sea
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Various analyses
3-D gas hydrate
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MultiAutoklavCorer
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Pressurised? YES!!
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LabTransferChamber positioned in CT scanner
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Results LTC4
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Slices from LTC4
shell/carbonate gas hydrate gas mud
10 cm subseafloor depth
27 cm subseafloor depth
29 cm subseafloor depth
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2-D and 3-D
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Conclusions

• CT is an appropriate tool to quantify gas
  hydrate, gas and host sediment on a mm-scale and
  to determine internal structures
• Together with autoclave technology the above is
  possible close to in situ conditions
• A frozen core from the Sorokin Trough shows gas
  hydrates in elongated near-vertical, crack-like
  features
• In situ gas hydrate concentration at Hydrate
  Ridge reaches 50 Vol. in a horizontal layer with
  a gas content of up to 10 Vol.
• Thank you very much for your attention!

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