7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

STRUCTURE AND DISTRIBUTION OF GAS HYDRATES IN MARINE

SEDIMENTS

Contribution 4, by:

F. Abegg, G. Bohrmann, GEOMAR

J. Freitag & S. Kipfstuhl, AWI

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

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

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Tool: X-Ray CT scanner

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Frozen gas hydrate sample in a foam box

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Black Sea: core location

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Hydrate Ridge: core location

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Sample SO148-11

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Honeycomb structure

20 mm

gas hydrate(light grey)

mud(dark grey)

carbonate(black spots)

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Sample SO148-20

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Dense gas hydrate

40 mm

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Sample SO148-14

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Alternating layers

50 mm

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

SO148-5: 3-D using 227 slices

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

SO148-5: 3-D cutout

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Example of thresholding

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Quantification of components

Example fromsample SO148-11

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Frozen core from the Black Sea

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Various analyses

3-D gas hydrate

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

MultiAutoklavCorer

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Pressurised? YES!!

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

LabTransferChamber positioned in CT

scanner

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

Results LTC4

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

shell/carbonategas hydrategasmud

10 cm subseafloor depth 27 cm subseafloor depth 29 cm subseafloor depth

Slices from LTC4

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

2-D and 3-D

7th Shallow Gas Group MeetingBaku, Azerbaijan, 07.10. – 11.10.2002

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!

respond to:fabegg@geomar.de