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Attenuation of seismic waves in methane gas hydrate-bearing sand

Attenuation of seismic waves in methane gas hydrate-bearing sand
Attenuation of seismic waves in methane gas hydrate-bearing sand
Compressional wave (P wave) and shear wave (S wave) velocities (Vp and Vs, respectively) from remote seismic methods have been used to infer the distribution and volume of gas hydrate within marine sediments. Recent advances in seismic methods now allow compressional and shear wave attenuations (Q1p and Q1s, respectively) to be measured. However, the interpretation of these data is problematic due to our limited understanding of the effects of gas hydrate on physical properties. Therefore, a laboratory gas hydrate resonant column was developed to simulate pressure and temperature conditions suitable for methane gas hydrate formation in sand specimens and the subsequent measurement of both Q1p and Q1s at frequencies and strains relevant to marine seismic surveys. 13 dry (gas saturated) sand specimens were investigated with different amounts of methane gas hydrate evenly dispersed throughout each specimen. The results show that for these dry specimens both Q1p and Q1s are highly sensitive to hydrate saturation with unexpected peaks observed between 3 and 5 per cent hydrate saturation. It is thought that viscous squirt flow of absorbed water or free gas within the pore space is enhanced by hydrate cement at grain contacts and by the nanoporosity of the hydrate itself. These results show for the first time the dramatic effect methane gas hydrate can have on seismic wave attenuation in sand, and provide insight into wave propagation mechanisms. These results will aid the interpretation of elastic wave attenuation data obtained using marine seismic prospecting methods.
0956-540X
149-159
Priest, Jeffrey A.
b075689b-0700-484f-b9a6-11b1211a9aab
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Clayton, Christopher R.I.
8397d691-b35b-4d3f-a6d8-40678f233869
Priest, Jeffrey A.
b075689b-0700-484f-b9a6-11b1211a9aab
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Clayton, Christopher R.I.
8397d691-b35b-4d3f-a6d8-40678f233869

Priest, Jeffrey A., Best, Angus I. and Clayton, Christopher R.I. (2005) Attenuation of seismic waves in methane gas hydrate-bearing sand. Geophysical Journal International, 164 (1), 149-159. (doi:10.1111/j.1365-246X.2005.02831.x).

Record type: Article

Abstract

Compressional wave (P wave) and shear wave (S wave) velocities (Vp and Vs, respectively) from remote seismic methods have been used to infer the distribution and volume of gas hydrate within marine sediments. Recent advances in seismic methods now allow compressional and shear wave attenuations (Q1p and Q1s, respectively) to be measured. However, the interpretation of these data is problematic due to our limited understanding of the effects of gas hydrate on physical properties. Therefore, a laboratory gas hydrate resonant column was developed to simulate pressure and temperature conditions suitable for methane gas hydrate formation in sand specimens and the subsequent measurement of both Q1p and Q1s at frequencies and strains relevant to marine seismic surveys. 13 dry (gas saturated) sand specimens were investigated with different amounts of methane gas hydrate evenly dispersed throughout each specimen. The results show that for these dry specimens both Q1p and Q1s are highly sensitive to hydrate saturation with unexpected peaks observed between 3 and 5 per cent hydrate saturation. It is thought that viscous squirt flow of absorbed water or free gas within the pore space is enhanced by hydrate cement at grain contacts and by the nanoporosity of the hydrate itself. These results show for the first time the dramatic effect methane gas hydrate can have on seismic wave attenuation in sand, and provide insight into wave propagation mechanisms. These results will aid the interpretation of elastic wave attenuation data obtained using marine seismic prospecting methods.

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More information

Published date: 2005
Additional Information: Funded by European Commission - FP5: Techniques for the quantification of methane hydrate in european continental margins (HYDRATECH) (EVK3-CT-2000-00043)

Identifiers

Local EPrints ID: 19281
URI: http://eprints.soton.ac.uk/id/eprint/19281
ISSN: 0956-540X
PURE UUID: 49d64767-5f0c-4cc5-9a3b-7f0d38b04245
ORCID for Christopher R.I. Clayton: ORCID iD orcid.org/0000-0003-0071-8437

Catalogue record

Date deposited: 30 Jan 2006
Last modified: 02 Aug 2023 01:41

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Contributors

Author: Jeffrey A. Priest
Author: Angus I. Best

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