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Laboratory insights into the effect of sediment‐hosted methane hydrate morphology on elastic wave velocity from time‐lapse 4D synchrotron X‐ray computed tomography

Laboratory insights into the effect of sediment‐hosted methane hydrate morphology on elastic wave velocity from time‐lapse 4D synchrotron X‐ray computed tomography
Laboratory insights into the effect of sediment‐hosted methane hydrate morphology on elastic wave velocity from time‐lapse 4D synchrotron X‐ray computed tomography
A better understanding of the effect of methane hydrate morphology and saturation on elastic wave velocity of hydrate bearing sediments is needed for improved seafloor hydrate resource and geohazard assessment. We conducted X‐ray synchrotron time‐lapse 4D imaging of methane hydrate evolution in Leighton Buzzard sand, and compared the results to analogous hydrate formation and dissociation experiments in Berea sandstone, on which we measured ultrasonic P‐ and S‐wave velocity, and electrical resistivity. The imaging experiment showed that initially hydrate envelops gas bubbles and methane escapes from these bubbles via rupture of hydrate shells, leading to smaller bubbles. This process leads to a transition from pore‐floating to pore‐bridging hydrate morphology. Finally, pore‐bridging hydrate coalesces with that from adjacent pores creating an inter‐pore hydrate framework that interlocks the sand grains. We also observed isolated pockets of gas within hydrate. We observed distinct changes in gradient of P‐ and S‐wave velocity increase with hydrate saturation. Informed by a theoretical model of idealized hydrate morphology and its influence on elastic wave velocity, we were able to link velocity changes to hydrate morphology progression from initial pore‐floating, then pore‐bridging, to an inter‐pore hydrate framework. The latter observation is the first evidence of this type of hydrate morphology, and its measurable effect on velocity. We found anomalously low S‐wave velocity compared to the effective medium model, probably caused by the presence of a water film between hydrate and mineral grains.
1525-2027
4502-4521
Sahoo, Sourav K.
4c4db3a0-8fa2-4b7c-b09e-176b9c0343ae
Madhusudhan, B.N.
e139e3d3-2992-4579-b3f0-4eec3ddae98c
Marin-Moreno, H.
d1daa2dc-3ece-4b9b-914a-0e463b77d414
North, Laurence J
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Ahmed, Sharif
37570e92-ba6b-4e03-9144-c70fa7722c51
Falcon-Suarez, Ismael
9e8022b5-8799-4326-8d5b-0ed46de3b25a
Minshull, Timothy
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Best, Angus
fd094b23-2f48-41d3-a725-fb2bef223a8a
Sahoo, Sourav K.
4c4db3a0-8fa2-4b7c-b09e-176b9c0343ae
Madhusudhan, B.N.
e139e3d3-2992-4579-b3f0-4eec3ddae98c
Marin-Moreno, H.
d1daa2dc-3ece-4b9b-914a-0e463b77d414
North, Laurence J
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Ahmed, Sharif
37570e92-ba6b-4e03-9144-c70fa7722c51
Falcon-Suarez, Ismael
9e8022b5-8799-4326-8d5b-0ed46de3b25a
Minshull, Timothy
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Best, Angus
fd094b23-2f48-41d3-a725-fb2bef223a8a

Sahoo, Sourav K., Madhusudhan, B.N., Marin-Moreno, H., North, Laurence J, Ahmed, Sharif, Falcon-Suarez, Ismael, Minshull, Timothy and Best, Angus (2018) Laboratory insights into the effect of sediment‐hosted methane hydrate morphology on elastic wave velocity from time‐lapse 4D synchrotron X‐ray computed tomography. Geochemistry, Geophysics, Geosystems, 19 (11), 4502-4521. (doi:10.1029/2018GC007710).

Record type: Article

Abstract

A better understanding of the effect of methane hydrate morphology and saturation on elastic wave velocity of hydrate bearing sediments is needed for improved seafloor hydrate resource and geohazard assessment. We conducted X‐ray synchrotron time‐lapse 4D imaging of methane hydrate evolution in Leighton Buzzard sand, and compared the results to analogous hydrate formation and dissociation experiments in Berea sandstone, on which we measured ultrasonic P‐ and S‐wave velocity, and electrical resistivity. The imaging experiment showed that initially hydrate envelops gas bubbles and methane escapes from these bubbles via rupture of hydrate shells, leading to smaller bubbles. This process leads to a transition from pore‐floating to pore‐bridging hydrate morphology. Finally, pore‐bridging hydrate coalesces with that from adjacent pores creating an inter‐pore hydrate framework that interlocks the sand grains. We also observed isolated pockets of gas within hydrate. We observed distinct changes in gradient of P‐ and S‐wave velocity increase with hydrate saturation. Informed by a theoretical model of idealized hydrate morphology and its influence on elastic wave velocity, we were able to link velocity changes to hydrate morphology progression from initial pore‐floating, then pore‐bridging, to an inter‐pore hydrate framework. The latter observation is the first evidence of this type of hydrate morphology, and its measurable effect on velocity. We found anomalously low S‐wave velocity compared to the effective medium model, probably caused by the presence of a water film between hydrate and mineral grains.

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Accepted/In Press date: 18 October 2018
e-pub ahead of print date: 27 October 2018
Published date: November 2018

Identifiers

Local EPrints ID: 425766
URI: http://eprints.soton.ac.uk/id/eprint/425766
ISSN: 1525-2027
PURE UUID: db06f032-e0d8-41ff-bad3-22cb7847b7cc
ORCID for B.N. Madhusudhan: ORCID iD orcid.org/0000-0002-2570-5934
ORCID for Sharif Ahmed: ORCID iD orcid.org/0000-0002-3290-3592
ORCID for Timothy Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 02 Nov 2018 17:30
Last modified: 08 Oct 2020 04:12

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