Small-scale morphology of gas hydrate is important for understanding the formation of gas
hydrate deposits, for estimating the concentrations of gas hydrate from geophysical data, and for
predicting their response to climate change or commercial production. The recent use of borehole
pressure coring tools has allowed marine gas-hydrate-bearing sediments to be recovered with
centimeter to sub-millimeter gas hydrate structures preserved in their in situ condition. Once
these sediment samples are recovered at in situ temperature and pressure, nondestructive
analyses, including gamma density, P-wave velocity, and X-ray imaging, are used to examine the
character of the gas hydrate relative to the structure of the surrounding sediment. Gas hydrate
morphology from pressure core data is summarized from the recent national gas hydrate
expeditions of India, China, and Korea, as well as from Ocean Drilling Program Leg 204,
Integrated Ocean Drilling Program Expedition 311, and the Gulf of Mexico Chevron-Texaco
Joint Industry Project. The most striking result is the variability of gas hydrate morphology in
clay, ranging from complex vein structures to an invisible pore-filling matrix. Both of these
morphologies have been observed in clay sediments at gas hydrate saturations equivalent to
30-40% of pore volume. A clear knowledge of detailed gas hydrate morphology will provide
important data to help determine the mechanisms of gas hydrate deposit formation and also
provide crucial data for modeling the kinetics of deposit dissociation, from both natural and
artificial causes. The morphology also has large effects on sedimentary physical properties, from
seismic velocities on a large scale to borehole electrical resistivities on a smaller scale, and gas
hydrate morphology will therefore impact estimation of gas hydrate saturation from geophysical
data. The detailed morphology of gas hydrate is an essential component for a full understanding
of the past, present, and future of any gas hydrate environment.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1201 |
| Date | 07 1900 |
| Creators | Holland, Melanie, Schultheiss, Peter, Roberts, John, Druce, Matthew |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Holland, Melanie |
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