Active marine electromagnetic methods have proven to be a powerful tool to detect resistivity
anomalies associated with gas hydrate. However, because the propagation of electromagnetic
fields for these methods works in the diffusive regime the spatial resolution of the resistivity
structure is limited. So far only bulk electrical properties have been estimated from measured
data, although hydrate bearing layers are found to be highly heterogeneous. We computed
response curves for synthetic one- and two-dimensional models to investigate the resolution
capabilities for various measurement geometries with respect to resistive features. Electric dipole
transmitters (TXs) are used as sources. In the marine case, the in-line electric dipole-dipole
configuration has proven its capabilities to detect the shallow resistive gas-hydrate. Our model
study demonstrates that both the depth to a resistive feature can be resolved nicely using data for
multiple TX-RX offsets. However, resolving smaller features of the resistive zone, for example if
the zone is split in separate resistive layers, is extremely difficult. The resolution of the target can
be improved using electrical downhole transmitters. So far there have been no reports of the
detection of permafrost gas hydrate deposits with surface electromagnetic methods. Our
calculations show that a similar setup to that used in the marine case is capable of detecting gas
hydrate on land. The resolution, however, is lower than for the marine case, because of the
significantly greater depths to the target.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/2472 |
| Date | 07 1900 |
| Creators | Scholl, Carsten, Mir, R., Willoughby, E.C., Edwards, R.N. |
| 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 | Scholl, Carsten |
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