Advances in Marine Electromagnetic Instrumentation
Abstract
Marine electromagnetic methods, originally developed by academia to study the oceanic lithosphere, underwent rapid improvement around the turn of the century, supported by industry interest in deepwater hydrocarbon exploration on the continental shelf. A steady decline in offshore exploration over the past decade has inhibited further industry development of marine EM systems, leaving academia to again take the lead, but from a position strengthened by the recent interest and investment in the methods. Continuously towed transmitter and receiver arrays have been particularly successful at imaging the upper kilometer of the seafloor in both deep and shallow water. Targets include permafrost, methane hydrate, groundwater, and even shallow hydrocarbons such as gas and tar seeps. Precise control of timing and navigation allow data to be fit to around 1% in amplitude and half a degree in phase. Sensitivity to electrical anisotropy has become a particularly useful diagnostic tool, as permafrost and gas hydrate can have anisotropies that are an order of magnitude larger than the surrounding sediment. Recent advances in instrumentation will be reviewed, and a portfolio of examples will be presented to illustrate the utility of the marine EM method for imaging near-surface geology.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMNS012..01C
- Keywords:
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- 0920 Gravity methods;
- EXPLORATION GEOPHYSICS;
- 0925 Magnetic and electrical methods;
- EXPLORATION GEOPHYSICS;
- 0935 Seismic methods;
- EXPLORATION GEOPHYSICS;
- 0999 General or miscellaneous;
- EXPLORATION GEOPHYSICS