Back to Search
Start Over
Opposing-coils transient electromagnetic method focused near-surface resolution
- Source :
- GEOPHYSICS. 81:E279-E285
- Publication Year :
- 2016
- Publisher :
- Society of Exploration Geophysicists, 2016.
-
Abstract
- The transient electromagnetic (TEM) method is a commonly used, nonintrusive, geophysical method, but inherent mutual induction between the transmitter (TX) and receiver (RX) coils strongly influences the measurements. We have developed an opposing-coils configuration to greatly reduce this effect. Three coils are used in this system. The upper opposing coil is physically the same as the lower TX coil, and they are concentric and parallel to the middle RX coil. A pair of currents with equal amplitudes but reverse directions is injected into the opposing and TX coils. Theoretical calculations in free space show that the received magnetic field by the RX coil is zero, which indicates that the mutual induction effect could be largely reduced. Physical experiments prove that an almost-pure secondary field could be acquired using this system. We have studied an optimal separation between the TX and opposing coils to guarantee that the primary magnetic field is powerful and the instrument is compacted for field work. Then, the efficient exploration depth of this system for typical geoelectric models was simulated to be approximately 15–50 m. Comparisons of simulated responses over highly conductive thick plates in free space and a field test over a culvert structure between this system and EM-47 showed that the system has enhanced sensitivity and lateral resolution. This system can be used in near-surface investigations, e.g., groundwater, environmental, and engineering investigations.
- Subjects :
- Physics
Electromagnetics
business.industry
Transmitter
0211 other engineering and technologies
02 engineering and technology
Concentric
010502 geochemistry & geophysics
01 natural sciences
Magnetic field
Geophysics
Optics
Amplitude
Nuclear magnetic resonance
Geochemistry and Petrology
Electromagnetic coil
Time domain
Transient (oscillation)
business
021101 geological & geomatics engineering
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 19422156 and 00168033
- Volume :
- 81
- Database :
- OpenAIRE
- Journal :
- GEOPHYSICS
- Accession number :
- edsair.doi...........176a692047641193ee8c23babd06c8b9