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Numerical Study of Electromagnetic Waves Generated By a Prototype Dielectric Logging Tool

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Abstract:To understand the electromagnetic waves generated by a prototype dielectric logging tool, a
numerical study was conducted using both the finite-difference, time-domain method and a frequency- wavenumber method. When the propagation velocity in the borehole was greater than that in the formation (e.g., an air-filled borehole in the unsaturated zone), only a guided wave propagated along the borehole. As the frequency decreased, both the phase and the group velocities of the guided wave asymptotically approached the phase velocity of a plane wave in the formation. The guided wave radiated electromagnetic energy into the formation, causing its amplitude to decrease. When the propagation velocity in the borehole was less than that in the formation (e.g., a water-filled borehole in the saturated zone), both a refracted wave and a guided wave propagated along the borehole. The velocity of the refracted wave equaled the phase velocity of a plane wave in the formation, and the refracted wave preceded the guided wave. As the frequency decreased, both the phase and the group velocities of the guided wave asymptotically approached the phase velocity of a plane wave in the formation. The guided wave did not radiate electromagneticenergy into the formation. To analyze traces recorded by the prototype tool during laboratory test, they were compared to traces calculated with the finite differences method. The first parts of both the recorded and the calculated traces were similar, indicating that guided and refracted waves indeed propagated along the prototype tool.
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Citation:Ellefsen, K. J., J. D. Abraham, D. L. Wright, and A. T. Mazzella. Numerical Study of Electromagnetic Waves Generated By a Prototype Dielectric Logging Tool. GEOPHYSICS 69(1):64-77, (2004).
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Characterization & Monitoring Branch
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Product Type: Journal
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Published: 07/20/2004
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Related Entries:
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Bullet Item Ground-Water Sampling and Geophysical Methods Development and Evaluation
spacer Relationship Reason:   A Project of the Product
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