Transient radiation from an unloaded, finite dipole antenna in a borehole: Experimental and numerical results

Sixin Liu, Motoyuki Sato

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Dipole antennas in boreholes are used for tomographic imaging or electromagnetic well logging. A cylindrically layered structure within the borehole will change the radiation characteristics of a dipole antenna. Our objective is to understand the effects of the borehole structure upon the impedance, waveform distortion, and directivity patterns of a dipole antenna. We use a finite-difference, time-domain (FDTD) technique to simulate borehole-antenna radiation, while the geometry of both the dipole and the borehole are modeled with a subgrid technique. The simulated input impedances are verified by experimental results. Both the water-filled and the air-filled boreholes distort the radiated wavefronts, waveforms, and resonant frequencies relative to the same characteristics of a dipole in homogeneous media. A water-filled borehole lowers the first resonant frequency, while an air-filled borehole raises it. At high frequencies, the antenna in the water-filled borehole exhibits radiation side lobes. The borehole effects for water- and air-filled boreholes differ and should not be neglected for borehole antenna design.

Original languageEnglish
Pages (from-to)K43-K51
JournalGeophysics
Volume70
Issue number6
DOIs
Publication statusPublished - 2005

ASJC Scopus subject areas

  • Geochemistry and Petrology

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