Frequency Dependence of Electrical Rock Parameters in the VLF Range.
Abstract
The effect of induced polarization (IP) is used to prove electrically at the in situ rock, concentration and grain size of polarizable material in dead rock. For this purpose a sinusoidal alternating current (0.01 Hz to 10 kHz) is fed into a Wenner array. The potential difference measured between 1/3 and 2/3 of the total distance is compared with the feeding current in amplitude and phase. Exact phase velocity measurements at VLF waves increase the resolution for the measurements of the electric rock parameters by several powers of ten as compared to previous methods. A special type of unsymmetrical small self-resonant helical antenna was designed for measuring the electrical properties of the rock surrounding the borehole from changes in the electrical properties of the helical antenna. The electronic transducer for the determination of the antenna impedance as a function of the frequency is built into the helix. Measuring equipment and applicability are described.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1975
- Accession Number
- ADA022995
Entities
People
- Dieter Fritz
- Michael Oberladstatter
- Norbert H. Nessler
Organizations
- University of Innsbruck