Electrical Anisotropy Near Boreholes: An Obstacle to Deep Strata Radio Communications.
ARMY ELECTRONICS COMMAND FORT MONMOUTH N J
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The electrical field distribution in the vicinity of a rod antenna suspended in a deep borehole is derived assuming the existence of a stress-strain electrical anisotropy in the earth material near the borehole. It is shown that the electrical field gradient and the stress-strain related gradient of the dielectric permittivity affect the capacitance and conductance of the rod antenna in the borehole. This causes borehole measurements of the electrical characteristics of rock and ice to yield apparent values well below those of the actual intrinsic electrical characteristics of the earth material at the same depth. With increasing depth, both the apparent and the intrinsic electrical characteristics increase rapidly, though at different rates. Hence, the resultant discrepancies become larger, and even slight changes of the intrinsic material properties will be observed as large changes of the apparent characteristics. Similarly, an increasing dependence of the discrepancies on antenna dimensions and borehole diameter is observed with increasing depth. Author
- Electrical and Electronic Equipment
- Radio Communications