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Title: Method and apparatus for geophysical exploration in drill holes by means of very low frequency waves

Abstract

A method and apparatus for geophysical exploration that does not require the installation of a low-frequency transmission source in the proximity of the drill hole are disclosed. A surface pick-up detects the magnetic field component of a low-frequency signal, which, after amplification and filtering, is supplied as one input of a comparator. A pick-up disposed in a drill hole detects the corresponding magnetic field components within the earth, and its output is supplied as the other comparator input. The amplitude ratios of the signals and their phase difference are provided at the outputs of the comparator. These values make it possible to determine the resistivity variations of the ground. The extent of the detected conductivity layer(s) may be determined by repeating the operation by using a second low-frequency transmitter positioned at a different azimuth angle from the first, and comparing the output readings. 2 figures.

Inventors:
Publication Date:
OSTI Identifier:
5156061
Patent Number(s):
US 3984758
Assignee:
Bureau de Recherches Geologiques et Minieres TIC; EDB-80-108315
Resource Type:
Patent
Resource Relation:
Patent Priority Date: Priority date 14 Jun 1974, France
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; BOREHOLES; ELECTROMAGNETIC SURVEYS; EARTH CRUST; ELECTRIC CONDUCTIVITY; HZ RANGE; LOGIC CIRCUITS; RADIOWAVE RADIATION; CAVITIES; ELECTRICAL PROPERTIES; ELECTRICAL SURVEYS; ELECTROMAGNETIC RADIATION; ELECTRONIC CIRCUITS; FREQUENCY RANGE; GEOPHYSICAL SURVEYS; PHYSICAL PROPERTIES; RADIATIONS; SURVEYS; 580203* - Geophysics- Geophysical Survey Methods- (1980-1989)

Citation Formats

Millon, R.F. Method and apparatus for geophysical exploration in drill holes by means of very low frequency waves. United States: N. p., 1976. Web.
Millon, R.F. Method and apparatus for geophysical exploration in drill holes by means of very low frequency waves. United States.
Millon, R.F. Tue . "Method and apparatus for geophysical exploration in drill holes by means of very low frequency waves". United States.
@article{osti_5156061,
title = {Method and apparatus for geophysical exploration in drill holes by means of very low frequency waves},
author = {Millon, R.F.},
abstractNote = {A method and apparatus for geophysical exploration that does not require the installation of a low-frequency transmission source in the proximity of the drill hole are disclosed. A surface pick-up detects the magnetic field component of a low-frequency signal, which, after amplification and filtering, is supplied as one input of a comparator. A pick-up disposed in a drill hole detects the corresponding magnetic field components within the earth, and its output is supplied as the other comparator input. The amplitude ratios of the signals and their phase difference are provided at the outputs of the comparator. These values make it possible to determine the resistivity variations of the ground. The extent of the detected conductivity layer(s) may be determined by repeating the operation by using a second low-frequency transmitter positioned at a different azimuth angle from the first, and comparing the output readings. 2 figures.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Oct 05 00:00:00 EDT 1976},
month = {Tue Oct 05 00:00:00 EDT 1976}
}