Measurement of subterranean lithology using electromagnetic energy
First Claim
1. An apparatus for measuring the electrical properties of subsurface geologic formations and media within the interstices of the geologic formation comprising the following:
- a. means for moving the apparatus though the axial length of an uncased borehole;
b. an electromagnetic antenna having a first side and a second side and comprising material that is electrically conductive and magnetically permeable;
c. a magnetic flux transmitter proximate to the first side of the electromagnetic antenna for engaging the antenna material with magnetic flux sufficient to reduce the magnetic permeability of at least a portion of the antenna material;
d. a second magnetic flux transmitter proximate to the antenna material area having reduced magnetic permeability capable of inducing eddy currents in the antenna material that emit an electromagnetic wave from the second side of the antenna material; and
e. at least one electromagnetic wave receiver located near the first side of the antenna to detect any return oscillating magnetic flux engaging with the second side of the antenna.
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Abstract
The invention subject of this application pertains to a method and apparatus for measuring the subterranean lithology using electromagnetic energy. The invention is applicable to the measurement from within uncased boreholes, i.e., and open-holes. The present invention transmits and receives electromagnetic energy deep into a geologic formation from a borehole, while also providing high resolution for distant measurements and the ability to control the direction in which the measurements are taken. The invention does not require a receiver to be located at the ground surface or in another borehole. In simple terms, the apparatus of this invention is able to “look around” into the surrounding geologic formation from a stationary position.
35 Citations
15 Claims
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1. An apparatus for measuring the electrical properties of subsurface geologic formations and media within the interstices of the geologic formation comprising the following:
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a. means for moving the apparatus though the axial length of an uncased borehole;
b. an electromagnetic antenna having a first side and a second side and comprising material that is electrically conductive and magnetically permeable;
c. a magnetic flux transmitter proximate to the first side of the electromagnetic antenna for engaging the antenna material with magnetic flux sufficient to reduce the magnetic permeability of at least a portion of the antenna material;
d. a second magnetic flux transmitter proximate to the antenna material area having reduced magnetic permeability capable of inducing eddy currents in the antenna material that emit an electromagnetic wave from the second side of the antenna material; and
e. at least one electromagnetic wave receiver located near the first side of the antenna to detect any return oscillating magnetic flux engaging with the second side of the antenna. - View Dependent Claims (2, 3, 4, 5)
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6. The apparatus of claim one wherein the magnetic permeability of the antenna material is variably reduced.
- 7. The apparatus of claim one wherein the magnetic permeability of the antenna material is variably reduced across the surface of the second side.
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9. A method for measuring the electrical properties of subsurface geologic formations and media within the interstices of the geologic formation comprising the steps of:
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(a) moving an apparatus containing an antenna having a first side and a second side and comprising material that is electrically conductive and magnetically permeable, a magnetic flux generator, an oscillating magnetic flux transmitter, and an electromagnetic wave receiver for detecting magnetic flux though the axial length of an uncased borehole;
(b) creating at least one magnetic flux near a first side of an antenna;
(c) engaging at least a portion of the antenna with the magnetic flux to reduce the magnetic permeability of the antenna;
(d) transmitting separate oscillating magnetic flux from the first side of the antenna into the area of reduced permeability of the antenna thereby inducing eddy currents within the antenna that create separate oscillating electromagnetic wave emitted from the second side of the antenna; and
(e) detecting any return oscillating magnetic flux engaging with the second side of the antenna. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification