Active geophysical prospecting system
First Claim
1. A system for determining the physical characteristics and geological composition of subterranean formations comprising:
- at least one movable transmit antenna in the far-field of a prospecting point capable of being held stationary at an incidence station during transmission, and capable of transmitting electromagnetic waves of an explicit polarization at specified frequencies wherein the transmit antenna is capable of rotation in a plane orthogonal to the transmit propagation line;
at least one movable receive antenna, capable of receiving electromagnetic waves of said explicit polarization at said specified frequencies and capable of being held stationary at said incidence station during reception, wherein the receive antenna is capable of rotation in a plane orthogonal to the receive propagation line;
means for transmitting said electromagnetic waves of an explicit polarization state at said specified frequencies from said transmit antenna;
means for receiving said electromagnetic waves of an explicit polarization state at said specified frequencies from said receive antenna as data; and
means for controlling said emitting means and/or said receiving means and/or for processing said data effective to reduce ionospheric affects.
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Abstract
An active system and method for determining the physical characteristics and geological composition of subterranean formations is described. Plane polarized electromagnetic waves at specific frequencies are transmitted by a mobile transmitting antenna held stationary in the far-field about a prospecting point. The plane polarized electromagnetic waves penetrate the Earth and return to the surface to be picked up at a separate mobile receiving antenna held stationary about a prospecting point. The differences in intensity and polarization between transmitted and received waves are measured and carry geological information. Further, a coordinated series of transmissions, receptions, and measurements are made, in which the angle of incidence and the revolution angle about a centerline emanating perpendicularly from the prospecting point are carefully and systematically varied and repeated for a specific set of frequencies. The entire data set is processed to give stratigraphy and geological composition in three-dimensions including, for example, the location of commercially important ore deposits or reservoirs of oil and gas. The transmission time, the reception time, and/or the data window are controlled to minimize the ionospheric effect. The method seeks the steady, repeatable part of a received signature and changes in the received signal for two or more identical probing transmissions are filtered out, as unwanted noise. The system employs a frequency/time duality for not resolving deep features to the same detail as shallow features.
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Citations
20 Claims
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1. A system for determining the physical characteristics and geological composition of subterranean formations comprising:
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at least one movable transmit antenna in the far-field of a prospecting point capable of being held stationary at an incidence station during transmission, and capable of transmitting electromagnetic waves of an explicit polarization at specified frequencies wherein the transmit antenna is capable of rotation in a plane orthogonal to the transmit propagation line;
at least one movable receive antenna, capable of receiving electromagnetic waves of said explicit polarization at said specified frequencies and capable of being held stationary at said incidence station during reception, wherein the receive antenna is capable of rotation in a plane orthogonal to the receive propagation line;
means for transmitting said electromagnetic waves of an explicit polarization state at said specified frequencies from said transmit antenna;
means for receiving said electromagnetic waves of an explicit polarization state at said specified frequencies from said receive antenna as data; and
means for controlling said emitting means and/or said receiving means and/or for processing said data effective to reduce ionospheric affects. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining the physical characteristics and geological composition of subterranean formations comprising the steps of:
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transmitting, from a mobile transmit antenna, held stationary at an incidence station during transmission, electromagnetic wave pulses in at least one frequency and at least two distinct far-field polarizations;
receiving, at a mobile receive antenna, held stationary at an incidence station during reception, electromagnetic wave pulses in at least said one frequency and said at least two distinct polarization states as data; and
controlling said transmitted or received electromagnetic wave pulses and/or processing said data to minimize ionospheric affects. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A system for determining subsurface strata thicknesses and chemical compositions associated with changes in intensity and polarization of transmitted electromagnetic waves comprising:
- means for transmitting, in the far-field, and receiving polarized electromagnetic waves from an elevated, and specifically oriented and positioned, spatial antenna system about a prospecting point such that a three-dimensional stratigraphy and geological layer composition of subterranean formations is obtained.
- View Dependent Claims (15, 16, 17, 18, 19, 20)
Specification