Active geophysical prospecting system

• US 20070007966A1
• Filed: 07/08/2005
• Published: 01/11/2007
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: David Meyer
• Original Assignee: David Meyer
• Inventors: Meyer, David
• Granted Patent: US 7,262,602 B2
• Time in Patent Office: Days
• US Class Current: 324/337
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

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.

Claims

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.

2. The system of claim 1 further comprising means for positioning said transmit antenna and said receive antenna to affect at least two angles of incidence and reflection.

3. The system of claim 1 further comprising means for positioning said transmit antenna and said receive antenna to affect at least two angles of revolution about a centerline.

4. The system of claim 1 wherein said transmit antenna and said receive antenna are line antennas each separately suspended between two aerial, maneuverable platforms.

5. The system of claim 1 wherein repeatable data is retained and non-repeatable data is excluded.

6. The system of claim 1 further comprising a frequency/time duality for not resolving deep features to the same detail as shallow features.

7. A method for determining the physical characteristics and geological composition of subterranean formations comprising the steps of:

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.

8. The method of claim 7 comprising the further step of varying said incidence station by varying the angle of incidence.

9. The method of claim 7 comprising the further step of varying said incidence station by varying the angle of revolution about the centerline.

10. The method of claim 7 wherein repeatable data is retained and non-repeatable data is excluded.

11. The method of claim 7 comprising the further step of employing a frequency/time duality for not resolving deep features to the same detail as shallow features.

12. The method of claim 7 wherein said transmit antenna and said receive antenna are line antennas each separately suspended between two aerial, maneuverable platforms.

13. The method of claim 7 wherein for each configuration within a plane orthogonal to the transmit propagation line required of the transmit antenna to transmit a polarized electromagnetic wave, the receive antenna rotates in a plane orthogonal to the receive propagation line such that the intensity, and the polarization state of the received pulse are ascertained.

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.

15. The system of claim 14 wherein the antenna system is a line antenna system comprising a transmit line antenna and a receive line antenna, each separately suspended between two aerial platforms.

16. The system of claim 14 wherein the ionospheric effect is mitigated by regulating the transmit duration, and/or the receive duration and or/data manipulation as a function of a transmission timeline.

17. The system of claim 14 further comprising transmitting in a set of prospecting frequencies at two or more angles of incidence and reflection and two or more angles of revolution about a centerline.

18. The system of claim 14 further comprising a frequency/time duality for not resolving deep features to the same detail as shallow features.

19. The system of claim 14 wherein repeatable data is retained and non-repeatable data is excluded

20. The system of claim 14 wherein for each configuration within a plane orthogonal to the transmit propagation line required of the transmit antenna to transmit a polarized electromagnetic wave, the receive antenna rotates in a plane orthogonal to the receive propagation line such that the intensity and the polarization state of the received pulse is ascertained.