Active geophysical prospecting system

• US 7,262,602 B2
• Filed: 07/08/2005
• Issued: 08/28/2007
• Est. Priority Date: 07/08/2005
• Status: Expired due to Fees

• Current Assignee: David Gary Meyer
• Original Assignee: David Gary Meyer
• Inventors: Meyer, David Gary
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): WHITTINGTON, KENNETH
• Application Number:
  US11/177,372
• Publication Number:
  US 20070007966A1
• Time in Patent Office: 781 Days
• Field of Search: 324/326, 324/330, 324/332, 324334-337, 324/344, 342/22
• 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, wherein said incidence station has an angle of incidence which results in other than normal incidence, and capable of transmitting electromagnetic waves of a transmit explicit polarization state with said polarization state depending upon the transmit antenna'"'"'s orientation and at varying specific frequencies wherein the transmit antenna is capable of rotation in a plane orthogonal to a transmit propagation line;

at least one movable receive antenna, capable of receiving electromagnetic waves reflected from said subterranean formations of a receive explicit polarization state with said polarization state depending upon the receive antenna'"'"'s orientation, and at said varying specific 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 a receive propagation line;

means for transmitting said electromagnetic waves of said transmit explicit polarization state at said varying specific frequencies from said transmit antenna;

means for receiving reflected electromagnetic waves of said receive explicit polarization state at said specific frequencies from said receive antenna as data; and

,

means for manipulating said data such that the differences in intensity and polarization state between the transmitted and the received electromagnetic waves of varying specific frequencies at said explicit polarization states are used to map subterranean topology and identify geologic composition of the layers to determine the physical characteristics and geological composition of subterranean formations.

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. The system of claim 1 further comprising means for controlling said emitting means and/or said receiving means and/or for processing said data effective to reduce ionospheric affects.

8. 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, wherein said incidence station has an angle of incidence which results in other than normal incidence, electromagnetic waves in at least one frequency and at least two distinct far-field polarization states wherein said polarization states depend upon the transmit antenna'"'"'s orientation;

receiving, at a mobile receive antenna, held stationary at an incidence station during reception, electromagnetic waves reflected from said subterranean formations in at least said one frequency and said at least two distinct polarization states wherein said polarization states depend upon the transmit antenna'"'"'s orientation as data; and

manipulating said data such that the differences in intensity and said polarization states between the transmitted and the received electromagnetic waves of varying specified frequencies at explicit polarization states are used to map subterranean topology and identify geologic composition of the layers to determine the physical characteristics and geological composition of subterranean formations.

9. The method of claim 8 comprising the further step of varying said incidence station by varying the angle of revolution about the centerline.

10. The method of claim 8 wherein repeatable data is retained and non-repeatable data is excluded.

11. The method of claim 8 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 8 wherein said transmit antenna and said receive antenna are line antennas each separately suspended between two aerial, maneuverable platforms.

13. The method of claim 8 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 reflected electromagnetic wave are ascertained.

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

15. The method of claim 8 further comprising the step of controlling said transmitted or received electromagnetic wave pulses and/or processing said data to minimize ionospheric affects.

16. A system for determining subsurface strata thicknesses and chemical compositions associated with changes in intensity and polarization of transmitted and received electromagnetic waves at varying, specific frequencies comprising:

means for transmitting, in the far-field, polarized electromagnetic waves at varying specific frequencies from an elevated, and specifically oriented and positioned, spatial antenna system about a prospecting point in an incidence station that has an angle of incidence which results in other than normal incidence;

means for receiving polarized electromagnetic waves reflected from said subsurface strata of an explicit polarization state of varying specific frequencies from an elevated, and specifically oriented and positioned, spatial antenna system about a prospecting point as data; and

means for manipulating said data such that the changes in intensity and polarization of received electromagnetic waves at varing, specific frequencies are used to obtain a three-dimensional stratigraphy and geological layer composition of subterranean formations.

17. The system of claim 16 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 16 further comprising a frequency/time duality for not resolving deep features to the same detail as shallow features.

19. The system of claim 16 wherein repeatable data is retained and non-repeatable data is excluded.

20. The system of claim 16 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.

21. The system of claim 16 wherein said specific frequencies range from about 30 Hz to 800 KHz.

22. The system of claim 16 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.

23. The system of claim 16 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.

24. A system for determining the physical characteristics and geological composition of subterranean formations comprising:

a) at least one movable transmit antenna, positioned in the far-field of a prospecting point, wherein said movable transmit antenna is capable of

i) transmitting electromagnetic waves at specified frequencies,

ii) transmitting waves of a transmit explicit polarization state wherein said polarization state depends on the orientation of said transmit antenna, and

iii) being held stationary at an incidence station during transmission

wherein said transmit antenna is capable of rotation in a plane orthogonal to the transmit propagation line;

b) at least one movable receive antenna having a far-field polarization state that depends upon said receive antennas orientation, wherein said movable receive antenna is capable of

i) receiving electromagnetic waves reflected from said subterranean formations at said specified frequencies; and

ii) being held stationary at said incidence station during reception,

wherein the receive antenlla is capable of rotation in a plane orthogonal to the receive propagation line;

c) means for transmitting said electromagnetic waves of transmit explicit polarization states at said varying specified frequencies from said transmit antenna;

d) means for receiving said reflected electromagnetic waves of receive explicit polarization states at said specified frequencies from said receive antenna and recording the intensity thereof versus time as receive data;

e) means for changing the transmit polarization state by rotating said movable transmit antenna in the plane orthogonal to the transmit propagation line and holding it stationary for at least one read cycle,

f) means for changing the orientation of the movable receive antenna via rotation in the plane orthogonal to the receive propagation line and holding it stationary in at least two different orientations to accomplish a read cycle;

g) means for gathering a read cycle data record for each distinct read cycle; and

h) means for processing said read cycle data records such that the differences in intensity and polarization state between the transmitted and received electromagnetic waves, as a function of the transmit polarization state and as a function of the said specific frequencies, are used to map subterranean topology and identify geologic composition of the layers to determine the physical characteristics and geological composition of subterranean formations.

25. The system of claim 24 wherein the transmitted electromagnetic waves and/or the received waves are limited in time and/or the read cycle data record is windowed to eliminate reflections off the ionosphere from the read cycle data record.

26. The system of claim 24 wherein said transmit antenna and said receive antenna are line antennas each separately suspended between two aerial, maneuverable platforms.

27. The system of claim 24 wherein repeatable data is retained and non-repeatable data is excluded.

28. The system of claim 24 further comprising a means to collect and process data gathered over two or more distinct angles of incidence by suitable maneuvering of the transmit and receive antennas to affect a change of incidence station.

29. The system of claim 28 further comprising a means to collect and process data gathered at two or more distinct angles of revolution about the centerline by suitable maneuvering of the movable transmit and receive antennas to affect a change of incidence station.

30. A method for mapping 3D topology and geological composition of underground strata comprising the steps of:

a) transmitting, at least one frequency and at least two distinct far-field transmit polarization states from at least one movable transmit antenna, positioned in the far-field of a prospecting point, wherein the movable transmit antenna is capable of

i) transmitting electromagnetic waves at specified frequencies,

ii) being held stationary at an incidence station during transmission,

iii) rotation in a plane orthogonal to a transmit propagation line, and

iv) transmitting waves of transmit explicit polarization states wherein said polarization states depend on the orientation of said transmit antenna;

b) receiving, electromagnetic waves of at least one frequency reflected from said subterranean formations to at least one movable receive antenna, wherein the movable receive antenna is capable of

i) receiving electromagnetic waves reflected from said subterranean formations at said specified frequencies; and

ii) being held stationary at said incidence station during reception,

iii) rotation in a plane orthogonal to the receive propagation line, and

iv) changing said far-field polarization states by rotation in a plane orthogonal to the receive propagation line where said reflected wave'"'"'s polarization depends on the transmit antenna'"'"'s orientation;

c) systematically rotating the at least one movable receive antenna in the plane orthogonal to the receive propagation line to accomplish a read cycle;

d) recording a read cycle data record from said movable receive antenna;

e) identifying the change in intensity between the transmitted waves pulses and their reflections from the subterranean strata in said read cycle data record;

f) varying said specified frequencies of transmission and the Incidence Station of the at least one transmission antenna to ascertain the change in intensity and polarization state between the transmitted electromagnetic waves and their reflections from the subterranean strata as a function of transmission frequency, transmission polarization state, angle of incidence, and revolution about the centerline, and processing said intensity and polarization state change as a function of transmission frequency, transmission polarization state, angle of incidence, and revolution about the centerline into 3D topology and physical composition of subterranean geological strata.

31. The method of claim 30 wherein higher frequencies are used to map shallower features and lower frequencies are used to map deeper features via the skin depth effect.

32. The method of claim 30 wherein repeatable data is retained and non-repeatable data is excluded.

33. The method of claim 30 wherein the transmitted electromagnetic waves and/or the received waves are limited in time and/or the Read Cycle Data Records are windowed to eliminate ionospheric effects.

34. The method of claim 30 comprising the further step of respecting frequency/time duality and not resolving deep features to the same detail as shallow features.

35. The method of claim 30 wherein said transmit antenna and said receive antenna are line antennas each separately suspended between two aerial, maneuverable platforms.