Method and system for radio-imaging underground geologic structures

• US 6,593,746 B2
• Filed: 01/15/2002
• Issued: 07/15/2003
• Est. Priority Date: 08/27/2001
• Status: Expired due to Fees

• Current Assignee: Larry G. Stolarczyk
• Original Assignee: Larry G. Stolarczyk
• Inventors: Stolarczyk, Larry G.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US10/047,073
• Publication Number:
  US 20030062902A1
• Time in Patent Office: 546 Days
• Field of Search: 324/330, 324/331, 324/334, 324/335, 324/357, 324/202, 324/338, 324/339
• US Class Current: 324/334
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A coal bed anomaly detection and imaging system comprises a synchronous transmitter and receiver that are separated by a geologic structure with embedded and hidden anomalies. The transmitter sends out two signals from magnetic dipole antennas. Such signals are widely separated in frequency but synchronized internally in the transmitter to one another. The higher frequency is used to make phase shift and attenuation measurements at the receiver by synchronous detection. The lower frequency is used at the receiver to synchronize the receiver to the transmitter. The higher frequency signal is measurably affected by anomalies in the intervening geologic structure. The lower frequency signal is fixed low enough so it is not substantially affected by the intervening geologic structure. Geologic modeling tools are preferably downloaded by geoscientists to their personal computers. The total attenuation and phase shift measurements are plugged into a full-wave inversion code (FWIC) process. A hypothetical model is uploaded for processing by a forward solver so the nature of the anomalous geologic structure can be estimated. A resulting reconstructed image of the anomalies in silhouette is then downloaded for interpretation of the image by the geoscientist.

Claims

1. An anomaly sensing system, comprising:

a transmitter providing for at least one RF-probe signal and one RF-synchronizing signal at substantially different carrier frequencies and yet synchronous to one another;

a coherent receiver having a frequency synthesizer able to lock on to said RF-synchronizing signal and providing for synchronous detection of said RF-probe signal; and

a measurement device for detecting attenuation and phase shift affects on said RF-probe signal by an anomalous media that intervenes between the transmitter and receiver;

wherein, synchronization between the transmitter and coherent receiver is accomplished wirelessly and without a synchronizing cable, and such synchronization provides for the detection and measurement of small sinusoidal signals embedded in electrical noise, and synchronous detection is used in the receiver to measure the attenuation rate (alpha) and phase shift (beta) of an electromagnetic wave propagating between the transmitting and a receiving magnetic dipole antenna can be measured; and

wherein, images of geologic structure are constructed by dividing a geologic region into pixels or boxels include a lane or volume between location visited by the receiver and transmitter, and lines between the locations visited represent the edges of the image plane, and the depths width and height of each pixel or boxel is arbitrary, but is usually made unequal to the physical space between each transmitter and receiver location, and the electromagnetic wave propagation constants in each pixel are determined by an image reconstruction process that does not require a straight ray path assumption and that accounts for electromagnetic wave propagation phenomena of refraction, reflection, and scattering in a geologic target.

2. The system of claim 1, wherein:

the transmitter is disposed in a first passageway in an underground coal mine;

the receiver is disposed in a second passageway in an underground coal mine; and

the measurement device provides for measurements of any anomalies lying between said first and second passageways.

3. The system of claim 1, wherein:

the transmitter visits a number of locations in a first passageway in an underground coal mine;

the receiver visits a number of locations in a second passageway in an underground coal mine; and

the measurement device provides for tomographic measurements of anomalies intersected by ray paths between said locations along said first and second passageways.

4. The system of claim 1, further comprising:

a drillstring and drillhead for drilling boreholes in coal deposits, and which carries the transmitter along a number of transmitting locations in a borehole in an underground coal mine.

5. The system of claim 1, wherein:

the transmitter is attached to a drillhead in a borehole for transmitting from a number of different locations an underground coal mine.

6. The system of claim 1, wherein:

the receiver is disposed in a borehole and provides for reception of signals from the transmitter in another borehole in an underground coal mine.

7. The system of claim 1, further comprising:

means for repositioning the receiver in a borehole, and that provides for reception of signals from the transmitter in another borehole in an underground coal mine.

8. The system of claim 1, further comprising:

a tomographic processor for generating an image of any anomaly in said anomalous media that was intersected by said RF-probe signal.

9. The system of claim 1, wherein:

the transmitter and receiver are such that said RF-probe signal is at a carrier frequency that is substantially affected in signal amplitude and phase by anomalies in said anomalous media that are intersected by said RF-probe signal.

10. The system of claim 1, wherein:

the transmitter and receiver are such that said RF-synchronizing signal is at a carrier frequency that is not substantially affected in signal amplitude and phase by anomalies in said anomalous media.

11. The system of claim 1, further comprising:

a synchronous detector disposed in the receiver and able to use said RF-synchronizing signal to measure the strength and phase of said RF-probe signal.

12. The system of claim 1, further comprising:

a tomographic image reconstruction processor for employing full-wave inversion code (FWIC) to account for the affects of refraction, reflection, and bending of said RF-probe signal between the transmitter and receiver.

13. The system of claim 1, further comprising:

a tomographic image-reconstruction processor for displaying a graphic representation of an anomaly that lies hidden in the ground between the transmitter and receiver.

14. The system of claim 1, further comprising:

means for using simple layered models of hypothetical geology and introducing a suspect geologic anomaly into a generic model to determine its electromagnetic wave response using mathematical forward modeling code in which the forward model output is the total electromagnetic wave fields measurable at each receiver location.

15. The system of claim 14, further comprising:

means for processing modeled data with full-wave inversion code (FWIC) to form a hypothetical image.