System and method for receiving and decoding electromagnetic transmissions within a well

• US 20080253230A1
• Filed: 04/13/2007
• Published: 10/16/2008
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Thompson, M. Clark, Coates, Don M., Beck, David W.
• Granted Patent: US 8,106,791 B2
• Time in Patent Office: Days
• US Class Current: 367/129
• CPC Class Codes: E21B 47/13 by electromagnetic energy, e.g. radio frequency
• CPC Class Codes: G01V 11/002 Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B

Abstract

Exemplary systems and methods are directed to transmission of electromagnetic (EM) pulses in a downhole environment, which is located below a surface of a landform. A sequence of EM energy pulses is generated from a signal generator located at the surface of the landform. The energy pulses are reflected at a ring frequency by one or more downhole transducers. The reflected energy pulse is received at a receiver, which is located at the surface, during a predetermined time interval. The receiver detects the received energy pulses through a time domain or frequency domain technique. The detected ring frequency is correlated to a parameter or condition of the downhole environment.

Claims

1. A method for interrogating a downhole environment below a surface of a landform, the method comprising the steps of:

directing at least one electromagnetic energy pulse into a downhole environment such that the electromagnetic energy pulse interacts with at least one downhole transducer such that at least some of the electromagnetic energy contained within the pulse is reflected at a ring frequency determined by the at least one downhole transducer;

receiving the reflected energy pulse at a receiver located at the surface of the landform during a predetermined time interval;

processing the received energy pulse to extract the ring frequency using a processing method selected from the group consisting of time domain tracking, frequency domain tracking, and combinations thereof; and

correlating the ring frequency to a parameter of the transducer, wherein said parameter further correlates to a condition in the downhole environment.

2. The method of claim 1, wherein the processing is carried out using time domain tracking, and wherein the predetermined time interval is synchronized based on a depth-determined delay of the reflected energy pulse.

3. The method of claim 2, further comprising recording the ring frequency of the reflected energy pulse.

4. The method of claim 2, wherein the receiving step comprises controlling a gating of the receiver based on a delay preset.

5. The method of claim 2, wherein the receiving step comprises excluding low power signals that are equal or nearly equal to the ring frequency.

6. The method of claim 2, wherein the reflected energy pulses are generated at a frequency within a range of 10 MHz to 100 KHz.

7. The method of claim 1, wherein the processing step is carried out using frequency domain tracking, and wherein the receiving step involves locking onto the ring frequency of the reflected energy pulse.

8. The method of claim 7, wherein the reflected energy pulses are generated at a frequency within a range of 10 MHz to 100 KHz.

9. The method of claim 7, wherein the receiving step comprises controlling a gating of the receiver based on a depth determined delay of the reflected energy pulse.

10. The method of claim 7, wherein the locking step comprises comparing the ring frequency of the reflected energy pulse with a desired frequency.

11. The method of claim 10, wherein the ring frequency is locked when a result of the correlating is within a tolerance range.

12. The method of claim 7, wherein the receiver maintains the locked ring frequency when outside of the predetermined time interval.

13. The method of claim 7, wherein the receiving step comprises synchronizing the predetermined time interval with a depth determined delay of the reflected energy pulse.

14. The method of claim 7, wherein the correlating comprises addressing a look-up table based on a value of the locked ring frequency.

15. The method of claim 1, wherein the at least one downhole transducer comprises at least one inductive component and at least one capacitive component.

16. The method of claim 15, wherein the ring frequency of the at least one transducer is modulated by environmentally-induced changes to the capacitive component of said transducer.

17. The method of claim 1, wherein the step of processing the received energy pulse comprises a sub-step of digitizing information contained within the received energy pulse using algorithms that can enhance signal-to-noise.

18. The method of claim 1, further comprising a step of relaying information contained within the received energy pulse, as a signal, to a remote surface receiver.

19. A system for interrogating a downhole environment, which is located below a surface of a landform, based on at least one energy pulse that is reflected at a modulation frequency from at least one downhole transducer to the surface of the landform, the system comprising:

a means for receiving the modulated energy pulse at the surface during a predetermined time interval;

a means for processing the received energy pulse to extract the modulation frequency; and

a means for correlating the modulation frequency of the energy pulse to a parameter of the transducer or a characteristic of the downhole environment.

20. The method of claim 19, wherein the at least one downhole transducer comprises at least one inductive and capacitive resonant structure.

21. The method of claim 20, wherein the at least one inductive structure isolates production tubing from casing in the downhole environment.

22. The system of claim 19, further comprising a means for controlling a gating of the receiving means based on a depth determined delay of the reflected energy pulse.

23. The system of claim 22, wherein the receiving means comprises a means for locking onto the modulation frequency of the energy pulse when the modulation frequency is within a threshold.

24. The system of claim 22, wherein the processing means is configured to exclude low power signals that are equal or nearly equal to the modulation frequency.

25. The system of claim 24, comprising a means for comparing the modulation frequency with a desired modulation frequency.

26. The system of claim 23, wherein the means for locking locks on the modulation frequency when a result produced by the comparing means is within a tolerance range.

27. The system of claim 19, said system comprising two or more downhole transducers having different resonant ring frequencies.

28. The system of claim 19, further comprising a means for actuating a device downhole, wherein said actuation is effected by an electromagnetic energy pulse that rings a transducer coupled to said device.

29. The system of claim 19, further comprising a directional wave coupler to minimize spurious signal reflections.

30. An apparatus for interrogating a downhole environment located below a surface of a landform, the apparatus being included in a system that transmits energy pulses to at least one downhole transducer which modulates the energy pulses and returns the modulated energy pulses to a location at the surface of the landform, the apparatus comprising:

a means for receiving the modulated energy pulses at the surface;

a means for sampling the modulated energy pulses;

a means for detecting a modulating frequency of the sampled energy pulses; and

a means for correlating the modulating frequency to conditions of the downhole environment.

31. An apparatus for interrogating a downhole environment located below a surface of a landform, the apparatus being included in a system that transmits energy pulses to at least one downhole transducer which modulates the energy pulses and returns the modulated energy pulses to a location at the surface of the landform, the apparatus comprising:

a means for receiving the modulated energy pulses at the surface;

a means for locking onto a modulating frequency of the energy pulses when the modulating frequency is within a tolerance range; and

a means for correlating the modulating frequency to conditions of the downhole environment.