Detection Of Strain In Fiber Optics Cables Induced By Narrow-Band Signals

• US 20170268944A1
• Filed: 09/14/2015
• Published: 09/21/2017
• Est. Priority Date: 09/14/2015
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Nunes, Leonardo de Oliveira, Barfoot, David Andrew, Ellmauthaler, Andreas, Martinez, Yenny Natali, Lan, Xinwei
• Granted Patent: US 9,976,920 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 43/20 Displacing by water
• CPC Class Codes: E21B 47/005 Monitoring or checking of cementation quality or level
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: E21B 47/12 Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
• CPC Class Codes: E21B 49/08 Obtaining fluid samples or testing fluids, in boreholes or wells
• CPC Class Codes: E21B 49/0875 determining specific fluid parameters
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings

Abstract

A method may include transmitting a narrowband signal into a formation using a transmitter located in a wellbore. The narrowband signal is modified by passage of through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency. The method also includes sensing the modified narrowband signal with an optical waveguide positioned in the wellbore, transmitting a source signal along a length of the optical waveguide, and obtaining a backscattered return signal from the optical waveguide. The backscattered return signal is sampled at a second frequency that is less than the Nyquist rate of the modified narrowband signal. The method further includes processing the backscattered return signal to obtain an amplitude of the modified narrowband signal.

Claims

1. A method, comprising:

transmitting a narrowband signal into a formation using a transmitter located in a wellbore, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency;

sensing the modified narrowband signal with an optical waveguide positioned in the wellbore;

transmitting a source signal along a length of the optical waveguide and obtaining a backscattered return signal from the optical waveguide, the backscattered return signal being sampled at a second frequency that is less than a Nyquist rate of the modified narrowband signal; and

processing the backscattered return signal to obtain an amplitude of the modified narrowband signal sensed with the optical waveguide.

2. The method of claim 1, further comprising processing the backscattered return signal to obtain the amplitude of the modified narrowband signal independent of the first frequency of the modified narrowband signal.

3. The method of claim 1, wherein sensing the modified narrowband signal on the optical waveguide comprises inducing strain in the optical waveguide via the modified narrowband signal.

4. The method of claim 1, further comprising processing the backscattered return signal using interferometric phase modulation techniques.

5. The method of claim 1, wherein processing the backscattered return signal comprises filtering the backscattered return signal using a low-pass filter having a cut off frequency equal to or below the first frequency.

6. The method of claim 1, further comprising controlling the transmitter to vary the amplitude of the modified narrowband signal.

7. The method of claim 1, further comprising varying a frequency of the narrowband signal transmitted into the formation and obtaining the modified narrowband signal including a spectrum of frequencies.

8. A system, comprising:

a transmitter located in a wellbore and generating a narrowband signal into a formation, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency;

an optical waveguide positioned in the wellbore to sense the modified narrowband signal; and

an interface to transmit a source signal along a length of the optical waveguide, obtain a backscattered return signal from the optical waveguide, sample the backscattered return signal at a second frequency less than a Nyquist rate of the modified narrowband signal, and process the backscattered return signal to obtain an amplitude of the modified narrowband signal.

9. The system of claim 8, wherein the interface processes the backscattered return signal to obtain the amplitude of the modified narrowband signal independent of the first frequency of the modified narrowband signal.

10. The system of claim 8, wherein the interface processes the backscattered return signal using interferometric phase modulation techniques.

11. The system of claim 8, wherein the interface filters the backscattered return signal using a low-pass filter having a cut off frequency equal to or below the first frequency.

12. The system of claim 8, wherein the interface controls the transmitter to vary the amplitude of the modified narrowband signal.

13. The system of claim 8, wherein the interface varies a frequency of the narrowband signal transmitted into the formation to obtain the modified narrowband signal including a spectrum of frequencies.

14. A computer program product comprising a non-transitory computer readable medium having computer readable computer program code stored thereon that, when executed by a computer, configures the computer to:

transmit a narrowband signal into a formation using a transmitter located in a wellbore, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency, the modified narrowband signal being sensed by an optical waveguide positioned in the wellbore;

program an interface to transmit a source signal along a length of the optical waveguide and obtain a backscattered return signal from the optical waveguide, the backscattered return signal being sampled at a second frequency that is less than a Nyquist rate of the modified narrowband signal; and

program the interface to process the backscattered return signal to obtain an amplitude of the modified narrowband signal.

15. The computer program product of claim 14, wherein the computer is further configured to program the interface to process the backscattered return signal such that the amplitude of the modified narrowband signal is obtained independent of the first frequency of the modified narrowband signal.

16. The computer program product of claim 14, wherein the computer is further configured to program the interface to process the backscattered return signal using interferometric phase modulation techniques.

17. The computer program product of claim 14, wherein the computer is further configured to program the interface to filter the backscattered return signal using a low-pass filter having a cut off frequency equal to or below the first frequency.

18. The computer program product of claim 14, wherein the computer is further configured to program the interface to control the transmitter to vary the amplitude of the modified narrowband signal.

19. The computer program product of claim 14, wherein the computer is further configured to vary a frequency of the narrowband signal transmitted into the formation and obtain the modified narrowband signal including a spectrum of frequencies.