Distributed sensing systems and methods with efficient energy spectrum analysis

Patent metadata

Field	Value
Publication number	US-2017130574-A1
Application number	US-201415323079-A
Country	US
Kind code	A1
Filing date	Jul 18, 2014
Priority date	Jul 18, 2014
Publication date	May 11, 2017
Grant date	—

Abstract

A system includes an optical fiber and an interrogator to provide source light to the optical fiber. The system also includes a receiver coupled to the optical fiber. The receiver includes at least one fiber optic coupler that receives backscattered light and that produces one or more optical interferometry signals from the backscattered light. The receiver also includes photo-detectors that produce an electrical signal for each of the one or more optical interferometry signals. The system also includes at least one digitizer that digitizes each electrical signal. The system also includes at least one processing unit that processes each digitized electrical signal to obtain a distributed sensing signal and related energy spectrum information. The energy spectrum information corresponds to energy calculated for each of a limited number of frequency subbands by segmenting the distributed sensing signal into blocks having a predetermined block length and by applying a filter having a filter length that is smaller than the predetermined block length.

First claim

1 . A system, comprising:
an optical fiber; an interrogator to provide source light to the optical fiber; and a receiver coupled to the optical fiber, wherein the receiver comprises:
at least one fiber optic coupler that receives backscattered light and that produces one or more optical interferometry signals from the backscattered light;
photo-detectors that produce an electrical signal for each of the one or more optical interferometry signals;
at least one digitizer that digitizes each electrical signal; at least one processing unit that processes each digitized electrical signal to obtain a distributed sensing signal and related energy spectrum information, wherein the energy spectrum information corresponds to energy calculated for each of a limited number of frequency subbands by segmenting the distributed sensing signal into blocks having a predetermined block length and by applying a filter having a filter length that is smaller than the predetermined block length.

2 . The system of claim 1 , wherein the filter has a frequency response corresponding to a plurality of different bandpass regions.

3 . The system of claim 2 , wherein the filter corresponds to a filter matrix that stacks a plurality of different frequency responses.

4 . The system of claim 1 , wherein the filter has an adjustable frequency response.

5 . The system of claim 4 , wherein the adjustable frequency response is based on a filter bank design.

6 . The system of claim 1 , wherein the at least one processing unit obtains the energy spectrum information by performing a Fast Fourier Transform (FFT) for each block, squaring a magnitude for each FFT coefficient, and for each frequency band, combining those squared magnitude FFT coefficients corresponding to that frequency band.

7 . The system of claim 1 , wherein the predetermined block length is at least ten times greater than the filter length.

8 . The system of claim 1 , wherein the distributed sensing signal corresponds to a phase signal as a function of time.

9 . The system of claim 1 , wherein the distributed sensing signal represents acoustic data at different points along the optical fiber.

10 . The system of claim 1 , wherein the optical fiber is deployed downhole via at least one of drill pipe, coiled tubing, slick line or electric line, or is spooled off of a component that is dropped or pumped downhole.

11 . The system of claim 1 , further comprising a monitor in communication with the at least one processing unit to display the distributed sensing signal, the energy spectrum information, or data derived from the distributed sensing signal and the energy spectrum information.

12 . The system of claim 1 , further comprising a tool that initiates or adjusts a downhole operation based on the distributed sensing signal, the energy spectrum information, or data derived from the distributed sensing signal and the energy spectrum information.

13 . A method, comprising:
providing source light to an optical fiber deployed in a downhole environment; receiving backscattered light from the optical fiber and producing one or more optical interferometry signals from the backscattered light; converting each of the one or more optical interferometry signals to an electrical signal and digitizing each electrical signal; determining a distributed sensing signal from each digitized electrical signal; and obtaining energy spectrum information corresponding to energy calculated for each of a limited number of frequency subbands of the distributed sensing signal by segmenting the distributed sensing signal into blocks having a predetermined block length and by applying a filter having a filter length that is smaller than the predetermined block length.

14 . The method of claim 13 , further comprising selecting a frequency response for the filter corresponding to a plurality of different bandpass regions.

15 . The method of claim 14 , further comprising adjusting the frequency response of the filter.

16 . The method of claim 13 , wherein obtaining the energy spectrum information further comprises performing a Fast Fourier Transform (FFT) for each block, squaring an absolute value for each FFT, and multiplying the squared absolute value by the filter.

17 . The method of claim 13 , wherein the predetermined block length is at least ten times greater than the filter length.

18 . The method of claim 13 , wherein the distributed sensing signal corresponds to a phase signal as a function of time.

19 . The method of claim 13 , further comprising deploying the optical fiber downhole via at least one of drill pipe, coiled tubing, slick line or electric line, or spooling the optical fiber off of a component that is dropped or pumped downhole.

20 . The method of claim 13 , further comprising initiating or adjusting a downhole operation based on the distributed sensing signal, the energy spectrum information, or data derived from the distributed sensing signal and energy spectrum information.

21 . The method of claim 13 , further comprising displaying the distributed sensing signal, the energy spectrum information, or data derived from the distributed sensing signal and energy spectrum information.

Assignees

• Halliburton Energy Services Inc

Inventors

• Nunes Leonardo De Oliveira
• Stokely Christopher Lee
• Barfoot David Andrew

Classifications

• E21B47/002

  by visual inspection · CPC title

• G01V1/226 Primary

  Optoseismic systems · CPC title

• G01H9/004 Primary

  using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125) · CPC title

• E21B47/0002 Primary

  Fixed Constructions · mapped topic

• E21B47/123

  Fixed Constructions · mapped topic