Determination of strain components for different deformation modes using a filter

Patent metadata

Field	Value
Publication number	US-9557239-B2
Application number	US-96011910-A
Country	US
Kind code	B2
Filing date	Dec 3, 2010
Priority date	Dec 3, 2010
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A method, apparatus and computer-readable medium for determining a strain component for a deformation mode of a member is disclosed. A plurality of measurements is obtained, wherein each of the plurality of measurements relates to a strain at a location of the member. A deformation mode is selected and an adjustable filter is applied to the plurality of strain measurements to determine the strain component for the selected deformation mode.

First claim

What is claimed is:

1. A method of determining a strain component for a selected deformation mode of a member, comprising:
propagating a light through a fiber optic cable wrapped around the member, the fiber optic cable having a plurality of sensors therein;
receiving light reflected at the plurality of sensors to determine a wavelength shift of the propagated light at each of the plurality of sensors, wherein each wavelength shift indicates a strain on the member at a location of a related sensor; and
using a processor to:
form a dataset that relates each wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member,
perform a transform on the dataset to obtain a spatial frequency spectrum, wherein a peak of the spatial frequency spectrum corresponds to the selected deformation mode of the member,
apply an adjustable filter to the spatial frequency spectrum to select a peak of the spatial frequency spectrum that corresponds to the selected deformation mode, wherein a frequency response of the adjustable filter includes a parameter defining frequency attenuation and a cut-off frequency i c (k) given by:

j
c

⁡

(
k
)

=

M
N

⁢

(

2
⁢
k

+
1

)

where M is a total number of strain measurements, N is a total number of sensors in a single wrap of the member, and k is an index for selecting the deformation mode, and
perform an inverse transform on the selected peak to determine the strain components for the selected deformation mode.

2. The method of claim 1 , wherein the adjustable filter is one of a lowpass filter and a bandpass filter.

3. The method of claim 1 , wherein applying the adjustable filter selects a spatial frequency of the selected deformation mode.

4. The method of claim 1 , wherein the attenuation parameter is selected to remove a phase noise.

5. The method of claim 1 , wherein the frequency response is convolved with the plurality of measurements.

6. The method of claim 1 , wherein the member is one of: (1) a casing; (2) a sand screen; (3) a subsea riser; (4) an umbilical; (5) a tubing; (6) a pipeline; (7) a cylindrical structure bearing a load.

7. The method of claim 1 , wherein the selected deformation mode is one of: (1) a compression/tensile mode; (2) a bending mode; (3) an ovalization mode; (4) a triangularization mode; (5) a rectangularization mode; and (6) a deformation mode having a spatial frequency that is an integer multiple of a spatial frequency of a bending deformation.

8. The method of claim 1 , wherein the plurality of measurements include at least one of: (1) a measurement of wavelength shift; (2) a measurement of frequency change; and (3) a measurement of a change in impedance.

9. An apparatus for determining a strain component for a selected deformation mode of a member, comprising:
a fiber optic cable wrapped around the member and including a plurality of sensors;
an interrogation unit configured to read the plurality of sensors and obtain a measurement from the plurality of sensors to determine a wavelength shift of light propagated in the fiber optic cable at each of the plurality of sensors, wherein each wavelength shift indicates a strain on the member at a location of a related sensor; and
a processor configured to:
form a dataset that relates each wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member,
obtain a spatial frequency spectrum, wherein a peak of the spatial frequency spectrum corresponds to the selected deformation mode of the member,
apply an adjustable filter to the spatial frequency spectrum to select a peak of the spatial frequency spectrum that corresponds to the selected deformation mode, wherein a frequency response of the filter includes a parameter defining frequency attenuation and a cut-off frequency given by:

j
c

⁡

(
k
)

=

M
N

⁢

(

2
⁢
k

+
1

)

where M is a total number of measurements, N is a total number of sensors in a single wrap of the member, and k is an index for selecting the deformation mode, and
perform an inverse transform on the selected peak to determine the strain components for the selected deformation mode.

10. The apparatus of claim 9 , wherein the adjustable filter is one of a lowpass filter and a bandpass filter.

11. The apparatus of claim 9 , wherein the processor is configured to adjust the filter to select a spatial frequency related to the selected deformation mode.

12. The apparatus of claim 9 , wherein the attenuation parameter is selected to remove a phase noise.

13. The apparatus of claim 9 , wherein the frequency response is convolved with the plurality of measurements.

14. The apparatus of claim 9 , wherein the member is one of: (1) a casing; (2) a sand screen; (3) a subsea riser; (4) an umbilical; (5) a tubing; (6) a pipeline; (7) a cylindrical structure bearing a load.

15. The apparatus of claim 9 , wherein the selected deformation mode is one of: (1) a compression/tensile mode; (2) a bending mode; (3) an ovalization mode; (4) a triangularization mode; (5) a rectangularization mode; and (6) a deformation mode having a spatial frequency that is an integer multiple of a spatial frequency of a bending deformation.

16. The apparatus of claim 9 , wherein the plurality of measurements include at least one of: (1) a measurement of wavelength shift; (2) a measurement of frequency change; and (3) a measurement of a change in impedance.

17. A non-transitory computer-readable medium having stored thereon instructions that when read by a processor enable the processor to perform a method, the method comprising:
propagating a light through a fiber optic cable wrapped around a member, the fiber optic cable having a plurality of sensors therein;
receiving light reflected at the plurality of sensors to determine a wavelength shift of the propagated light at each of the plurality of sensors, wherein each wavelength shift indicates a strain on the member at a location of a related sensor;
forming a dataset that relates each wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member;
performing a transform on the datase

Assignees

• Chen Jianfeng
• Yang Xudong
• Thigpen Brian L
• Childers Brooks A
• Baker Hughes Inc

Inventors

• Chen Jianfeng
• Yang Xudong
• Thigpen Brian L
• Childers Brooks A

Classifications

• E21B47/135

  using light waves, e.g. infrared or ultraviolet waves · CPC title

• E21B47/007

  Measuring stresses in a pipe string or casing (for locating blocked portions of pipes E21B47/09) · CPC title

• G01L25/00 Primary

  Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency · CPC title

• G01L1/246

  using integrated gratings, e.g. Bragg gratings · CPC title

• G01D5/35316

  using a Bragg gratings · CPC title