METHOD FOR ANALYZING STRAIN DATA

• US 20090254280A1
• Filed: 04/02/2008
• Published: 10/08/2009
• Est. Priority Date: 04/02/2008
• Status: Active Grant

• Current Assignee: Baker Hughes, a GE Company, LLC (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Stoesz, Carl W.
• Granted Patent: US 8,515,675 B2
• Time in Patent Office: Days
• US Class Current: 702/6
• CPC Class Codes: E21B 49/006 Measuring wall stresses in the borehole
• CPC Class Codes: G02B 6/0208 characterised by their structure, wavelength response G02B6/02114, G02B6/02171, G02B6/02195 take precedence; multiple layer cores or claddings G02B6/036, protective coverings G02B6/4429

Abstract

A method for estimating a shape, the method including: selecting a structure comprising a plurality of strain sensors inoperable communication with the structure, each strain sensor configured to provide a strain measurement; placing the structure in a borehole; receiving the strain measurements from the plurality of strain sensors; creating a mesh grid having nodes, each node related to a location of one strain sensor and assigned a strain value measured by the one strain sensor; creating an additional node for the mesh grid wherein a strain value assigned to the additional node is derived from the strain value corresponding to at least one adjacent node; and performing an inverse finite method using the mesh grid with the assigned strain values to estimate the shape.

Claims

1. A method for estimating a shape, the method comprising:

selecting a structure comprising a plurality of strain sensors inoperable communication with the structure, each strain sensor configured to provide a strain measurement;

placing the structure in a borehole;

receiving the strain measurements from the plurality of strain sensors;

creating a mesh grid comprising nodes, each node related to a location of one strain sensor and assigned a strain value measured by the one strain sensor;

creating an additional node for the mesh grid wherein a strain value assigned to the additional node is derived from the strain value corresponding to at least one adjacent node; and

performing an inverse finite method using the mesh grid with the assigned strain values to estimate the shape.

2. The method of claim 1, wherein the plurality of strain sensors comprises fiber Bragg gratings within an optical fiber.

3. The method of claim 1, wherein receiving the strain measurements comprises using a multiplex method.

7. The method of claim 1, wherein the mesh grid comprises at least one mesh element.

8. The method of claim 7, wherein the at least one mesh element has three sides.

9. The method of claim 7, wherein the at least one mesh element has four sides.

10. The method of claim 7, wherein the at least one mesh element is at least one of linear, quadratic, and cubic.

11. The method of claim 1, wherein the strain value assigned to the additional node is derived from a linear interpolation of the strain value corresponding to the at least one adjacent node.

12. The method of claim 1, wherein the strain value assigned to the additional mesh element is derived from a least squares interpolation of the strain value corresponding to the at least one adjacent node.

13. The method of claim 1, wherein the strain value assigned to the additional node is derived from a smooth curve fit of the strain value corresponding to the at least one adjacent node.

4. The method of claim 4, wherein the multiplex method comprises optical frequency domain multiplexing.

5. The method of claim 4, wherein the multiplex method comprises time domain multiplexing

6. The method of claim 4, wherein the multiplex method comprises at least one of amplitude multiplexing, phase multiplexing, and polarization multiplexing.

14. A system for estimating a shape of a downhole structure, the system comprising:

the downhole structure;

a plurality of strain sensors in operable communication with the downhole structure, each strain sensor providing a strain measurement; and

a processing unit in operable communication with the plurality of strain sensors wherein the processing unit;

processes the strain measurements from the strain sensors;

creates a mesh grid comprising nodes, each node related to a location of one strain sensor and assigned a strain value measured by the one strain sensor;

creates an additional node for the mesh grid wherein a strain value assigned to the additional node is derived from the strain value corresponding to at least one adjacent node; and

performs an inverse finite method using the mesh grid with the assigned strain values to estimate the shape.

15. The system of claim 14, wherein the plurality of strain sensors comprises fiber Bragg gratings within an optical fiber.

16. The system of claim 15, wherein at least one grating is less than 5 millimeters (mm) long and the space between two gratings is less than 10 mm.

17. The system of claim 14, further comprising a fiber optic strain system.

18. The system of claim 14, wherein the strain value assigned to the additional node is derived from the strain value corresponding to the at least one adjacent node using at least one of linear interpolation, least squares interpolation, and smooth curve fit.

19. The system of claim 14, wherein the mesh grid comprises mesh elements that are at least one of linear, quadratic, and cubic.

20. A computer program product comprising machine readable instructions stored on machine readable media for estimating a shape of a downhole structure, the product comprising machine executable instructions for:

receiving strain measurements from a plurality of strain sensors in operable communication with the downhole structure;

creating a mesh grid comprising nodes, each node related to a location of one strain sensor and assigned a strain value measured by the one strain sensor;

creating an additional node for the mesh grid wherein a strain value assigned to the additional node is derived from the strain value corresponding to at least one adjacent node;

performing an inverse finite method using the mesh grid with the assigned strain values to estimate the shape; and

at least one of recording the shape and displaying the shape to a user.