Evanescent wave downhole fiber optic spectrometer

• US 7,969,571 B2
• Filed: 01/15/2009
• Issued: 06/28/2011
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: DiFoggio, Rocco
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US12/354,117
• Publication Number:
  US 20100177310A1
• Time in Patent Office: 894 Days
• Field of Search: 356/326, 356/328, 250/269.1, 250/269.2
• US Class Current: 356/326
• CPC Class Codes: E21B 47/00 Survey of boreholes or wells monitoring pressure or flow of drilling fluid E21B21/08
• CPC Class Codes: E21B 47/135 using light waves, e.g. infrared or ultraviolet waves
• CPC Class Codes: G01N 2021/8528 Immerged light conductor
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01V 3/30 operating with electromagnetic waves

Abstract

An apparatus for estimating a property of a fluid downhole, is provided an includes: an optical fiber that receives light emitted from a light source and including an unclad portion adapted for contacting the fluid; a photodetector for receiving optical signals from the portion; and a spectrometer for obtaining an evanescent spectrum of the fluid from the portion. A method and a system are included.

Claims

1. An apparatus for estimating a property of a fluid downhole, the apparatus comprising:

a waveguide that receives electromagnetic energy emitted from a source of electromagnetic energy, the waveguide comprising a core portion configured to communicate electromagnetically with the fluid and an unclad portion configured to contact the fluid; and

a detector configured to receive a resultant signal from the core portion, the resultant signal being used at least in part for estimating the property;

wherein the waveguide comprises at least one of a thin film waveguide and a photonic wire waveguide.

2. The apparatus as in claim 1, wherein the waveguide comprises one of silicon, germanium and sapphire (Al₂O₃), boron, tellurium, diamond, gallium lanthanum sulphide, rutile (TiO₂), and yttrium aluminum garnet (YAG).

3. The apparatus as in claim 1, further comprising the source of electromagnetic energy.

4. The apparatus as in claim 3, wherein the source of electromagnetic energy comprises at least one of an incandescent light, a light-emitting-diode, a dual wavelength diode, a laser diode, a single band of wavelengths, a plurality of bands of wavelengths and a filter.

5. The apparatus as in claim 1, where the waveguide is attached to a substrate.

6. The apparatus as in claim 1, further comprising at least one attenuated reflectance optical window in optical communication with the fluid.

7. The apparatus as in claim 1, wherein the waveguide further comprises a plurality of optical fibers for receiving light emitted from the source of electromagnetic energy and having a portion without a cladding disposed thereon.

8. The apparatus as in claim 1, comprising one of a drill string, a wireline instrument and a tractor configured to convey the apparatus downhole.

9. The apparatus as in claim 1, wherein the core portion of the waveguide comprises a refractive index that is greater than a refractive index of the fluid.

10. The apparatus as in claim 1, wherein the waveguide comprises at least one of a low solubility in brine, a low reactivity with the fluid and a high thermal resistance.

11. The apparatus as in claim 1, further comprising a spectrometer configured to obtain an evanescent spectrum from the resultant signal wherein the spectrum is used to estimate the property.

12. The apparatus as in claim 1, wherein the waveguide further comprises an optical fiber.

13. A method for estimating a property of a fluid downhole, the method comprising:

receiving electromagnetic energy from a source of electromagnetic energy with a waveguide comprising a core portion configured to communicate electromagnetically with the fluid and an unclad portion configured to contact the fluid;

at least partially contacting the unclad portion in the fluid downhole;

detecting a resultant signal from the core portion; and

estimating the property using at least in part the resultant signal.

14. The method as in claim 13, wherein contacting comprises at least one of pumping, porting, adding, flowing, loading, letting and moving the fluid.

15. The method as in claim 13, further comprising estimating an evanescent spectrum of the fluid from the resultant signal wherein the spectrum is used to estimate the property.

16. The method as in claim 15, further comprising classifying the fluid according to the evanescent spectrum.

17. The method as in claim 16, wherein classifying comprises searching a library of sample data.

18. The method as in claim 16, wherein classifying comprises performing a regression of data from the evanescent spectrum.

19. A system for estimating a property of a fluid downhole, the system comprising:

at least one source of electromagnetic energy for inputting electromagnetic energy to a waveguide comprising a core portion configured to communicate electromagnetically with the fluid and an unclad portion configured to contact the fluid, wherein the waveguide comprises at least one of a thin film waveguide and a photonic wire waveguide;

a detector configured to receive a resultant signal from the core portion;

an electronics unit configured to receive the resultant signal and to estimate the property using at least in part the resultant signal.

20. The system as in claim 19, wherein the estimating is performed on a real time basis.

21. The system as in claim 19, further comprising a spectrometer configured to obtain an evanescent spectrum from the resultant signal wherein evanescent spectrum information from the spectrometer is communicated to the electronics unit to estimate the property.