Multi-Channel Source Assembly for Downhole Spectroscopy

• US 20110108719A1
• Filed: 11/06/2009
• Published: 05/12/2011
• Est. Priority Date: 11/06/2009
• Status: Active Grant

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Precision Energy Services Incorporated (Weatherford International PLC)
• Inventors: Kasperski, Bryan W., Blankinship, Thomas, Ford, Jess V., Christian, Sean M., Waid, Margaret C.
• Granted Patent: US 8,164,050 B2
• Time in Patent Office: Days
• US Class Current: 250/262
• CPC Class Codes: G01J 2003/1226 Interference filters
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0202 Mechanical elements; Supports for optical elements
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators
• CPC Class Codes: G01J 3/4338 Frequency modulated spectrometry
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 2201/0612 Laser diodes
• CPC Class Codes: G01N 2201/0625 Modulated LED
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G01N 2201/0691 Modulated (not pulsed supply)
• CPC Class Codes: G01N 2201/0826 Fibre array at source, distributing
• CPC Class Codes: G02B 6/4215 the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres

Abstract

A multi-channel source assembly for downhole spectroscopy has individual sources that generate optical signals across a spectral range of wavelengths. A combining assembly optically combines the generated signals into a combined signal and a routing assembly that splits the combined signal into a reference channel and a measurement channel. Control circuitry electrically coupled to the sources modulates each of the sources at unique or independent frequencies during operation.

Claims

1. A source assembly for downhole spectroscopy, comprising:

a plurality of individual sources generating optical signals across a spectral range of wavelengths;

a routing assembly combining the generated signals of the sources into a combined signal and routing the combined signal into a reference channel and one or more measurement channels; and

control circuitry electrically coupled to the sources and operable to electronically modulate each of the sources at an independent frequency.

2. The assembly of claim 1, wherein the sources are selected from the group consisting of light emitting diodes (LEDs), laser diodes (LDs), vertical cavity side emitting lasers (VCSELs), and super-luminescent light emitting diodes (SLEDs).

3. The assembly of claim 1, wherein the sources provide a continuous spectral distribution over a broad spectral range of wavelengths.

4. The assembly of claim 1, wherein the sources provide a non-continuous spectral distribution of two or more spectrally continuous regions interposed by at least one spectrally dark region over a broad spectral range of wavelengths.

5. The assembly of claim 1, wherein one or more of the sources are spectrally filtered.

6. The assembly of claim 1, wherein one or more of the sources are spatially shaped using one or more optical elements.

7. The assembly of claim 1, wherein to electronically modulate each of the sources, the control circuitry turns each of the individual sources on and off or electronically modulate each source about a mean amplitude.

8. The assembly of claim 1, wherein to electronically modulate each of the sources, the control circuitry electronically modulates one or more of the individual sources at a unique frequency different from one another.

9. The assembly of claim 1, wherein to electronically modulate each of the sources, the control circuitry electronically modulates one or more of the individual sources at the same frequency.

10. The assembly of claim 1, wherein the routing assembly comprises:

one or more couplers optically coupled to each of the sources; and

a router coupled to the one or more couplers and routing the optically combined signals from the one or more couplers into the reference channel and the one or more measurement channels.

11. The assembly of claim 10, wherein the one or more couplers comprise optical fibers, each of the sources imaged into one of the optical fibers, each of the fibers bundled together into a fiber bundle optically coupled to the router.

12. The assembly of claim 10, wherein the one or more couplers comprise optical fibers optically coupled to the sources, each of the sources imaged into one of the optical fibers, one or more of the optical fibers fused with another of the optical fibers using a tree coupling topology, wherein output of the tree coupling topology is optically coupled to the router.

13. The assembly of claim 10, wherein the one or more couplers comprise a segmented mirror having the sources arranged thereabout, the segmented mirror imaging optical signals from each of the sources into the combined signal that is optically coupled to the router.

14. The assembly of claim 10, wherein the one or more couplers comprises a series of filters disposed adjacent the sources and at least one optic element imaging at least a portion of the optical signals from each of the adjacent sources to a combined signal optically coupled to the router.

15. The assembly of claim 1, wherein the routing assembly comprises a micro-optical bench.

16. The assembly of claim 1, wherein the routing assembly comprises a splitter fractionally splitting the combined signal into the reference and the one or more measurement channels.

17. The assembly of claim 1, wherein the routing assembly comprises an adaptive optical element optically coupled to the combined signal and oscillating between a first orientation and one or more second orientations, the adaptive optical element in the first orientation producing the reference channel, the adaptive optical element in the one or more second orientations producing the one or more measurement channels.

18. The assembly of claim 1, wherein the sources are spatially configured on an array topology arranged in one or more dimensions, and wherein the routing assembly comprises a grating optically coupled to the spatially configured sources and combining the signals from the sources into a common optical beam.

19. The assembly of claim 18, wherein the routing assembly images a first portion of the optical beam into a first optic fiber for the reference channel and images one or more second portions of the optical beam into one or more second optic fibers for the one or more measurement channels.

20. The assembly of claim 18, wherein the routing assembly comprises a router optically coupled to the optical beam and routing the optical beam into the reference channel and the one or more measurement channels.

21. The assembly of claim 18, wherein the grating generates first and second optical beams, the first optical beam generated using a first order reflection of the grating, the second optical beam generated using a second order reflection of the grating, the one or more measurement channels imaged using the first order reflection, the reference channel imaged using the second order reflection.

22. The assembly of claim 1, wherein the control circuitry receives input indicative of measured energy of the reference channel and controls an amplitude of the sources based on the input.

23. The assembly of claim 1, wherein the control circuitry electronically modulates the sources in a synchronous encoding mode in which the control circuitry operates each of two or more sources simultaneously using an independent frequency to generate optical signals, the synchronous encoding mode enabling Fast-Fourier Transform analysis of the measurement and reference channels.

24. The assembly of claim 1, wherein the control circuitry electronically modulates the sources in a synchronous encoding mode in which the control circuitry operates the sources simultaneously using fixed frequency increments, the synchronous encoding mode enabling deconvolution of the measurement and reference channels based on predefined temporal characteristics of the fixed frequency increments.

25. The assembly of claim 1, wherein the control circuitry electronically modulates the sources in an asynchronous encoding mode in which the control circuitry operates each of two or more sources in a serial fashion with only one of the sources in operation at any point in time, the asynchronous encoding mode enabling raster scanning analysis of the measurement and reference channels.

26. The assembly of claim 1, wherein the control circuitry electronically modulates the sources in an asynchronous encoding mode in which the control circuitry operates a unique sequence of subsets of the sources in a cyclic fashion with only one of the subsets of the sources in operation at a given point in time, the asynchronous encoding mode enabling Hadamard Transform analysis of the measurement and reference channels.

27. A downhole fluid analysis tool, comprising:

a tool housing deployable downhole and having a flow passage for a fluid sample; and

a fluid analysis device disposed in the tool housing relative to the flow passage, the fluid analysis device at least including

a plurality of individual sources generating optical signals across a spectral range of wavelengths,

a routing assembly optically combining the generated signals of each of the sources into a combined signal and routing the combined signal into a reference channel and one or more measurement channels, and

control circuitry electrically coupled to the sources and operable to electronically modulate each of the sources at an independent frequency.

28. A downhole fluid analysis method, comprising:

deploying a fluid analysis device downhole;

obtaining a fluid sample downhole;

generating a plurality of optical signals across a spectrum of wavelengths by electronically modulating each of a plurality of sources at an independent frequency;

combining the generated signals into a combined signal; and

routing the combined signal concurrently into one or more measurement channels for interacting with the fluid sample and into a reference channel for dynamically scaling the measurement channel.

29. The method of claim 28, wherein generating the optical signals comprises spectrally filtering one or more of the sources.

30. The method of claim 28, wherein modulating each of the sources comprises turning each of the individual sources on and off.

31. The method of claim 28, wherein modulating each of the sources comprises modulating each of the individual sources about a mean amplitude.

32. The method of claim 28, wherein modulating each of the sources comprises modulating one or more of the individual sources at the same frequency.

33. The method of claim 28, wherein modulating each of the sources comprises modulating one or more of the individual sources at unique frequencies different from one another.

34. The method of claim 28, wherein combining the generated signals into a combined signal comprises imaging each of the individual sources into an optical coupler.

35. The method of claim 28, wherein routing the combined signal comprises fractionally splitting the combined signal into the reference and measurement channels.

36. The method of claim 28, wherein routing the combined signal comprises oscillating the combined signal between a first orientation producing the reference channel and a second orientation producing the measurement channel.

37. The method of claim 28, wherein the acts of generating, combining, and routing comprise:

spatially configuring the individual sources in one or more dimensions;

combining the optical signals from the spatially configured sources using a grating; and

routing the combined signal into the measurement and reference channels.

38. The method of claim 37, wherein imaging the signal comprises imaging a first portion of the signal into the reference channel and imaging a second portion of the signal into the measurement channel.

39. The method of claim 37, wherein the acts of routing comprises:

routing a first order reflection of the grating,

imaging the first order reflection into the measurement channel;

routing a second order reflection of the grating; and

imaging the second order reflection into the reference channel.

40. The method of claim 28, wherein modulating each of a plurality of sources is controlled based on measured energy of the reference channel.

41. The method of claim 28, wherein modulating each of a plurality of sources comprises synchronously encoding the sources by simultaneously operating each of two or more of the sources and modulating each with an independent frequency.

42. The method of claim 28, wherein modulating each of a plurality of sources comprises synchronously encoding the sources by operating the sources simultaneously using fixed frequency increments.

43. The method of claim 28, wherein modulating each of a plurality of sources comprises asynchronously encoding the sources by operating each of two or more of the sources in a serial fashion with only one of the sources in operation at any point in time.

44. The method of claim 28, wherein modulating each of a plurality of sources comprises asynchronously encoding the sources by operating a unique sequence of subsets of the sources in a cyclic fashion with only one of the subsets of the sources in operation at a given point in time.