Method and apparatus for a downhole spectrometer based on tunable optical filters
Thermally tunable optical sensors are used in sampling tools for analysis of samples from a wellbore. The thermally tunable optical sensors generate a series passbands of wavelength emissions and detect attenuation in a signal thereof. The attenuation detected is processed and used to determine aspects of the samples. Analysis may be completed remotely (outside of the wellbore), within the wellbore (during drilling or otherwise), or as a part of another process such as fluid management, transport and refinement.
1. An apparatus for providing spectroscopic data for a sample, the apparatus comprising:
a downhole tool that comprises a thermally tunable optical filter for filtering light traversing the sample to provide the spectroscopic data.
2. The apparatus as in claim 1 , further comprising:
an emitter for producing broadband light which travels along a light path that passes through a sample chamber that receives the sample; and
a detector for receiving light that passes through the sample and for producing a detection signal corresponding to the light the detector receives, wherein the detector and the thermally tunable optical filter are disposed in the light path.
3. The apparatus as in claim 2 , further comprising a reflector for concentrating the broadband light produced by the emitter.
4. The apparatus as in claim 2 , wherein the emitter generates a series of passband emissions within an operating range.
5. The apparatus as in claim 4 , wherein the operating range is centered about an absorption band for a constituent of interest in the sample.
6. The apparatus as in claim 1 , wherein the spectroscopic data comprises at least one of:
a correlation of spectral measurements to one of physical properties and chemical identity; at least one of a ratio of isotopes and a quantity of isotopes; at least one of a determination and an estimation of phytane to pristane ratios; at least one of a determination and an estimation of a dissolved H 2 S quantity; a synthetic course-scale gas chromatogram; at least one of a determination and an estimation of a percentage of oil based mud filtrate contamination; and, quantification of at least one of aromatics, olefins, saturates, methane, ethane, propane, and butane in the sample.
7. The apparatus as in claim 1 , wherein the sample comprises a mixture of water, drilling fluid and formation fluid.
8. The apparatus as in claim 1 , wherein the sample chamber is comprised within in-line process equipment.
9. A method for providing spectroscopic data downhole for a sample, the method comprising:
illuminating the sample with a series of passbands of wavelength emissions using a thermally tunable optical filter;
detecting the series emissions that pass through the sample; and,
processing the detected emissions to provide the spectroscopic data.
10. The method as in claim 9 , wherein illuminating comprises:
producing light having a first wavelength spectrum; and,
selectively filtering the spectrum to produce filtered light comprising the series of passbands of wavelength emissions.
11. The method as in claim 9 , wherein illuminating comprises microtuning the series of passbands of wavelength emissions over an operating range.
12. The method as in claim 11 , wherein the operating range at least partially correlates to an absorption band of a constituent of interest in the sample.
13. The method as in claim 9 , wherein providing spectroscopic data comprises using a sampling tool to provide the spectroscopic data.
14. The method as in claim 9 , wherein providing spectroscopic data comprises using in-line process equipment.
15. The method as in claim 9 , wherein providing the spectroscopic data comprises at least one of:
correlating spectral measurements to physical properties; determining a chemical identity; determining at least one of a ratio of isotopes and a quantity of isotopes; at least one of determining and estimating phytane to pristane ratios; at least one of determining and estimating a dissolved H 2 S component; providing a synthetic course-scale gas chromatogram; at least one of determining and estimating a percentage of oil based mud filtrate contamination; and, quantifying at least one of aromatics, olefins, saturates, methane, ethane, propane, and butane in the sample.
16. The method as in claim 9 , wherein the sample comprises a mixture of water, drilling fluid and formation fluid.
17. A computer program product stored on machine readable media and comprising instructions for providing spectroscopic data downhole for a sample, the instructions for:
illuminating the sample with a series of passbands of wavelength emissions using a thermally tunable optical filter;
detecting the series emissions that pass through the sample; and,
processing the detected emissions to provide the spectroscopic data.
18. The method as in claim 9 , wherein producing filtered light comprises:
varying a temperature of the tunable optical filter to produce the series of passbands of wavelength emissions.