Fluid analysis by optical spectroscopy with photoacoustic detection

Patent metadata

Field	Value
Publication number	US-9651476-B2
Application number	US-201414166593-A
Country	US
Kind code	B2
Filing date	Jan 28, 2014
Priority date	Jan 28, 2014
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

A method for downhole fluid analysis by optical spectroscopy with photoacoustic detection includes positioning a photoacoustic system within a wellbore, applying a laser pulse to the fluid sample using the pulsed laser system, detecting, by the acoustic sensor, a time-resolved acoustic pulse generated by absorption of the laser pulse by the fluid sample, and determining a property of the fluid sample using the detected time resolved acoustic pulse. The photoacoustic system includes a pulsed laser system and an acoustic sensor.

First claim

What is claimed is:

1. A wellbore tool comprising: a photoacoustic spectroscopy system for analyzing a fluid sample, the system comprising: a laser system that is configured to generate laser pulses; a window disposed between the fluid sample and the laser system and configured to transmit the laser pulses to the fluid sample; an acoustic sensor configured to receive acoustic pulses that are generated in response to absorption of the laser pulses by the fluid sample; and a processing system configured to determine an optical absorption property of the fluid sample by (a) fitting an exponential function to a pressure rise of an acoustic pulse or (b) measuring a slope of a semi-log plot of a pressure rise of the acoustic pulse.

2. The wellbore tool of claim 1 , wherein the window is disposed on an exterior wall of a wellbore tool and the fluid sample is disposed outside the wellbore tool.

3. The wellbore tool of claim 2 , wherein the acoustic sensor is disposed on the window.

4. The wellbore tool of claim 1 , wherein the window is disposed along a flow line of the wellbore tool and the fluid sample is disposed within the flow line.

5. The wellbore tool of claim 4 , the acoustic sensor is disposed along the flow line of the wellbore tool.

6. The wellbore tool of claim 1 , wherein the laser system comprises a laser cavity with a monolithic body having a first end and a second end, the monolithic body comprising a first reflector disposed on the first end, a second reflector disposed on the second end, a solid state gain medium and a Q-switch, wherein the solid state gain medium and the Q-switch are disposed between the first reflector and the second reflector of the monolithic cavity.

7. The wellbore tool of claim 6 , further comprising a pump source, wherein the pump source is configured to cause a population inversion in the solid state gain medium to cause the monolithic body to generate laser pulses.

8. The wellbore tool of claim 1 , wherein the laser system comprises:
a pump laser configured to generate a pulse of pump laser light; and
an optical parametric oscillator configured to generate the laser pulses, wherein a wavelength of the laser pulses depends on a wavelength of the pulse of pump laser light and a control signal applied to a nonlinear crystal of the optical parametric oscillator.

9. The wellbore tool of claim 1 , further comprising a processing system configured to (i) receive an electric signal from the acoustic sensor representative of the acoustic pulses and (ii) determine a property of the fluid sample using the electric signal.

10. A method for analyzing a fluid sample, the method comprising:
positioning a photoacoustic system within a wellbore, wherein the photoacoustic system comprises a pulsed laser system and an acoustic sensor;
applying a laser pulse to the fluid sample using the pulsed laser system;
detecting, by the acoustic sensor, a time-resolved acoustic pulse generated by absorption of the laser pulse by the fluid sample; and
determining an optical absorption property of the fluid sample by (a) fitting an exponential function to a pressure rise of the time-resolved acoustic pulse or (b) measuring a slope of a semi-log plot of a pressure rise of the time-resolved acoustic pulse.

11. The method of claim 10 , further comprising:
determining presence of at least one component within the fluid sample using the optical absorption property.

12. The method of claim 10 , further comprising:
determining a quantity of at least one component within the fluid sample using the optical absorption property.

13. The method of claim 12 , wherein the at least one component comprises asphaltenes.

14. The method of claim 10 , wherein (i) applying the laser pulse to the fluid sample comprises applying a plurality of laser pulses using a plurality of different wavelengths and (ii) detecting the time-resolved acoustic pulse comprises detecting time-resolved acoustic pulses for each of the plurality of different wavelengths.

15. The method of claim 14 , wherein determining the property of the fluid sample comprises determining a plurality of optical absorption properties for each of the plurality of wavelengths.

16. The method of claim 15 , further comprising:
determining at least one component within the fluid sample using the plurality of optical absorption properties.

17. The method of claim 10 , wherein applying the laser pulse comprises modulating a quality factor of a gain medium within the laser system using a passive Q-switch.

18. The method of claim 14 , wherein applying a plurality of pulses using a plurality of different wavelengths comprises varying at least one of a nonlinear crystal temperature and a nonlinear crystal orientation.

19. The method of claim 14 , wherein a range of wavelengths of the plurality of wavelengths is a range from 355 nm to 4500 nm.

20. A method for analyzing a fluid sample, the method comprising:
applying a laser pulse to the fluid sample using a laser system, wherein less than 37% of light from the laser pulse is transmitted through the fluid sample;
detecting a time-resolved acoustic pulse generated by absorption of the laser pulse by the fluid sample using an acoustic sensor; and
determining an optical absorption property of the fluid sample by (a) fitting an exponential function to a pressure rise of the time-resolved acoustic pulse or (b) measuring a slope of a semi-log plot of a pressure rise of the time-resolved acoustic pulse.

21. The method of claim 20 , wherein the fluid sample comprises a heavy oil.

22. The method of claim 20 , wherein the fluid sample comprises an emulsion.

23. The method of claim 20 , wherein the fluid sample comprises asphaltenes.

Assignees

• Schlumberger Technology Corp

Inventors

• Speck Andrew J
• Pomerantz Andrew E
• Mullins Oliver C

Classifications

• G01N2201/06113

  Coherent sources; lasers · CPC title

• G02F1/39

  for parametric generation or amplification of light, infrared or ultraviolet waves · CPC title

• G01N2201/0697

  Pulsed lasers · CPC title

• G01N2021/1704

  in gases · CPC title

• G01N2021/1708

  with piezotransducers · CPC title