Determining a specific gravity of a sample

Patent metadata

Field	Value
Publication number	US-10371633-B2
Application number	US-201715797938-A
Country	US
Kind code	B2
Filing date	Oct 30, 2017
Priority date	Oct 30, 2017
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

Methods and systems use fluorescence to determine specific gravity of samples. A first light pulse is applied to a sample at a first angle-of-incidence. A second light pulse is applied to the sample at a second angle-of-incidence. A first ratio based on the intensity of a first fluorescence emission over a first time interval and the intensity of the first fluorescence emission over a second time interval is calculated. A second ratio based on the intensity of a second fluorescence emission over a third time interval and the intensity of the second fluorescence emission over a fourth time interval is calculated. An intensity ratio based on the first ratio and the second ratio is calculated. A specific gravity of the sample based on the intensity ratio is determined.

First claim

What is claimed is:

1. A method comprising:
applying a first light pulse to a sample at a first angle-of-incidence;
detecting an intensity of a first fluorescence emission emitted from the sample over a first time interval and a second time interval;
applying a second light pulse to the sample at a second angle-of-incidence;
detecting an intensity of a second fluorescence emission emitted from the sample over a third time interval and a fourth time interval;
calculating, by a processor, a first ratio based on the intensity of the first fluorescence emission over the first time interval and the intensity of the first fluorescence emission over the second time interval;
calculating, by a processor, a second ratio based on the intensity of the second fluorescence emission over the third time interval and the intensity of the second fluorescence emission over the fourth time interval;
calculating, by a processor, an intensity ratio based on the first ratio and the second ratio; and
determining a specific gravity of the sample based on the intensity ratio.

2. The method of claim 1 , wherein applying the first light pulse comprises producing the first light pulse using a first single-wavelength light source.

3. The method of claim 2 , wherein the first single-wavelength light source comprises a laser operating at 250 to 450 nm.

4. The method of claim 2 , wherein applying the second light pulse comprises producing the second light pulse using the first single-wavelength light source.

5. The method of claim 4 , comprising moving the first single-wavelength light source between producing the first light pulse and producing the second light pulse.

6. The method of claim 4 , comprising moving the sample between producing the first light pulse and producing the second light pulse.

7. The method of claim 1 , wherein applying the second light pulse comprises producing the second light pulse using a second single-wavelength light source.

8. The method of claim 1 , wherein the sample comprises hydrocarbon fluid and the specific gravity is an API gravity.

9. The method of claim 1 , wherein the first angle-of-incidence is between 5 and 30 degrees.

10. The method of claim 1 , wherein the second angle-of-incidence is between 40 and 65 degrees.

11. The method of claim 1 , wherein the difference between the first angle-of-incidence and the second angle-of-incidence is between 25 and 65 degrees.

12. The method of claim 1 , further comprising:
normalizing, by a processor, the first fluorescence emission over the first time interval and the second time interval; and
normalizing, by a processor, the second fluorescence emission over the third time interval and the fourth time interval.

13. The method of claim 1 , wherein the first time interval and the third time interval are synchronized to a maximum of the first light pulse and the second light pulse, respectively.

14. The method according to claim 1 , wherein the second time interval and the fourth time interval are synchronized to 3 ns after a maximum of the first light pulse and the second light pulse, respectively.

15. A method comprising:
applying a first light pulse to a sample at a first angle-of-incidence;
detecting an intensity of a first fluorescence emission as the intensity of the first fluorescence emission fades;
applying a second light pulse to the sample at a second angle-of-incidence;
detecting an intensity of a second fluorescence emission as the intensity of the second fluorescence emission fades;
comparing, by a processor, the fading of the first fluorescence emission with the fading of the second fluorescence emission; and
determining a specific gravity of the sample based on a ratio calculated based on a comparison of the fading of the first fluorescence emission and the fading of the second fluorescence emission.

16. The method of claim 15 , wherein applying the first light pulse comprises producing the first light pulse using a first single-wavelength light source.

17. The method of claim 16 , wherein applying the second light pulse comprises producing the second light pulse using the first single-wavelength light source.

18. The method of claim 17 , comprising moving the first single-wavelength light source between producing the first light pulse and producing the second light pulse.

19. The method of claim 17 , comprising moving the sample between producing the first light pulse and producing the second light pulse.

20. An API gravity measurement system comprising:
a fluorescence-measuring apparatus, comprising:
a first single-wavelength light source configured to generate a first excitation light pulse to contact a sample at a first angle-of-incidence;
a second single-wavelength light source configured to generate a second excitation light pulse to contact the sample at a second-angle of incidence;
a sample holder configured to hold the sample; and
a detector configured to detect an intensity of a fluorescence emission from the sample;
a processor; and
a computer-readable storage medium storing instructions executable by the processor, the instructions comprising:
applying a first light pulse to a sample at a first angle-of-incidence;
detecting an intensity of a first fluorescence emission emitted from the sample over a first time interval and a second time interval;
applying a second light pulse to the sample at a second angle-of-incidence;
detecting an intensity of a second fluorescence emission emitted from the surface over a third time interval and a fourth time interval;
calculating, by a processor, a first ratio based on the intensity of the first fluorescence emission over the first time interval and the intensity of the first fluorescence emission over the second time interval;
calculating, by a processor, a second ratio based on the intensity of the second fluorescence emission over the third time interval and the intensity of the second fluorescence emission over the fourth time interval;
calculating, by a processor, an intensity ratio based on the first ratio and the second ratio; and
determining a specific gravity of the sample based on the intensity ratio.

Assignees

• Saudi Arabian Oil Co

Inventors

• Hegazi Ezzat
• Cunningham Vincent
• Alsayegh Maha Ali N

Classifications

• G01N33/241

  for hydrocarbon content · CPC title

• G01N21/64 Primary

  Fluorescence; Phosphorescence · CPC title

• G01N2021/6417

  Spectrofluorimetric devices · CPC title

• G01N33/2823

  Raw oil, drilling fluid or polyphasic mixtures · CPC title

• G01N21/6408 Primary

  with measurement of decay time, time resolved fluorescence · CPC title