Determining the plus fraction of a gas chromatogram

Patent metadata

Field	Value
Publication number	US-9458715-B2
Application number	US-201414572724-A
Country	US
Kind code	B2
Filing date	Dec 16, 2014
Priority date	Dec 16, 2014
Publication date	Oct 4, 2016
Grant date	Oct 4, 2016

Abstract

Methods and devices for determining a plus fraction of a plus fraction of a gas chromatogram are provided. A gas chromatogram may obtained, such as from a downhole gas chromatograph module of a fluid analysis tool. The plus fraction of the gas chromatogram may be determined using one or more of a ratiometric determination, fitting an exponential decay function, and fitting a probability density gamma function.

First claim

What is claimed is:

1. A method for analyzing a fluid having a plurality of components, comprising:
obtaining a gas chromatogram of the fluid, the gas chromatogram comprising a plus fraction;
determining, from the gas chromatogram, a first ratio of a first at least one component of the fluid to a second at least one component of the fluid;
comparing the first ratio to a dataset of a plurality of fluids having a respective plurality of component ratios;
determining the plus fraction using the comparison; and
quantifying at least one of the components in the fluid using the determined plus fraction.

2. The method of claim 1 , wherein the gas chromatogram is obtained from a downhole gas chromatograph inserted into a well and configured to generate the gas chromatogram from a sample of the first fluid.

3. The method of claim 1 , wherein the first at least one component comprises C22 and the second at least one component comprises C16.

4. The method of claim 1 , comprising wherein the plus fraction comprises a C20+ fraction.

5. The method of claim 1 , wherein the first at least one component and the second at least one component are separated by at least five carbon numbers.

6. The method of claim 1 , comprising:
determining the plus fraction by extrapolating an exponential decay function or by fitting a probability density gamma function to produce a second determined plus fraction.

7. The method of claim 6 , comprising:
calculating an average of the determined plus fraction and the second determined plus fraction to determine an averaged plus fraction; and
quantifying at least one of the plurality components in the fluid using the averaged plus fraction.

8. The method of claim 1 , wherein the dataset comprises relationships between the plurality of component ratios and a respective plurality of known plus fractions.

9. A fluid analyzer for analyzing a fluid having a plurality of components, comprising:
a gas chromatograph configured to obtain a sample of the fluid and determine a gas chromatogram, the gas chromatogram comprising a plus fraction;
one or more processors in communication with the gas chromatogram and configured to perform operations comprising:
determining, from the gas chromatogram, a first ratio of a first at least one component of the fluid to a second at least one component of the fluid;
comparing the first ratio to a dataset of a plurality of fluids having a respective plurality of component ratios;
determining the plus fraction using the comparison; and
quantifying at least one of the components in the fluid using the determined plus fraction.

10. The fluid analyzer of claim 9 , wherein the first at least one component comprises C22 and the second at least one component comprises C16.

11. The fluid analyzer of claim 9 , comprising wherein the plus fraction comprises a C36+ fraction.

12. The fluid analyzer of claim 9 , wherein the first at least one component and the second at least one component are separated by at least five carbon numbers.

13. The fluid analyzer of claim 9 , comprising:
determining the plus fraction by extrapolating an exponential decay function or by fitting a probability density gamma function to produce a second determined plus fraction.

14. The fluid analyzer of claim 13 , comprising:
calculating an average of the determined plus fraction and the second determined plus fraction to determine an averaged plus fraction; and
quantifying at least one of the plurality components of the first fluid using the averaged plus fraction.

15. The fluid analyzer of claim 9 , wherein the dataset comprises relationships between the plurality of component ratios and a respective plurality of known plus fractions.

16. A method for analyzing a fluid having a plurality of components, comprising:
obtaining a gas chromatogram of the fluid, the gas chromatogram comprising a plus fraction;
determining a fitting curve through the two or more relative concentrations of the fluid;
determining the plus fraction using the extrapolation of the fitting curve; and
quantifying at least one of the plurality components in the fluid using the determined plus fraction.

17. The method of claim 16 , wherein the fitting curve is an exponential decay function.

18. The method of claim 16 , wherein the fitting curve is a probability density gamma function.

19. The method of claim 16 , wherein the gas chromatogram is obtained from a downhole gas chromatograph inserted into a well and configured to generate the gas chromatogram from a sample of the fluid.

20. The method of claim 16 , comprising wherein the plus fraction comprises a C20+ fraction.

Assignees

• Schlumberger Technology Corp

Inventors

• Van Hal Ronald E G
• Crank Jeffrey
• Zuo Youxiang
• Gisolf Adriaan

Classifications

• E21B49/0875

  determining specific fluid parameters · CPC title

• G01N33/2823

  Raw oil, drilling fluid or polyphasic mixtures · CPC title

• G01N2030/8854

  involving hydrocarbons · CPC title

• E21B49/087 Primary

  Well testing, e.g. testing for reservoir productivity or formation parameters · CPC title

• G01N30/8675 Primary

  Evaluation, i.e. decoding of the signal into analytical information (for analysis of specific compounds see also G01N30/88 and subgroups of G01N33/00; chemical libraries per se C40B) · CPC title