Methods and Apparatus to Characterize Stock-Tank Oil During Fluid Composition Analysis

• US 20080173445A1
• Filed: 04/20/2007
• Published: 07/24/2008
• Est. Priority Date: 01/24/2007
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Hegeman, Peter S., Dong, Chengli
• Granted Patent: US 7,586,087 B2
• Time in Patent Office: Days
• US Class Current: 166/264
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: E21B 49/087 Well testing, e.g. testing for reservoir productivity or formation parameters

Abstract

Methods and apparatus to characterize stock-tank oil during fluid composition analysis are disclosed. A disclosed example method to characterize a fluid associated with an underground geological formation comprises obtaining a sample of the fluid associated with the underground geological formation, determining, in a borehole associated with the underground geological formation, a stock-tank oil type for the sample of the fluid associated with the underground geological formation, and determining a property of the fluid associated with the underground geological formation based on the stock-tank oil type.

Claims

1. A method to characterize a fluid associated with an underground geological formation, the method comprising:

obtaining a sample comprising the fluid associated with the underground geological formation;

determining, in a borehole associated with the underground geological formation, a stock-tank oil type for the sample associated with the underground geological formation; and

determining a property of the sample associated with the underground geological formation based on the stock-tank oil type.

2. A method as defined in claim 1, wherein determining the stock-tank oil type for the fluid associated with the underground geological formation comprises:

transmitting light to the fluid;

measuring an effect on the transmitted light caused by the fluid; and

comparing the measured effect to two or more reference effects for hydrocarbon types to determine the stock-tank oil type.

3. A method as defined in claim 2, wherein the measured effect is a light absorption.

4. A method as defined in claim 1, wherein the stock-tank oil type represents a fraction of the fluid that is a waxy stock-tank oil.

5. A method as defined in claim 1, wherein the stock-tank oil type represents a fraction of the fluid that is a branched alkane stock-tank oil.

6. A method as defined in claim 1, further comprising measuring, in the borehole, an optical property of the fluid, wherein the stock-tank oil type is determined based on the optical property.

7. A method as defined in claim 6, wherein the optical property is measured by a grating spectrometer and a filter-array spectrometer.

8. A method as defined in claim 6, wherein the optical property comprise a light absorption spectrum, and further comprising normalizing the spectrum based upon the absorption measured at about 1740 nanometers.

10. A method as defined in claim 1, further comprising:

measuring one or more optical densities of the fluid at one or more wavelengths; and

computing a normalized live oil spectrum based on the one or more measured optical densities, wherein the stock-tank oil type is determined based on the normalized live oil spectrum.

12. A method as defined in claim 1, wherein the property of the fluid is one of a gas-oil-ratio (GOR) value, a mass ratio and a partial density

13. A method as defined in claim 1, wherein the property of the fluid is representative of the composition of the fluid.

14. A method as defined in claim 1, further comprising logging at least one of the determined stock-tank oil type or the determined fluid property.

9. (canceled)

11. (canceled)

15. An apparatus to characterize a fluid associated with an underground geological formation, the apparatus comprising:

a device to obtain a sample of the fluid associated with the underground geological formation;

an optical sensor to measure an optical property of the sample of the fluid; and

an analyzer to determine a stock-tank oil type for the sample of the fluid based on the optical property.

16. An apparatus as defined in claim 15, wherein the optical sensor is to be operated in a borehole associated with the underground geological formation.

17. An apparatus as defined in claim 15, wherein the analyzer is to determine at least one of a gas-oil-ratio or a mass ratio based on the stock-tank oil, type.

18. An apparatus as defined in claim 15, wherein the stock-tank oil type represents a fraction of the sample of the fluid that is a waxy stock-tank oil.

19. An apparatus as defined in claim 15, wherein the stock-tank oil type represents a fraction of the sample of the fluid that is a branched-alkane stock-tank oil.

20. An apparatus as defined in claim 15, further comprising a grating spectrometer and a filter-array spectrometer.

21. (canceled)

22. A method to characterize a fluid associated with an underground geological formation, the method comprising:

obtaining a sample of the fluid associated with the underground geological formation;

detecting in situ indications of absorbance of light by the sample of the fluid;

determining a stock-tank oil type for the sample of the fluid associated wit the underground geological formation based on the detected indications; and

determining a property of the fluid associated with the underground geological formation based on the stock-tank oil type.

23. A method as defined in claim 22, wherein the absorbance of the sample of the fluid is measured at least one of a near infrared wavelength and a visible wavelength.

24. A method as defined in claim 22, wherein the stock-tank oil type represents one of a fraction of the sample of the fluid that is a waxy stock-tank oil and a branched alkane stock-tank oil.

25. A method as defined, in claim 22, wherein the optical density is measured by a grating spectrometer and a filter-array spectrometer.

26. A method comprising:

transmitting light to a sample of an underground geological formation;

measuring an indication of absorption of the transmitted light by the sample; and

comparing the measured indication of absorption to two or more absorptions for respective ones of two or more hydrocarbon types to determine a parameter of the sample, wherein the two or more hydrocarbon types include at least a waxy hydrocarbon and a non-waxy hydrocarbon.

27. A method as defined in claim 26, wherein the parameter of the sample is a stock-tank oil type.

28. A method as defined in claim 27, wherein the stock-tank oil type represents one of a fraction of the sample comprising a waxy stock-tank oil and a fraction of the sample comprising a branched alkane stock-tank oil.

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)