Asphaltene content of heavy oil

• US 10,012,074 B2
• Filed: 01/11/2013
• Issued: 07/03/2018
• Est. Priority Date: 01/12/2012
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Pomerantz, Andrew E., Hamad, Zied Ben, Andrews, Albert Ballard, Zuo, Youxiang, Mullins, Oliver Clinton
• Primary Examiner(s): Decenzo, Shawn
• Application Number:
  US14/371,987
• Publication Number:
  US 20150000902A1
• Time in Patent Office: 1,999 Days
• Field of Search: None
• CPC Class Codes: E21B 47/114 using light radiation
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
• CPC Class Codes: E21B 49/081 with down-hole means for trapping a fluid sample E21B49/10 takes precedence
• CPC Class Codes: E21B 49/10 using side-wall fluid samplers or testers

Abstract

A downhole tool is conveyed within a borehole extending into a subterranean formation. Fluid is drawn from the subterranean formation into the downhole tool, wherein the fluid comprises heavy oil. Fluorescence intensity of the drawn fluid is measured via a sensor of the downhole tool, and asphaltene content of the drawn fluid is estimated based on the measured fluorescence intensity.

Claims

1. A method, comprising:

conveying a downhole tool within a borehole extending into a subterranean formation, wherein the subterranean formation comprises a fluid of varying viscosity;

drawing fluid from the subterranean formation into the downhole tool;

measuring fluorescence intensity of the drawn fluid via a sensor of the downhole tool; and

estimating asphaltene content of the drawn fluid based on the measured fluorescence intensity utilizing a relationship between fluorescence intensity and asphaltene content given by;

2. The method of claim 1 wherein the fluid comprises hydrocarbons.

3. The method of claim 1 wherein the fluid comprises heavy oil.

4. The method of claim 1 wherein the fluid comprises heavy oil having an asphaltene content of at least about 2% by weight.

5. The method of claim 1 wherein the fluid comprises heavy oil having a minimum viscosity of about 1500 cP.

6. The method of claim 1 wherein conveying the downhole tool within the borehole is via wireline or tubular string.

7. The method of claim 1 wherein estimating asphaltene content of the drawn fluid based on the measured fluorescence intensity is performed downhole by the downhole tool.

8. The method of claim 7 further comprising transmitting information regarding the estimated asphaltene content from the downhole tool to equipment at the Earth'"'"'s surface in communication with the downhole tool.

9. The method of claim 1 further comprising measuring viscosity of the drawn fluid via an additional sensor of the downhole tool, wherein estimating asphaltene content of the drawn fluid is further based on the measured viscosity.

10. The method of claim 1 further comprising estimating viscosity of the drawn fluid based on previously obtained logging data associated with the subterranean formation, wherein estimating asphaltene content of the drawn fluid is further based on the estimated viscosity.

11. The method of claim 1 further comprising determining whether viscosity of the drawn fluid has been measured, wherein:

if viscosity of the drawn fluid has been measured, estimating asphaltene content of the drawn fluid is further based on the measured viscosity; and

if viscosity of the drawn fluid has not been measured, the method further comprises estimating viscosity of the drawn fluid based on previously obtained logging data associated with the subterranean formation, wherein estimating asphaltene content of the drawn fluid is further based on the estimated viscosity.

12. The method of claim 1 further comprising estimating viscosity of the drawn fluid based on the measured fluorescence intensity, wherein estimating asphaltene content of the drawn fluid is further based on the estimated viscosity.

13. The method of claim 1 further comprising determining whether viscosity of the drawn fluid has been measured, wherein:

if viscosity of the drawn fluid has been measured, estimating asphaltene content of the drawn fluid is further based on the measured viscosity; and

if viscosity of the drawn fluid has not been measured, the method further comprises estimating viscosity of the drawn fluid based on the measured fluorescence intensity, wherein estimating asphaltene content of the drawn fluid is further based on the estimated viscosity.

14. The method of claim 1 further comprising adjusting an operational parameter of the downhole tool based on the estimated asphaltene content.

15. The method of claim 1 further comprising:

directing the drawn fluid into a sample chamber of the downhole tool based on the estimated asphaltene content; and

retrieving the downhole tool from the borehole to the Earth'"'"'s surface and then withdrawing the fluid from the sample chamber.

16. The method of claim 1 further comprising adjusting an operational parameter of a pump of the downhole tool based on the estimated asphaltene content.

17. A method, comprising:

conveying a downhole tool within a borehole extending into a subterranean formation, wherein the subterranean formation comprises a fluid of varying viscosity;

drawing fluid from the subterranean formation into the downhole tool;

measuring fluorescence intensity of the drawn fluid via a sensor of the downhole tool; and

estimating asphaltene content of the drawn fluid based on the measured fluorescence intensity utilizing a relationship between fluorescence intensity and asphaltene content given by;

I_f<sup>−

1</sup>=α

[1+β

″

(1−

K′

[A])^ν

[A]],

wherein;

I_f is the measured fluorescence intensity;

α

is a fitting parameter;

β

″

is a parameter defined as;

8RTτ

₀/(3η

_m);

R is the universal gas constant;

T is temperature of the drawn fluid;

τ

₀ is intrinsic fluorescence lifetime;

K′

is a constant;

[A] is the asphaltene content;

ν

is a constant; and

η

_m is the viscosity of free maltine.

18. The method of claim 17 wherein K′

may have a value of about 1.88 and ν

may have a value of about 6.9.