Oil based drilling mud filtrate contamination monitoring using gas to oil ratio

Patent metadata

Field	Value
Publication number	US-9606260-B2
Application number	US-201313865839-A
Country	US
Kind code	B2
Filing date	Apr 18, 2013
Priority date	Apr 18, 2013
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

A method for monitoring oil based mud filtrate contamination is provided including steps of analytically dividing a fluid stream into two parts, determining a gas/oil ratio for a native fluid determining an apparent gas/oil ratio for the contaminated fluid and determining on a volume fraction, an oil based contamination level based upon the gas/oil ratio for the native fluid and the apparent gas/oil ratio for the contaminated fluid.

First claim

What is claimed is:

1. A method for monitoring oil based mud filtrate contamination, comprising:
analytically dividing a fluid stream into two parts;
determining a gas/oil ratio for a native fluid;
determining an apparent gas/oil ratio for the contaminated fluid; and
determining on a volume fraction at downhole conditions, an oil based mud filtrate contamination level based upon the gas/oil ratio for the native fluid, the apparent gas/oil ratio for the contaminated fluid, and a formation volume factor of the contaminated fluid.

2. The method according to claim 1 , wherein the gas/oil ratio is measured using optical density analysis.

3. The method according to claim 1 , wherein a single packer is used to determine the gas/oil ratio for the native fluid.

4. The method according to claim 1 , further comprising:
estimating an endpoint gas/oil ratio for native oil from data from at least one nearby well.

5. The method according to claim 1 , wherein the gas/oil ratio is determined from a live fluid density.

6. The method according to claim 5 , wherein the live fluid density is obtained from pressure gradients.

7. The method according to claim 5 , wherein the live fluid density is obtained during a cleanup process.

8. The method according to claim 1 , wherein the apparent gas/oil ratio is calculated by curve fitting.

9. The method according to claim 8 , wherein the curve fitting is performed through a formula:
GOR=GOR 0 −βV −γ .

10. The method according to claim 1 , further comprising:
determining an endpoint gas/oil ratio.

11. The method according to claim 10 , wherein the endpoint gas/oil ratio is determined through an analysis of live fluid density.

12. The method according to claim 10 , further comprising:
analyzing a live fluid density regression to determine the endpoint gas/oil ratio.

13. A method for monitoring oil based mud filtrate contamination in a downhole environment, comprising:
lowering a downhole device into the downhole environment;
sampling a fluid from the downhole environment;
analytically dividing the fluid into two parts, an oil based mud and a native fluid;
determining a gas/oil ratio for the native fluid;
determining an apparent gas/oil ratio for the contaminated fluid; and
determining on a volume fraction at downhole conditions, an oil based mud filtrate contamination level based upon the gas/oil ratio for the native fluid, the apparent gas/oil ratio for the contaminated fluid, and a formation volume factor of the contaminated fluid.

14. The method according to claim 13 , further comprising:
determining an endpoint gas/oil ratio for the native fluid.

15. The method according to claim 14 , wherein the endpoint gas/oil ratio for the native fluid is determined through an analysis of live fluid density.

16. The method according to claim 14 , further comprising:
analyzing a live fluid density regression to determine the endpoint gas/oil ratio.

Assignees

• Schlumberger Technology Corp

Inventors

• Zuo Youxiang
• Gisolf Adriaan
• Smits Anthony
• Mullins Oliver C

Classifications

• E21B49/088

  combined with sampling · CPC title

• G01N33/2823 Primary

  Raw oil, drilling fluid or polyphasic mixtures · CPC title

• G01V8/10 Primary

  Detecting, e.g. by using light barriers (by reflection from the object G01S17/00) · CPC title