Multi-sensor contamination monitoring

Patent metadata

Field	Value
Publication number	US-9733389-B2
Application number	US-201213721981-A
Country	US
Kind code	B2
Filing date	Dec 20, 2012
Priority date	Dec 20, 2012
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A downhole sampling tool is operated to obtain formation fluid from a subterranean formation, which then flows through a flowline of the downhole sampling tool. Real-time density and optical density sensors of the downhole sampling tool are co-located proximate the flowline. Contamination of the formation fluid in the flowline is then determined based, at least in part, on the real-time density and optical density measurements obtained utilizing the co-located sensors.

First claim

What is claimed is:

1. A method, comprising:
conveying a downhole sampling tool within a borehole extending into a subterranean formation;
operating the downhole sampling tool to obtain formation fluid from the subterranean formation;
flowing the obtained formation fluid through a flowline of the downhole sampling tool;
obtaining real-time measurements of the formation fluid flowing through the flowline, including:
obtaining real-time density measurements via a densimeter of the downhole sampling tool; and
obtaining real-time optical density measurements via a multi-channel optical sensor of the downhole sampling tool, wherein the densimeter and the multi-channel optical sensor are co-located proximate the flowline such that the real-time density measurements and the real-time optical density measurements are obtained substantially simultaneously; and
estimating actual contamination of the formation fluid flowing through the flowline based on a relation between the obtained real-time density measurements and the obtained real-time optical density measurements.

2. The method of claim 1 further comprising:
obtaining wavelength-dependent optical density of uncontaminated formation oil for one wavelength channel of the multi-channel optical sensor;
determining wavelength-dependent optical density of uncontaminated formation oil for other wavelength channels of the multi-channel optical sensor based on the obtained wavelength-dependent optical density of formation oil for the one wavelength channel;
obtaining a multi-channel optical density response of uncontaminated formation oil based on the obtained wavelength-dependent optical density of uncontaminated formation oil for the one wavelength channel and the other wavelength channels; and
determining at least one of a composition and a gas-to-oil ratio (GOR) of uncontaminated formation oil based on the obtained multi-channel optical density response of uncontaminated formation oil.

3. The method of claim 2 wherein determining wavelength-dependent optical density of uncontaminated formation oil for the other wavelength channels of the spectrometer based on the obtained wavelength-dependent optical density of formation oil for the one wavelength channel utilizes a cross-plot of multi-wavelength channel data.

4. The method of claim 1 wherein obtaining the real-time measurements of the formation fluid flowing through the flowline comprises substantially continuously obtaining the real-time measurements.

5. The method of claim 1 further comprising determining an uncontaminated formation oil density, and wherein estimating the actual contamination of the formation fluid is further based on the determined uncontaminated formation oil density.

6. The method of claim 5 wherein determining the uncontaminated formation oil density utilizes a pressure gradient that is based on formation pressure measurements at multiple depths.

7. The method of claim 1 further comprising determining a filtrate density, and wherein estimating the actual contamination of the formation fluid is further based on the determined filtrate density.

8. The method of claim 7 wherein determining the filtrate density is based on at least one downhole measurement.

9. The method of claim 1 further comprising:
determining an uncontaminated formation oil density;
determining a filtrate density; and
estimating initial contamination based on the obtained real-time density measurements, the determined uncontaminated formation oil density, and the determined filtrate density;
wherein estimating the actual contamination of the formation fluid is further based on the estimated initial contamination.

10. The method of claim 9 further comprising:
obtaining a wavelength-dependent optical density of filtrate;
iteratively obtaining instantaneous first estimates of wavelength-dependent optical density of uncontaminated formation oil based on:
the obtained real-time optical density data;
the obtained wavelength-dependent optical density of the filtrate; and
the estimated initial contamination; and
obtaining a second estimate of the wavelength-dependent optical density of uncontaminated formation oil based on accumulated ones of the iteratively obtained instantaneous first estimates of the wavelength-dependent optical density of uncontaminated formation oil;
wherein estimating actual contamination of the formation fluid is further based on the obtained real-time optical density measurements, the wavelength-dependent optical density of the filtrate, and at least one of:
the iteratively obtained instantaneous first estimates of wavelength-dependent optical density of uncontaminated formation oil; and
the second estimate of the wavelength-dependent optical density of uncontaminated formation oil.

11. The method of claim 1 further comprising preprocessing the real-time optical density measurements to remove effects of optical scattering from the real-time optical density measurements, and wherein estimating the actual contamination of the formation fluid is based on the preprocessed real-time optical density measurements.

12. The method of claim 1 further comprising adjusting an operational parameter of the downhole sampling tool based on the estimated actual contamination of the formation fluid, wherein adjusting an operational parameter of the downhole sampling tool comprises at least one of:
initiating storage of a sample of the formation fluid within the downhole sampling tool; and
adjusting a rate of pumping of formation fluid into the downhole sampling tool.

13. The method of claim 1 further comprising determining first and second coefficients collectively relating density and optical density of the formation fluid, and wherein wavelength-dependent optical density of the formation fluid is equal to the sum of the first coefficient and the product of the second coefficient and density of the formation fluid.

14. The method of claim 13 wherein determining the first and second coefficients comprises fitting the obtained real-time density and optical density measurements with the relationship between the wavelength-dependent optical density of the formation fluid, the density of the formation fluid and the first and second coefficients.

15. The method of claim 14 further comprising:
obtaining uncontaminated formation oil density; and
obtaining wavelength-dependent optical density of uncontaminated formation oil based on the obtained uncontaminated formation oil density.

16. The method of claim 15 wherein:
one of filtrate density and wavelength-dependent optical density of the filtrate is known and the other one is unknown;
the method further comprises determining a value of the unknown one based on the known one; and
estimating actual contamination of the formation fluid is based on:
the value determined for the unknown one;
the obtained wavelength-dependent optical density of uncontaminated formation oil; and
the obtained real-time optical density measurements.

17. An apparatus, comprising:
a downhole sampling tool conveyable within a wellbore extending into a subterranean formation, wherein the downhole sampling tool comprises:
a flowline conducting formation fluid obtained from the subterranean formation via operation of the downhole sampling tool;
a plurality of co-located sensors proximate the flowline and including a densimeter and an optical density sensor such that density measurements and optical density measurements are obtained substantially simultaneously;
a multi-channel spectrometer comprising the optical densit

Assignees

• Schlumberger Technology Corp

Inventors

• Hsu Kai
• Pop Julian J
• Indo Kentaro

Classifications

• G01V8/00

  Prospecting or detecting by optical means · CPC title

• G01V11/00 Primary

  Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00 · CPC title

• E21B49/10

  using side-wall fluid samplers or testers · CPC title