Correcting for magnetic interference in azimuthal tool measurements

Patent metadata

Field	Value
Publication number	US-9360582-B2
Application number	US-201113175514-A
Country	US
Kind code	B2
Filing date	Jul 1, 2011
Priority date	Jul 2, 2010
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

Methods and systems that compensate for magnetic interference in azimuthal tool measurements. At least some method embodiments include a downhole logging method that includes taking measurements as a function of orientation from inside a borehole. The measurements are associated with different azimuthal bins, and an azimuthal direction is determined for each azimuthal bin. Because the tool rotates at a constant rate, the relative number of measurements associated which the different bins can be used to measure the effective sizes of the different bins and to redetermine the effective angles of the bins in the presence of magnetic interference. The tool measurements may include, but are not limited to, formation resistivity, magnetic field, and formation density.

First claim

What is claimed is:

1. A downhole logging method that comprises:
using a magnetometer to track an orientation of a rotating downhole tool as the tool acquires azimuthally-sensitive measurements from inside a borehole;
based on said orientation, associating said measurements with different azimuthal bins; and
determining an azimuthal direction for each of said azimuthal bins based at least in part on a ratio of the number of measurements in each bin to the number of measurements in all bins.

2. The method of claim 1 , wherein said rotating logging tool rotates at a constant speed for each rotation.

3. The method of claim 1 , wherein said rotating logging tool acquires said measurements as a function of tool position along said borehole.

4. The method of claim 1 , further comprising determining the size of each bin based at least in part on a ratio of the number of measurements in each bin to the number of measurements in all bins.

5. The method of claim 1 , wherein a sampling number for each of said azimuthal bins are recorded and provided in real-time for each rotation.

6. The method of claim 1 , wherein said determining an azimuthal direction for each bin is repeated at each major depth.

7. The method of claim 1 , wherein said determining an azimuthal direction for each bin is repeated at each rotation.

8. The method of claim 1 , wherein said measurements include at least one of: formation resistivity, magnetic field, and formation density.

9. The method of claim 1 , wherein said measurements and said azimuthal directions is used for post-processing.

10. A downhole logging system that comprises:
an azimuthally sensitive logging tool to obtain measurements;
a memory device to store said measurements in different azimuthal bins; and
a processor that retrieves said measurements from said tool and determines for each bin a related azimuthal direction based at least in part on a ratio of the number of measurements in that bin to the number of measurements in all bins.

11. The system of claim 10 , wherein said logging tool is rotated at a constant speed for each rotation to obtain said measurements.

12. The system of claim 10 , wherein said logging tool is used during wireline logging, if said tool is rotating.

13. The system of claim 10 , wherein said logging tool is used during logging while drilling (LWD).

14. The system of claim 10 , wherein said logging tool is used during measurements while drilling (MWD).

15. The system of claim 10 , wherein said logging tool further comprises a tilted antenna.

16. The system of claim 15 , wherein said tilted antenna includes various tilt angles.

17. The system of claim 15 , wherein said logging tool takes measurements as a function of orientation from inside a borehole.

18. The system of claim 15 , wherein said measurements include at least one of: formation resistivity, magnetic field, and formation density.

19. A downhole logging system that comprises:
an azimuthally sensitive logging tool that obtains measurements;
a memory device that stores said measurements in different azimuthal bins; and
a processor that retrieves said measurements from said tool and determines an adjusted azimuthal direction for each bin, wherein the adjusted azimuthal direction for each bin i is representable as:

β
i
′

=

2
⁢

⁢
π
⁢

-

S
i

2

+

∑

k
=
1

i

⁢

S
k

∑

k
=
1

N

⁢

S
k

,

i
=
1

,
…
⁢

,
N

where S i is the number of samples in bin i and N is the number of bins.

20. A downhole logging method that comprises:
using a magnetometer to track an orientation of a rotating downhole tool as the tool acquires azimuthally-sensitive measurements from inside a borehole;
based on said orientation, associating said measurements with different azimuthal bins; and
determining an azimuthal direction for each of said azimuthal bins, wherein the azimuthal direction for each bin i is representable as:

β
i
′

=

2
⁢

⁢
π
⁢

-

S
i

2

+

∑

k
=
1

i

⁢

S
k

∑

k
=
1

N

⁢

S
k

,

i
=
1

,

Assignees

• Bittar Michael S
• Wu Hsu-Hsiang
• Golla Christopher
• Halliburton Energy Services Inc

Inventors

• Bittar Michael S
• Wu Hsu-Hsiang
• Golla Christopher

Classifications

• G01V3/28 Primary

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