Stacked Soft Magnetic Inserts and Slotted Shield Designs for Tilted Coil Antennas

• US 20190331824A1
• Filed: 01/10/2017
• Published: 10/31/2019
• Est. Priority Date: 01/10/2017
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Bittar, Michael, Ma, Jin, Wu, Hsu-Hsiang
• Granted Patent: US 11,061,161 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 47/00 Survey of boreholes or wells monitoring pressure or flow of drilling fluid E21B21/08
• CPC Class Codes: G01V 3/28 using induction coils
• CPC Class Codes: H01Q 1/04 Adaptation for subterranean or subaqueous use
• CPC Class Codes: H01Q 1/526 Electromagnetic shields
• CPC Class Codes: H01Q 7/08 Ferrite rod or like elongated core

Abstract

An antenna assembly includes a tool mandrel having a tool axis and a coil including a plurality of windings wrapped about the tool mandrel at a winding angle offset from the tool axis. An antenna shield is secured to the tool mandrel and positioned radially outward from the coil. The antenna shield defines a plurality of slots extending perpendicular to the coil at any angular location about a circumference of the tool mandrel and the plurality of slots is provided in two or more dissimilar lengths.

Claims

1. An antenna assembly, comprising:

a tool mandrel having a tool axis;

a coil including a plurality of windings wrapped about the tool mandrel, wherein portions of the plurality of windings are wrapped about the tool mandrel at a winding angle offset from the tool axis; and

an antenna shield secured to the tool mandrel and positioned radially outward from the coil, wherein the antenna shield defines a plurality of slots extending perpendicular to the coil at any angular location about a circumference of the tool mandrel and the plurality of slots comprises slots of different lengths.

2. The antenna assembly of claim 1, wherein the antenna shield is made of a material selected from the group consisting of fiberglass, a polymer, stainless steel, a nickel-based alloy, a chromium-based alloy, a copper-based alloy, and any combination thereof.

3. The antenna assembly of claim 1, wherein the plurality of slots cooperatively form a discontinuous annular ring that extends about a circumference of the antenna shield at a slot angle that is similar to the winding angle.

4. The antenna assembly of claim 1, wherein the tool mandrel defines a saddle and the coil is positioned in the saddle, and wherein the antenna shield spans an axial length of the saddle.

5. The antenna assembly of claim 1, wherein the two or more dissimilar lengths of the plurality of slots comprise a first length and a second length shorter than the first length, and wherein the first and second lengths alternate about a circumference of the antenna shield in a one-to-one ratio.

6. The antenna assembly of claim 1, wherein the two or more dissimilar lengths of the plurality of slots comprise a first length and a second length shorter than the first length, and wherein the first and second lengths alternate about a circumference of the antenna shield in a two-to-two ratio.

7. The antenna assembly of claim 1, wherein the two or more dissimilar lengths of the plurality of slots comprise a first length and a second length shorter than the first length, and wherein the first and second lengths alternate about a circumference of the antenna shield in a two-to-one ratio.

8. The antenna assembly of claim 1, further comprising a soft magnetic band radially interposing the coil and the tool mandrel and extending about a circumference of the tool mandrel at a band angle parallel to the winding angle,

wherein the soft magnetic band includes a plurality of stacked inserts extending perpendicular to the coil about the circumference of the tool mandrel and each stacked insert includes a plurality of rods positioned end-to-end.

9. The antenna assembly of claim 8, wherein the plurality of rods in each stacked insert cooperatively forms a corresponding straight stacked insert that follows a curvature of an outer surface of the tool mandrel while extending perpendicular to the coil.

10. The antenna assembly of claim 8, wherein the plurality of stacked inserts are aligned radially with the plurality of slots.

11. The antenna assembly of claim 8, wherein the plurality of stacked inserts are radially misaligned with the plurality of slots.

12. The antenna assembly of claim 8, further comprising a bobbin positioned about the circumference of the mandrel, wherein the plurality of stacked inserts is positioned on the bobbin.

13. The antenna assembly of claim 12, wherein the plurality of stacked inserts is positioned on an outer radial surface of the bobbin.

14. A method, comprising:

introducing a wellbore logging tool into a wellbore, the wellbore logging tool including an antenna assembly that includes;

a tool mandrel having a tool axis;

a coil including a plurality of windings wrapped about the tool mandrel, wherein portions of the plurality of windings are wrapped about the tool mandrel at a winding angle offset from the tool axis; and

an antenna shield secured to the tool mandrel and positioned radially outward from the coil, wherein the antenna shield defines a plurality of slots extending perpendicular to the coil at any angular location about a circumference of the tool mandrel and the plurality of slots comprises slots of different lengths; and

obtaining measurements of a surrounding subterranean formation with the wellbore logging tool.

15. The method of claim 14, wherein the tool mandrel is operatively coupled to a drill string and introducing the wellbore logging tool into the wellbore further comprises:

extending the wellbore logging tool into the wellbore on the drill string; and

drilling a portion of the wellbore with a drill bit secured to a distal end of the drill string.

16. The method of claim 14, wherein introducing the wellbore logging tool into the wellbore further comprises extending the wellbore logging tool into the wellbore on wireline as part of a wireline instrument sonde.

17. The method of claim 14, wherein the antenna assembly further includes a bobbin arranged about the circumference of the mandrel and the plurality of stacked inserts is positioned on the bobbin.

18. The method of claim 14, wherein the antenna assembly further includes a soft magnetic band radially interposing the coil and the tool mandrel and extending about a circumference of the tool mandrel at a band angle parallel to the winding angle, wherein the soft magnetic band includes a plurality of stacked inserts extending perpendicular to the coil about the circumference of the tool mandrel and each stacked insert includes a plurality of rods positioned end-to-end.

19. The method of claim 18, wherein the plurality of stacked inserts are aligned radially with the plurality of slots.

20. The method of claim 18, wherein the plurality of stacked inserts are radially misaligned with the plurality of slots.