Downhole magnetic dipole antenna

• US 6,249,259 B1
• Filed: 09/30/1999
• Issued: 06/19/2001
• Est. Priority Date: 09/30/1999
• Status: Expired due to Term

• Current Assignee: Gas Technology Institute
• Original Assignee: Gas Research Institute (GTI Energy)
• Inventors: Goodman, William L., Sweeny, Mark
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Alemu, Ephrem
• Application Number:
  US09/409,222
• Time in Patent Office: 628 Days
• Field of Search: 343/788, 343/789, 343/790, 343/787, 324/303, 340/854.5, 340/854.6, 340/854.3
• US Class Current: 343/788
• CPC Class Codes: H01Q 7/08 Ferrite rod or like elongated core

Abstract

A downhole magnetic hollow core dipole antenna has a high permeability material magnetic core composed of laminated sections placed around a section of drill pipe and running substantially along the length of the pipe. The magnetic core is then surrounded by electrically conductive windings, which in turn are surrounded by a protective sleeve which, if conductive, is split to prevent power-robbing eddy current generation.

Claims

1. A downhole magnetic antenna comprising:

a) a mechanical support inside a tubular magnetic core;

b) the magnetic core contacting and surrounding the mechanical support, wherein the magnetic core is a cylindrical sleeve composed of high magnetic permeability material laminations; and

c) electrically conductive windings surrounding the magnetic core.

2. The antenna of claim 1 wherein the mechanical support is a pipe.

3. The antenna of claim 1 further comprising a protective outer cover surrounding the windings.

4. The antenna of claim 1, further comprising an outer protective cover that is electrically conductive and having a longitudinal split.

5. The antenna of claim 1, wherein the sleeve is composed of two semicircular halves with laminations of each half being bent in semicircular fashion.

6. The antenna of claim 5, wherein the two halves are held by a clamp.

7. The antenna of claim 1, wherein the sleeve is composed of laminations bent annularly into an open ring.

8. The antenna of claim 1, wherein the sleeve is composed of flat laminations of varying width stacked to produce an annular sleeve.

9. The antenna according to claim 8, wherein the annular sleeve is composed of two semicircles.

10. The antenna of claim 1, wherein the sleeve is composed of radially arranged sections of laminate.

11. The antenna according to claim 10, wherein the laminates are arranged in more than one circumferential shell surrounding the pipe.

12. The antenna of claim 2, wherein the pipe is a drill pipe and the magnetic core is electrically insulated from the drill pipe.

13. The antenna of claim 1, wherein the laminations are selected to have a magnetic-easy axis oriented on the longituidinal axis of the magnetic core.

21. The antenna of claim 1, wherein the sleeve is composed of radially arranged sections of laminate.

22. The antenna according to claim 21, wherein the laminates are arranged in more than one circumferential shell surrounding the pipe.

14. A downhole magnetic antenna comprising:

a) a drill pipe;

b) a magnetic core cylindrical sleeve contacting and surrounding the drill pipe, the sleeve being composed of high magnetic permeability material laminations and being electrically insulated from the drill pipe;

c) electrically conductive windings surrounding the cylindrical sleeve; and

d) a protective outer cover surrounding the windings.

15. The antenna of claim 14, wherein the protective cover is electrically conductive and has a longitudinal split.

16. The antenna of claim 14, wherein the sleeve is composed of two semicircular halves with laminations of each half being bent in semicircular fashion.

17. The antenna of claim 14, wherein the two halves are held by a clamp.

18. The antenna of claim 14, wherein the sleeve is composed of laminations bent annularly into an open ring.

19. The antenna of claim 14, wherein the sleeve is composed of flat laminations of varying width stacked to produce an annular sleeve.

20. The antenna according to claim 19, wherein the annular sleeve is composed of two semicircles.