Drill string inground isolator in an MWD system and associated method

Patent metadata

Field	Value
Publication number	US-9000940-B2
Application number	US-201213593439-A
Country	US
Kind code	B2
Filing date	Aug 23, 2012
Priority date	Aug 23, 2012
Publication date	Apr 7, 2015
Grant date	Apr 7, 2015

Abstract

An inground isolator and associated method can provide an electrically isolated break in a drill string using electrical insulating members/isolators that are supported by a housing. During drill string operations, the isolators are subject only compressive forces responsive to both extension (pushing) and retraction (pulling) by the drill string. The isolators can be formed from an electrically insulating material such as a ceramic material. An interchangeable inground tool system is described which integrally serves to provide an electrically isolating gap in the drill string.

First claim

What is claimed is:

1. An apparatus for use in combination with a drill string that is electrically conductive and extends from an inground distal end, that includes an inground tool, to a drill rig, said apparatus comprising:
a first group of electrical isolators and a second group of electrical isolators; and
a housing that defines a through passage along a length thereof and said housing is configured to support the first group and the second group in a spaced apart relationship along said length and surrounding the through passage such that, responsive to the drill rig pushing on the drill string, a first one of the first and second groups is subject to a first compressive force and responsive to the drill rig pulling on the drill string the other one of the first and second groups is subject to a second compressive force without subjecting either of the first and second groups to a tension force during said pushing and pulling by the drill rig to form an electrically isolating break in the drill string.

2. The apparatus of claim 1 wherein said housing is configured such that, responsive to the drill rig pushing on the drill string, a first one of the first and second groups is subject to the first compressive force without subjecting the second group to the first compressive force and, responsive to the drill rig pulling on the drill string, and responsive to the drill rig pulling on the drill string a second one of the first and second groups is subject to the second compressive force without subjecting the other one of the first and second groups to the second compressive force.

3. The apparatus of claim 1 configured for insertion into the drill string to thereafter form part of an overall length of the drill string.

4. The apparatus of claim 1 configured to form part of said inground tool.

5. The apparatus of claim 1 configured to subject a selected one of the first and second groups of electrical isolators to an additional compressive force responsive to a rotational torque that is applied to the drill string by the drill rig.

6. The apparatus of claim 5 wherein only the selected one of the first and second groups is subject to said further additional compressive force.

7. The apparatus of claim 1 wherein the first group of electrical isolators and the second group of electrical isolators are formed from an identical material.

8. The apparatus of claim 1 wherein the first insulating members and the second insulating members are a ceramic material.

9. The apparatus of claim 8 wherein the ceramic material is selected as at least one of a toughened zirconia and a silicon nitride ceramic.

10. The apparatus of claim 1 wherein each electrical isolator is spherical in configuration.

11. The apparatus of claim 1 wherein said first group of electrical isolators comprises a plurality of elongated members and said housing captures the plurality of elongated members in a uniformly spaced apart distribution around a centerline of the housing.

12. The apparatus of claim 11 wherein each one of the plurality of elongated members is a cylindrical member defining an elongation axis and said housing supports each one of the plurality of cylindrical members having said elongation axis at least approximately parallel to said centerline.

13. The apparatus of claim 12 wherein each cylindrical member is formed having a solid core.

14. The apparatus of claim 12 wherein the plurality of cylindrical members is subject to said second compressive force responsive to the drill rig pulling on the drill string.

15. The apparatus of claim 14 wherein said second compressive force is applied to a pair of opposing end surfaces of each cylindrical member.

16. The apparatus of claim 12 wherein said housing supports six of said cylindrical members.

17. The apparatus of claim 1 wherein said second group of electrical isolators comprises a plurality of elongated members and said housing captures the plurality of elongated members in a uniformly spaced apart distribution around a centerline of the housing.

18. The apparatus of claim 17 wherein each one of the plurality of elongated members is a cylindrical member defining an elongation axis and said housing supports each one of the plurality of cylindrical members having said elongation axis extending at least approximately radially from said centerline.

19. The apparatus of claim 18 wherein the plurality of cylindrical members is subject to said first compressive force responsive to the drill rig pushing on the drill string.

20. The apparatus of claim 19 wherein said compressive force is applied to opposing side margins of a cylindrical sidewall of each cylindrical member.

21. The apparatus of claim 18 wherein said drill rig is configured to apply rotation to the drill string and the housing is configured to apply an additional compressive force to the cylindrical members for transferring the rotational torque to the inground tool.

22. The apparatus of claim 21 wherein said additional compressive force is applied to a cylindrical sidewall of each cylindrical member.

23. The apparatus of claim 19 wherein said housing supports six of said cylindrical members.

24. The apparatus of claim 1 further comprising:
said first group of electrical isolators comprises a first plurality of cylindrical members and said housing captures the first plurality of cylindrical members in a first uniformly spaced apart distribution around a centerline of the housing; and
said second group of electrical isolators comprises a second plurality of cylindrical members and said housing captures the second plurality of cylindrical members in a second uniformly spaced apart distribution around the centerline of the housing.

25. The apparatus of claim 24 wherein each one of said first plurality of cylindrical members defines an elongation axis that is supported at least approximately parallel to the centerline and each one of the second plurality of cylindrical members defines an elongation axis that is supported to extend at least approximately radially from said centerline.

26. The apparatus of claim 1 wherein said housing includes a drive dog housing having (i) a first end configured to engage a first end fitting for fixed rotation as well as electrical contact therewith and (ii) a second, opposing end that is configured to rotationally engage a second end fitting.

27. The apparatus of claim 26 wherein the first end fitting is a pin fitting and the second end fitting is a box fitting.

28. The apparatus of claim 26 wherein the drive dog housing and the second end fitting are configured to cooperate to capture the second group of electrical isolators therebetween.

29. The apparatus of claim 28 wherein said second group of electrical isolators comprises a plurality of cylindrical elongated members captured in a uniformly spaced apart distribution around a centerline of the housing.

30. The apparatus of claim 29 wherein the second end of the drive dog housing defines a peripheral endwall that is arranged in a confronting relationship with a peripheral side margin of the second end fitting when the drive dog housing rotationally engages the second end fitting to cooperatively define a plurality of pockets that such that one of the cylindrical elongated members is captured in each pocket.

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Assignees

• Chau Albert W
• Theimer Kenneth J
• Merlin Technology Inc

Inventors

• Chau Albert W
• Theimer Kenneth J

Classifications

• E21B47/12 Primary

  Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling · CPC title

• E21B17/003

  with electrically conducting or insulating means (E21B17/028 and E21B17/023 take precedence) · CPC title

• G01V3/34 Primary

  Transmitting data to recording or processing apparatus; Recording data · CPC title

• E21B7/028

  the drilling apparatus being detachable from the vehicle, e.g. hand portable drills · CPC title

• E21B47/024

  of devices in the borehole (determining slope or direction of the borehole E21B47/022) · CPC title