Drill string inground isolator in an MWD system and associated method

Patent metadata

Field	Value
Publication number	US-9500041-B2
Application number	US-201514629269-A
Country	US
Kind code	B2
Filing date	Feb 23, 2015
Priority date	Aug 23, 2012
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

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 drill rig configured to apply each of a push force, a pull force and a rotational force to the drill string, said apparatus comprising:
a housing assembly that is configured to support a plurality of electrical isolators to electrically isolate a downhole portion of the drill string from an uphole portion of the drill string and configured to support the electrical isolators subject to no more than compressive forces responsive to the push force, the pull force and the rotational force.

2. The apparatus of claim 1 wherein said housing assembly defines a through passage that aligns with a through hole of the drill string when the housing is inserted into the drill string.

3. The apparatus of claim 1 wherein the electrical isolators are formed from a ceramic material.

4. The apparatus of claim 3 wherein the ceramic material is at least one of a toughened zirconia and a silicon nitride ceramic.

5. The apparatus of claim 2 wherein said plurality of electrical isolators comprises a plurality of elongated members and said housing assembly captures the plurality of elongated members in a uniformly spaced apart distribution around a centerline of the housing assembly.

6. The apparatus of claim 5 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.

7. The apparatus of claim 6 wherein the compressive force is applied to a cylindrical sidewall of each cylindrical member.

8. The apparatus of claim 6 wherein said housing supports twelve of said cylindrical members.

9. The apparatus of claim 1 wherein said housing assembly is configured such that, responsive to the drill rig pushing on the drill string, a first group of the plurality of electrical isolators is subject to a compressive push force without subjecting a second group of the plurality of electrical isolators to the compressive push force and, responsive to the drill rig pulling on the drill string, the second group is subject to a compressive pull force without subjecting the first group to the compressive pull force.

10. The apparatus of claim 9 configured to subject a selected one of the first and second groups of electrical isolators to an additional compressive force responsive to said rotational force simultaneously with either one of the compressive push force and the compressive pull force.

11. The apparatus of claim 10 wherein only the selected one of the first and second groups is subject to said additional compressive force.

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

13. The apparatus of claim 1 wherein each electrical isolator is at least partially spherical in configuration.

14. The apparatus of claim 1 wherein each electrical isolator is formed having a solid core.

15. The apparatus of claim 1 wherein said housing assembly 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.

Assignees

• Merlin Technology Inc

Inventors

• Chau Albert W
• Theimer Kenneth J

Classifications

• E21B17/003 Primary

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

• 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

• G01V3/34

  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