Nuclear magnetic resonance apparatus, systems, and methods

Patent metadata

Field	Value
Publication number	US-9784881-B2
Application number	US-201615103782-A
Country	US
Kind code	B2
Filing date	Feb 10, 2016
Priority date	Mar 5, 2015
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Apparatus and systems include a magnet assembly comprising a central magnet having a first axial end and a second, opposite axial end; a first end piece magnet having a proximal end and a distal end, the proximal end spaced apart from the first axial end of the central magnet; and a second end piece magnet spaced apart from the second axial end of the central magnet; at least one first shim magnet disposed adjacent to or at least partially surrounded by first magnetically permeable material, the at least one first shim magnet disposed next to an end of the first end piece magnet that is proximal to the central magnet, or next to an end of the first end piece magnet that is distal to the central magnet; and a downhole tool attached to the magnet assembly. Additional apparatus, systems, and methods are disclosed.

First claim

The invention claimed is:

1. An apparatus, comprising:
a magnet assembly to produce a magnetic field in a volume in a geological formation, the magnet assembly comprising:
a central magnet having a first axial end and a second axial end that is opposite the first axial end;
a first end piece magnet spaced apart from the first axial end of the central magnet; and
a second end piece magnet spaced apart from the second axial end of the central magnet;

multiple antennas disposed at respective locations along a longitudinal axis of a downhole tool to which the magnetic assembly is attached, each one of the antennas to detect a nuclear magnetic response from a respective one of multiple corresponding distinct magnetic field sub-volumes defined by the central and first and second end piece magnets; and
at least one first shim magnet disposed between the central magnet and the first end piece magnet, the first shim magnet disposed adjacent to or at least partially surrounded by a first magnetically permeable material, the first shim magnet to shape a first static magnetic field sub-volume provided by the central magnet and the first end piece magnet.

2. The apparatus of claim 1 , further comprising:
copper radially disposed between the first shim magnet and the first magnetically permeable material, or between the central magnet and a central magnetically permeable material.

3. The apparatus of claim 1 , wherein the at least one first shim magnet comprises multiple unitary ring-shaped elements and/or a series of rectangular elements shaped to form a ring.

4. The apparatus of claim 1 , further comprising:
at least one second shim magnet disposed between the central magnet and the second end piece magnet, the second shim magnet disposed adjacent second magnetically permeable material or at least partially surrounded by the second magnetically permeable material and a copper material.

5. The apparatus of claim 4 , further comprising:
at least one set of additional shim magnets adjacent to or at least partially surrounded by additional magnetically permeable material, to outwardly extend an arrangement of the at least one first and second shim magnets, and the first and second magnetically permeable material in a symmetrical fashion along a longitudinal axis of the tool.

6. The apparatus of claim 4 , wherein geological formation depths of inspection associated with the first shim magnet and the second shim magnet are different.

7. The apparatus of claim 1 , wherein the central magnet defines a first magnetic field orientation, and the first and second end piece magnets each define a second magnetic field orientation that is substantially orthogonal to the first magnetic field orientation.

8. The apparatus of claim 1 , wherein at least one of the central magnet or the first and second end piece magnets comprise one or more permanent magnets.

9. The apparatus of claim 1 , wherein the central magnet and the first and second end piece magnets define an overall static magnetic field volume that comprises multiple distinct sub-volumes, the multiple distinct sub-volumes including the first static magnetic field sub-volume that is elongate in a first direction parallel to a longitudinal axis of the tool the magnetic field in the first static magnetic field sub-volume being substantially uniformly oriented in the first direction,
and wherein each of the antennas detect a nuclear magnetic resonance response from a respective one of the distinct sub-volumes when the antennas are operating.

10. The apparatus of claim 1 , wherein conductivity of the first magnetically permeable material is selected to reduce losses in the first magnetically permeable material to less than expected losses in the antennas or the geological formation.

11. The apparatus of claim 1 , further comprising:
an antenna assembly comprising a transversal-dipole antenna disposed over the central magnet, with copper and central magnetically permeable material disposed between the central magnet and the antenna assembly.

12. An apparatus, comprising:
a magnet assembly to produce a magnetic field in a volume in a subterranean region, the magnet assembly comprising:
a central magnet having a first axial end and a second axial end that is opposite the first axial end;
a first end piece magnet having a proximal end and a distal end, the proximal end spaced apart from the first axial end of the central magnet; and
a second end piece magnet spaced apart from the second axial end of the central magnet;

multiple antennas disposed at respective locations along a longitudinal axis of a downhole tool to which the magnetic assembly is attached, each one of the antennas to detect a nuclear magnetic response from a respective one of multiple corresponding distinct magnetic field sub-volumes defined by the central and first and second end piece magnets; and
at least one first shim magnet spaced apart from the distal end of the first end piece magnet; and
the downhole tool further comprising first magnetically permeable material disposed adjacent to or at least partially surrounding the longitudinal axis of the tool, the first magnetically permeable material disposed between the first end piece magnet and the first shim magnet.

13. The apparatus of claim 12 , further comprising:
at least one second shim magnet disposed adjacent to or at least partially surrounded by the first magnetically permeable material.

14. The apparatus of claim 13 , further comprising:
copper disposed between the first magnetically permeable material and the at least one second shim magnet.

15. The apparatus of claim 12 , further comprising:
at least one second shim magnet spaced apart from a distal end of the second end piece magnet and second magnetically permeable material disposed between the second end piece magnet and the second shim magnet, to mirror an arrangement of the first shim magnet and the first magnetically permeable material about a center point of the central magnet.

16. The apparatus of claim 12 , further comprising:
at least one second shim magnet disposed between the central magnet and the second end piece magnet and second magnetically permeable material disposed adjacent to or at least partially surrounding the at least one second shim magnet.

17. A system, comprising:
a magnet assembly to produce a magnetic field in a volume in a subterranean region, the magnet assembly comprising:
a central magnet having a first axial end and a second axial end that is opposite the first axial end;
a first end piece magnet having a proximal end and a distal end, the proximal end spaced apart from the first axial end of the central magnet;
a second end piece magnet spaced apart from the second axial end of the central magnet;
at least one first shim magnet disposed adjacent to or at least partially surrounded by first magnetically permeable material the at least one first shim magnet disposed next to an end of the first end piece magnet that is proximal to the central magnet or next to an end of the first end piece magnet that is distal to the central magnet;

a downhole tool attached to the magnet assembly, further comprising a transmitter and a receiver to excite and receive a nuclear magnetic resonance response in the magnetic field volume; and
multiple antennas disposed at respective locations along a longitudinal axis of the tool, each one of the antennas to detect a nuclear magnetic response from a respective one of multiple corresponding distinct magnetic field sub-volumes defined by the central and first and second end pi

Assignees

• Halliburton Energy Services Inc

Inventors

• Jachmann Rebecca Corina
• Li Lilong
• Reiderman Arcady

Classifications

• G01N24/081

  Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity · CPC title

• G01V3/18

  specially adapted for well-logging · CPC title

• G01R33/3678

  involving quadrature drive or detection, e.g. a circularly polarized RF magnetic field · CPC title

• E21B47/00 Primary

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• G01R33/34092

  RF coils specially adapted for NMR spectrometers · CPC title