Configurable magnet assembly for using in NMR well logging instrument

• US 7,834,622 B2
• Filed: 10/18/2007
• Issued: 11/16/2010
• Est. Priority Date: 10/18/2007
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Beard, David R., Reiderman, Arcady, Edwards, Carl M.
• Primary Examiner(s): Arana; Louis M
• Application Number:
  US11/874,532
• Publication Number:
  US 20090102478A1
• Time in Patent Office: 1,125 Days
• Field of Search: 324/303, 324/307, 324/309
• US Class Current: 324/303
• CPC Class Codes: G01V 3/32 operating with electron or nuclear magnetic resonance
• CPC Class Codes: H01F 7/0278 for generating uniform fields, focusing, deflecting electrically charged particles for magnetic separation by Lorentz force B03C1/023; specially adapted for NMR applications G01R33/383
• CPC Class Codes: H01F 7/04 Means for releasing the attractive force
• CPC Class Codes: H01F 7/20 without armatures cores H01F3/00; coils H01F5/00 ; shaping metal by applying magnetic forces B21D26/14; electromagnets specially adapted for NMR applications G01R33/381
• CPC Class Codes: Y10T 29/49075 including permanent magnet or core

Abstract

A magnet assembly for measuring properties of a formation from a borehole, the magnet assembly including a first device and a second device, each device adapted for insertion into the borehole, the first device producing a first magnetic field, the second device producing a second magnetic field; wherein the second magnetic field is configurable for one of reinforcing and reducing the first magnetic field; and wherein the first device comprises a permanent magnet and the second device comprises at least one of one of a switchable magnet and switching windings.

Claims

1. A magnet assembly for measuring properties of a formation from a borehole, the magnet assembly comprising:

a first device and a second device, each device adapted for insertion into the borehole, the first device producing a first magnetic field, the second device producing a second magnetic field;

wherein the second magnetic field is configurable for one of reinforcing and reducing the first magnetic field to produce a magnetic field used for the measuring; and

wherein the first device comprises a permanent magnet and the second device comprises at least one of one of a switchable magnet configured to have a direction of the second magnetic field reversed within the switchable magnet and switching windings.

2. The assembly as in claim 1, wherein the reinforcing enables nuclear magnetic resonance (NMR) measurements.

3. The assembly as in claim 1, wherein the reducing enables at least one of nuclear quadrapole resonance measurements, nuclear magnetic resonance (NMR) measurements with a substantially separate frequency range, and movement of the magnet assembly in the borehole without a substantial magnetic attraction to a magnetic casing.

4. The assembly as in claim 1, further comprising a magnetic material disposed between magnetic poles of the permanent magnet and the switchable magnet, the material for conducting magnetic flux.

5. The assembly as in claim 4, wherein the magnetic material comprises at least one of high saturation and non-conductivity properties.

6. The assembly as in claim 4, wherein the magnetic material comprises an antenna winding for nuclear magnetic resonance measurements.

7. The assembly as in claim 4, further comprising a magnetic shield for reducing a residual magnetic field external to the assembly to essentially zero.

8. The assembly as in claim 4, wherein the switching windings and at least one of the permanent magnet, the switchable magnet, and the magnetic material are divided into sections essentially aligned about a longitudinal axis, wherein the switching windings are adapted for being energized sequentially.

9. The assembly as in claim 1, further comprising a magnetic probe for adjusting an amplitude of the second magnetic field to reduce the first magnetic field.

10. The assembly as in claim 1, wherein the permanent magnet comprises a hollow cylindrical shape and the switchable magnet comprises a cylindrical shape, wherein the switchable magnet is adapted for placement internal to the permanent magnet.

11. The assembly as in claim 10, wherein the switching windings and at least one of the permanent magnet and the switchable magnet are divided into sections essentially aligned about a longitudinal axis, wherein the switching windings are adapted for being energized sequentially.

12. The assembly as in claim 1, wherein the permanent magnet comprises a hollow cylindrical shape and the switching windings are disposed internal and external to the permanent magnet.

13. A method for producing a magnet assembly, the assembly adapted for use in a borehole, the method comprising:

selecting a permanent magnet configured to produce a first magnetic field;

selecting at least one of switching windings and a switchable magnet, each configured to produce a second magnetic field configurable for one of reinforcing and reducing the first magnetic field, the switchable magnet being further configured to have a direction of the second magnetic field reversed within the switchable magnet; and

combining the permanent magnet and at least one of the switching windings and the switchable magnet to form the assembly.

14. The method as in claim 13, further comprising placing an antenna winding in the assembly.

15. The method as in claim 13, further comprising placing a magnetic shield in the assembly.