Electromagnetic linear drive source for logging-while-drilling/wireline acoustic applications

• US 8,261,873 B2
• Filed: 12/08/2008
• Issued: 09/11/2012
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Richenstev, Valeriy, Dubinsky, Vladimir, Patterson, Douglas J., Hook, Jonathan F., Lilly, David H.
• Primary Examiner(s): Phillips, Forrest M
• Application Number:
  US12/330,340
• Publication Number:
  US 20100142319A1
• Time in Patent Office: 1,373 Days
• Field of Search: 181/166, 181/167, 181/171, 181/172, 181/104, 181/106, 181/113, 381/400
• US Class Current: 181/104
• CPC Class Codes: G01V 1/04 Details
• CPC Class Codes: G01V 1/52 Structural details

Abstract

An apparatus and method for providing a downhole acoustic source is disclosed. The acoustic source includes a piston configured to oscillate in an axial direction of the acoustic source and produce an acoustic signal in a medium in contact with an exterior surface of the piston, and an elastomer disposed on an interior side of the piston, an acoustic impedance of the elastomer selected to match an acoustic impedance of the piston. A permanent magnet is configured to provide a permanent magnetic field oriented in the axial direction, and a coil disposed on an interior side of the piston produces an alternating magnetic field in the region of the permanent magnetic field. The elastomer may be, for example, a silicon rubber, a silicone jelly, and a silicone oil. A plurality of acoustic sources may be arranged to produce an acoustic dipole configuration or an acoustic quadrupole configuration.

Claims

1. A downhole acoustic source, comprising:

a piston configured to oscillate in an axial direction of the acoustic source and produce an acoustic signal in a fluid in an annulus in contact with an exterior surface of the piston, the exterior surface of the piston extending into the annulus, and the axial direction of the acoustic source being transverse to an axial direction of the tool; and

an elastomer disposed on an interior side of the piston, an acoustic impedance of the elastomer selected to match an acoustic impedance of the piston.

2. The downhole acoustic source of claim 1 further comprising a stator disposed on a side of the elastomer opposite the piston, the stator configured to house the piston.

3. The downhole acoustic source of claim 1 further comprising a permanent magnet configured to provide a permanent magnetic field oriented in an axial direction of the acoustic source.

4. The downhole acoustic source of claim 3 further comprising a coil coupled to the piston and configured to produce an alternating magnetic field in the region of the permanent magnetic field.

5. The downhole acoustic source of claim 4 further comprising an alternating current source in electrical contact with the coil to produce the alternating magnetic field.

6. The downhole acoustic source of claim 1, wherein the elastomer is one of:

i) a silicon rubber, ii) a silicone jelly, and iii) a silicone oil.

7. The downhole acoustic source of claim 1, wherein the source is configured to be conveyed on one of:

i) a wireline, and ii) a drillstring.

8. The downhole acoustic source of claim 1, wherein the source is configured as part of:

at least one of;

i) an acoustic dipole configuration, and ii) an acoustic quadrupole configuration.

9. The downhole acoustic source of claim 1, wherein the source is configured to reduce an acoustic tool mode.

10. The downhole acoustic source of claim 1, wherein the acoustic source is configured to be coupled to a surface of a bottom hole assembly.

11. A method of providing an acoustic source, comprising:

oscillating a piston in an axial direction of the acoustic source to produce an acoustic signal in a fluid in an annulus in contact with an exterior surface of the piston, the exterior surface of the piston extending into the annulus, and the axial direction of the acoustic source being transverse to an axial direction of the tool; and

matching an acoustic impedance of an elastomer disposed on an interior side of the piston to an acoustic impedance of the piston.

12. The method of claim 11 further comprising a disposing a stator on a side of the elastomer opposite the piston.

13. The method of claim 11 further comprising providing a permanent magnetic field oriented in the axial direction of the acoustic source.

14. The method of claim 13 further comprising producing an alternating magnetic field in a region of the permanent magnetic field to oscillate the piston.

15. The method of claim 14 further comprising providing an alternating current to produce the alternating magnetic field in the coil.

16. The method of claim 11, wherein the elastomer is one of:

i) a silicon rubber, ii) a silicone jelly, and iii) a silicone oil.

17. The method of claim 11 further comprising conveying the acoustic source downhole on one of:

i) a wireline, and ii) a drillstring.

18. The method of claim 11 further comprising using the source as part of at least one of:

i) a dipole source, and ii) a quadrupole source.

19. The method of claim 11 further comprising orienting the acoustic source to reduce an acoustic tool mode.

20. The method of claim 11, wherein the acoustic source is configured to be coupled to a surface of a bottom hole assembly.