Focused acoustic transducer

Patent metadata

Field	Value
Publication number	US-9363605-B2
Application number	US-201113980266-A
Country	US
Kind code	B2
Filing date	Jan 18, 2011
Priority date	Jan 18, 2011
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

A focused acoustic transducer suitable for use in a downhole environment is disclosed. At least some embodiments employ a disk of piezoelectric material with low planar coupling and low Poisson's ratio mounted on a backing material and sealed inside an enclosure. The piezoelectric material disk has a pattern of electrodes deposited on an otherwise smooth, ungrooved surface. Despite the lack of grooves, the material's low planar coupling and low Poisson's ratio enables the electrodes to operate in a phased relationship to provide and receive focused acoustic pulses. Moreover, the elimination of deep cuts offers a much lower cost of construction. The electrode material may be any conductive material, though silver and silver alloys are contemplated. The patterning of electrodes can occur during the deposition process (e.g., using a silk-screen or other printing technique) or afterwards (e.g., mechanically or chemically with an etch technique that uses a pre- or post-deposition photoresist layer).

First claim

What is claimed is:

1. A focused acoustic transducer that comprises:
a disk of piezoelectric material having a flat, smooth surface on both sides, wherein said piezoelectric material has a planar coupling coefficient of less than 0.05 and Poisson's ratio less than 0.2;
a pattern of electrodes laid over said piezoelectric material, wherein said pattern of electrodes operates in a phased relationship to transmit a focused acoustic wave.

2. The transducer of claim 1 , said pattern of electrodes operate to provide focused reception of a reflected acoustic wave.

3. The transducer of claim 1 , wherein said piezoelectric material comprises lead metaniobate.

4. The transducer of claim 1 , wherein said disk is circular with a thickness-to-diameter aspect ratio greater than 0.0625.

5. The transducer of claim 4 , wherein said pattern of electrodes includes a central disk surrounded by a series of annular rings.

6. The transducer of claim 1 , wherein said pattern of electrodes includes at least one annular ring.

7. The transducer of claim 1 , further comprising a backing material to which the disk is mounted.

8. The transducer of claim 7 , further comprising an encapsulation layer that encloses the disk, electrodes, and backing material to enable the transducer to operate in a downhole environment.

9. An acoustic logging tool that comprises:
a focused acoustic transducer that employs an ungrooved planar piece of piezoelectric material having a low planar coupling coefficient and low Poisson's ratio; and
electronics coupled to electrodes of the focused acoustic transducer to transmit or receive acoustic signals in a phased relationship.

10. The tool of claim 9 , further comprising a wireline sonde that houses the electronics and focused acoustic transducer.

11. The tool of claim 9 , further comprising a drill collar that houses the electronics and focused acoustic transducer.

12. The tool of claim 9 , further comprising position and orientation sensors that associate acoustic measurements with a position on the borehole wall.

13. The tool of claim 9 , wherein the acoustic signals comprise pulses and wherein the electronics measure travel time of the pulses.

14. The tool of claim 9 , wherein the electronics measure amplitude of received acoustic signals.

15. The tool of claim 9 , wherein the planar piece of piezoelectric material is a circular disk with a thickness-to-diameter ratio greater than 0.0625.

16. An acoustic transducer manufacturing method comprising:
forming a disk from piezoelectric material having a low planar coupling coefficient and low Poisson's ratio;
creating a pattern of electrodes on one flat, smooth surface of the disk and a reference electrode on an opposite surface of the disk, wherein said creating does not include cutting deep grooves to define and isolate the electrodes;
attaching at least one lead to each of the electrodes in the pattern of electrodes;
attaching the disk to a backing material; and
encapsulating the disk and backing material.

17. The method of claim 16 , wherein the disk has thickness-to-diameter ratio greater than 0.0625, and wherein said pattern of electrodes includes at least one annular ring.

18. The method of claim 16 , wherein the piezoelectric material comprises lead metaniobate and has a planar coupling coefficient of less than 0.05 and Poisson's ratio less than 0.2.

19. The method of claim 16 , wherein the backing material comprises a mixture of polymer and tungsten.

20. The method of claim 16 , wherein said encapsulating includes providing a housing comprising glass-filled PEEK.

Assignees

• Goodman George David
• Maki Jr Voldi E
• Halliburton Energy Services Inc

Inventors

• Goodman George David
• Maki Jr Voldi E

Classifications

• B06B1/0651

  of circular shape · CPC title

• B06B1/0644

  using a single piezoelectric element (B06B1/0688 takes precedence) · CPC title

• H04R17/00 Primary

  Piezoelectric transducers; Electrostrictive transducers (piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners {H10N30/00}) · CPC title

• H04R31/00

  Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor {(manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182)} · CPC title

• G01V1/44 Primary

  using generators and receivers in the same well (G01V1/52 takes precedence) · CPC title