Acoustic transducer with impedance matching layer

• US 9,555,444 B2
• Filed: 05/15/2015
• Issued: 01/31/2017
• Est. Priority Date: 02/15/2011
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Goodman, George David, Maki, Voldi E. Jr.
• Primary Examiner(s): ALLEN, ANDRE J
• Application Number:
  US14/713,822
• Publication Number:
  US 20160016199A1
• Time in Patent Office: 627 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B06B 1/0625 Annular array
• CPC Class Codes: B06B 1/0633 Cylindrical array
• CPC Class Codes: B06B 1/067 which is used as, or combined with, an impedance matching layer
• CPC Class Codes: G01V 1/159 using piezoelectric or magnetostrictive driving means generating mechanical vibrations by using piezoelectric or magnetostrictive effect in general, B06B1/06, B06B1/08
• CPC Class Codes: G01V 1/40 specially adapted for well-logging
• CPC Class Codes: G10K 11/02 Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Abstract

A piezoelectric transducer is mounted in a housing. An impedance matching layer is provided between the piezoelectric transducer and the housing. The impedance matching layer includes high-permittivity regions that have a first permittivity, and low-permittivity regions that separate the high-permittivity regions and have a second permittivity. The second permittivity is lower than the first permittivity.

Claims

1. A device comprising:

a piezoelectric transducer, the transducer having N independent transducer regions wherein N is an integer, each of the N independent transducer regions having a thickness, each of the N independent transducer regions having an acoustic impedance AIT, each of the N independent transducer regions being independently excitable to oscillate in the thickness mode when electrically excited by a potential difference applied across the thickness;

a first impedance matching layer having an acoustic impedance AI1 between AIT and a borehole fluid acoustic impedance AIBF, the first impedance matching layer being situated such that an acoustic signal emitted by the piezoelectric transducer will pass through the first impedance matching layer, the first impedance matching layer comprising;

high-permittivity regions that match and overlay the N independent transducer regions and have a first permittivity, and

low-permittivity regions that separate the high-permittivity regions and have a second permittivity wherein the second permittivity is lower than the first permittivity; and

a second impedance matching layer having an acoustic impedance AI2 between AI1 and AIBF, the second impedance matching layer being situated in the device such that an acoustic signal emitted by the transducer will pass through the second impedance matching layer after it passes through the first impedance matching layer;

wherein the first impedance matching layer has N independent first impedance matching layer regions that match and overlay the N independent transducer regions.

2. The device of claim 1 wherein the low-permittivity regions are formed by cuts in the first impendence matching layer.

3. The device of claim 1 wherein the low-permittivity regions impede displacement currents.

4. The device of claim 1 wherein the low-permittivity regions act as series elements between the high-permittivity regions.

5. The device of claim 1 wherein the low-permittivity regions cause the device to present a smaller load than without the low-permittivity regions.

6. A method comprising:

emitting an acoustic pulse from a piezoelectric transducer, the transducer having N independent transducer regions wherein N is an integer, each of the N independent transducer regions having a thickness, each of the N independent transducer regions having an acoustic impedance AIT, each of the N independent transducer regions being independently excitable to oscillate in the thickness mode when electrically excited by a potential difference applied across the thickness;

passing the acoustic pulse through a first impedance matching layer having an acoustic impedance AI1 between AIT and a borehole fluid acoustic impedance AIBF, the first impedance matching layer comprising;

high-permittivity regions that match and overlay the N independent transducer regions and have a first permittivity, and

low-permittivity regions that separate the high-permittivity regions and have a second permittivity wherein the second permittivity is lower than the first permittivity; and

passing the acoustic pulse that has passed through the first impedance matching layer through a second impedance matching layer having an acoustic impedance AI2 between AI1 and AIBF.

7. The method of claim 6 wherein the low-permittivity regions are formed by cuts in the first impendence matching layer.

8. The method of claim 6 wherein the low-permittivity regions impede displacement currents.

9. The method of claim 6 wherein the low-permittivity regions act as series elements between the high-permittivity regions.

10. The method of claim 6 wherein the low-permittivity regions cause the device to present a smaller load than without the low-permittivity regions.

11. An apparatus comprising:

a housing;

a piezoelectric transducer mounted in the housing; and

an impedance matching layer provided between the piezoelectric transducer and the housing, the impedance matching layer comprising;

high-permittivity regions that have a first permittivity, and

low-permittivity regions that separate the high-permittivity regions and have a second permittivity wherein the second permittivity is lower than the first permittivity.

12. The device of claim 11 wherein the low-permittivity regions are formed by cuts in the impendence matching layer.

13. The device of claim 11 wherein the low-permittivity regions impede displacement currents.

14. The device of claim 11 wherein the low-permittivity regions act as series elements between the high-permittivity regions.

15. The device of claim 11 wherein the low-permittivity regions cause the device to present a smaller load than without the low-permittivity regions.

16. The device of claim 11 wherein the impedance matching layer comprises a plurality of slots extending therethrough, said slots also extending partially through the piezoelectric transducer.