Ultrasonic transducer with improved backing element

Patent metadata

Field	Value
Publication number	US-2017299751-A1
Application number	US-201515511936-A
Country	US
Kind code	A1
Filing date	Oct 2, 2015
Priority date	Oct 2, 2015
Publication date	Oct 19, 2017
Grant date	—

Abstract

In accordance with embodiments of the present disclosure, systems and methods for improving performance of ultrasonic transducers, particularly those used in borehole environments, are provided. The disclosed ultrasonic transducers all feature a backing element that is a ceramic backing material. The ceramic backing material may include a solid piece of ceramic material that is disposed on a back end of a piezoelectric element used in the ultrasonic transducer. The disclosed ceramic backing material may be used to mechanically match the backing element to the piezoelectric source element, while minimizing the amplitude of reflections of the ultrasonic pulse generated by the piezoelectric element and reflected at the far end of the backing element. This ceramic backing material may provide consistent performance regardless of the surrounding pressure and temperature, making it particularly useful in borehole applications.

First claim

What is claimed is:

1 . A system, comprising:
an ultrasonic transducer for use in a borehole environment, comprising:
a piezoelectric element;
a pair of electrodes disposed one on each side of the piezoelectric element to enable a current flow through the piezoelectric element; and
a backing element disposed on one side of the piezoelectric element to attenuate vibrations in the ultrasonic transducer from the piezoelectric element, wherein the backing element is a ceramic backing material.

2 . The system of claim 1 , wherein the ceramic backing material has a mechanical Q factor of less than approximately 10.

3 . The system of claim 1 , wherein a mechanical impedance of the ceramic backing material is approximately the same as a mechanical impedance of the piezoelectric element.

4 . The system of claim 1 , wherein the ultrasonic transducer further comprises a bonding material disposed between the ceramic backing material and the piezoelectric element to bond the ceramic backing material to the piezoelectric element, wherein the bonding material comprises an epoxy with ceramic powder or metal powder disposed therein.

5 . The system of claim 1 , wherein the backing element comprises a back end facing away from the piezoelectric element, wherein the back end is angled to reduce acoustic reflections through the backing element.

6 . The system of claim 1 , wherein the backing element comprises an angled back end facing away from the piezoelectric element to form a wedge-shaped ultrasonic transducer.

7 . The system of claim 1 , wherein the piezoelectric element is diced.

8 . The system of claim 1 , wherein the backing element is mechanically stable at temperatures up to approximately 320° Celsius.

9 . The system of claim 1 , wherein a coefficient of thermal expansion of the ceramic backing material is approximately equal to a coefficient of thermal expansion of the piezoelectric element.

10 . A system, comprising:
a borehole tool designed for use in a borehole, the borehole tool comprising at least one ultrasonic transducer, wherein the at least one ultrasonic transducer comprises:
a piezoelectric element;
a pair of electrodes disposed one on each side of the piezoelectric element to enable a current flow through the piezoelectric element; and
a backing element disposed on one side of the piezoelectric element to attenuate vibrations in the ultrasonic transducer from the piezoelectric element, wherein the backing element is a ceramic backing material.

11 . The system of claim 10 , wherein the borehole tool comprises a drill string comprising a plurality of ultrasonic transducers disposed circumferentially around the drill string to determine a distance from a drill cutter to a wall of the borehole, wherein each of the plurality of ultrasonic transducers comprise a backing element that is a ceramic backing material.

12 . The system of claim 10 , wherein the borehole tool comprises a wireline tool comprising the at least one ultrasonic transducer to measure corrosion of a casing disposed in the borehole, to detect a quality of a cement bond within the borehole, to map a shape of the borehole, or a combination thereof.

13 . The system of claim 10 , wherein the borehole tool comprises at least two ultrasonic transducers positioned to perform pitch-catch measurements within the borehole, wherein the at least two ultrasonic transducers each comprise a backing element that is a ceramic backing material.

14 . The system of claim 10 , wherein the backing element is machined to feature a sloping back end facing away from the piezoelectric element.

15 . A method, comprising:
outputting an acoustic signal in a borehole environment via a piezoelectric element of an ultrasonic transducer; and attenuating waves formed by the acoustic signal from the piezoelectric element, via a backing element disposed in the ultrasonic transducer, wherein the backing element is a ceramic backing material.

16 . The method of claim 15 , further comprising maintaining a bonding layer of epoxy between the piezoelectric element and the backing element during temperature changes as the backing element expands and contracts according to approximately the same coefficient of thermal expansion as the piezoelectric element.

17 . The method of claim 15 , further comprising reducing reflections from the back end of the backing element via a machined surface of the backing element facing away from the piezoelectric element.

18 . The method of claim 15 , further comprising performing pitch-catch operations in the borehole environment via the ultrasonic transducer.

19 . The method of claim 15 , further comprising:
supporting the ultrasonic transducer in the borehole environment via a drill string; and performing measurements of distance between a borehole wall and a drill cutter via the ultrasonic transducer.

20 . The method of claim 15 , further comprising:
supporting the ultrasonic transducer in the borehole environment via a wireline; and performing measurements of casing corrosion, cement bond quality, borehole shape, or a combination thereof, via the ultrasonic transducer.

Assignees

• Halliburton Energy Services Inc

Inventors

• Chang Chung
• Jin Jing
• Ge Yao

Classifications

• B06B1/0685

  on the back only of piezoelectric elements · CPC title

• G01V1/523

  Damping devices · CPC title

• E21B47/005

  Monitoring or checking of cementation quality or level · CPC title

• E21B47/085

  using radiant means, e.g. acoustic, radioactive or electromagnetic · CPC title

• G10K11/002

  Devices for damping, suppressing, obstructing or conducting sound in acoustic devices (G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002) · CPC title