# US 2006/0185430 A1 · Piezocomposite transducer for a downhole measurement tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2006/0185430 A1 - Document ID: US20060185430A1 - Status: Published application - Kind: A1 - Application number: 11/390,585 - Filed: 2006-03-28 - Published: 2006-08-24 - Earliest claimed: 2003-07-03 - Assignees: PathFinder Energy Services, Inc. - Inventors: Elan Yogeswaren - Web page: https://patentgrep.com/patent/US20060185430A1 ## CPC - B06B 1/0622: {on one surface} - E21B 47/01: Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like - G01N 29/222: {Constructional or flow details for analysing fluids (optoacoustic fluid cells G01N29/2425)} - G01N 29/245: {Ceramic probes, e.g. lead zirconate titanate [PZT] probes} - G01N 29/2462: {Probes with waveguides, e.g. SAW devices} - G01N 29/2468: {Probes with delay lines} - G01V 1/18: Receiving elements, e.g. seismometer, geophone {or torque detectors, for localised single point measurements} - G01V 1/52: Structural details - G01N 2291/0422: Shear waves, transverse waves, horizontally polarised waves - G01N 2291/106: one or more transducer arrays - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract An acoustic sensor for use in a downhole measurement tool includes a piezo-composite transducer element. In various exemplary embodiments, the acoustic sensor further includes a composite backing layer, at least one matching layer, and a barrier layer deployed at an outermost surface of the sensor. Exemplary embodiments of this invention may advantageously withstand the extreme temperatures, pressures, and mechanical shocks frequent in downhole environments and thus may exhibit improved reliability. Exemplary embodiment of this invention may further provide improved signal to noise characteristics. Methods for fabricating acoustic sensors and downhole measurement tools are also provided. ## Claims ### Claim 1 A downhole measurement tool, comprising: a substantially cylindrical tool body having a cylindrical axis; at least one acoustic sensor deployed on the tool body, the acoustic sensor including a piezo-composite transducer element with anterior and posterior faces, the piezo-composite transducer in electrical communication with an electronic control module via conductive electrodes disposed on each of said faces; and the piezo-composite transducer element including regions of piezoelectric material deployed in a matrix of a substantially non piezoelectric polymeric material, the regions extending through a thickness of the transducer element in at least one dimension, the polymeric material having a glass transition temperature of greater than about 200 degrees C. ### Claim 2 (depends on 1) The downhole tool of claim 1, wherein the piezoelectric material is selected from the group consisting of lead zirconate titanates and lead metaniobates. ### Claim 3 (depends on 1) The downhole tool of claim 1, wherein the piezoelectric material has a Curie temperature greater than about 250 degrees C. ### Claim 4 (depends on 1) The downhole tool of claim 1, wherein the polymeric material comprises an epoxy resin. ### Claim 5 (depends on 1) The downhole tool of claim 1, wherein the regions of piezoelectric material comprise a periodic array of spaced piezoelectric material posts. ### Claim 6 (depends on 5) The downhole tool of claim 5, wherein the piezo-composite transducer element is a product of the process comprising: providing a piezo-ceramic disk having first and second faces; cutting a first set and a second set of grooves in the first face, the grooves in the first set being substantially orthogonal to the grooves in the second set, wherein removal of piezo-ceramic material in said groove cutting is operative to shape the piezoelectric material posts; casting the non piezoelectric material into the grooves to form, in combination with the piezo-ceramic disc, a specimen of piezo-composite material having first and second faces corresponding substantially to those of the piezo-ceramic disk; polishing the specimen to a predetermined thickness; and disposing conductive electrodes on each of the first and second faces of the specimen. ### Claim 7 (depends on 1) The downhole tool of claim 1, wherein the piezo-composite transducer element includes alternating concentric rings of the piezoelectric material and the non piezoelectric material disposed about a central element of the piezoelectric material. ### Claim 8 (depends on 7) The downhole tool of claim 7, wherein each of the rings of the piezoelectric material has a predetermined radial thickness selected to decrease with increasing distance from the central element. ### Claim 9 (depends on 8) The downhole tool of claim 8, wherein the radial thickness of the rings of piezoelectric material is selected to decrease according a mathematical function selected from the group consisting of Bessel functions and Gaussian functions. ### Claim 10 (depends on 7) The downhole tool of claim 7, wherein the piezo-composite transducer element comprises a plurality of axial slots formed in a periphery of the transducer. ### Claim 11 (depends on 7) The downhole tool of claim 7, wherein the piezo-composite transducer element is a product of the process comprising: providing a piezo-ceramic slurry; casting the piezo-ceramic slurry in a reverse mold to form the concentric rings of piezoelectric material about the central element; casting the non piezoelectric material in open spaces between the concentric rings of piezoelectric material to form, in combination with the concentric rings of piezoelectric material, a specimen of piezo-composite material having first and second faces; polishing the specimen to a predetermined thickness; and disposing conductive electrodes on each of the first and second faces of the specimen. ### Claim 12 (depends on 1) The downhole tool of claim 1, wherein: the piezo-composite transducer element includes first and second separate piezoelectric elements, the first piezoelectric element serving as a transmitter, the second piezoelectric element serving as a receiver; and the first and second piezoelectric elements are substantially isolated electromechanically from one another by a non piezoelectric material. ### Claim 13 (depends on 12) The downhole tool of claim 12, wherein the first piezoelectric element includes a lead zirconate titanate piezoelectric material and the second piezoelectric element includes a lead metaniobate piezoelectric material. ### Claim 14 (depends on 1) The downhole tool of claim 1, wherein the conductive electrodes comprise gold. ### Claim 15 (depends on 1) The downhole tool of claim 1, in which the downhole tool is selected from the group consisting of logging while drilling tools and measurement while drilling tools. ### Claim 16 An acoustic sensor, comprising: a piezo-composite transducer element including regions of piezoelectric material deployed in a matrix of a substantially non piezoelectric polymeric material, the regions extending through a thickness of the transducer element in at least one dimension; the polymeric material having a glass transition temperature of greater than about 200 degrees C.; the piezoelectric material having a Curie temperature greater than about 250 degrees C.; and the acoustic sensor being configured for use in a downhole measurement tool. ### Claim 17 (depends on 16) The downhole tool of claim 16, wherein the regions of piezoelectric material comprise a periodic array of spaced piezoelectric material posts. ### Claim 18 (depends on 16) The downhole tool of claim 16, wherein the piezo-composite transducer element includes alternating concentric rings of the piezoelectric material and the non piezoelectric material disposed about a central element of the piezoelectric material. ### Claim 19 (depends on 16) The downhole tool of claim 16, wherein: the piezo-composite transducer element includes first and second separate piezoelectric elements, the first piezoelectric element serving as a transmitter, the second piezoelectric element serving as a receiver; and the first and second piezoelectric elements are substantially isolated electromechanically from one another by a non piezoelectric material. ### Claim 20 A method for fabricating a downhole measurement tool, the method comprising: (a) providing a substantially cylindrical tool body having an electronic control module, the tool body being couplable with a drill string; (b) providing at least one acoustic sensor including a piezo-composite transducer element with anterior and posterior faces, the piezo-composite transducer element including regions of piezoelectric material deployed in a matrix of substantially non piezoelectric polymeric material, the regions extending through a thickness of the transducer element in at least one dimension; the polymeric material having a glass transition temperature of greater than about 200 degrees C., the piezo-composite transducer element further including conductive electrodes disposed on each of said faces; (c) deploying the at least one acoustic sensor on the tool body in electrical communication with the electronic control module via said conductive electrodes, the at least one acoustic sensor operable to transmit and receive acoustic signals in a borehole.