Composite transducer for downhole ultrasonic imaging and caliper measurement
First Claim
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1. An apparatus configured to evaluate an earth formation, the apparatus comprising:
- a rotatable transducer assembly surrounded by an acoustically transparent window and immersed in a fluid filling a cavity defined by the acoustically transparent window;
a composite transducer on the rotatable transducer assembly configured to propagate an acoustic signal through the acoustically transparent window into a borehole filled with borehole fluid and receive a reflection from a wall of the borehole; and
at least one processor configured to use the reflection obtained at a plurality of orientations of the transducer during rotation of the transducer assembly to provide an image of the earth formation;
wherein the rotatable transducer assembly comprises an impedance matching material disposed between the composite transducer and the fluid; and
wherein the assembly maintains a distance greater than zero between the composite transducer and the acoustically transparent window during rotation of the assembly, the assembly being configured via the distance selected to;
(i) reduce a reverberation time of a reverberation therebetween, and (ii) improve acoustic coupling with the acoustically transparent window.
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Abstract
A transducer assembly for downhole imaging includes a 1-3 Piezoelectric composite transducer of high Q ceramic rods in a polymer matrix. The assembly also includes a Teflon® window, a fluid-filled cavity adjacent to the window, and impedance matching material between the composite transducer and the fluid. The transducer is positioned to reduce the reverberation time.
20 Citations
11 Claims
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1. An apparatus configured to evaluate an earth formation, the apparatus comprising:
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a rotatable transducer assembly surrounded by an acoustically transparent window and immersed in a fluid filling a cavity defined by the acoustically transparent window; a composite transducer on the rotatable transducer assembly configured to propagate an acoustic signal through the acoustically transparent window into a borehole filled with borehole fluid and receive a reflection from a wall of the borehole; and at least one processor configured to use the reflection obtained at a plurality of orientations of the transducer during rotation of the transducer assembly to provide an image of the earth formation; wherein the rotatable transducer assembly comprises an impedance matching material disposed between the composite transducer and the fluid; and wherein the assembly maintains a distance greater than zero between the composite transducer and the acoustically transparent window during rotation of the assembly, the assembly being configured via the distance selected to;
(i) reduce a reverberation time of a reverberation therebetween, and (ii) improve acoustic coupling with the acoustically transparent window. - View Dependent Claims (2, 3, 4, 5, 6, 9, 10, 11)
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7. A non-transitory computer-readable medium product having instructions thereon that enable at least one processor to perform a method, the method comprising:
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producing an image of an earth formation using a reflected signal from a borehole wall resulting from generation an acoustic signal by a composite transducer on a rotatable transducer assembly surrounded by an acoustically transparent window and immersed in a fluid filling a cavity defined by the acoustically transparent window in the borehole and transmission of the generated acoustic signal through the acoustically transparent window on the transducer assembly into the borehole wherein the assembly maintains a distance greater than zero between the composite transducer and the acoustically transparent window during rotation of the assembly, the assembly being configured via the distance selected to;
(i) reducing a reverberation time of a reverberation therebetween, and (ii) improving acoustic coupling with the acoustically transparent window;and wherein the rotatable transducer assembly further comprises an impedance matching material disposed between the composite transducer and the fluid. - View Dependent Claims (8)
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Specification