U.S. patent application number 14/308415 was filed with the patent office on 2014-12-25 for method and apparatus for measuring deformation of elastomeric materials.
The applicant listed for this patent is Weatherford/Lamb, Inc.. Invention is credited to Martin W. LAWREY, Jeremy Buc SLAY, Lucio Nelson TELLO.
Application Number | 20140373619 14/308415 |
Document ID | / |
Family ID | 50972575 |
Filed Date | 2014-12-25 |
United States Patent
Application |
20140373619 |
Kind Code |
A1 |
SLAY; Jeremy Buc ; et
al. |
December 25, 2014 |
METHOD AND APPARATUS FOR MEASURING DEFORMATION OF ELASTOMERIC
MATERIALS
Abstract
A method for measuring the deformation of elastomeric materials
using acoustic signals involves obtaining a sample, positioning the
sample in a sealable chamber, sealing the chamber, and setting a
temperature and pressure inside the chamber. A test fluid may be
introduced to the chamber. An acoustic signal is used to measure a
characteristic of the sample, such as a dimension or a modulus.
Repeated measurements may be made overtime to monitor changes in
the sample in response to temperature and pressure. The acoustic
signal may be generated by an acoustic transducer including a
backing component including a fluorine-containing polymer in which
metal particles are incorporated. The sample may be a non-metallic
material. Conditions inside the chamber may be set to simulate a
wellbore environment.
Inventors: |
SLAY; Jeremy Buc; (Fort
Worth, TX) ; LAWREY; Martin W.; (Joshua, TX) ;
TELLO; Lucio Nelson; (Benbrook, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Weatherford/Lamb, Inc. |
Houston |
TX |
US |
|
|
Family ID: |
50972575 |
Appl. No.: |
14/308415 |
Filed: |
June 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61836924 |
Jun 19, 2013 |
|
|
|
61942458 |
Feb 20, 2014 |
|
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Current U.S.
Class: |
73/152.58 |
Current CPC
Class: |
G01N 2203/0226 20130101;
G01N 3/32 20130101; G01N 2203/0232 20130101; G01N 2203/0055
20130101; G01N 29/227 20130101; G01N 29/228 20130101; G01N 29/223
20130101; E21B 47/14 20130101; G01N 2291/02827 20130101; G01N 29/07
20130101; G01N 29/30 20130101; G01N 2291/0235 20130101; G01N
2291/0421 20130101; G01N 2203/024 20130101; G01N 2291/02854
20130101; G01N 29/24 20130101 |
Class at
Publication: |
73/152.58 |
International
Class: |
E21B 47/14 20060101
E21B047/14 |
Claims
1. A method of measuring deformation of a non-metallic material,
comprising: placing a sample of a non-metallic material in a
sealable chamber; sealing the sealable chamber; generating an
acoustic signal; bringing the sealable chamber to a test pressure;
bringing the sealable chamber to a test temperature; supplying a
test medium to the sealable chamber; and measuring a characteristic
of the sample using the acoustic signal.
2. The method of claim 1, wherein the test medium is a hydrocarbon
fluid.
3. The method of claim 1, wherein the characteristic is a modulus
of the sample.
4. The method of claim 1, wherein the acoustic signal is generated
by an acoustic transducer.
5. The method of claim 4, wherein the acoustic transducer
comprises: a piezoelectric element configured to generate acoustic
signals according to an electrical signal that is applied to the
piezoelectric element; a backing component contacting a back-side
surface of the piezoelectric element; and an encasing material that
surrounds the piezoelectric element and the backing component,
wherein the backing component comprises a fluorine-containing
polymer in which metal particles are incorporated, and the metal
particles comprise greater than 60% of the backing component by
volume.
6. The method of claim 4, further comprising positioning an
acoustic reflecting plate between the acoustic transducer and the
sample such that only a first portion of the acoustic signal
generated by the transducer reaches the sample and a second portion
of the acoustic signal generated by the transducer is reflected
back to the acoustic transducer by the acoustic reflecting
plate.
7. An apparatus for measuring deformation of a non-metallic
material, comprising: a sealable chamber; a sample holder for
holding a sample of a non-metallic material inside the sealable
chamber; a port for introducing a test medium; and an acoustic
transducer positioned to supply an acoustic signal to the
sample.
8. The apparatus of claim 7, wherein a temperature and a pressure
inside of the sealable chamber can be controlled.
9. The apparatus of claim 7, wherein the acoustic transducer
comprises: a piezoelectric element configured to generate acoustic
signals according to an electrical signal that is applied to the
piezoelectric element; a backing component contacting a back-side
surface of the piezoelectric element; and an encasing material that
surrounds the piezoelectric element and the backing component,
wherein the backing component comprises a fluorine-containing
polymer in which metal particles are incorporated, and the metal
particles comprise greater than 60% of the backing component by
volume.
10. The apparatus of claim 9, wherein the fluorine-containing
polymer is a fluoroelastomer that comprises a di-polymer of
vinylidene fluoride and hexafluoropropylene having a Mooney
viscosity of less than 20 Mooney units as measured in a Mooney
scorch test using a large rotor, a one minute preheat time, a ten
minute test time, and a 100.degree. C. test temperature.
11. The apparatus of claim 9, wherein the fluorine-containing
polymer comprises a perfluoroelastomer having a Mooney viscosity of
less than 20 Mooney units as measured in a Mooney scorch test using
a large rotor, a one minute preheat time, a ten minute test time,
and a 100.degree. C. test temperature.
12. The apparatus of claim 9, wherein the fluorine-containing
polymer comprises a terpolymer of vinylidene fluoride,
hexafluoropropylene, and tetrafluoroethylene having a Mooney
viscosity of less than 20 Mooney units as measured in a Mooney
scorch test using a large rotor, a one minute preheat time, a ten
minute test time, and a 100.degree. C. test temperature
13. The apparatus of claim 7, wherein the sealable chamber
comprises a body and lid.
14. The apparatus of claim 7, wherein the sample holder includes a
plurality of sample cups.
15. The apparatus of claim 7, further comprising: an acoustic
reflecting plate positioned between the acoustic transducer and the
sample holder such that only a first portion of the acoustic signal
generated by the acoustic transducer reaches the sample holder and
a second portion of the acoustic signal generated by the transducer
is reflected back to the acoustic transducer by the acoustic
reflecting plate.
16. The apparatus of claim 15, further comprising a plurality of
acoustic transducers.
17. A method of measuring a downhole characteristic, comprising:
placing an acoustic transducer in a wellbore; and using the
acoustic transducer to measure a characteristic of a portion of a
downhole device, wherein the acoustic transducer comprises: a
piezoelectric element configured to generate acoustic signals
according to an electrical signal that is applied to the
piezoelectric element; a backing component contacting a back-side
surface of the piezoelectric element; and an encasing material that
surrounds the piezoelectric element and the backing component,
wherein the backing component comprises a fluorine-containing
polymer in which metal particles are incorporated, and the metal
particles comprise greater than 40% of the backing component by
volume.
18. The method of claim 17, wherein the downhole device comprises a
packer.
19. The method of claim 17, wherein the electrical signal is
supplied from a battery positioned in the wellbore.
20. An acoustic transducer, comprising: a piezoelectric element
configured to generate acoustic signals according to an electrical
signal that is applied to the piezoelectric element; a backing
component contacting a back-side surface of the piezoelectric
element; and an encasing material that surrounds the piezoelectric
element and the backing component, wherein the backing component
includes a fluorine-containing polymer containing metal particles
in an amount greater than 40% of the backing component by volume
and the fluorine-containing polymer is selected from the group
consisting of: a. a terpolymer of vinylidene fluoride,
hexafluoropropylene, and tetrafluoroethylene having a Mooney
viscosity of less than 20 Mooney units as measured in a Mooney
scorch test using a large rotor, a one minute preheat time, a ten
minute test time, and a 100.degree. C. test temperature; b. a
fluoroelastomer that comprises a di-polymer of vinylidene fluoride
and hexafluoropropylene having a Mooney viscosity of less than 20
Mooney units as measured in a Mooney scorch test using a large
rotor, a one minute preheat time, a ten minute test time, and a
100.degree. C. test temperature; and c. a perfluoroelastomer having
a Mooney viscosity of less than 20 Mooney units as measured in a
Mooney scorch test using a large rotor, a one minute preheat time,
a ten minute test time, and a 100.degree. C. test temperature.
Description
INCORPORATION BY REFERENCE
[0001] This application incorporates by reference, in their
respective entirety, the following patent applications: U.S.
Provisional Pat. App. No. 61/836,924, filed in the USPTO on Jun.
19, 2013 (Attorney Docket No. WEAT/1123USL), and U.S. Provisional
Pat. App. No. 61/932,458, filed in the USPTO on Feb. 20, 2014
(Attorney Docket No. WEAT/1186USL).
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention generally relates to an apparatus and
method for measuring deformation of non-metallic materials using
acoustic signals.
[0004] 2. Description of the Related Art
[0005] In oil and gas extraction, it is often desirable during
completion or operation of a wellbore to isolate different geologic
zones from each other. For example, the wellbore may pass through
water-infiltration zones, gas-producing formations, and
oil-producing formations, and it may be preferable to produce from
different zones in specific sequences or using different recovery
methods in each zone. This requires wellbore segments to be
isolated from each other.
[0006] A typical means of isolating wellbore segments uses a
"packer." A completed wellbore generally comprises a series of
concentric structures, including the wellbore/formation wall,
casings, liners, and production tubing, and a packer can be
deployed downhole and between a pair of concentric structures. Once
positioned, the packer expands (or is expanded) to create a seal
between adjacent structures to thereby prevent mixing of fluids
from above and below the seal.
[0007] Generally, to fit down the wellbore, the packer must have an
initial dimension less than the radial cross-section being sealed,
but after positioning the packer must somehow expand (or alter
shape) to fill the cross-section. There are various packer types,
including mechanical packers, swellable packers, inflatable
packers, and shape-memory packers. All of these packer types
generally incorporate polymeric materials to make the seal between
the pair of concentric structures.
[0008] A mechanical packer expands by applying physical pressure,
for example by squeezing a polymeric material placed between an
upper plate and lower plate such that the material extrudes from
between the plates in a radial direction. Here, mechanical force is
used to cause a physical deformation of the polymer.
[0009] A swellable packer relies on the phenomenon of polymeric
swelling upon exposure to certain solvents/chemicals. It is
well-known that certain solvents will dissolve some materials, but
not others. Swelling of polymers is a related phenomenon as
swelling occurs when solvent molecules penetrate into the polymer
and thereby cause the polymeric structure to expand. Like with
dissolution, certain chemicals will swell some polymers but not
others. For example, butyl rubber will swell significantly in a
hydrocarbon solvent like cyclohexane but is effectively inert to
water.
[0010] With a swellable packer, the packer is positioned in its
initial (unswollen) state in the wellbore and then exposure to the
downhole environment causes the material of the packer to deform by
swelling. The amount of expansion depends on the specific packer
material being used, the downhole chemical environment, the
temperature, and the pressure. Here, the downhole chemical
environment may be a hydrocarbon-rich phase (e.g., petroleum) or an
aqueous-rich phase (e.g., a brine solution), and the packer
material must be selected accordingly.
[0011] Inflatable packers are deployed in an un-inflated state.
Once positioned, a pressurizing fluid (liquid or gas) is used to
inflate the packer, much like a balloon or an inner tube. The
inflation process causes the packer to expand to thereby create the
seal. The amount of deformation/expansion for an inflatable packer
depends on the differential pressure applied to packer and the
material forming the packer.
[0012] A shape-memory packer responds to some triggering event
(e.g., change in temperature) to alter shape. Upon the triggering
event, the packer alters its shape to form the required seal.
[0013] Also known are expandable tools, such as liner hangers, that
rely on, for example, a wedge/cone system that plastically deforms
a mandrel and polymer system to form the required seal. The
polymeric portions of these tools are generally very similar to
packer materials.
[0014] Whichever packer type is selected, it is generally important
to understand the response of the packer material to the conditions
experienced downhole. For example, an elastomeric material used in
a mechanical packer may also swell due to its chemical environment
or a shape-memory polymer may not retain the required shape past a
given temperature. Also, the elastomeric material may eventually
breakdown under constant exposure to a harsh environment. Thus, it
is required to study the materials under conditions that match or
at least substantially approximate actual conditions experienced
during usage, particularly the harsh conditions experienced in a
wellbore. The chemical environment experienced downhole can be a
function of temperature and pressure as well as the various
chemical components present downhole. The chemical components may
be liquids, gases, or even solids (such as colloid suspensions) or
combinations thereof.
[0015] Current methods for measuring the deformation of
non-metallic materials used in packers and expandable tools are
generally unable to measure deformation under conditions that match
actual temperature, pressure, and chemical environment conditions
found downhole in a wellbore.
[0016] Various mechanical measurement techniques are known, but
mechanical devices with moving pieces are inherently susceptible to
corrosive or abrasive conditions. For example, the measurement
environment may be a saltwater environment, which would be
corrosive to certain metals. The measurement environment may also
be a fluid with many suspended particulates, such as sand or
drilling mud. Additionally, mechanical devices must make physical
contact with the test sample. Where the mechanical device makes
contact, local test conditions are altered as the sample is no
longer fully exposed to the chemical environment because the
mechanical device covers a portion of the sample. Thus, there
remains a need in the art for methods allowing measurements of the
deformation of non-metallic materials under conditions which
correspond to actual usage conditions, for example, at high
temperatures and pressures in varied chemical environments.
[0017] An acoustic transducer deployed down a wellbore will,
typically, be exposed to harsh conditions. Temperatures and
pressures may be elevated well above those typically found at the
surface level. The chemical environment may be corrosive to metals
and the transducer may be exposed to physical abrasives (e.g.,
entrained sand or aggregate). Additionally, the conditions may vary
significantly with depth and/or time such that the transducer must
be able to withstand, for example, both brine and hydrocarbon-rich
conditions found in different segments of the wellbore. Therefore,
a sensor which is to be operated in a wellbore environment must be
able to operate in these conditions while also being robust against
physical shocks and abrasions associated with down-hole
deployment.
[0018] To provide protection against harsh down-hole conditions,
acoustic transducers are typically encased in an epoxy resin
material. Epoxy resins can provide physical protection while still
permitting the acoustic signal generated by the transducer to be
transmitted to (and/or received from) wellbore components. Although
epoxy resins can be selected to be stable against expected thermal
and chemical conditions, they may still gradually fail due to
accumulated stresses caused by thermal cycling events.
[0019] When the encasing material fails, the transducer components
will likely also fail due to exposure to harsh wellbore conditions.
Thus, there is need to provide acoustic transducer components that
are more stable during thermal cycling events.
SUMMARY
[0020] Embodiments include methods and apparatus allowing
deformation of non-metallic materials to be measured under
conditions which correspond to high temperature, high pressure
environments found in wellbores.
[0021] An embodiment of a method for measuring deformation of a
non-metallic material includes obtaining a sample (also referred to
as a specimen) of a non-metallic material, and then placing the
sample in a sealable chamber. The sealable chamber can then be
sealed. The interior of the sealable chamber can be brought to a
test pressure and a test temperature and, a test media (e.g.,
chemical components whether liquid, solids, gases, or combinations
thereof) can be introduced into the sealable chamber. The interior
conditions (e.g., temperature, pressure, presence of chemical
components) of the sealable chamber can be set to approximate a
downhole environment. A generated acoustic signal can be used to
measure a characteristic of the sample, such as a dimension or a
modulus.
[0022] An embodiment of an apparatus for measuring deformation of a
non-metallic material includes a sealable chamber and a sample
holder for holding a sample of a non-metallic material inside the
sealable chamber. An acoustic transducer is positioned to supply an
acoustic signal to the sample in the sample holder when the
sealable chamber is sealed. The sealable chamber can include means
allowing the sealable chamber to be brought to a test pressure and
a test temperature, as well as means allowing a test media (e.g.,
chemical components whether liquid, solids, gases, or combinations
thereof) to be introduced into the sealable chamber.
[0023] Another embodiment of an apparatus for measuring deformation
of an elastomer includes a sealable chamber and a sample holder for
holding a sample of a non-metallic material inside the sealable
chamber. Also included are a temperature control system for
controlling a temperature of the sealable chamber and a pressure
control system for controlling a pressure of the sealable chamber.
The sealable chamber can include a port (or ports) for introducing
and/or removing chemical components (e.g., gases, liquids, solids,
or combinations thereof). An acoustic transducer is positioned to
supply an acoustic signal to the sample in the sample holder when
the sealable chamber is sealed.
[0024] A method and apparatus for measuring the deformation of
non-metallic materials using acoustic signals is described. The
method involves obtaining a sample, positioning the sample in a
sealable chamber, sealing the chamber, and setting a temperature
and pressure inside the chamber. A test fluid (also referred to as
a test medium) may be placed in the chamber. The combination of
temperature, pressure, and test fluid may approximate a downhole
environment. A characteristic of the sample is measured using an
acoustic signal. The characteristic of the sample may, for example,
be a dimension or a modulus. Repeated measurements on the sample
may be made over time so as to monitor changes in the sample in
response to temperature and pressure, for example. The acoustic
signal may be in the ultrasonic range. The sample may be, for
example, a polymer used in wellbore packer devices.
[0025] In another embodiment, a method of measuring deformation of
a non-metallic material includes obtaining a sample of a
non-metallic material; placing the sample in a sealable chamber;
sealing the sealable chamber; generating an acoustic signal;
adjusting the sealable chamber to approximate a downhole condition;
and measuring a characteristic of the sample using the acoustic
signal. In yet another embodiment, the downhole condition is
selected from the group consisting of a downhole pressure, a
downhole temperature, a downhole medium, and combinations
thereof.
[0026] In an embodiment of an acoustic transducer, the transducer
includes a piezoelectric element configured to generate acoustic
signals according to an applied electrical signal. A backing
component in the acoustic transducer contacts a back-side surface
of the piezoelectric element. An encasing material surrounds the
piezoelectric element and the backing component. The backing
component comprises a polymer, such as a fluoropolymer, which may
be a fluoroelastomer, in which metal particles have been
incorporated, and the metal particles may comprise greater than 60%
of the backing component by volume. In some embodiments, the metal
may be tungsten and the polymer may be an elastomer with vinylidene
fluoride (VDF) and hexafluoropropylene (HFP) as components.
[0027] In a method of manufacturing an acoustic transducer, the
steps include: placing a metal powder on a surface of a polymer,
such as a fluoroelastomer; mixing the metal powder into the
polymer; forming the polymer now including the metal powder into a
backing component; and affixing the backing component formed of the
polymer including the metal powder to a piezoelectric material. In
some embodiments, the metal powder may include tungsten and the
polymer may be a fluoroelastomer including vinylidene fluoride
(VDF) and hexafluoropropylene (HFP) as components.
[0028] In still another embodiment, a method of measuring a
characteristic of a downhole device or environment, comprises
placing an acoustic transducer in a wellbore; and using the
acoustic transducer to measure a characteristic of a portion of the
downhole device or environment, wherein the acoustic transducer
comprises: a piezoelectric element configured to generate acoustic
signals according to an electrical signal that is applied to the
piezoelectric element; a backing component contacting a back-side
surface of the piezoelectric element; and an encasing material that
surrounds the piezoelectric element and the backing component,
wherein the backing component comprises a fluorine-containing
polymer as described herein in which metal particles are
incorporated, and the metal particles comprise greater than 60% of
the backing component by volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 depicts an acoustic transducer in a cross-sectional
view.
[0030] FIG. 2 depicts an acoustic transducer deployed in a wellbore
environment.
[0031] FIG. 3 depicts a backing material used in an acoustic
transducer.
[0032] FIG. 4 depicts a process flow for fabricating an acoustic
transducer
[0033] FIG. 5 depicts a process flow for measuring deformation of a
material.
[0034] FIG. 6 depicts a measurement result from a sample.
[0035] FIG. 7 depicts measurement results from a sample over a
period of time.
[0036] FIG. 8a depicts an apparatus for measuring deformation of a
material.
[0037] FIG. 8b depicts an example of a sample holder that can be
used in an apparatus for measuring deformation of a material.
[0038] FIG. 9 depicts another example of a sample holder that can
be used in an apparatus for measuring deformation of a non-metallic
material. Also depicted is a possible arrangement of acoustic
sensors.
[0039] FIG. 10a depicts a portion of another embodiment of an
apparatus for measuring deformation of a sample.
[0040] FIG. 10b depicts a sample cup used in an embodiment of an
apparatus for measuring deformation of a sample.
[0041] FIG. 11 depicts a reference half shelf which may be
incorporated in an apparatus for measuring deformation of a
sample.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0042] In the following description, numerous details are included
in reference to example embodiments presented to aid understanding
of the present disclosure. However, it will be apparent to one
skilled in the art that many of these specific details may be
varied without departing from the scope of the present invention.
In other instances, description of features well-known in the art
may have been omitted to aid understanding of the present
disclosure.
[0043] Non-metallic materials used in packers and expandable tools
can include polymers, rubbers, plastics, foams, and the like. As
used herein, non-metallic materials may refer to any material that
is not a metal. These materials must generally change shape and/or
dimension after they are deployed downhole to provide a seal
between wellbore segments. The change in shape and/or dimension may
be referred to as "deformation."
[0044] The amount of change after deployment is an important
parameter, as is the speed with which the change occurs. If the
material expands/changes too little, then sealing might not occur.
If the material expands/changes too much, then unwanted stresses
may be placed on wellbore structures.
[0045] While absolute dimension change is important, the speed with
which the change occurs has practical consequences relating to
potential production delays. If the packer expands too quickly
(i.e., before it is properly positioned), then well completion may
be inadvertently hindered by a misplaced expanded packer. If the
packer expands too slowly, then well completion may be delayed
until the seal is formed.
[0046] Additionally, deployed materials may degrade with time and
cause seal failures, therefore methods and devices for monitoring
and/or studying these materials in conditions that approach or
match actual usage conditions are required.
[0047] Polymeric materials can have a wide variety of chemical
formulations that, with seemingly minor differences, will produce
significantly different responses to the same conditions. While
polymers can have various chemical compositions, polymeric
materials also have properties which vary with other things like
molecular weight, extent of cross-linking, and the method of
polymerization. It is not uncommon for a polymer to have properties
that vary significantly batch-to-batch even though the material is
nominally the same composition in each instance.
Acoustic Transducer
[0048] As depicted in FIG. 1, an acoustic transducer 100 for use in
an embodiment of the present disclosure includes a piezoelectric
element 110 attached to a backing component 120. The piezoelectric
element 110 has a wire lead 130. Piezoelectric element 110 and
backing component 120 are encased by a coating 140.
[0049] Piezoelectric element 110 comprises a material, such as
barium titanate (BaTiO.sub.3), which varies in size in response to
an applied electrical current. This response is generally referred
to as an inverse piezoelectric effect. Application of an
alternating current (via wire lead 130) can cause the piezoelectric
element 110 to rapidly fluctuate in size and thereby generate sound
waves (depicted as arrows in FIG. 1) emitted by acoustic transducer
100.
[0050] Piezoelectric element 110 also generates an electric current
in response to being compressed. This response is generally
referred to as a piezoelectric effect. When an acoustic wave
impinges on acoustic transducer 100, piezoelectric element 110
generates an electric current due to compression by the acoustic
wave. Thus, in this example embodiment, piezoelectric element 110
can both generate an acoustic signal and detect a return acoustic
signal.
[0051] In other embodiments, the generation of an acoustic signal
and the detection of acoustic signals may occur in separate
piezoelectric elements. These separate piezoelectric elements may
be in different acoustic transducers 100 or within the same
acoustic transducer 100. Furthermore, piezoelectric element 110 can
be divided into multiple portions, such that one or more portion
generates acoustic signals and another portion or portions respond
to acoustic signals.
[0052] In general, piezoelectric element 110 can be operated to
produce a range of acoustic frequencies or a single frequency. In
general, it is preferable for the acoustic transducer 100 to have a
wide range of possible operating frequencies. The operating
frequency (or operating frequency band) may be adjustable or fixed.
The operating frequency may controllable by external control
systems (not specifically depicted in FIG. 1) providing control
signals along wire lead 130.
[0053] In this example embodiment, the acoustic transducer 100
operates at ultrasonic frequencies. Ultrasonic frequency, for the
purposes of this specification, may be considered to be frequencies
greater than 20 kHz (kilohertz) up to several gigahertz. In other
embodiments, the acoustic transducer may operate at any frequency
appropriate to the materials being measured or the materials
through which the sound waves are being transmitted.
[0054] Wire lead 130 is an electrically conductive material for
transmitting electric signals to and from the piezoelectric element
110. Wire lead 130 may comprise multiple wires electrically
insulated from one another such that distinct signals or voltages
may travel along wire lead 130. In some embodiments, multiple wire
leads 130 may be provided.
[0055] As depicted in FIG. 1, wire lead 130 is connected at a side
portion of piezoelectric element 110, but the connection may be at
any appropriate surface (e.g., the surface between piezoelectric
element 110 and backing component 120 may be the connection point).
Wire lead 130 may also be connected to the outward facing surface,
though this may interfere with the transmission and reception of
acoustic signals, so is not typically preferred. The wire lead 130
may also be routed through the backing component 120 before exiting
the encasing material 140, rather than being routed directly from
the piezoelectric element 110 as depicted in FIG. 1. Additionally,
wire lead 130 may be formed as a contact terminal on an outer
surface of encasing material 140 rather than a wire extending
substantially past encasing material 140.
[0056] Backing component 120 contacts piezoelectric element 110. In
general, backing component 120 is positioned on a side of
piezoelectric element 110 that is opposite the side from which
acoustic signals are transmitted from acoustic transducer 100. The
expansion and contraction of piezoelectric element 110 in response
to an applied electrical signal cause the generation of sound waves
in a non-directional manner. That is, sound waves from
piezoelectric element 110 are output in what can be referred to as
the measurement direction and also in the opposite
(non-measurement) direction into backing component 120. Sound waves
from piezoelectric element 110 may also be output in lateral
directions or oblique to the intended measurement direction.
Backing component 120 is intended to dissipate/absorb sound waves
transmitted in the non-measurement direction. Backing component 120
thus prevents unwanted reflections and interference caused by sound
waves from piezoelectric element 110 transmitted in the
non-measurement direction.
[0057] Backing component 120 provides acoustical dampening of the
sound waves transmitted from piezoelectric element 110 in the
non-measurement direction, but, for the reasons discussed above,
should have a coefficient of thermal expansion (in the intended
operating temperature range) that matches or nearly matches the
coefficient of thermal expansion of the encasing material 140. For
example, the backing component 120 should have a coefficient of
thermal expansion that is within 15% of the coefficient of thermal
expansion of the encasing material 140; preferably, within 8%; and
more preferably, within 3%.
[0058] In this example embodiment, backing component 120 comprises
a fluoropolymer material impregnated (mixed) with tungsten
particles. The mixing of tungsten particles with the fluoropolymer
can be accomplished by any means available. For example, if the
fluoropolymer is melt-processable, the particles can be added to a
melt including the fluoropolymer before molding/processing into the
backing component 120 shape. When the fluoropolymer is available as
a powder, the mixing could be a dry mixing of powders, before
molding/processing into the backing component 120 shape.
Fluoropolymer could be spray coated onto the tungsten, then molded
into shape. When using a fluoroelastomer, mixing could be done on a
milling machine, internal mixer, or screw-type mixer.
[0059] The tungsten particles may comprise greater than 60% (by
volume) of the backing component 120. The tungsten particles may
comprise greater than 65% (by volume) of the backing component 120.
The tungsten particles may comprise between 65-70% (by volume) of
the backing component 120. The tungsten particles may comprise
greater than 70% (by volume) of the backing component 120. In yet
another embodiment, the tungsten particles may comprise greater
than 40% (by volume), greater than 50% (by volume), or greater than
55% (by volume) of the backing component 120. It is contemplated
that the backing component 120 may incorporate any suitable amount
of tungsten particles, other suitable metal particles, or
combinations thereof such that the backing component 120 has a
coefficient of thermal expansion that is within 15% of the
coefficient of thermal expansion of the encasing material 140;
preferably, within 8%; and more preferably, within 3%. The tungsten
particles may be of two or more nominal sizes (diameters) to
enhance packing efficiency. A material other than tungsten may be
incorporated in addition to or instead of tungsten. For example,
gold particles may be incorporated into backing component 120.
High-density (e.g., approximately the specific gravity of tungsten
particles or higher) particles of any type material may be
incorporated into the polymer material of backing component
120.
[0060] The backing material used in backing component 120 for
supporting the crystal (piezoelectric element 110) has a great
influence on the performance of an acoustic transducer. Using a
backing material with acoustic impedance similar to that of the
piezoelectric element 110 will provide the widest operating
frequency "bandwidth" for the transducer and will generally provide
higher sensitivity (i.e., allow detection of lower amplitude return
signals).
[0061] A backing material that matches the acoustic impedance of
the piezoelectric element 110 is preferred and, in general, the
closer the acoustic impendence of the backing material to the
piezoelectric element 110, the better the performance of the
acoustic transducer. In an actual device, a difference between
acoustic impedance of piezoelectric element 110 and acoustic
impedance of the backing component 120 may be on the order of 10%,
with the backing component 120 typically having the lower acoustic
impedance of the two components.
[0062] As an example of the acoustic impedance values in an
embodiment, when lead-metanoibate ceramic is used as a
piezoelectric material, the piezoelectric element 110 has an
acoustic impedance of approximately 20 MRayls (20.times.10.sup.6
Rayls). When lead-titanate-zirconate is used as a piezoelectric
material, the piezoelectric element 110 has an acoustic impedance
of approximately 30 MRayls. Thus, the backing component 120
preferably has an acoustic impedance equal to or approaching 20
MRayls when lead-metanoibate ceramic is used as a piezoelectric
material and equal to or approaching approximately 30 MRayls when
lead-titanate-zirconate is used as a piezoelectric material.
[0063] A Rayl as used herein has the base units (kg/(sm.sup.2)).
MRayl=1.times.10.sup.6 Rayls.
[0064] The acoustic transducer 100 may also include a impedance
matching layer 150 to provide a transition between piezoelectric
element 110 and the outside of the transducer (for example, a
material contacted by the transducer in a contact mode, such as a
steel pipe wall). The matching layer may be comprised of multiple
layers and/or a composite material. The matching layer may comprise
any material having acoustic impedance between the piezoelectric
element 110 and the intended measurement environment. In some
embodiments, the matching layer may be a ceramic material, a rubber
material, or an epoxy material. The matching layer may incorporate
metallic particles into such materials. A wear plate 160 may also
be incorporated into acoustic transducer 100 in some embodiments.
The wear plate 160 protects transducer components from abrasion or
other physical damage.
[0065] The impedance matching layer 150 may preferably have a
thickness which corresponds to 1/4 of the desired output wavelength
of the acoustic signal. A 1/4 wavelength thickness allows waves
that are reflected within the matching layer 150 to be in phase
with the primary (un-reflected) signal. Matching layer 150 may have
any suitable thickness and is not necessarily limited to
quarter-wavelength thickness. If a range of acoustic signals are to
be output, the matching layer 150 may be sized for either a
specific wavelength of interest or according to a midpoint of some
portion of the intended output range, for example. The impedance
matching layer 150 is preferably placed between the piezoelectric
element 110 and the output face of the acoustic transducer 100.
[0066] The material of the matching layer 150 is preferably
selected to provide a transition from the acoustical impedance of
piezoelectric element 110 and the material outside the transducer.
Avoiding too abrupt of a transition in acoustical impedance help
prevents unwanted reflections of the output signal at the output
interface and generally improves output signal strength.
[0067] For contact transducers, the matching layer 150 can be made
from a material that is between an acoustical impedance of the
piezoelectric element 110 and the intended contacted material
(e.g., steel of a steel pipe). Immersion transducers may have a
matching layer 150 with an acoustical impedance between the
piezoelectric element 110 and the immersion fluid (e.g., water or
oil). Immersion transducers may incorporate an encasing material
140 that prevents or limits fluid infiltration.
[0068] Piezoelectric element 110 comprises a material, such as
barium titanate (BaTiO.sub.3), which varies in size in response to
an applied electrical current. This response is generally referred
to as an inverse piezoelectric effect. Application of an
alternating current (via wire lead 130) can cause the piezoelectric
element 110 to rapidly fluctuate in size and thereby generate sound
waves (depicted as arrows in FIG. 1) emitted by acoustic transducer
100.
[0069] Piezoelectric element 110 also generates an electric current
in response to being compressed. This response is generally
referred to as a piezoelectric effect. When an acoustic wave
impinges on acoustic transducer 100, piezoelectric element 110
generates an electric current due to compression by the acoustic
wave. Thus, in this example embodiment, piezoelectric element 110
can both generate an acoustic signal and detect a return acoustic
signal.
[0070] In other embodiments, the generation of an acoustic signal
and the detection of acoustic signals may occur in separate
piezoelectric elements. These separate piezoelectric elements may
be in different acoustic transducers 100 or within the same
acoustic transducer 100. Furthermore, piezoelectric element 110 can
be divided into multiple portions, such that one or more portion
generates acoustic signals and another portion or portions respond
to acoustic signals.
[0071] In general, piezoelectric element 110 can be operated to
produce a range of acoustic frequencies or a single frequency. In
general, it is preferable for the acoustic transducer 100 to have a
wide range of possible operating frequencies. The operating
frequency (or operating frequency band) may be adjustable or fixed.
The operating frequency may controllable by external control
systems (not specifically depicted in FIG. 1) providing control
signals along wire lead 130.
[0072] In this example embodiment, the acoustic transducer 100
operates at ultrasonic frequencies. Ultrasonic frequency, for the
purposes of this specification, may be considered to be frequencies
greater than 20 kHz (kilohertz) up to several gigahertz. In other
embodiments, the acoustic transducer may operate at any frequency
appropriate to the materials being measured or the materials
through which the sound waves are being transmitted.
[0073] Wire lead 130 is an electrically conductive material for
transmitting electric signals to and from the piezoelectric element
110. Wire lead 130 may comprise multiple wires electrically
insulated from one another such that distinct signals or voltages
may travel along wire lead 130. In some embodiments, multiple wire
leads 130 may be provided.
[0074] As depicted in FIG. 1, wire lead 130 is connected at a side
portion of piezoelectric element 110, but the connection may be at
any appropriate surface (e.g., the surface between piezoelectric
element 110 and backing component 120 may be the connection point).
Wire lead 130 may also be connected to the outward facing surface,
though this may interfere with the transmission and reception of
acoustic signals, so is not typically preferred. The wire lead 130
may also be routed through the backing component 120 before exiting
the encasing material 140, rather than being routed directly from
the piezoelectric element 110 as depicted in FIG. 1. Additionally,
wire lead 130 may be formed as a contact terminal on an outer
surface of encasing material 140 rather than a wire extending
substantially past encasing material 140.
[0075] Backing component 120 contacts piezoelectric element 110. In
general, backing component 120 is positioned on a side of
piezoelectric element 110 that is opposite the side from which
acoustic signals are transmitted from acoustic transducer 100. The
expansion and contraction of piezoelectric element 110 in response
to an applied electrical signal cause the generation of sound waves
in a non-directional manner. That is, sound waves from
piezoelectric element 110 are output in what can be referred to as
the measurement direction and also in the opposite
(non-measurement) direction into backing component 120. Sound waves
from piezoelectric element 110 may also be output in lateral
directions or oblique to the intended measurement direction.
Backing component 120 is intended to dissipate/absorb sound waves
transmitted in the non-measurement direction. Backing component 120
thus prevents unwanted reflections and interference caused by sound
waves from piezoelectric element 110 transmitted in the
non-measurement direction.
[0076] Backing component 120 provides acoustical dampening of the
sound waves transmitted from piezoelectric element 110 in the
non-measurement direction, but, for the reasons discussed above,
should have a coefficient of thermal expansion (in the intended
operating temperature range) that matches or nearly matches the
coefficient of thermal expansion of the encasing material 140. For
example, the backing component 120 should have a coefficient of
thermal expansion that is within 15% of the coefficient of thermal
expansion of the encasing material 140; preferably, within 8%; and
more preferably, within 3%.
[0077] In this example embodiment, backing component 120 comprises
a fluoropolymer material impregnated (mixed) with tungsten
particles. The mixing of tungsten particles with the fluoropolymer
can be accomplished by any means available. For example, if the
fluoropolymer is melt-processable, the particles can be added to a
melt including the fluoropolymer before molding/processing into the
backing component 120 shape. When the fluoropolymer is available as
a powder, the mixing could be a dry mixing of powders, before
molding/processing into the backing component 120 shape.
Fluoropolymer could be spray coated onto the tungsten, then molded
into shape. When using a fluoroelastomer, mixing could be done on a
milling machine, internal mixer, or screw-type mixer.
[0078] The tungsten particles may comprise greater than 60% (by
volume) of the backing component 120. The tungsten particles may
comprise greater than 65% (by volume) of the backing component 120.
The tungsten particles may comprise between 65-70% (by volume) of
the backing component 120. The tungsten particles may comprise
greater than 70% (by volume) of the backing component 120. In yet
another embodiment, the tungsten particles may comprise greater
than 40% (by volume), greater than 50% (by volume), or greater than
55% (by volume) of the backing component 120. It is contemplated
that the backing component 120 may incorporate any suitable amount
of tungsten particles, other suitable metal particles, or
combinations thereof such that the backing component 120 has a
coefficient of thermal expansion that is within 15% of the
coefficient of thermal expansion of the encasing material 140;
preferably, within 8%; and more preferably, within 3%. The tungsten
particles may be of two or more nominal sizes (diameters) to
enhance packing efficiency. A material other than tungsten may be
incorporated in addition to or instead of tungsten. For example,
gold particles may be incorporated into backing component 120.
High-density (e.g., approximately the specific gravity of tungsten
particles or higher) particles of any type material may be
incorporated into the polymer material of backing component
120.
[0079] The backing material used in backing component 120 for
supporting the crystal (piezoelectric element 110) has a great
influence on the performance of an acoustic transducer. Using a
backing material with acoustic impedance similar to that of the
piezoelectric element 110 will provide the widest operating
frequency "bandwidth" for the transducer and will generally provide
higher sensitivity (i.e., allow detection of lower amplitude return
signals).
[0080] A backing material that matches the acoustic impedance of
the piezoelectric element 110 is preferred and, in general, the
closer the acoustic impendence of the backing material to the
piezoelectric element 110, the better the performance of the
acoustic transducer. In an actual device, a difference between
acoustic impedance of piezoelectric element 110 and acoustic
impedance of the backing component 120 may be on the order of 10%,
with the backing component 120 typically having the lower acoustic
impedance of the two components.
[0081] As an example of the acoustic impedance values in an
embodiment, when lead-metanoibate ceramic is used as a
piezoelectric material, the piezoelectric element 110 has an
acoustic impedance of approximately 20 MRayls (20.times.10.sup.6
Rayls). When lead-titanate-zirconate is used as a piezoelectric
material, the piezoelectric element 110 has an acoustic impedance
of approximately 30 MRayls. Thus, the backing component 120
preferably has an acoustic impedance equal to or approaching 20
MRayls when lead-metanoibate ceramic is used as a piezoelectric
material and equal to or approaching approximately 30 MRayls when
lead-titanate-zirconate is used as a piezoelectric material.
[0082] A Rayl as used herein has the base units (kg/(sm.sup.2)).
MRayl=1.times.10.sup.6 Rayls.
[0083] The acoustic transducer 100 may also include a impedance
matching layer 150 to provide a transition between piezoelectric
element 110 and the outside of the transducer (for example, a
material contacted by the transducer in a contact mode, such as a
steel pipe wall). The matching layer may be comprised of multiple
layers and/or a composite material. The matching layer may comprise
any material having acoustic impedance between the piezoelectric
element 110 and the intended measurement environment. In some
embodiments, the matching layer may be a ceramic material, a rubber
material, or an epoxy material. The matching layer may incorporate
metallic particles into such materials. A wear plate 160 may also
be incorporated into acoustic transducer 100 in some embodiments.
The wear plate 160 protects transducer components from abrasion or
other physical damage.
[0084] The impedance matching layer 150 may preferably have a
thickness which corresponds to 1/4 of the desired output wavelength
of the acoustic signal. A 1/4 wavelength thickness allows waves
that are reflected within the matching layer 150 to be in phase
with the primary (un-reflected) signal. Matching layer 150 may have
any suitable thickness and is not necessarily limited to
quarter-wavelength thickness. If a range of acoustic signals are to
be output, the matching layer 150 may be sized for either a
specific wavelength of interest or according to a midpoint of some
portion of the intended output range, for example. The impedance
matching layer 150 is preferably placed between the piezoelectric
element 110 and the output face of the acoustic transducer 100.
[0085] The material of the matching layer 150 is preferably
selected to provide a transition from the acoustical impedance of
piezoelectric element 110 and the material outside the transducer.
Avoiding too abrupt of a transition in acoustical impedance help
prevents unwanted reflections of the output signal at the output
interface and generally improves output signal strength.
[0086] For contact transducers, the matching layer 150 can be made
from a material that is between an acoustical impedance of the
piezoelectric element 110 and the intended contacted material
(e.g., steel of a steel pipe). Immersion transducers may have a
matching layer 150 with an acoustical impedance between the
piezoelectric element 110 and the immersion fluid (e.g., water or
oil). Immersion transducers may incorporate an encasing material
140 that prevents or limits fluid infiltration.
[0087] FIG. 2 depicts the acoustic transducer 100 deployed in a
"down hole" environment. Acoustic transducer 100 is placed within
wellbore 200. An electrical connection 220 is made to acoustic
transducer 100 from a surface station 210. Electrical current for
driving acoustic transducer 100 is supplied via electrical
connection 220. The power source for driving acoustic transducer
may be a generator, a battery pack, a solar panel, or a combination
of power sources. Surface station 210 includes various electronic
components for interpreting, displaying, and recording data
corresponding to return signals provided by the acoustic transducer
100. For example, a wall thickness of pipe 230 may be determined by
signals supplied by acoustic transducer 100 operating in a contact
mode according to the detected timing of return signal pulses. In
some embodiments, the acoustic transducer 100 could receive
electrical power from a power source located downhole with the
acoustic transducer 100, such as a battery pack. Communication
between acoustic transducer 100 and surface station 210 may use
wireless transmission technology rather than, or in conjunction
with, wired connections.
[0088] In an embodiment, the distance between the acoustic
transducer 100 and an expandable packer 240 placed between wellbore
segments may be determined by signals supplied by acoustic
transducer 100 operating in an immersion mode. The detected
distance may be used to determine the extent of expansion of
expandable packer 240, which can be used to determine if packer 240
has generated a proper seal between wellbore segments above and
below the packer 240.
[0089] FIG. 3 depicts a material 300 that may be used in backing
component 120. The material used in backing component 120 may
comprise a polymer portion 310 and particulate portion 320. The
particulate portion 320 is dispersed within polymer portion 310.
Particulate portion 320 may be, for example, metallic particles on
the order of 1 micron to 100 microns in nominal dimension.
Generally, particulate portion 320 serves to increase the acoustic
impedance of backing component 120. Note that the depiction of
material 300 is not necessarily to scale. And as noted elsewhere,
the particulate portion may, in some embodiments, consist of
particles having the same nominal diameter. It is also not
necessary that the particles be spherical or generally spherical,
but may be any shape, regular or irregular.
[0090] The particulate portion 320 may be dispersed within the
polymer portion 310 by a milling process or similar method when the
polymer portion comprises an elastomeric material. The polymer
portion 310 may be melt processable to promote the incorporation of
the particulate portion 320.
[0091] The polymer portion 310 may comprise a material such as, for
example, a fluoroelastomeric material. The polymer portion 310 may
comprise a co-polymer (or a combination) of two or more different
fluoropolymers. The elastomeric portion 310 may also comprise a
perfluorinated polymer or a copolymer of two or more perfluorinated
polymers. Assuming suitable phase-compatibility, a mixture of
different fluoropolymers and/or perfluoropolymers may be used in
elastomeric portion 310.
[0092] In some embodiments, the elastomeric portion 310 may
comprise co-polymer of vinylidene fluoride (VDF) and
hexafluoropropylene (HFP). Several different elastomeric materials
incorporating VDF as a monomeric component are sometimes referred
to collectively in the art as "FKM" materials. These "FKM"
materials are available under various trade names, such as
Viton.TM. and Dyneon FKM.TM..
[0093] In some embodiments, the polymer portion 310 may comprise a
fluorine-containing polymer having a Mooney Viscosity ML1+10 @
100.degree. C. (212.degree. F.) equal to 20 or less Mooney units
(MU) as measured in a Mooney scorch test according to ASTM
D1646--Standard Test Methods for Rubber-Viscosity, Stress
Relaxation, and Pre-Vulcanization Characteristics (Mooney
Viscometer). In this context, "L" designates a "large rotor" on the
viscometer, "1" designates the "pre-heat" time in minutes, and "10"
designates the time in minutes after the start of the rotor at
which the measurement is made. The time at which the measurement is
made may be referred to as the "test time." The test temperature is
100.degree. C. (212.degree. F.).
[0094] In general, the Mooney scorch test is a method of measuring
a viscosity of a rubber material or a compound using a shearing
disk viscometer. This shearing disk may be referred to as a
"rotor." Viscosity in MU corresponds to a torque required to rotate
the disk while in the measured rubber material or compound. Test
sample preparation can conform to industry standards for sample
preparation including processing the sample with an initial number
of milling passes at a specified temperature and spacing (nip
width) of the milling rollers. The specimen to be measured, once
prepared, is kept within a die cavity that is heated to a specified
temperature for a specified time (pre-heat time). The die cavity
may be maintained in a sealed condition by application of a
specified pressure. Temperature and pressure conditions of the die
cavity may conform to commonly used industry standard temperature
and pressures for Mooney viscosity measurement of rubber and/or
elastomeric materials.
[0095] The polymer portion 310 may also comprise a tertiary
co-polymer (terpolymer) of VDF, HFP, and tetrafluoroethylene (TFE).
The polymeric material may include perfluoromethylvinylmethylether
(PVME) as a component in conjunction with one or more of VDF, HFP,
and TFE. Non-fluorinated components may also be included in the
polymeric material, such as hydrocarbon components including
ethylene and propylene.
[0096] The polymer portion 310 is preferably, in an initial state,
a readily malleable (low viscosity) material that can be
subsequently cured, set, or cooled to a more rigid (higher
viscosity) final state. For example, the elastomeric portion 310
may be cured by thermal processing to form crosslinked portions or
higher molecular weight portions to thereby increase viscosity. A
crosslinking component and/or a crosslinking promoter may be
incorporated in the elastomeric portion 310. Various polyamines,
diamines, dihydroxy compounds, and peroxides may be used for
crosslinking the polymer portion 310. In some embodiments, the
polymer portion 310 can have a specific gravity in the range of 1.5
to 1.75, or more specifically approximately 1.6.
[0097] FIG. 4 depicts a process flow 400 for forming a backing
component for use in an acoustic transducer. In the process
depicted in FIG. 4, an elastomeric material, such as a "FKM" rubber
material, is processed to incorporate a particulate material, such
as tungsten particles, to provide a backing component with improved
characteristics, such as a coefficient of thermal expansion that is
closer to the coefficient of thermal expansion of the piezoelectric
element of the acoustic transducer. Typical values of acoustic
impedance of the polymer are between 2 to 3 MRayls; while for the
tungsten in particulate form has acoustic impedance about 100
MRayls. The mixture of the polymer and particles can approach a
desired acoustic impendence that matches the piezoelectric element
110.
[0098] In an initial step 410, a polymer, such as an elastomeric
material including a fluoroelastomer, is obtained. The polymeric
material in this embodiment increases viscosity via a thermal
curing process. That is, after thermal processing, via baking,
milling, or other means, the polymeric material has a higher
viscosity than the initial state polymer. The polymer may be a
fluorine-containing elastomer, thermoset, or thermoplastic
material.
[0099] In step 420, tungsten particulates are incorporated into the
polymer. In this example, tungsten particulates are incorporated
into the polymer by a milling process. A first portion of tungsten
powder (comprised of tungsten particulates) is dispensed on to the
polymer material. The polymer/powder component is passed through
rollers of a milling machine. The rollers may or may not be heated
and the spacing of between rollers in a vertical direction may be
adjusted as deemed appropriate for the overall quantity of polymer
being processed in a single batch. The rollers press the powder
into polymer to thereby physically incorporate (mix) the
particulates into the polymer.
[0100] In step 430, a second portion of tungsten powder may
incorporated by dispensing the second portion on to the polymer
material and passing the polymer/powder component through the
rollers of the milling machine (or a second milling machine). The
settings of the milling machine may be different from or the same
as those used in step 420.
[0101] Steps 420 and 430 may be repeated several times until a
desired or otherwise suitable amount of particulate is incorporated
into the polymer. The first portion of tungsten powder may include
particulates having a nominal diameter that is different from a
nominal diameter of the particulates in the second portion of the
tungsten powder. That is, particulates of at least two different
sizes can be incorporated into the polymer. In general, it is
thought the particulate packing density may be improved with use of
different diameter particulates. The process may be modified to
include only a single nominal particulate size or three or more
nominal particulate sizes. In some embodiments, the tungsten powder
may comprise a mixture of particles with two or more nominal
particulate sizes. That is, different particle sizes may be
incorporated using a single step (e.g., step 420 or step 430).
[0102] In some embodiments, a first portion of particulates may
have a different nominal shape than a second portion of
particulates. In these instances the first and second portions may
have the same or different nominal sizes.
[0103] The polymer material may be preferably folded upon itself
prior to passing through the milling machine rollers. That is,
tungsten powder can be dispensed on to a surface of the polymer
material, which is then folded, placing the powdered surface
between different portions of the polymer material.
[0104] In step 440, the polymer/powder material may be processed
into a desired shape after the desired or suitable amount of
particulate is incorporated into the polymer. The desired shape
generally corresponds to the size and shape requirements of a
backing component (such as backing component 12) to be included in
an acoustic transducer (such as acoustic transducer 100). In this
example, the polymer/powder material is processed into the desired
shape by a molding process. For example, the polymer/powder
material (or portions thereof) may be placed in a hot-press mold
and molded into the desired shape using any suitable temperature,
pressure, and molding time.
[0105] In step 450, the molded polymer/material may be finish
processed into a backing component by, for example, machining the
material to within desired dimensional tolerances, polishing
surfaces to a desired flatness, and/or cleaning surfaces to remove
residues or stray particulates.
[0106] When the backing component is completed, it may be
incorporated into an acoustic transducer by affixing the backing
component to a backside surface of a piezoelectric element.
Affixing of the backing component may be accomplished by a variety
of means such as by gluing or physically clamping the backing
component to the backside of a piezoelectric component. As
described with respect to acoustic transducer 100, the backing
component and the piezoelectric element may subsequently be encased
in an epoxy resin.
[0107] The mixing of metal particles, such as tungsten particles,
into a fluorine-containing polymer can be performed in a variety of
ways. When the polymer is a melt-processable thermoplastic, the
metal particles may be mixed into the polymer melt before (or
during processing). Metal particles may be spray coated onto the
surface of the polymer then particulate-coated polymer material can
be further processed and molded. In some embodiments, the polymer
may be spray coated onto the metal particles and then the
polymer/particle mixture can be further processed and molded. If
the polymer is available as a powder, the polymeric powder and the
metal particles can be dry blended before molding/processing. The
polymer can be ground into the small particles and mixed with the
metal particles during the grinding process. The polymeric
particles and the metal particles can be generated by a grinding
process performed on both the polymer and metal materials at the
same time.
First Example
[0108] FIG. 5 depicts an example process flow of a method 500 for
monitoring the deformation of a non-metallic sample using an
acoustic signal. The acoustic signal can be generated by an
acoustic transducer 100 described above, for example. In this
embodiment, a sample is monitored in a chamber allowing the
simulation of downhole conditions. In other embodiments, the
deformation of the sample may be monitored in an actual downhole
environment, as depicted in FIG. 2. The deformation can be tracked
by the measurement of one or more characteristic of the sample,
such as a dimension or a modulus.
[0109] In addition to use of an acoustic signal to monitor a
characteristic of the sample, additional probes or sensors may be
incorporated. For example, a spectrographic probe may be used to
monitor the chemical environment of the sample or the chemical
composition of the sample itself. Two or more acoustic sensors
(e.g., acoustic transducers 100) may be incorporated to allow
monitoring of multiple characteristics of the sample, for example,
dimension changes for different portions of the sample or in
different directions.
[0110] As an initial step, a sample to be tested is obtained
(element 510) and then positioned (element 520) in a sealable
chamber. The sealable chamber may be as depicted in FIG. 6a and
FIG. 6b or may be of another appropriate design. The initial
characteristics of the sample may optionally be measured prior to
positioning the sample in the chamber. For example, physical
measurements of sample dimensions can be made using, for example,
rulers, calipers, or other measurement techniques performed outside
of the chamber. In another example, initial measurements may be
made on the sample after the sample is positioned, but before the
chamber is sealed.
[0111] After the sample is positioned, the chamber can be sealed
(element 530). An acoustic signal provided ("generated," element
540) by an acoustic transducer is then used to monitor ("measure,"
element 570) a characteristic of the sample. The characteristic may
be a dimension in a given direction or may be a modulus of the
sample. A dimension of the sample can be determined with the
acoustic signal by monitoring detected reflection times. Signal
reflection times change with distance of the surface(s) of the
sample from the acoustic transducer. The modulus of the sample can
be determined by monitoring the speed of the acoustic signal
through the sample, with generally a lower modulus corresponding to
a slower acoustic signal speed. Modulus may also be determined by
the vibratory response of the sample to the acoustic signal.
[0112] The sealed chamber can be brought to a controlled
temperature (element 550). The temperature may be altered using
resistive heating elements, heat exchangers, ovens, furnaces, heat
lamps, or the like. For example, the entire chamber could be placed
in an oven or furnace. The controlled temperature may be a constant
temperature or may vary with time. Temperature control may involve
use of temperature sensors inside or outside the chamber and
computerized controller units.
[0113] While downhole temperatures are generally higher than
surface conditions, the controlled temperature could also be lower
than, for example, 25.degree. C. In such a case, the temperature
may be altered using heat exchangers, refrigerating the chamber,
immersion in ice, or the like.
[0114] The sealed chamber can be brought to a controlled pressure
(element 550). The pressure may be altered by supplying compressed
gases or fluids. The pressure may be controlled with valves, pumps,
or compressors. The controlled pressure may be a constant pressure
or may vary with time. Pressure control may involve use of pressure
sensors and computerized controller units. As is well known in the
art, pressure inside a sealed chamber may be a function of
temperature, thus pressure control may also involve controlling or
monitoring temperatures.
[0115] While downhole pressures are generally higher than surface
conditions, the controlled pressure could also be a pressure lower
than atmospheric pressure (1 atm). In such a case, the pressure may
be altered using vacuum pumps and the like.
[0116] After the sample is positioned in the chamber, the sample
can be monitored with the acoustic signal either constantly or
periodically. The sample can be monitored while the controlled
temperature and/or controlled pressure are/is being established or
only after the controlled temperature and/or controlled pressure
are/is established.
[0117] A test fluid (liquid or gas or combinations thereof) may be
introduced (element 560) into the chamber either before or after
the chamber is sealed. The test fluid may be introduced before or
after the chamber is at a controlled temperature or pressure. The
chamber may receive a single charge of test fluid or test fluid may
be flowed continuously through the chamber. In addition, test fluid
can be extracted or removed as required. For example, test fluid
may be introduced or removed as required to maintain desired
pressure conditions in the sealed chamber. Generally, the sample is
immersed in the test fluid, that is, the sample is covered by the
test fluid, but this is not absolutely required and the chamber may
be designed or operated such that only a portion of the sample is
in contact with the test fluid. The temperature of the test fluid
may be controlled in conjunction with chamber temperature.
[0118] The test fluid may correspond to an expected chemical
environment in a wellbore location. For example, the test fluid
could be petroleum or natural gas. The test fluid could be water or
a brine solution. As minor variations in fluid composition could
potentially make significant differences in sample material
behavior, the test fluid could be drawn from a specific wellbore of
interest at a specific depth of interest. Alternatively, a more
generic test fluid can be used--for example, vegetable oil could be
used as a less volatile (and less dangerous) stand-in for crude
oil. The test fluid can include suspended solids, which may, for
example, be components of a drilling mud.
[0119] Monitoring of the sample using an acoustic signal may
involve an integrated acoustic signal generator and sensor (e.g.,
an acoustic transducer such as acoustic transducer 100) or the
acoustic signal may be generated at a location that is not the same
as the sensor location. For example, the acoustic sensor system
could be operated in a transmission mode with the signal generator
opposite the signal sensor with the sample placed in between. A
reflection mode system where the signal generator and sensor are
placed at an angle to each other that is greater than 0.degree. but
less than 180.degree. may be used.
[0120] The frequency of the acoustic signal generated may be in the
ultrasonic frequency range (above 20 kHz). The acoustic signal may
also be in the audible range or less. The acoustic signal may be a
discrete frequency or encompass a range of frequencies. The
frequency of the signal may be constant or scanned through a range
or a band.
[0121] The method may encompass the use of multiple acoustic
sensors monitoring a single sample and the use of multiple sensor
monitoring separate samples in the same chamber.
[0122] The specific ordering of the steps of the method is
generally not critical. For example, in some embodiments, the
acoustic signal may be generated before or after the chamber is
sealed or the temperature/pressure has been set. In some
embodiments, the sample may be positioned after the chamber is
sealed or after the temperature or pressure has been set.
Additionally, the sample may be repositioned after a measurement of
a characteristic.
[0123] In FIG. 6, a measurement result from a sample is depicted.
The measurement is from a reflection mode system. The distance from
the sensor to the sample surface can be determined by a reflection
from the sample surface. If an initial distance of the sample from
the sensor is known, then changes in thickness can be determined
using only the reflection from the sample surface, assuming test
conditions do not change appreciably. But to accurately determine
the distance from the sensor to the specimen when pressure,
temperature, and/or test fluid composition changes, the acoustic
impedance of the test fluid must be known. The acoustic impedance
of the test fluid can be determined in-situ by reflecting a signal
off of a reference shelf positioned at a known and constant
distance from the sensor. For example, if the sample swells when
exposed to the test fluid, then the distance to the sensor will
decrease allowing one to calculate the change in specimen
thickness. Repeated distance measurements may be made over time or
with changing conditions to track the response of the sample. For
example, the chamber may be filled with a test fluid and placed at
constant temperature and pressure and changes in sample thicknesses
over multiple days may be monitored, as depicted in FIG. 7 showing
a comparison of sample swell (change in thickness in a radial
sample direction) as measured using physical techniques (calipers)
and acoustic reflectance measurements over four days.
[0124] Though in this example embodiment a thickness of the sample
is the monitored characteristic, other things such as the modulus
of the sample may be monitored instead of or in addition to the
thickness. Thickness may be monitored directly or may correspond to
a measurement of sample surface location.
[0125] Measurement of the modulus can be made using a sample with a
known thickness so that the speed of sound (acoustic energy)
through the sample can be determined. In some instances, the
acoustic signal generator could be placed in direct contact with
the sample to measure sample modulus. A p-wave (primary wave) can
also be used to monitor changes in modulus when the sample is
exposed to a gas, such as hydrogen sulfide (H.sub.2S), for example.
When the sample is exposed to a liquid dimension changes can be
monitored.
[0126] Also, though described as a thickness in this example, any
physical dimension may be monitored as the sample characteristic.
That is, a width, a length, a height, a diameter, or the like may
be monitored as the sample characteristic. The sample
characteristic may be a distance of a sample surface from the
acoustic signal generator. The sample characteristic may correspond
to a deformation or movement of the sample. Deformation of a
specimen due to swelling, shape-memory responses, inflation, or
mechanical loading can be monitored by measuring changes in the
reflection times between the sensor and the specimen.
Second Example
[0127] Example details of an apparatus for measuring deformation of
non-metallic materials are described with reference to FIG. 8a and
FIG. 8b. In this embodiment, the apparatus may be a laboratory test
bed for studying the response of non-metallic materials to
simulated downhole conditions. As depicted in FIG. 8a, the
apparatus comprises a sealable chamber 800 with one or more ports
(e.g., an opening) through which wires, tubes, sensors, or the like
may pass through the chamber wall. Here, the sealable chamber 800
is depicted as circular structure, but the chamber may be of any
shape. As depicted, the sealable chamber 800 is formed of a body
805 and a lid 810, though the chamber 800 could also be formed of a
single body with an access door/panel providing for inserting a
sample into the chamber. The lid 6810 can be bolted to the body 805
using a plurality of bolts or other fasteners. The depicted lid 810
has multiple ports, though not depicted here body 805 may also have
a port or ports. An analog pressure gauge 830 is attached to a
port. Wire leads 850 for one or more acoustic sensors are passed
through a port. Wire leads 850 for one or more thermocouples are
also passed through a port. A digital pressure sensor (transducer)
840 may also be incorporated into the apparatus with associated
leads and/or tubes passed through a port.
[0128] Once appropriately sealed, the chamber 800 can be
pressurized. The apparatus may include a pressure control system
(which may incorporate a controller 880) to control the pressure of
the chamber. For example, the chamber can be pressurized to
approximately 1700 psi, between 500 psi and 4,000 psi, or between 0
psig and 6,500 psi or higher if appropriately designed. The chamber
800 can be designed for vacuum operations if deemed necessary.
[0129] The chamber 800 holds a sample holder 820. A sample holder
820 is depicted in FIG. 8a as within the sealed chamber and in a
standalone view in FIG. 8b. The sample holder 820 is designed to
hold the sample 828 substantially stationary during measurement
made using an acoustic transducer 890a (which may correspond to an
acoustic transducer 100). For example, the sample 828 may be a
donut-shaped sample and can be held by a pin, rod, clamp, screw, or
bolt (fastener) 826 extending through the interior void of the
donut-shaped sample 828 from plate 822a to plate 822b. Of course,
the sample need not be donut-shaped and other shapes may be
incorporated. For example, block samples can be held between plates
using one or more fastener 826 located proximate to a corner of the
block sample.
[0130] A flange (reference plate) 824 is, in this embodiment,
attached to a surface of plate 822b. The reference plate 824 is
positioned at a known distance from an acoustic transducer 890b.
With the depicted arrangement, a reference signal can be acquired
from acoustic transducer 890b can be used to calibrate a signal
from acoustic transducer 890a that is positioned to acquire
measurements on sample 828. This depicted arrangement requires at
least two acoustic transducers 890 to be incorporated into the
apparatus. The physical separation between acoustic transducers
890a and 890b may cause the acquired signals to be obtained under
somewhat different conditions, which may affect calibration
accuracy when not properly accounted for during the sample
measurement process. FIG. 11, discussed below, describes a modified
embodiment of an apparatus that allows the reference signal and the
measurement signal to be acquired under the same conditions using a
single acoustic transducer 890 (corresponding to element 20 in FIG.
11).
[0131] The chamber 800 may incorporate various safety features such
as pressure relief valves. Additionally, it may be preferable to
purge the sealed chamber of oxygen to limit the potential for
ignition of flammable test fluids within the chamber. The purge gas
may be, for example, nitrogen or an inert gas such as argon.
[0132] The test fluid may be added to the chamber either prior to
sealing or via a fluid port 860 after sealing. The test fluid may
be any fluid of interest, for example, crude oil, hexane, water,
salt solutions, or natural gas. The test fluid may be a mixture of
components and may also incorporate dissolved or suspended solids,
such as, for example, drilling mud.
[0133] In many instances the test fluid will be highly corrosive to
certain materials. To limit corrosion of the chamber interior, it
may be preferable to coat the interior surfaces with a protective
coating--for example, a phenolic resin or the like may be used.
[0134] The apparatus may include a thermal control component
(temperature control system) to bring the temperature of the test
fluid to a controlled temperature. The controlled temperature will
generally by a temperature above room temperature when simulating
downhole conditions, and thus the thermal control component would
incorporate a heater unit, but the apparatus may also be used
simulate less than room temperature conditions, if the desired. In
such instances, the thermal control component would incorporate a
cooling unit. The thermal control component may include resistive
heating elements, combustion systems, heat lamps, heat exchangers,
refrigeration units, or the like. The thermal control component may
incorporate a controller 880.
[0135] The apparatus may additionally include a data acquisition
component. The data acquisition component may be configured to
continuously or periodically acquire data from one or more sensors,
such as thermocouples, pressure transducers, and/or acoustic
sensors. The data acquisition component may include a data logger
to store data acquired from the sensors over a period of time. The
data acquisition component may comprise special-purpose electronic
components or may be implemented in a computer system running
specialized software. The computer system may operate over, or in
conjunction with, a computer network, including the Internet.
[0136] The apparatus may additionally include a control component.
The control component may be used to control the temperature and/or
pressure of the in the sealed chamber by, for example, the
operation of valves and/or the thermal control component. The
control component may comprise special-purpose electronic
components, for example, microcontroller units, or may be
implemented in a computer system running specialized software. The
computer system may operate over, or in conjunction with, a
computer network, including the Internet. The data acquisition
component and the control component may optionally be implemented
in the same computer system.
Third Example
[0137] Example details of an apparatus for measuring deformation of
non-metallic materials are described. In this embodiment, the
apparatus may be used for studying the response of non-metallic
materials to simulated downhole conditions.
[0138] FIG. 9 depicts a sample holder 900 and an arrangement of
acoustic sensors (transducers) 920. The test sample 910 is depicted
as a doughnut-shaped sample. A base plate 905 has pin or threaded
rod (a sample pin) 940 extending in a direction perpendicular to
the base plate 905. The sample 910 is placed on the sample pin 950.
An upper and a lower sample plate (930a and 930b, respectively) are
used to secure the sample 910. The upper sample plate 930a may
optionally be allowed to move up or down according to the
expansion/contraction of the sample 910. The upper (930a) and lower
(930b) sample plate may optionally each incorporate an opening for
an acoustic sensor 950 for measuring vertical compliance (thickness
changes) and a dynamic elastic bulk modulus. As depicted in FIG. 9,
the apparatus has two radial acoustic sensors 920 and a vertical
acoustic sensor 950, though additional radial sensors 920 and
additional vertical acoustic sensors 950 are contemplated. In
general, a greater or less number of sensors 920/950 can be used as
desired; though increasing the number of sensors may complicate
acquisition of signals due to possible cross-talk and noise
effects. Additionally, each sensor will generally have separate
leads, which must be passed through the sealable chamber wall.
[0139] The sample holder 900 depicted in FIG. 9 could, if desired,
be incorporated into a chamber 800 described in connection with
FIG. 8a.
Fourth Example
[0140] Example details of an apparatus for measuring deformation of
non-metallic materials are described. In this embodiment, the
apparatus may be used for studying the response of non-metallic
materials to simulated downhole conditions.
[0141] FIG. 10 depicts a portion of another embodiment of an
apparatus for measuring deformation of materials. Here, instead of
a donut-shaped sample, the sample 1010 is a disk (sometimes
referred to as a button) of material which fits into a sample cup
1030. A single or multiple sample cups 1030 could be positioned in
a sealable chamber as described in relation to the first
embodiment. Each sample cup 1030 could have dedicated acoustic
transducer 1020, or if desired a single acoustic transducer 1020
could be mechanically positioned above each sample cup 1030 in
turn, though this would be expected to result in a relatively
complex apparatus.
[0142] The sample holder 1000 depicted in FIG. 10a depicts three
sample cup 1030 positions and a fourth reference signal position,
which could be an empty sample cup 1030. The reference signal
reflection can be compared to the three sample signals to allow
thickness changes to be measured. The number of sample cup
positions is not limited to three. Any number of positions may be
used. FIG. 10b depicts an example of a sample cup 1030 used in some
embodiments. The sample placed in each sample cup may be a
different material for testing. That is, multiple sample types may
be tested simultaneously in the chamber 800 adopting the sample
holder 1000 depicted in FIG. 10a.
[0143] A thinner sample disk-shaped sample, as used in this
embodiment, would be expected to stabilize sooner than the
relatively thick donut-shaped samples described above. This might
be useful for making quicker comparisons between materials. Thinner
samples may also allow for a smaller, lighter sealable chamber. A
smaller, lighter chamber could potentially be easier to incorporate
into a mobile apparatus that might be placed at, for example, a
drill site.
[0144] Instead of simply placing a sample disk 1010 in a sample cup
1030, the sample disk 1010 can be bonded to the sample cup 1030.
Alternatively, the sample cup can incorporate a compression ring or
a capping mechanism that holds the sample disk 1010 in the sample
cup 1030. The capping mechanism may be, for example, a ring which
overlaps an edge portion of the disk. The capping mechanism can be
bolted or screwed into the sample cup, for example. Bonding or use
of a compression ring or capping mechanism may be useful when the
specific gravity of the test fluid is greater than the sample.
Under such conditions, the sample would float and might not remain
in the sample cup.
Other Embodiments
[0145] Disclosed methods for determining deformation of
non-metallic materials may be implemented, fully or partially, as
computer software programs stored in non-transitory,
computer-readable media. Where computer control is possible, such
control may be made via a network (including the Internet).
[0146] As depicted in FIG. 11, the apparatus used to monitor
deformation may incorporate a reference half-shelf (reference
plate) 40. The reference half-shelf 40 is a metal plate that
extends partially into the signal path of an acoustic sensor
(transducer) 20. Part of the acoustic signal hits the half-shelf 40
and reflects back to the acoustic sensor 20 and part of the
acoustic signal hits the test sample 10 and reflects back. The
reference half-shelf 40 provides a reference signal from a known
distance from the same acoustic sensor performing the sample
measurement. Use of a reference half-shelf 40 can eliminate the
need for a separate reference sensor and the need to calibrate each
acoustic signal separately to the reference sensor. The reference
half-shelf 40 may be combined with embodiments discussed above.
[0147] Instead of placing a test sample in a sealable chamber to be
monitored by an acoustic sensor, an acoustic sensor could be placed
downhole at a location of a packer deployment within the wellbore
and the acoustic sensor could monitor characteristics (e.g.,
thickness or modulus) in situ. In yet another embodiment, the
acoustic sensor may be used to monitor a characteristic of an
expandable device such as an expandable tubular device or packer.
In one example, the sensor may be used to monitor the amount of
radial expansion experienced by the expandable tubular device. The
expandable tubular device may be expanded using a cone, a roller,
hydraulic pressure, and combinations thereof.
[0148] Embodiments of an apparatus for measuring deformation of
non-metallic materials may incorporated into a mobile platform or
platforms. For example, a sample holder and acoustic transducer may
be incorporated in a carrying case that may be transported to test
site locations, such as wellbore locations. In some embodiments,
the carrying case may be briefcase size. In some embodiments, the
carrying case may be less than three feet long, three feet wide,
and two feet deep. In some embodiments, the carrying case may be
transportable by a single person of approximately average strength
and may, optionally, incorporate handles and/or wheels. A sealable
chamber may be incorporated into a mobile platform with the sample
holder and acoustic transducer or may comprise a separate element
that may be transported separately and combined with other
components at the test site. A control system for the acoustic
transducer may be incorporated into a mobile platform or may
comprise a separate element, which may be combined with other
components at the test site.
[0149] In an embodiment, a method of measuring deformation of a
non-metallic material includes: obtaining a sample of a
non-metallic material; placing the sample in a sealable chamber;
sealing the sealable chamber; generating an acoustic signal;
adjusting the sealable chamber to approximate a downhole condition;
and measuring a characteristic of the sample using the acoustic
signal. In some variants of the method, the downhole condition is
selected from the group consisting of a downhole pressure, a
downhole temperature, a downhole medium, and combinations thereof.
In some variants, the non-metallic material is a polymer, which can
be an elastomeric material in additional variants. In some
embodiments the non-metallic material is swellable, such as a
swellable packer. The characteristic that is measured can be a
thickness of the sample. The characteristic that is measured can be
a distance of a surface of the sample from an acoustic transducer
used for generating the acoustic signal. The test temperature, test
pressure, and test medium can be set to approximate a downhole
condition of a wellbore.
[0150] Acoustic transducers of embodiments described herein or
fabricated using methods described herein may be incorporated in
any application for which an acoustic transducer is required. Such
applications include, without limitation, use in test stands for
evaluating material(s) in simulated downhole conditions, monitoring
of wellbore apparatus or components in downhole environments,
pipeline thickness measurements. Acoustic transducers of
embodiments described herein or fabricated using methods described
herein can reduced mismatch in component thermal coefficients of
expansion and as such may be particularly advantageous in
applications where the transducer is exposed to repeated thermal
cycling or thermal extremes, such as found in test bed equipment
used to simulate downhole environments or in downhole
environments.
[0151] In one embodiment, an acoustic transducer includes a
piezoelectric element configured to generate acoustic signals
according to an electrical signal that is applied to the
piezoelectric element; a backing component contacting a back-side
surface of the piezoelectric element; and an encasing material that
surrounds the piezoelectric element and the backing component,
wherein the backing component comprises a fluorine-containing
polymer in which metal particles are incorporated. In some
embodiments the metal particles comprise greater than 40% of the
backing component by volume.
[0152] In another embodiment, a backing component for use in an
acoustic transducer includes a fluorine-containing polymer; a
plurality of metal particles dispersed in the fluorine-containing
polymer, wherein the metal particles comprise greater than 60% of
the backing component by volume.
[0153] In another embodiment, a method of manufacturing an acoustic
transducer includes placing a metal powder on a surface of
fluoroelastomeric resin material; mixing the metal powder into the
fluoroelastomeric resin material; forming the fluoroelastomeric
resin material including the metal powder into a backing component;
and affixing the backing component formed of the fluoroelastomeric
resin material including the metal powder to a piezoelectric
material.
[0154] In one or more of the embodiments described herein, the
metal is tungsten.
[0155] In one or more of the embodiments described herein, the
metal particles comprise greater than 65% of the backing component
by volume.
[0156] In one or more of the embodiments described herein, the
metal particles comprise between 65% and 70% of the backing
component by volume.
[0157] In one or more of the embodiments described herein, the
metal particles comprise 70% or greater of the backing component by
volume.
[0158] In one or more of the embodiments described herein, the
fluorine-containing polymer is a fluoroelastomer that comprises a
di-polymer of vinylidene fluoride and hexafluoropropylene having a
Mooney viscosity of less than 20 Mooney units as measured in a
Mooney scorch test using a large rotor, a one minute preheat time,
a ten minute test time, and a 100.degree. C. test temperature.
[0159] In one or more of the embodiments described herein, the
fluorine-containing polymer comprises a perfluoroelastomer having a
Mooney viscosity of less than 20 Mooney units as measured in a
Mooney scorch test using a large rotor, a one minute preheat time,
a ten minute test time, and a 100.degree. C. test temperature.
[0160] In one or more of the embodiments described herein, the
fluorine-containing polymer comprises a terpolymer of vinylidene
fluoride, hexafluoropropylene, and tetrafluoroethylene having a
Mooney viscosity of less than 20 Mooney units as measured in a
Mooney scorch test using a large rotor, a one minute preheat time,
a ten minute test time, and a 100.degree. C. test temperature.
[0161] In one or more of the embodiments described herein, the
fluorine-containing polymer includes
perfluoromethylvinylmethylether as component.
[0162] In one or more of the embodiments described herein, the
metal particles are of at least two different nominal shapes or
sizes.
[0163] In another embodiment, a method of incorporating metal into
a fluoropolymer to make a backing material includes mixing a metal
into a melt processable fluoropolymer; and forming the mixture of
the metal and the fluoropolymer into a desired shape.
[0164] In another embodiment, a method of incorporating metal into
a fluoropolymer to make a backing material includes spraying a
fluoropolymer onto a metal; and forming the metal with the
fluoropolymer sprayed thereon into a desired shape.
[0165] In another embodiment, an apparatus for measuring
deformation of a non-metallic material, includes: a sealable
chamber including a port for introducing a test medium; a sample
holder for holding a sample of a non-metallic material inside the
sealable chamber; a temperature control system for controlling a
temperature of the sealable chamber; a pressure control system for
controlling a pressure of the sealable chamber; and an acoustic
transducer positioned to supply an acoustic signal to the sample in
the sample holder when the sealable chamber is sealed.
[0166] While the foregoing is directed to example embodiments of
the present disclosure, other and further embodiments of the
present disclosure may be devised without departing from the basic
scope thereof, and the scope thereof is determined by the claims
that follow.
* * * * *