Note: Descriptions are shown in the official language in which they were submitted.
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VARIABLE Tg SHAPE MEMORY MATERIALS FOR WELLBORE DEVICES
TECHNICAL FIELD
[0001] The present invention relates to devices used in oil and gas
wellbores employing shape-memory materials that remain in an altered
geometric state during run-in; once the devices are in place downhole and are
exposed to a given temperature at a given amount of time, the devices attempt
to return to their original geometric position prior to alteration.
TECHNICAL BACKGROUND
[0002] Various methods of filtration, wellbore isolation, production
control, wellbore lifecycle management, and wellbore construction are known in
the art. The use of shaped memory materials in these applications have been
disclosed for oil and gas exploitation. Shape-memory materials are smart
materials that have the ability to return from a deformed state (temporary
shape) to their original (permanent) shape induced by an external stimulus or
trigger (e.g. temperature change). In addition to temperature change, the
shape
memory effect of these materials may also be triggered by an electric or
magnetic field, light or a change in pH. Shape-memory polymers (SMPs) cover
a wide property range from stable to biodegradable, from soft to hard, and
from
elastic to rigid, depending on the structural units that constitute the SMP.
SMPs
include thermoplastic and thermoset (covalently cross-linked) polymeric
materials. SMPs are known to be able to store multiple shapes in memory.
[0003] Dynamic Mechanical Analysis (DMA), dynamic mechanical
thermal analysis (DMTA) or dynamic thermomechanical analysis is a technique
used to study and characterize SMP materials. It is most useful for observing
the viscoelastic nature of these polymers. The sample deforms under a load.
From this, the stiffness of the sample may be determined, and the sample
modulus may be calculated. By measuring the time lag in the displacement
compared to the applied force it is possible to determine the damping proper-
ties of the material. The time lag is reported as a phase lag, which is an
angle.
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The damping is called tan delta, as it is reported as the tangent of the phase
lag.
[0004] Viscoelastic materials such as shape-memory polymers typically
exist in two distinct states. They exhibit the properties of a glass (high
modulus)
and those of a rubber (low modulus). By scanning the temperature during a
DMA experiment this change of state, the transition from the glass state to
the
rubber state, may be characterized. It should be noted again that shaped
memory may be altered by an external stimulus other than temperature
change.
[0005] The storage modulus E' (elastic response) and loss modulus E"
(viscous response) of a polymer as a function of temperature are shown in FIG.
1. The nature of the transition state of the shaped memory polymer affects
material's shape recovery behavior and can be descriptive of the polymer's
shape recovery. Referring to FIG. 1, the Glass State is depicted as a change
in
storage modulus in response to change in temperature which yields a line of
constant slope. The Transition State begins when a slope change occurs in the
storage modulus as the temperature is increased. This is referred to as the Tg
Onset which in FIG. 1 is approximately 90 C. The Tg Onset is also the point
where shape recovery can begin. Tg for a shape-memory polymer described by
FIG. 1 is defined as the peak of the loss modulus, which in FIG. 1 is approxi-
mately 110 C. If the slope's change of the storage modulus were represented
by a vertical line of undefined slope, the material shape recovery would occur
at a specific temperature and transition immediately from the glassy state to
the
rubber state. Generally, the more gradual the slope change of the storage
modulus in the transition state, the greater the range of temperatures which
exhibit characteristics of both the glass and rubber states. The transition
state
is the area of interest for the SMP material's shape recovery characteristics.
It
should also be evident that shape recovery would occur more slowly if stimulus
temperature is closer the Tg Onset temperature and shape recovery would be
more rapid as the stimulus temperature approached or exceeded the Tg.
[0006] One method of making use of the unique behavior of shape-
memory polymers is via temperature response described above. An example is
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seen in FIG. 2. The finished molded part 100 of shape-memory polymer has a
defined Tg and Tg Onset. This may be considered an original geometric position
of the shape-memory material. The part is then heated close to the Tg of the
polymer. Force is applied to the finished part to reshape the part into a
differ-
ent configuration or shape 100'. This may be considered an altered geometric
position of the shape-memory material. The reshaped part 100' is then cooled
below the shape-memory polymer's Tg Onset and the force removed. The
finished part 100' will now retain the new shape until the temperature of the
part is raised to the Tg Onset at which point shape recovery will begin and
the
part will attempt to return to its original shape 100" or if constrained, the
part
will conform to the new constrained shape 100'. This shape 100" may be
considered the shape-memory material's recovered geometric position.
[0007] U.S. Pat. No. 7,318,481 assigned to Baker Hughes Incorporated
disclosed a self-conforming expandable screen which comprises a thermoset-
ting open cell shape-memory polymeric foam. The foam material composition is
formulated to achieve the desired transition temperature slightly below the
anticipated downhole temperature at the depth at which the assembly will be
used. This causes the conforming foam to expand at the temperature found at
the desired depth.
[0008] It would thus be very desirable and important to discover a
method and device for deploying an element made of shaped memory materi-
als at a particular location downhole to achieve some desired element of
filtra-
tion, wellbore isolation, production control, wellbore lifecycle management,
and
wellbore construction. Generally, the more versatility for deploying an
element
the better, as this gives more flexibility in device designs and provides the
operator more flexibility in designing, placement and configuration of the
wellbore devices.
SUMMARY
[0009] There is provided, in one non-limiting form, a wellbore
filtration
device involving at least two shape-memory materials. The device includes a
first shape-memory material which is a cross-linked polymer having a first
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crosslinking ratio, where the first shape-memory material has a position of
altered geometry and where the original geometry is recoverable, where the
shape-memory material is maintained in the altered geometry at a temperature
below a first onset glass transition temperature, and where the shape-memory
material expands from its altered geometric position to its original geometric
position when it is heated to a temperature above the first onset glass
transition
temperature. Additionally, the device includes a second shape-memory mate-
rial that comprises a cross-linked polymer having a second crosslinking ratio,
where the second shape-memory material has an altered geometric shape and
an original geometric shape where the shape-memory material is maintained in
the altered geometric shape at a temperature below a second onset glass
transition temperature. The second onset glass transition temperature is
different than the first onset glass transition temperature, and the shape-
memory material recovers from its altered geometric shape to its original
geometric shape when it is heated to a temperature above the second onset
glass transition temperature. The polymers and crosslinkers of the first and
second shape memory materials may be the same or different.
[0010] In another non- limiting embodiment the onset glass transition
temperatures may be the same for the two shaped memory materials. However
the slope change during the transition state from glass state to rubber state
may vary. This would allow the altered geometric shapes of the two shaped
memory materials to recover their respective original geometric shape but at
differing recovery rates.
[0011] There is additionally provided in another non-restrictive
version a
method of manufacturing a wellbore device. The method includes placing in
any order or simultaneously, a first shape-memory material and a second
shape-memory material on a billet, each in a respective original geometric
position. The first shape-memory material has a first onset glass transition
temperature and a first slope change during a first transition state from a
first
glass state to a first rubber state. The first shape-memory material comprises
a
cross-linked polymer having a first crosslinking ratio. The second shape-
memory material has a second onset glass transition temperature and a
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second slope change during a second transition state from a second glass
state to a second rubber state. The second shape-memory material comprises
a cross-linked polymer having a second crosslinking ratio different from the
first
crosslinking ratio. The method further involves altering the original
geometric
positions of the first and second shape-memory materials at a temperature
above both the first and second onset Tg to change the original geometric
positions of the first and second shape-memory materials respectively. Further
the method includes lowering the temperature of the first and second shape-
memory materials to a temperature below the first and second onset Tgs,
respectively, where the first and second shape-memory materials each
maintain their respective altered geometric positions. The first shape-memory
material and the second shape-memory material are further different by a
parameter where the first onset glass transition temperature is different from
the second onset glass transition temperature and/or the first slope change is
different from the second slope change.
[0012] In another non-limiting embodiment there is provided a wellbore
device with a variable onset glass transition temperature within a single
molded
part. One method of manufacturing such a part involves mixing a first isocya-
nate portion (comprising an isocyanate) with a first polyol portion
(comprising a
polyol) in a first ratio of polyol to isocyanate to form a first polyurethane
material
having a first onset glass transition temperature. The method also involves
mixing a second isocyanate portion (comprising an isocyanate, which may be
the same as or different from the isocyanate in the first isocyanate portion)
with
a second polyol portion (comprising a polyol, which may be the same as or
different from the polyol in the first polyol portion) in a second ratio to
form a
second material having a second onset glass transition temperature. The first
onset Tg and the second onset Tg may be different from one another. Alterna-
tively or in addition thereto, a first slope change of the first polyurethane
material is different from a second slope change of the second polyurethane
material. The method additionally involves altering the geometric shape of the
first and second shaped memory materials at a temperature above both the
first and second onset Tgs to change the first and second original geometric
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shape to a first and second altered geometric shape, respectively. Further,
the
method involves lowering the temperature of the respective altered geometric
shapes of the first and second materials to a temperature below the first and
second onset Tgs where the first and second materials each maintain their
respective altered geometric shape.
[0013] Further there is provided in a different, non-restrictive
version a
method of installing a wellbore device on a downhole tool in a wellbore. The
method may include securing a downhole tool to a string of perforated tubing.
The downhole tool may involve a filtration device including a first shape-
memory material, where the first shape-memory material (e.g. a polyurethane)
has an altered geometric shape for run-in position and an original geometric
shape recoverable at a predetermined wellbore position. The first shape-
memory material is maintained in the run-in geometry below a first onset glass
transition temperature of the first shape-memory porous material. The device
may also include a second shape-memory material, which may also be a
polyurethane. The second shape-memory material also has an altered
geometric shape for run-in and an original geometric shape recoverable at a
predetermined position in the wellbore. The second shape-memory material is
maintained in the run-in geometric shape below a second onset glass transition
temperature of the second shape-memory material. The first onset glass
transition temperature Tg is different from the second onset glass transition
temperature Tg. The method additionally includes running the downhole tool in
a wellbore, as well as expanding the first shape-memory material from its run-
in
geometric shape to its original geometric shape for instance when the material
is heated beyond its onset Tg. The second shape-memory material may be
separately recovered at a separate onset Tg different from the onset Tg of the
first shape-memory material, at a different time. Alternatively, the first and
second shape-memory materials are not polyurethane, but are instead other
crosslinked polymers, where the crosslinking ratio for each shape-memory
material (first and second, or more, if present) is different one from the
other.
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[0013a] Accordingly, in one aspect there is provided a wellbore device
comprising: at least two shape-memory materials: a first shape-memory material
comprising a cross-linked polymer having a first crosslinking ratio, where the
first
shape-memory material has an altered geometric position and an original
geometric position, where the first shape-memory material is maintained in the
altered geometric position at a temperature below a first onset glass
transition
temperature, and where the first shape-memory material expands from its
altered geometric position to its recovered geometric position when it is
heated
to a temperature above the first onset glass transition temperature, where the
first shape-memory material has a first slope change during a first transition
state
from a first glass state to a first rubber state, and a second shape-memory
material comprising a cross-linked polymer having a second crosslinking ratio
different from the first crosslinking ratio, where the second shape-memory
material has an altered geometric position and an original geometric position,
where the second shape-memory material is maintained in the altered geometric
position at a temperature below a second onset glass transition temperature,
and where the second shape-memory material recovers from its altered
geometric position to its recovered geometric position when it is heated to a
temperature above the second onset glass transition temperature, where the
second shape-memory material has a second slope change during a second
transition state from a second glass state to a second rubber state, and where
the first shape-memory material and the second shape-memory material are
further different by a parameter selected from the group consisting of: the
first
onset glass transition temperature is different from the second onset glass
transition temperature, the first slope change is different from the second
slope
change, and both.
[0013b] According to another aspect there is provided a method of
manufacturing a wellbore device, the method comprising, (a) placing in any
order
or simultaneously: a first shape-memory material on a billet in an original
geometric position where the first shape-memory material has a first onset
glass
transition temperature and a first slope change during a first transition
state from
a first glass state to a first rubber state, the first shape-memory material
comprising a cross-linked polymer having a first crosslinking ratio, and a
second
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shape-memory material on the billet in an original geometric position where
the
second shape-memory material has a second onset glass transition temperature
and a second slope change during a second transition state from a second glass
state to a second rubber state, the second shape-memory material comprising a
cross-linked polymer having a second crosslinking ratio different from the
first
crosslinking ratio; (b) altering the original geometric shapes of the first
and
second shape-memory materials at a temperature at or above both the first and
second onset Tgs to change the original geometric positions of the first and
second polyurethane materials respectively; and (c) lowering the temperature
of
the first and second shape-memory materials to a temperature below the first
and second onset Tgs, respectively, where the first and second shape-memory
materials each maintain their respective altered geometric positions, where
the
first shape-memory material and the second shape-memory material are further
different by a parameter selected from the group consisting of: the first
onset
glass transition temperature being different from the second onset glass
transition temperature, the first slope change being different from the second
slope change, and both.
[0013c] According to yet another aspect there is provided a method of
manufacturing a wellbore device, the method comprising: (a) mixing a polymer
with a crosslinker at a first crosslinker / polymer ratio to form a first
crosslinked
polymer having a first original geometric position and having a first onset
glass
transition temperature Tg; (b) mixing the polymer with the crosslinker at a
second
crosslinker / polymer ratio to form a second crosslinked polymer having a
second
original geometric position and having a second onset glass transition
temperature Tg, where the first onset Tg and the second onset Tg are
different;
(c) altering the geometric shapes of the first and second crosslinked polymers
at
a temperature above both the first and second onset Tgs to change the
geometric shapes of the first and second crosslinked polymers respectively;
and
(d) lowering the temperature of the first and second crosslinked polymers to a
temperature below the first and second onset Ts, respectively, where the first
and second crosslinked polymers each maintain their respective altered
geometry.
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[0013d] According to still yet another aspect there is provided a method of
installing a wellbore device on a downhole tool in a formation, the method
comprising: (a) securing a downhole tool to a string of tubing, the downhole
tool
comprising a device comprising; a first shape-memory material, the first shape-
memory material having an altered geometric position for run-in and an
original
geometric position, wherein the first shape-memory material is maintained in
the
altered geometric position for run-in below a first onset glass transition
temperature Tg of the first shape-memory material, the first shape-memory
material comprising a cross-linked polymer having a first crosslinking ratio,
and a
second shape-memory material, the second shape-memory material having an
altered geometric position for run-in position and an original geometric
position,
wherein the second shape-memory material is maintained in the altered
geometric position for run-in below a second onset glass transition
temperature
Tg of the second shape-memory material, where the first Tg is different from
the
second Tg, the second shape-memory material comprising a cross-linked
polymer having a second crosslinking ratio; (b) running the downhole tool in a
wellbore; and (c) recovering the first shape-memory material from its altered
geometric position for run-in to a recovered geometric position.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a graph of storage modulus E' (elastic response)
(left
vertical axis) and modulus E" (viscous response) as a function of temperature
for a shape memory polymers illustrating the change in each modulus as the
polymer is heated from the Glass State through the Transition State to the
Rubber State;
[0015] FIG. 2 is a photograph of a finished shape-memory polymer part
before it is heated close to the Tg of the polymer and force is applied to
reshape it to a different configuration or shape and then cooled below the
polymer's onset Tg, and finally when the part is heated to the onset Tg at
which
point recovery will begin and the part returns to at or near its original
shape;
[0016] FIG. 3 is a schematic, cross-section view of a device which
bears
two shape-memory materials having different onset Tgs in concentric, layered
configuration in their altered geometry, run-in thicknesses or volumes;
[0017] FIG. 4 is a schematic, cross-section view of the device of FIG.
3
where the outer shape-memory material has been permitted to recover or
deploy so that it reaches part-way to the inner wall surface of the wellbore,
[0018] FIG. 5 is a schematic, cross-section view of the device of FIG.
4
where the inner shape-memory material has also been permitted to recover or
deploy so that it firmly engages and fits to the inner wall surface of the
wellbore,
[0019] FIG. 6 is a schematic, cross-section view of an alternate
embodi-
ment of a device which bears two shape-memory materials having different
onset Tgs in a side-by-side configuration along at least a portion of the
length of
the device in their altered geometric states, run-in thicknesses or volumes;
[0020] FIG. 7 is a schematic, cross-section view of the alternate
embodi-
ment of a device of FIG. 6 where one of the shape-memory materials has been
permitted to recover or deploy so that it firmly engages and fits to the inner
wall
surface of the wellbore,
[0021] FIG. 8 is a schematic, cross-section view of the alternate
embodi-
ment of a device of FIG. 7 where the other of the shape-memory materials has
been permitted to recover or deploy so that it firmly engages and fits to the
inner wall surface of the wellbore.
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[0022] It will be appreciated that Figures 3 through 8 are simply sche-
matic illustrations which are not to scale and that the relative sizes and
propor-
tions of different elements may be exaggerated for clarity or emphasis.
DETAILED DESCRIPTION
[0023] It has been discovered that wellbore devices, such as those
used
in filtration, wellbore isolation, production control, lifecycle management,
well-
bore construction and the like may be improved by including at least two
differ-
ent shape-memory materials that are run into the wellbore in altered geometric
positions or shapes where the shape-memory materials change to their respec-
tive original geometric positions or shapes at different Tgs and/or different
slope
changes (the slope change in the respective transition state from a glass
state
to a rubber state).
[0024] The shape-memory material is made in one non-limiting embodi-
ment from one or more polyol, such as, but not limited to, a polycarbonate
polyol and at least one isocyanate, including, but not necessarily limited to,
a
modified diphenylmethane diisocyanate (MDI), as well as other additives
including, but not necessarily limited to, blowing agents, molecular cross
linkers, chain extenders, surfactants, colorants and catalysts.
[0025] Alternatively, the shape-memory materials may be made using
cross-linked polymers, where the degree of crosslinking is different for the
various shape-memory materials. The crosslinking is a bond that links one
polymer chain to another. They can be covalent bonds or ionic bonds. Polymer
chains can refer to synthetic polymers or natural polymers (such as proteins).
When the term "cross-linking" is used in the synthetic polymer science field,
it
usually refers to the use of cross-links to promote a difference in the
polymers'
physical properties.
[0026] Cross-linking is used refer to the linking of polymer chains,
the
extent of crosslinking and specificities of the crosslinking agents vary.
[0027] When polymer chains are linked together by cross-links, they
lose
some of their ability to move as individual polymer chains. For example, a
liquid
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polymer (where the chains are freely flowing) can be turned into a "solid" or
"gel" by cross-linking the chains together.
[0028] When a synthetic polymer is said to be cross linked, it usually
means that the entire bulk of the polymer has been exposed to the cross-
linking
method. The resulting modification of mechanical properties depends strongly
on the cross-link density. Low cross-link densities decrease the viscosities
of
polymer melts. Intermediate cross-link densities transform gummy polymers
into materials that have elastomeric properties and potentially high
strengths.
Very high cross-link densities can cause materials to become very rigid or
glassy, such as phenol-formaldehyde, epoxies, urethanes, and polyethylenes.
Cross-links can be formed by chemical reactions that are initiated by heat,
pressure, change in pH, or radiation. For example, mixing of an unpolymerized
or partially polymerized resin with specific chemicals called crosslinking
reagents results in a chemical reaction that forms cross-links. Cross-linking
can
also be induced in materials that are normally thermoplastic through exposure
to a radiation source, such as electron beam exposure, gamma-radiation, or
UV light. For example, electron beam processing is used to cross-link polyeth-
ylene. Other types of cross-linked polyethylene are made by addition of perox-
ide during extruding or by addition of a cross-linking agent such as
vinylsilane
and a catalyst during extruding and then performing a post-extrusion curing.
[0029] The chemical process of vulcanization, sulfur crosslinking, is
a
type of cross-linking which changes the property of rubber to the hard,
durable
material. Crosslinking accelerators such as 2-benzothiazolethiol or
tetramethyl-
thiuram disulfide contain a sulfur atom in the molecule that initiates the
reaction
of the sulfur chains with rubber. Accelerators increase the rate of cure by
catalyzing the addition of sulfur chains to the rubber molecules.
[0030] A class of polymers known as thermoplastic elastomers rely on
physical cross-links in their microstructure to achieve stability, and offer a
much
wider range of properties than conventional cross-linked elastomers.
[0031] Many polymers undergo oxidative cross-linking, typically when
exposed to oxygen with an oxidizer such as hydrogen peroxide.
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[0032] The shape-memory polyurethane materials are capable of being
geometrically altered, in one non-limiting embodiment compressed substan-
tially, e.g., 20-30% of their original volume, at temperatures above their
onset
glass transition temperatures (Tg) at which the material becomes soft. While
still being geometrically altered, the material may be cooled down well below
its
onset Tg, or cooled down to room or ambient temperature, and it is able to
remain in the altered geometric state even after the applied shape altering
force is removed. When the material is heated near or above its onset Tg, it
is
capable of recovery to its original geometric state or shape, or close to its
original geometric position; a state or shape which may be called a recovered
geometric position. In other words, the shape-memory material possesses
hibernated shape-memory that provides a shape to which the shape-memory
material naturally takes after its manufacturing. The compositions of the
shape-
memory materials are able to be formulated to achieve desired onset glass
transition temperatures which are suitable for the downhole applications,
where
deployment can be controlled for temperatures below onset Tg of devices at the
depth at which the assembly will be used.
[0033] It has been further discovered that in the non-limiting case
where
the shape-memory materials are polyurethanes, various ratios of polyol to
isocyanate may be used to provide a polyurethane formulation having various
onset Tgs. As noted, the polyurethane with different onset Tgs may be geo-
metrically altered and then run downhole. When various target temperatures
are reached, the device will then deploy at various rates allowing for soft,
conformable deployments reinforced by hard, rigid, material. That is, the
differing onset Tg of different portions of the device not only affect the
tempera-
ture at which that portion of the device will return to its original shape,
but will
also affect the hardness of the material and rates of deployment. These
various
different onset Tgs are also applicable for crosslinked polymers having
different
crosslinking ratios from each other.
[0034] Generally, polyurethane polymer or polyurethane foam is consid-
ered poor in thermal stability and hydrolysis resistance, especially when it
is
made from polyether or polyester. It has been previously discovered herein
that
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the thermal stability and hydrolysis resistance are significantly improved
when
the polyurethane is made from polycarbonate polyols and MDI diisocyanates.
The compositions of polyurethane foam and the crosslinked polymer materials
herein are able to be formulated to achieve different glass transition tempera-
tures within the range from 60 C to 170 C, which is especially suitable to
meet
most downhole application temperature requirements. More details about these
particular polyurethane foams or polyurethane elastomers may be found in U.S.
Patent No. 7,926,565.
[0035] In one specific non-limiting embodiment, the shape-memory
material is a polyurethane material that is extremely tough and strong and
that
is capable of being geometrically altered and returned to substantially its
original geometric shape. As noted, the Tg of the shape-memory polyurethane
foam ranges from about 40 C to about 200 C and it is geometrically altered by
mechanical force at 40 C to 190 C. It will be appreciated that in the embodi-
ment where two or more shape-memory materials are employed and each
have a different Tg from each other, all of the Tgs will fall with the range
of
about 40 C to about 200 C, but they will be different from each other. While
still
in geometrically altered state, the material may be cooled down to room
temperature or some other temperature below the Tg of each shape-memory
material. The shape-memory polyurethane is able to remain in the altered
geometric state even after applied mechanical force is removed. When material
is heated to above its onset Tg, it is able to return to its original shape,
or close
to its original shape. The time required for geometric shape recovery can vary
from about 20 minutes to 40 hours or longer depending on the slope of the
transition curves as the material moves from a glass state to a rubber state.
If
the material remains below the onset Tg it remains in the geometrically
altered
state and does not change its shape.
[0036] Ideally, when shape-memory polyurethane is used as a downhole
device, it is preferred that the device remains in an altered geometric state
during run-in until it reaches the desired downhole location. Usually,
downhole
tools traveling from surface to the desired downhole location take hours or
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days. Thus, it is important to match the onset Tgs of the material with the
expected downhole temperatures.
[0037] In some non-limiting embodiments, when the temperature is high
enough during run-in, the devices made from the shape-memory material could
start to recover. To avoid undesired early recovery during run-in, delaying
methods may or must be taking into consideration. In one specific, but non-
limiting embodiment, a poly(vinyl alcohol) (PVA) film or other suitable film
may
be used to wrap or cover the outside surface of devices made from shape-
memory material to prevent recovery during run-in. Once devices are in place
downhole for a given amount of time at temperature, the PVA film is capable of
being dissolved in the water, emulsions or other downhole fluids and, after
such
exposure, the shape-memory devices may recover to their original geometric
shape or conform to the bore hole or other space. In another alternate, but
non-
restrictive specific embodiment, the devices made from the shape-memory
material may be coated with a thermally fluid-degradable rigid plastic such as
polyester polyurethane plastic and polyester plastic. By the term "thermally
fluid-degradable plastic" is meant any rigid solid polymer film, coating or
cover-
ing that is degradable when it is subjected to a fluid, e.g. water or
hydrocarbon
or combination thereof and heat. The covering is formulated to be degradable
within a particular temperature range to meet the required application or down-
hole temperature at the required period of time (e.g. hours or days) during
run-
in. The thickness of delay covering and the type of degradable plastics or
other
materials may be selected to be able to keep devices of shape-memory mate-
rial from recovery during run-in. Once the device is in place downhole for a
given amount of time at temperature, these degradable plastics decompose
which allows the devices to recover their original geometric shape or conform
to
the inner wall of the bore hole or the casing. In other words, the covering
that
inhibits or prevents the shape-memory material from returning to its original
geometric position or being prematurely deployed may be removed by dissolv-
ing, e.g. in an aqueous or hydrocarbon fluid, or by thermal degradation or
hydrolysis, with or without the application of heat, in another non-limiting
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example, destruction of the crosslinks between polymer chains of the material
that makes up the covering.
[0038] In the case where the shape-memory material is or comprises
polyurethane, the polyurethane material may be formed by combining two
separate portions of chemical reactants and reacting them together. These two
separate portions are referred to herein as the isocyanate portion and polyol
portion. The isocyanate portion may comprise a modified isocyanate (MI) or a
modified diphenylmethane diisocyanate (MDI) based monomeric diisocyanate
or polyisocyanate. The polyol portion may include, but not necessarily be
limited to, a polyether, polyester or polycarbonate-based di- or
multifunctional
hydroxyl-ended prepolymer.
[0039] Water may be included as part of the polyol portion and may act
as a blowing agent to provide a porous foam structure when carbon dioxide is
generated from the reaction with the isocyanate and water when the isocyanate
portion and the polyol portion are combined.
[0040] In one non-restrictive embodiment, the isocyanate portion may
contain modified MDI MONDUR PC sold by Bayer or MDI prepolymer LUPRA-
NATE 5040 sold by BASF, and the polyol portion may contain (1) a poly(cyclo-
aliphatic carbonate) polyol sold by Stahl USA under the commercial name PC-
1667, (2) a tri-functional hydroxyl cross linker trimethylolpropane (TMP) sold
by
Alfa Aesar, (3) an aromatic diamine chain extender dimethylthiotoluenediamine
(DMTDA) sold by Albemarle under the commercial name ETHACURE 300; (4)
a catalyst sold by Air Products under the commercial name POLYCAT 77; (5) a
surfactant sold by Air Products under the commercial name DABCO DC198,
(6) a cell opener sold by Degussa under the commercial name ORTEGOL 501,
(7) a colorant sold by Milliken Chemical under the commercial name REAC-
TINT Violet X8OLT, and (8) water.
[0041] The ratio between two separate portions of chemical reactants
which are referred to herein as the isocyanate portion and polyol portion may,
in one non-limiting embodiment, be chemically balanced close to 1:1 according
to their respective equivalent weights. The equivalent weight of the
isocyanate
portion is calculated from the percentage of NCO (isocyanate) content which is
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referred to herein as the modified MDI MONDUR PC and contains 25.8 % NCO
by weight. Other isocyanates such as MDI prepolymer LUPRANATE 5040 sold
by BASF contains 26.3% NCO by weight are also acceptable. The equivalent
weight of the polyol portion is calculated by adding the equivalent weights of
all
reactive components together in the polyol portion, which includes polyol,
e.g.,
P0-1667, water, molecular cross linker, e.g., TMP, and chain extender, e.g.,
DMTDA. The glass transition temperature of the finished polyurethane foam
may be adjustable via different combinations of isocyanate and polyol. In
general, the more isocyanate portion, the higher the Tg that is obtained. In
one
non-limiting embodiment, the equivalent ratio of isocyanate portion to polyol
portion ranges from 1.2:1 to 1:1.2, alternatively from 1.1 to 1 to 1 to 1.1.
When
the one or more polyurethanes are used, in one non-restrictive versions, each
polyurethane has a different ratio, but the ratio is within these ranges.
[0042] As previously mentioned, various ratios of polyol to isocyanate
may be used to provide polyurethane polymers with variable Tgs throughout the
molded polymer part. This will allow the polymer molded to have unique
properties, such as various sections of the downhole tool and/or wellbore
device to undergo shaped memory influences as the temperatures change
within the wellbore, such as heating up or cooling down. In one non-
restrictive
instance, the foam could be open cell foam for filtration, sand control or
other
application. After various target temperatures are experienced the screen or
tool will then deploy at various rates allowing for soft conformable
deployments
(in a non-limiting embodiment, an outer layer or layers) reinforced by
relatively
harder, more rigid compacted foam (the inner layer or layers).
[0043] Altering or varying the injection rates during processing will
allow
for imbedded layers of polyurethane with varying levels of Tg. Ultimately, the
varying Tgs will permit parts of the material to be deployed at certain target
temperatures while keeping other layers properly altered and "frozen". It will
be
understood that the portions of the material with different Tgs may or may not
be in discrete, discernible layers or portions on the tool or device.
[0044] Other foam components include a chain extender, in one non-
limiting embodiment, dimethylthiotoluenediamine (DMTDA) sold by Albemarle
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under the commercial name ETHACURE 300, which is a liquid aromatic di-
amine curative that provides enhanced high temperature properties. Other
suitable chain extenders include but are not limited to 4,4'-methylene bis (2-
chloroaniline), "MOCA", sold by Chemtura under the commercial name
VIBRACURE A 133 HS, and trimethylene glycol di-p-aminobenzoate,
"MCDEA", sold by Air Products under the commercial name VERSALINK
740M.
[0045] In certain embodiments, either amine-based or metal-based
catalysts are included to achieve good properties of polyurethane foam
materials. Such catalysts are commercially available from companies such as
Air Products. Suitable catalysts that provide especially good properties of
polyurethane foam materials include, but are not necessarily limited to,
pentamethyldipropylenetriamine, an amine-based catalyst sold under the
commercial name POLYCAT 77 by Air Products, and dibutyltindilaurate, a
metal-based catalyst sold under the commercial name DABCO T-12 by Air
Products.
[0046] A small amount of surfactant, e.g., 0.5% of total weight, such
as
the surfactant sold under the commercial name DABCO DC-198 by Air
Products and a small amount of cell opener, e.g., 0.5% of total weight, such
as
cell openers sold under the commercial names ORTEGOL 500, ORTEGOL
501, TEGOSTAB B8935, TEGOSTAB B8871, and TEGOSTAB B8934 by
Degussa may be added into the formulations. DABCO DC-198 is a silicone-
based surfactant from Air Products. Other suitable surfactants include, but
are
not necessarily limited to, fluorosurfactants sold by DuPont under commercial
names ZONYL 8857A and ZONYL FSO-100. Colorant may be added in the
polyol portion to provide desired color in the finished products. Such
colorants
are commercially available from companies such as Milliken Chemical which
sells suitable colorants under the commercial name REACTINT.
[0047] In one particular, but non-restrictive embodiment, the polyol
portion including poly(cycloaliphatic carbonate) or other polyol and other
additives such as cross linker, chain extender, surfactant, colorant, water,
and
catalyst is pre-heated to 90 C before being combined with the isocyanate
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portion. The isocyanate portion is combined with the polyol portion and a
reaction is immediately initiated and the mixture's viscosity increases
rapidly.
As mentioned, the amount of polyol relative to isocyanate should be varied at
least once, potentially numerous times, to give a varied polyurethane where
different portions have different Tgs.
[0048] Due to the high viscosity of the mixture and the fast reaction
rate,
a suitable mixer is recommended to form the polyurethane material. Although
there are many commercially available fully automatic mixers specially
designed for two-part polyurethane processing, it is found that mixers such as
KITCHENAID type mixers with single or double blades work particularly well
for batch quantities. In large-scale mixing, eggbeater mixers and drill
presses
have been found to work particularly well.
[0049] In mixing the isocyanate and polyol portions, the amount of
isocyanate and polyol included in the mixture should be chemically balanced
according to their equivalent weight and the desired Tgs or range of glass
transition temperatures. In one specific non-limiting embodiment, up to 5%
more isocyanate by equivalent weight is combined with the polyol portion.
[0050] In one embodiment, the ratio between isocyanate and polycar-
bonate polyol is about 1:1 by weight. In one non-limiting embodiment, the
polyol portion may be formed by 46.0 g of P0-1667 poly(cycloaliphatic
carbonate) polycarbonate combined with 2.3 g of TMP cross-linker, 3.6 g of
DMTDA chain extender, 0.9 g DABCO DC-198 surfactant, 0.4 g of ORTEGOL
501, 0.1 g of REACTINT Violet X8OLT colorant, 0.01 g of POLYCAT 77
catalyst, and 0.7 g of water blowing agent to form the polyol portion. The
polyol
portion is preheated to 90 C and mixed in a KITCHENAID type single blade
mixer with 46.0 g of MDI MONDUR PC. As will be recognized by persons of
ordinary skill in the art, these formulations can be scaled-up to form larger
volumes of this shape-memory material.
[0051] The mixture containing the isocyanate portion and the polyol
portion may be mixed for about 10 seconds and then poured into a mold and
the mold immediately closed by placing a top metal plate thereon. Due to the
significant amount of pressure generated by foaming process, a C-clamp may
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be used to hold the top metal plate and mold together to prevent any leakage
of mixture. After approximately 2 hours at room temperature, the polyurethane
foam material including a mold and a C-clamp may be placed inside an oven
and "post-cured" at a temperature of 110 C for approximately 8 hours so that
the polyurethane foam material reaches its full strength. These times and
temperatures are simply representative and should not be taken as limiting.
After cooled down to room temperature, the polyurethane material is
sufficiently
cured such that the mold may be removed.
[0052] At this point, the polyurethane material is in its original,
expanded
shape having an original, or expanded, thickness. The Tgs of the polyurethane
material are measured by Dynamic Mechanical Analysis (DMA) as 94.4 C from
the peak of loss modulus, G". The polyurethane material may be capable of
being geometrically altered to at least 25% of original thickness or volume at
temperature 125.0 C in a confining mold. While still in the altered geometric
state, the material is cooled down to room temperature. The shape-memory
polyurethane is able to remain in the altered geometric state even after
applied
mechanical force is removed. When the material is heated to about 88 C, in
one non-restrictive version, it is able to return to its original shape within
20
minutes. However, when the same material is heated to about 65 C for about
40 hours, it does not expand or change its shape at all. In one non-limiting
embodiment, a first portion of polyurethane foam may be heated to about 88 C
and thus return to its original shape and size at that temperature and a
second
portion of polyurethane foam may be heated to about 100 C for sufficient time
to return to its original shape and size to complete the expansion of the
screen,
e.g. This is possible because the different portions of the foam have
different
Tgs.
[0053] In another non-limiting embodiment, the ratio between
isocyanate
and polycarbonate polyol is about 1.5:1 by weight. In one non-restrictive em-
bodiment, the polyol portion may be formed by 34.1 g of PC-1667 poly(cycloali-
phatic carbonate) polycarbonate combined with 2.3 g of TMP cross linker, 10.4
g of DMTDA chain extender, 0.8 g DABCO DC-198 surfactant, 0.4 g of ORTE-
GOL 501 cell opener, 0.1 g of REACTINT Violet X8OLT colorant, 0.01 g of
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POLYCAT 77 catalyst, and 0.7 g of water blowing agent to form the polyol
portion. The polyol portion is preheated to 90 C and mixed in a KITCHENAID
type single blade mixer with 51.2 g of MDI MONDUR PC. As will be recognized
by persons of ordinary skill in the art, these formulations can be scaled-up
to
form larger volumes of this shape-memory material. Again, a change in the
ratio of polyol to isocyanate will change the Tg.
[0054] The mixture containing the isocyanate portion and the polyol
portion may be mixed for about 10 seconds and then poured into a mold and
the mold immediately closed by placing a top metal plate thereon. Due to the
significant amount pressure generated by foaming process, a C-clamp or other
device may be used to hold the top metal plate and mold together to prevent
any leakage of mixture. After approximately 2 hours, the polyurethane foam
material including a mold and a C-clamp may be transferred into an oven and
"post-cured" at a temperature of 110 C for approximately 8 hours so that the
polyurethane material reaches its full strength. After cooled down to room
temperature, the polyurethane material is sufficiently cured such that the
mold
can be removed.
[0055] The Tg of this particular polyurethane material in this non-
limiting
example, may be measured as 117.0 C by DMA from the peak of loss
modulus, G".
[0056] As may be recognized, the polyurethane having more isocyanate
than polyol by weight results in higher glass transition temperature. The poly-
urethane having less isocyanate than polyol by weight results in lower Tg. By
formulating different combinations of isocyanate and polyol, different glass
transition temperatures of shape-memory polyurethane may be achieved.
Compositions of a shape-memory polyurethane material having a specific Tg
may be formulated based on actual downhole deployment/application tempera-
ture. In one non-restrictive version, the Tgs of a shape-memory polyurethane
is
designed to be about 20 C higher than actual downhole deployment/application
temperatures. Because the application temperature is lower than Tg, the
material retains good mechanical properties.
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[0057] In one non-restrictive embodiment, the shape-memory polyure-
thane in tubular shape may be altered under hydraulic pressure above glass
transition temperature, and then cooled to a temperature well below the Tg or
room temperature while it is still under altering force. After the pressure is
removed, the shape-memory polyurethane is able to remain at the new
geometric state or shape.
[0058] With reference to FIGS. 3, 4 and 5 in operation, the tubing
string
20 having device 30 including shape-memory materials 32 and 40 is run-in
wellbore 50, which is defined by wellbore casing 52, to the desired location.
Device 30 may include a billet which may be a cylinder of material with
varying
outer diameters (ranging from about 6 to about 12 inches (about 15 to about 30
cm)) and of different lengths (e.g. from about 4 to 5 feet (about 1.2 to about
1.5
m) in height), which may be understood as a substrate upon which the polymer
is placed. As shown in FIG. 3, first shape-memory material 32 has an altered,
run-in, thickness 34. Second shape-memory material 40 overlying first shape-
memory material 32 and concentric therewith, has an altered, run-in thickness
36, which may be the same as or different from thickness 34. After a
sufficient
amount of time at a sufficient temperature at or above the onset Tg of second
shape-memory material 40, it expands from the run-in shape position (FIG. 3)
to the recovered or set position (FIG. 4) having an expanded thickness.
Similarly, after a sufficient amount of time at or above the Tg of first shape-
memory material 32, it expands from the run-in or altered position (FIG. 3) to
the recovered or set position (FIG. 5) having an expanded thickness. In so
doing, second shape-memory material 40 engages with inner wall surface 54 of
wellbore casing 52. The entire distance 38 from billet 30 of the device to
inner
wall surface 54 will be occupied by the device ¨ the device being understood
as
the combined first shape-memory material 32 and second shape-memory
material 40. It will be appreciated that although the first and second shape-
memory materials 32 and 40 of FIGS. 3-5 may be about the same thicknesses
as shown in the FIGS., it is not necessary that they be ¨ they may be of
differ-
ent thicknesses or geometries. Further, the positions of first and second
shape-
memory materials 32 and 40 may be reversed. In one non-limiting embodiment,
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the relatively harder, more rigid material may be the inner one. Additionally,
it is
not necessary that there be a clear boundary or demarcation between the
shape-memory materials having different Tgs, as shown in FIGS 3-5, and there
may be more than two different materials each having their own, different Tg.
[0059] Shown in
FIGS. 6-8 is another non-limiting embodiment where the
first shape-memory material 32' and second shape-memory material 40' are
oriented next to each other along at least a portion of the length of the
billet 30
or in a side-by-side relationship. In one non-restrictive version, they are
not
touching each other, but may be separated. In this embodiment, the Tg of
second shape-memory material 40' is lower than the Tg of first shape-memory
material 32' and is subject to an effective temperature for a sufficient
amount of
time to cause it to recover or enlarge to the recovered or set position shown
in
FIG. 7. In this embodiment, its recovered or set position would be sufficient
to
substantially contact and engage inner wall surface 54 across the entire
distance 38. For instance, it may be desirable for a filtration device that
certain
size of particle to flow through the expanded device 40'. However, if there is
a
subsequent time when no particles are desired to be permitted to flow through
the annulus 60, but only liquids are permitted to flow, then the tool 30 may
be
subjected to a higher temperature for a sufficient period of time to expand or
enlarge first shape-memory material 32' to its original or expanded shape, as
shown in FIG. 8, to completely bridge or occupy the distance 38. In this non-
restrictive embodiment, for instance, the filtration device may contain open
cells
of polymer material 32' that are much smaller than the open cells of polymer
material 40' so that only fluids are passed through annulus 60 and no
particles
of appreciable size are permitted to pass through the smaller cells of the
filtra-
tion device. Of course, it will be appreciated that the configurations of
FIGS. 3-5
and 6-8 may be combined and that first shape-memory material 32 and second
shape-memory material 40 may be arranged or configured in any number of
designs. Indeed, the two or more shape memory materials having different Tgs
and/or different slope changes from each other may be mixed together in
complex geometrical configurations.
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[0060] Further, when it is described herein that a device "totally con-
forms" to the borehole, what is meant is that the shape-memory material
recovers or deploys to fill the available space up to the borehole wall. The
borehole wall will limit the final, recovered shape of the shape-memory
material
and in fact not permit it to expand to its original, geometric shape. In this
way
however, the recovered or deployed shape-memory material, will perform the
desired function within the wellbore.
[0061] It is to be understood that the invention is not limited to the
exact
details of construction, operation, exact materials, or embodiments shown and
described, as modifications and equivalents will be apparent to one skilled in
the art. Accordingly, the invention is therefore to be limited only by the ap-
pended claims. Further, the specification is to be regarded in an illustrative
rather than a restrictive sense. For example, specific combinations of compo-
nents to make the polyurethane/urea thermoplastic, crosslinked polymers,
particular Tgs, specific downhole tool configurations, designs and other compo-
sitions, components and structures falling within the claimed parameters, but
not specifically identified or tried in a particular method or apparatus, are
anticipated to be within the scope of this invention.
[0062] The terms "comprises" and "comprising" in the claims should be
interpreted to mean including, but not limited to, the recited elements.
[0063] The present invention may suitably comprise, consist or consist
essentially of the elements disclosed and may be practiced in the absence of
an element not disclosed. For a non-limiting instance, a wellbore device may
comprise at least two shape-memory materials, at least a first shape memory
material and at least a second shape memory material. The first shape memory
material may consist essentially of or consist of a cross-linked polymer
having a
first crosslinking ratio, where the first shape-memory material has an altered
geometric position and an original geometric position, where the first shape-
memory material is maintained in the altered geometric position at a tempera-
ture below a first onset glass transition temperature, and where the shape-
memory material expands from its altered geometric position to its recovered
geometric position when it is heated to a temperature above the first onset
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glass transition temperature, where the first shape-memory material has a
first
slope change during a first transition state from a first glass state to a
first
rubber state. The second shape-memory material may consist of or consist
essentially of a cross-linked polymer having a second crosslinking ratio
different
from the first crosslinking ratio, where the second shape-memory material has
an altered geometric position and an original geometric position, where the
shape-memory material is maintained in the altered geometric position at a
temperature below a second onset glass transition temperature, and where the
shape-memory material recovers from its altered geometric position to its
recovered geometric position when it is heated to a temperature above the
second onset glass transition temperature, where the second shape-memory
material has a second slope change during a second transition state from a
second glass state to a second rubber state. The first shape-memory material
and the second shape-memory material of the wellbore device are further
different by one or both of the parameters: the first onset glass transition
temperature is different from the second onset glass transition temperature or
the first slope change is different from the second slope change.
