Note: Descriptions are shown in the official language in which they were submitted.
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SELF-ACTUATING DEVICE FOR CENTRALIZING AN OBJECT
FIELD OF THE INVENTION
[0001] The present invention claims priority on United States Provisional
Application Serial
No. 62/416,872 filed November 2, 2016, which is incorporated herein by
reference.
[0002] The present invention is directed to centralizers for use in
drilling and completion
operations, and particularly to centralizer devices which employ
interventionless mechanisms to
deploy and/or retract a tube, liner, casing, etc. in a drilling or well
operation.
BACKGROUND OF THE INVENTION
[0003] Centralizers are often employed in oilfield and related industries
where controlled
positioning of a device within a well may be of importance. A well is any
boring through the
earth's surface that is designed to find and acquire liquids and/or gases.
Wells for acquiring oil
are termed "oil wells." A well that is designed to produce mainly gas is
called a "gas well."
Typically, wells are created by drilling a bore, typically 5 inches to 40
inches (12 cm to 1 meter)
in diameter, into the earth with a drilling rig that rotates a drill string
with an attached bit. After
the hole is drilled, sections of steel pipe, commonly referred to as a
"casing" and which are slightly
smaller in diameter than the borehole, are dropped "downhole" into the bore
for obtaining the
sought after liquid or gas.
[0004] The difference in diameter of the wellbore and the casing creates an
annular space.
When completing oil and gas wells, it is important to seal the annular space
with cement. This
cement is pumped in, often flushing out drilling mud, and allowed to harden to
seal the well. To
properly seal the well, the casing should be positioned so that it is in the
middle or center of the
annular space. The casing and cement provides structural integrity to the
newly drilled wellbore
in addition to isolating potentially dangerous high pressure zones from each
other and from the
surface. Thus, centralizing a casing inside the annular space is critical to
achieve a reliable seal
and, thus, good zonal isolation. With the advent of deeper wells and
horizontal drilling,
centralizing the casing has become more important and more difficult to
accomplish.
[0005] Additionally, in the case of a hydrocarbon well, there may arise the
need to deliver a
downhole tool several thousand feet down into the well for performance of an
operation. In
performing the operation, it may be preferable that the tool arrive at the
operation site in a
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circumferentially centered manner (with respect to the diameter of the well).
Therefore, a
centralizer may be associated with the downhole tool in order to ensure its
circumferentially-
centered delivery to the operation site. This may be especially beneficial
where the well is of a
horizontal or other configuration presenting a challenge to unaided
centralization.
[0006] Centralization of one or more components of a well may be
advantageous for a host of
other different types of operations. In many operations, the vertical
alignment of multiple
separately delivered downhole tools may be beneficial. In this manner,
centralization of such tools
at an operation site provides a known orientation or positioning of the tools
relative to one another.
This known orientation may be taken advantage of where the tools are to
interact during the course
of the operation, for example, where one downhole tool may be employed to grab
onto and fish
out another. Additionally, a host of other operations may benefit from the
circumferentially-
centered positioning of a single downhole tool. Such operations may relate to
drilling
performance, oil well construction, and the collection of logging information,
to name a few.
[0007] A traditional method to centralize a casing is to attach
centralizers to the casing prior
to its insertion into the annular space. Traditional centralizers are commonly
secured at intervals
along a casing string to radially offset the casing string from the wall of a
borehole in which the
casing string is subsequently positioned. Most traditional centralizers have
wings or bows that
exert force against the inside of the wellbore to keep the casing somewhat
centralized. The
centralizers generally include evenly-spaced arms or ribs that project
radially outwardly from the
casing string to provide the desired offset. The radially disposed arms or
ribs are biased outwardly
from a mandrel or other supporting body in order to contact sides of the well
wall and, thus,
centrally positioning the supporting body. Centralizers ideally center the
casing string within the
borehole to provide a generally continuous annulus between the casing string
and the interior wall
of the borehole. This positioning of the casing string within a borehole
promotes uniform and
continuous distribution of cement slurry around the casing string during the
subsequent step of
cementing the casing string in a portion of the borehole. Uniform cement
slurry distribution results
in a cement liner that reinforces the casing string, isolates the casing from
corrosive formation
fluids, prevents unwanted fluid flow between penetrated geologic formations,
and provides axial
strength. Unfortunately, these centralizers increase the profile of the
casing, thereby causing
increased resistance and potential snagging during casing installation.
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[0008] A bow-spring centralizer is a common type of centralizer that
employs flexible bow-
springs as the ribs. Bow-spring centralizers typically include a pair of
axially-spaced and generally
aligned collars that are coupled by multiple bow-springs. The bow-springs
expand outwardly from
the axis of the centralizer to engage the borehole sidewall to center a pipe
received axially through
the generally aligned bores of the collars. Configured in this manner, the bow-
springs provide
stand-off from the borehole and flex inwardly as they encounter borehole
obstructions (such as
tight spots or protrusions into the borehole) as the casing string is
installed into the borehole.
Elasticity allows the bow-springs to spring back to substantially their
original shape after passing
an obstruction to maintain the desired stand-off between the casing string and
the borehole.
[0009] Unfortunately, the delivery of a downhole tool through the use of a
centralizer is prone
to inflict damage at the wall of the well by the radially disposed arms of the
centralizer. This is
because the centralizer is configured with arms reaching an outer diameter
capable of stably
supporting itself within wider sections of the well. For example, the
centralizer may reach a natural
outer diameter of about 13 inches for stable positioning within a 12 inch
diameter section of a well.
However, the centralizer is generally a passive device with arms of a single
size that are biased
between the support body and the well wall. Therefore, as the diameter of the
well becomes
smaller, the described arms (often of a bow-spring configuration) are forced
to deform and
compress to a smaller diameter as well. For example, the same 12 inch diameter
well may become
about 3 inches in diameter at some point deeper within the well. This results
in a significant
amount of compressive force to distribute between the arms and the wall of the
narrowing well.
That is, as the bowed arms become forced down to a lower profile by the
narrowing well wall,
more force is exerted on the well wall, thereby potentially resulting in
damage to the well wall
and/or the centralizer.
[0010] The above described exertion of force can become quite extreme
depending on the
configuration and dimensions of the arms and the extent of the well's
narrowing. As a result, such
bow-spring arms may prematurely wear out or cause significant damage to the
well wall as the
centralizer is forced through narrower well sections, or may require excessive
amounts of force to
push down long laterals. Many of these narrower well sections may have no
relation to the actual
operation site. Thus, the damage to the well wall and/or centralizer may occur
in sections of the
well where centralization by the centralizer is unnecessary. Furthermore, due
to the forces between
the centralizer and the well wall, a significant amount of additional force,
for example, through
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coiled tubing advancement, may be required. This may leave coiled tubing, the
centralizer, and
even the well itself susceptible to damage from application of such greater
forces thereupon. This
excessive force may restrict the ability to unstick pipe or liner, cause
significant problems and non-
productive time, and potentially require using smaller diameter casing or
tubing to be used, thereby
restricting well output.
[0011] As an alternative to the passive centralizers described above,
active centralizers such
as tractoring mechanisms or other devices capable of interactive or dynamic
arm diameter changes
may be employed. However, these types of devices are fairly sophisticated and
generally require
the exercise of operator control over the centralizer's profile throughout the
advancement or
withdrawal of the device from the well. Thus, such mechanisms are prone to
operator error which
may lead to well damage from the above described passive centralizer.
Furthermore, rather than
reliance on the radially extending natural force of a bowing or similar arm,
such devices may
require the maintenance of power to the arms at all times in order to attain
biasing against the well
wall with the arms. Therefore, unlike a passive centralizer, the active
centralizer may fail to
centralize when faced with a loss of power.
[0012] Attempts have been made to develop low-profile, deployable
centralizers that can be
added to the outside of the casing/pipe. These are designed to reduce friction
and snagging due to
the fact that the supports or bows are retracted until in their final
position. The challenge in
developing an effective deployable centralizer is to make it as low profile as
possible, actuate
deployment upon demand, and to overcome de-centralizing force.
[0013] Centralizers are usually assembled at a manufacturing facility and
then shipped to the
well site for installation on a casing string. The centralizers, or
subassemblies thereof, may be
assembled by welding or by other means such as displacing a bendable and/or
deformable tab or
coupon into an aperture to restrain movement of the end of a bow-spring
relative to a collar. Other
centralizers are assembled into their final configuration by riveting the ends
of a bow-spring to a
pair of spaced apart and opposed collars. The partially or fully assembled
centralizers may then
be shipped in trucks or by other transportation to the well site.
[0014] U.S. Pat. No. 6,871,706 (incorporated herein by reference) discloses
a centralizer that
requires a step of bending a retaining portion of the collar material into a
plurality of aligned
openings, each to receive one end of each bow-spring. This requires that the
coupling operation
be performed in a manufacturing facility using a press. The collars of the
prior art centralizer are
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cut with a large recess adjacent to each set of aligned openings to
accommodate passage of the
bow-spring that is secured to the interior wall of the collar. The recess
substantially decreases the
mechanical integrity of the collar due to the removal of a large portion of
the collar wall to
accommodate the bow-springs. The collars of the casing centralizer disclosed
in this patent also
require several additional manufacturing steps, including the formation of
both internal and
external (alternating) upsets in each collar to form the aligned openings for
receiving and securing
bow-springs, a time-consuming process that further decreases the mechanical
integrity of the
collar.
[0015] U.S. Pat. No. 4,545,436 and Great Britain Patent No. 2242457
(incorporated herein by
reference) both disclose casing centralizers having a plurality of bow-springs
which are connected
at either end to the first and second collars. As described in U.S. Pat. No.
4,545,436, the bow-
springs are connected to the collars using rivets or by welding. Conversely,
in Great Britain Patent
No. 2242457, the bow-springs are connected using nuts and bolts.
[0016] Additional centralizers are discussed in US Patent Nos. 2,654,435;
3,746,092;
4,776,397; 5,379,838; 6,457,519; 7,140,431; 7,775,272; 7,857,063; 8,235,106;
8,360,161; and
9,458,672, all of which are incorporated herein by reference.
[0017] Improved centralizers and methods continue to be sought,
particularly in view of the
limitations of the prior art and the need for better and stronger
centralizers. Considerations for the
development of new centralizers and new methods of assembling the centralizers
include
manufacturing costs, shipping costs, the costs associated with installing the
centralizers onto pipe
strings, and the ease of running the pipe string into the well.
SUMMARY OF THE INVENTION
[0018] The present invention relates to the construction of subterranean
wells, particularly to
methods and constructions for centering components within a well, particularly
an oil or gas well,
more particularly to centralizers for use in drilling and completion
operations, and still more
particularly to centralizer devices which employ interventionless mechanisms
to deploy and retract
a tube, liner, casing, etc. in a drilling or well operation.
[0019] Dissolvable and/or degradable materials have been developed over the
last several
years. This technology has been developed in accordance with the present
invention to enable the
interventionless activation of wellbore devices using such materials. One non-
limiting application
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is devices for centralizing a casing or liner string. Using engineered
response materials (such as
those that dissolve and/or degrade and/or expand upon exposure to specific
environment), a
centralizing device can be run in in the closed position with low force and
without problems of
sticking. After the centralizer is positioned in a desired location in the
wellbore, the centralizer
device can be activated to cause expand components on the centralizer to
deploy to cause
centralization of a tube, liner, casing, etc. in the wellbore.
[0020] The present invention uses materials that have been developed to
react and/or respond
to wellbore conditions. These materials can be used to create various
responses in a wellbore such
as dissolution, structural degradation, shape change, expansion, change in
viscosity, reaction
(heating or even explosion), change in magnetic or electrical properties,
and/or others of such
materials. These responses can be triggered by a change in temperature from
the surface to a
particular location in the wellbore, by a change in pH about the material,
controlling salinity about
the region of the material, by the addition or presence of a chemical (e.g.,
CO2, etc.) to react with
the material, and/or by electrical stimulation (e.g., introducing an
electrical current, current pulse,
etc.) to the material, among others. These materials can be used in
conjunction with a centralizer
to activate and/or deactivate the centralizer.
[0021] When structural expandable materials are used with a centralizer,
these expandable
structural materials can be used to apply forces to the bow structure of a
centralizer, thereby
causing such bow structures to deploy once the centralizer is placed in a
desired position in the
wellbore. Similarly, when a degradable structural material is used with the
centralizer, such as,
but not limited to, a ring, sleeve, spring, bolt, rivet, bracket, pin, clip,
etc., such degradable
structural material can be used to retain, compress and/or constrain a
centralizer utilizing spring-
loaded wings or bows. As used in this application, a degradable material is a
material that is
dissolvable and/or degradable. In such a configuration, when the degradable
structural material is
caused to dissolve and/or degrade, thereby removing or weakening the
degradable structural
material, the spring-loaded wings or bows will be allowed to actuate and
deploy on the centralizing
device. By using degradable materials on a centralizing device, a novel
centralizing device can be
created that can be automatically deployed and/or retracted in a controlled
manner in a wellbore.
As can also be appreciated, after the centralizing device has been deployed,
the centralizing device
can be caused to be disabled by the degradable structural material. For
example, a degradable
structural material can be in the form of a retaining pin that can be designed
to dissolve and/or
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degrade to thereby cause the pin to fail, which pin failure causes the spring
force on the wings or
bows to be reduced or lost. As can be appreciated, many other or additional
components of the
centralizing device can be formed of a degradable structural material to cause
the centralizing
device to be activated or deactivated. As can be appreciated, one type of
degradable structural
material can be used to cause the activation of the centralizing device, and a
different degradable
structural material can be used to disable or deactivate the centralizing
device; however, this is not
required.
[0022] In one non-limiting aspect of the present invention, there are
provided expandable
materials on a centralizer device that are attached to a collar in an
unexpanded form. When the
expandable materials are caused to expand, the expansion of such material
causes one or more
arms or ribs on the centralizer to move or expand radially to cause
centralization of the
centralization device in the wellbore. In one non-limiting design, the arms or
ribs can be partially
or fully formed of the expandable material; however, this is not required.
[0023] In another and/or alternative non-limiting aspect of the present
invention, the
expandable material in the centralizer device is used as a force applier to
cause actuation, such as
by being inserted under a collar and actuating against a bow spring element,
of one or more bow
springs to be deployed on the centralizer device. In one non-limiting
configuration, the expandable
material in the centralizer device is applied as a coating, and/or added as
inserts onto the bow
element of the centralizer device to cause the bow to bend outward and deploy
on the centralizer
device when the expandable materials are caused to expand. As can be
appreciated, many other
configurations can be used on a centralizer device to cause the expandable
material to cause
centralization of a centralizer device in a wellbore.
[0024] In another and/or alternative non-limiting aspect of the present
invention, the
expandable material in the centralizer device can be caused to shrink after
being initially expanded;
however, this is not required. In one such application, after the expandable
material has been
expanded to cause a centralizer device to be centered in a wellbore, the
expandable material can
be caused to shrink so as to enable the centralizer device to move into a
partially or fully retracted
or deactivated position to once again move freely in the wellbore. The
expandable material can
be formed of materials that allow multiple expansion and/or shrinking of the
material; however,
this is not required.
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[0025] In another and/or alternative non-limiting aspect of the present
invention, the
centralizing device can include one or more degradable metals. Such degradable
metals on the
centralizer device can be used to create a centralizer device that passively
activates and/or self-
activates in a wellbore when the degradable metals partially or fully dissolve
and/or degrade on
the centralizer device. In one non-limiting configuration, there is provided a
centralizer device
that includes one or more precompressed springs which are restrained by one or
more degradable
metals. When the one or more degradable metals partially or fully dissolves
and/or degrades, the
one or more precompressed springs are released, thereby causing one or more
arms or ribs on the
centralizer device to be deployed. In such a configuration, the one or more
degradable metals can
be in the form of rings, sleeves, restraining blocks, screws, pins, clips,
etc.
[0026] In another and/or alternative non-limiting aspect of the present
invention, a wide variety
of mechanisms for harnessing and amplifying the force of the expandable
structural materials can
be designed to cause the centralization action on a centralizer device. A few
non-limiting examples
are described in the drawings and the non-limiting embodiments discussed
herein; however, these
are not limiting mechanisms capable of being used to create centralization
force by a centralizing
device using expandable or degradable, or other engineered response material.
[0027] In summary, there is provided a method and a device for centralizing
a well. The
centralizing device can be placed/attached to the outside diameter of a well
insertion structure such
as a tube or other structure that is designed to be inserted into a wellbore,
a cavity, a tube or the
like. The well insertion structure can optionally have a body that is
cylindrical in shape; however,
this is not required. The well insertion structure is generally configured to
include one or more
slats, wings, bows, leaves, ribbons, extensions, and/or ribs; however, this is
not required. The one
or more slats, wings, bows, leaves, ribbons, extensions, and/or ribs function
as radial extensions
that are positioned on the outer surface of the body of the well insertion
structure. Generally when
the one or more slats, wings, bows, leaves, ribbons, extensions, and/or ribs
are in a non-deployed
position, the one or more slats, wings, bows, leaves, ribbons, extensions,
and/or ribs lie flat or
semi-flat on the outer surface of the body of the well insertion structure. In
such a position, the
well insertion structure can be inserted into the wellbore, a cavity, a tube
or the like without
obstruction by or damage to the one or more slats, wings, bows, leaves,
ribbons, extensions, and/or
ribs. When the well insertion structure is positioned in a desired location in
the wellbore, a cavity,
a tube or the like, the one or more slats, wings, bows, leaves, ribbons,
extensions, and/or ribs can
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be caused to move to a partially or fully deployed position. The well
insertion structure includes
one or more expandable, degradable metals that can be used to cause one or
more of the slats,
wings, bows, leaves, ribbons, extensions, and/or ribs to partially or fully
move to the fully deployed
position. The one or more expandable, degradable metals can be controllably
caused or activated
to change shape, expand, dissolve, degrade, react, degrade, and/or
structurally weaken so as to
cause the one or more of the slats, wings, bows, leaves, ribbons, extensions,
and/or ribs to partially
or fully move to the fully deployed position. The activation of the one or
more expandable,
degradable metals on the centralization device can be caused to be activated
or triggered by one or
several events (e.g., by a change in temperature from the surface of the
wellbore to a particular
location in the wellbore; by a change in pH of liquids about the
centralization device; the salinity
of liquids about the centralization device; the exposure of the one or more
expandable, degradable
metals to one or more chemicals and/or compounds and/or gasses; application of
current and/or
voltage to the one or more expandable, degradable metals; exposure of certain
types of
electromagnetic waves and/or sound waves to the one or more expandable,
degradable metals;
exposure to certain pressures on the one or more expandable, degradable
metals, etc.). When the
one or more expandable, degradable metals on the centralization device are
caused to be activated
or triggered, the one or more expandable, degradable metals on the
centralization device cause the
one or more of the slats, wings, bows, leaves, ribbons, extensions, and/or
ribs to partially or fully
move to the fully deployed position. The slats, wings, bows, leaves, ribbons,
extensions, and/or
ribs can be fully or partially formed of the one or more expandable,
degradable metals, and/or can
1) cause the one or more slats, wings, bows, leaves, ribbons, extensions,
and/or ribs to partially or
fully move to the fully deployed position when the one or more expandable,
degradable metals
change shape, expand, dissolve, degrade, react, degrade, and/or structurally
weaken, and/or 2)
release constraints on the one or more slats, wings, bows, leaves, ribbons,
extensions, and/or ribs
so as to allow the one or more slats, wings, bows, leaves, ribbons,
extensions, and/or ribs to
partially or fully move to the fully deployed position when the one or more
expandable, degradable
metals change shape, expand, dissolve, degrade, react, degrade, and/or
structurally weaken. In one
non-limiting embodiment, the one or more expandable, degradable metals cause
the one or more
slats, wings, bows, leaves, ribbons, extensions, and/or ribs on the outer
surface of the body of the
well insertion structure to expand or cause an outer perimeter of the one or
more slats, wings,
bows, leaves, ribbons, extensions, and/or ribs to move at least about 0.25
inches outwardly from
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the outer surface of the outer surface of the body of the well insertion
structure (e.g., 0.25-20 inches
and all values and ranges therebetween). In another non-limiting embodiment,
the one or more
expandable, degradable metals cause the one or more slats, wings, bows,
leaves, ribbons,
extensions, and/or ribs on the outer surface of the body of the well insertion
structure to expand or
cause an outer perimeter of the one or more slats, wings, bows, leaves,
ribbons, extensions, and/or
ribs to move at least about 0.75 inches outwardly from the outer surface of
the outer surface of the
body of the well insertion structure. In another non-limiting embodiment, the
one or more
expandable, degradable metals cause the one or more slats, wings, bows,
leaves, ribbons,
extensions, and/or ribs on the outer surface of the body of the well insertion
structure to expand or
cause an outer perimeter of the one or more slats, wings, bows, leaves,
ribbons, extensions, and/or
ribs to move about 1-20 inches outwardly from the outer surface of the outer
surface of the body
of the well insertion structure. The expansion of the one or more expandable,
degradable metals
and/or the outward movement of the one or more slats, wings, bows, leaves,
ribbons, extensions,
and/or ribs results in the diameter or cross-sectional area of the well
insertion structure and thereby
centralizes in the wellbore, a cavity, a tube or the like. The expansion
and/or movement of the one
or more slats, wings, bows, leaves, ribbons, extensions, and/or ribs is
generally such that the one
or more one or more slats, wings, bows, leaves, ribbons, extensions, and/or
ribs engage the inner
wall of the wellbore, a cavity, a tube or the like; however, this is not
required.
[0028] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes ribbons that are comprised of a material that is
structural and a material
that interacts with the wellbore fluid to expand, and wherein the expanding
material is on the inner
section of the ribbons, and its expansion causes the ribbons to expand or bow
radially outward in
a controlled manner.
[0029] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes slats, wings, bows, leaves, ribbons, extensions,
and/or ribs that lie flat
along the outer surface of the body of the well insertion structure and
includes a rod of expanding
structural material constrained against a fixed end-ring in an axial slot at
the end of the slats, wings,
bows, leaves, ribbons, extensions, and/or ribs, and where the expansion of the
rod upon interaction
with the wellbore fluid causes the ribbon to bow outward from the body of the
well insertion
structure thereby resulting in the centralizing of the well insertion
structure the wellbore, a cavity,
a tube or the like.
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[0030] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes slats, wings, bows, leaves, ribbons, extensions,
and/or ribs that are
spring-loaded and restrained in diameter by a sleeve, locking rings or wire,
set screws, pins, or
other locking mechanisms, where such sleeves, rings, pins, screws, wire, or
other restraint or
locking fixture dissolves, degrades and/or weakens upon wellbore exposure,
thereby partially or
fully removing the restraint and/or weakening the restraint thereby causing
the slats, wings, bows,
leaves, ribbons, extensions, and/or ribs to bow or extend outward from the
body of the well
insertion structure.
[0031] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes slats, wings, bows, leaves, ribbons, extensions,
and/or ribs that are
partially or fully formed of expandable structural materials, and expand
outward due to their
inherent growth upon exposure to one or several events (e.g., change in
temperature from the
surface of the wellbore to a particular location in the wellbore; change in pH
of liquids about the
centralization device; the salinity of liquids about the centralization
device; the exposure of the
one or more expandable, degradable metals to one or more chemicals and/or
compounds and/or
gasses; application of current and/or voltage to the one or more expandable,
degradable metals;
exposure of certain types of electromagnetic waves and/or sound waves to the
one or more
expandable, degradable metals; exposure to certain pressures on the one or
more expandable,
degradable metals, etc.).
[0032] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes slats, wings, bows, leaves, ribbons, extensions,
and/or ribs that are
partially or fully formed of materials that are dissolving and/or degrading,
such that they remove
themselves after a predetermined length of time. Such materials can be
triggered or be caused to
partially or fully dissolve and/or degrade upon exposure to one or several
events (e.g., change in
temperature from the surface of the wellbore to a particular location in the
wellbore; change in pH
of liquids about the centralization device; the salinity of liquids about the
centralization device;
the exposure of the one or more expandable, degradable metals to one or more
chemicals and/or
compounds and/or gasses; application of current and/or voltage to the one or
more expandable,
degradable metals; exposure of certain types of electromagnetic waves and/or
sound waves to the
one or more expandable, degradable metals; exposure to certain pressures on
the one or more
expandable, degradable metals, etc.).
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[0033] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes fixed end-rings constraining the slats, wings,
bows, leaves, ribbons,
extensions, and/or ribs, and wherein the fixed end-rings are partially or
fully formed of a
degradeable structural material which releases the tension on the slats,
wings, bows, leaves,
ribbons, extensions, and/or ribs after exposure to one or more events thereby
allowing the slats,
wings, bows, leaves, ribbons, extensions, and/or ribs on the well insertion
structure to move to the
partially or fully open position, or move to a closed position.
[0034] In another and/or alternative non-limiting aspect of the present
invention, the well
insertion structure includes a degradable structural material that is coated,
which coating can be
used to delay the time at which the degradable structural material begins to
dissolve and/or
degrade, and/or controls when the degradable material begins to dissolve
and/or degrade.
[0035] In another and/or alternative non-limiting aspect of the present
invention, there is
provided a method of positioning a well insertion structure in a wellbore, a
cavity, a tube or the
like that includes the steps of 1) providing a wellbore, a cavity, a tube or
the like having a
substantially circular sidewall, 2) providing a pipe having a cylindrical
sidewall, 3) providing a
self-actuating annular well insertion structure that can be attached to the
pipe, 4) attaching one or
more of the self-actuating annular well insertion structure to the pipe, the
outer diameter of the
pipe with the attached self-actuating annular well insertion structure is less
than the diameter of
the wellbore, a cavity, a tube or the like, and wherein when more than one
self-actuating annular
well insertion structure are attached to the pipe, the self-actuating annular
well insertion structures
are spaced at specific intervals on the pipe, 5) running the pipe with the one
or more self-actuating
annular well insertion structures into the wellbore, the cavity, the tube or
the like while the self-
actuating annular well insertion structures are in an unexpanded position
until the self-actuating
annular well insertion structures are positioned in a desired position in the
cavity, the tube or the
like, and 6) allowing or causing the expanding or dissolving and/or degrading
of one or more
components of the self-actuating annular well insertion structures to cause
the self-actuating
annular well insertion structures to move to the partially or fully expanded
position such that one
or more structures on the self-actuating annular well insertion structures
contact a sidewall of the
cavity, the tube or the like to cause the self-actuating annular well
insertion structures to center the
pipe in the cavity, the tube or the like, thereby resulting in there being
spacing between the pipe
and the sidewall of the cavity, the tube or the like. In an optional
additional or alternative method,
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after the self-actuating annular well insertion structures are in the
partially or fully expanded
position, the self-actuating annular well insertion structures can be caused
to move to a partially
or fully unexpanded position and/or the self-actuating annular well insertion
structures can be
caused to degrade and/or dissolve.
[0036] In another and/or alternative non-limiting aspect of the present
invention, the one or
more expanding or degradable components of the self-actuating annular well
insertion structure
includes reactive particles dispersed in a polymer matrix. In one non-limiting
configuration, the
reactive particles have a concentration of 20-60 vol.% (and all values and
ranges therebetween) in
a polymer, and which reactive particles react with water to form oxides,
hydroxides, or carbonates
and are caused to expand 50 vol.% as compared to the original particle sizes.
In another non-
limiting configuration, the reactive particles include one or more particles
selected from the group
consisting of MgO, CaO, CaC, Mg, Ca, Na, Fe, Si, P, Zn, Ti, Li2O, Na2O,
borates, aluminosilicates,
and/or layered compounds. In another non-limiting configuration, the polymer
includes a
thermoset or thermoplastic polymer wherein such polymer can include one or
more compounds
selected from the group of polyesters, nylons, polycarbonates, polysulfones,
polyimides, PEEK,
PEI, epoxy, PPS, PPSU, and/or phenolic compounds. In another non-limiting
configuration, the
polymer includes a thermoset or thermoplastic polymer that is capable of
maintaining structural
load at the wellbore temperature. In another non-limiting configuration, the
polymer includes a
thermoset or thermoplastic polymer that has a preselected creep rate to relax
and remove loading
on the ribbon or bow over a period of time. In another non-limiting
configuration, the degradable
material on the self-actuating annular well insertion structure includes a
degradable magnesium
alloy. In another non-limiting configuration, the magnesium alloy can be
formulated to have a
controlled and/or engineered degradation rate at certain wellbore conditions.
[0037] In another and/or alternative non-limiting aspect of the present
invention, there is
provided an expandable material that is used with or in the centralizer, which
expandable material
uses one or two basic methods to deliver force: 1) use of in situ-thermally
activated shape change
materials, and 2) use of oxidative reaction of metals with subsequent
volumetric expansion. The
first technique can involve a reversible martensitic reaction. The second
technique can involve
reaction with water and/or carbon dioxide to turn metals into oxides,
hydroxides, or carbonates
(e.g., iron to rust, etc.), with a corresponding expansion of the material.
The percent volume
expansion is generally at least about 2%, and typically at least about 20%.
Generally, the volume
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expansion is up to about 200% (e.g., 2-200%, 20-200%, 42-141%, etc. and all
values and ranges
therebetween).
[0038] In another non-limiting aspect of the present invention, there is
provided an expandable
material that is configured and formulated to expand in a controlled or
predefined environment.
The expandable material has a compressive strength after expansion of at least
2,000 psig. The
expandable composite material has a compressive strength after expansion of up
to about
1,000,000 psig or more (e.g., 2,000 psig to 1,000,000 psig and all values and
ranges therebetween).
The expandable material typically has a compressive strength after expansion
of at least 10,000
psig, and typically at least 30,000 psig. The compressive strength of the
expandable material is
the capacity of the expandable material to withstand loads to the point that
the size or volume of
the expandable material reduces by less than 2%.
[0039] In another non-limiting aspect of the present invention, the
expandable material
includes 10-80% by volume of an expandable material. The expandable material
can be
formulated to undergo a mechanical and/or chemical change resulting in a
volumetric expansion
of at least 2% and typically at least 50% (e.g., 2-5000% and all values and
ranges therebetween)
by reaction and/or exposure to a fluid environment. In one non-limiting
arrangement, the
expandable material is formulated to undergo a mechanical and/or chemical
change resulting in a
volumetric expansion of at least 20% by reaction and/or exposure to a fluid
environment. In
another non-limiting arrangement, the expandable material can include a matrix
and/or binder
material that is used to bind together particles of the expandable material.
The matrix and/or binder
material is generally permeable or semi-permeable to water. In one non-
limiting arrangement, the
matrix and/or binder material is semi-permeable to high temperature (e.g., at
least 100 F, typically
100-210 F and all values and ranges therebetween) and high pressure water
(e.g., at least 10 psig,
typically 10-10,000 psig and all values and ranges therebetween). The
expandable material or the
expandable material in combination with the matrix and/or binder material can
have a compressive
strength before and/or after expansion of at least 2,000 psig, and typically
at least 10,000 psig (e.g.,
2,000 psig to 1,000,000 psig and all values and ranges therebetween); however
this is not required.
[0040] In another non-limiting aspect of the present invention, the
reaction of the expandable
material is selected from the group consisting of a hydrolization reaction, a
carbonation reaction,
and an oxidation reaction, or combination thereof.
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[0041] In another non-limiting aspect of the present invention, the
expandable material can
include one or more materials selected from the group consisting of flakes,
fibers, powders and
nanopowders; however, this is not required. When the expandable material is
combined with a
matrix and/or binder material, the expandable material can form a continuous
or discontinuous
system. When the expandable material is combined with a matrix and/or binder
material, the
expandable material can be uniformly or non-uniformly dispersed in the matrix
and/or binder
material.
[0042] In another non-limiting aspect of the present invention, the
expandable material can
include one or more materials selected from the group consisting of Ca, Li,
CaO, Li2O, Na2O, Fe,
Al, Si, Mg, K20 and Zn. The expandable material generally ranges in size from
about 106 IAM to
MM.
[0043] In another non-limiting aspect of the present invention, the
expandable material can
include one or more polymer materials; however, this is not required. When the
expandable
material includes a matrix or binder material, such matrix or binder material
can include or be
formed of a polymer material. The polymer material can include one or more
materials selected
from the group consisting of polyacetals, polysulfones, polyurea, epoxys,
silanes, carbosilanes,
silicone, polyarylate, and polyimide.
[0044] In another non-limiting aspect of the present invention, the
expandable material can
include one or more catalysts for accelerating the reaction of the expandable
material; however,
this is not required. The catalyst can include one or more materials selected
from the group
consisting of AlC13 and a galvanically-active material.
[0045] In another non-limiting aspect of the present invention, the
expandable material can
include strengthening and/or diluting fillers; however, this is not required.
The strengthening
and/or diluting fillers can include one or more materials selected from the
group consisting of
fumed silica, silica, glass fibers, carbon fibers, carbon nanotubes and other
finely divided inorganic
material.
[0046] In another non-limiting aspect of the present invention, the
expandable material can
include a surface coating or protective layer that is formulated to control
the timing and/or
conditions under which the reaction or expanding occurs; however, this is not
required. The
surface coating can be formulated to dissolve and/or degrade when exposed to a
controlled external
stimulus (e.g., temperature and/or pH, chemicals, etc.). The surface coating
can be used to control
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activation of the expanding of the core or core composite. The surface coating
can include one or
more materials such as, but not limited to, polyester, polyether, polyamine,
polyamide, polyacetal,
polyvinyl, polyureathane, epoxy, polysiloxane, polycarbosilane, polysilane,
and polysulfone. The
surface coating generally has a thickness of about 0.1 IAM to 1 mm and any
value or range
therebetween.
[0047] In another non-limiting aspect of the present invention, the
expandable material can
optionally include a shape memory alloy-coated microballoon, a microlattice,
reticulated foam, or
syntactic shape memory alloy which is stabilized in an expanded state, pre-
compressed, and then
expanded to provide an actuating force under conditions suitable for well
completion and/or
development; however, this is not required. In one non-limiting embodiment,
there is provided an
expandable material which comprises a shape memory alloy-coated microballoon,
a microlattice,
reticulated foam, or syntactic shape memory alloy which is stabilized in an
expanded state, pre-
compressed, and then expanded to provide an actuating force under conditions
suitable for well
completion and development.
[0048] In another non-limiting aspect of the present invention, the
expandable material can be
in the form of a proppant used to open cracks and control permeability in
underground formations;
however, this is not required.
[0049] Thus, it is an object of the present invention to provide improved
centralizers and
methods of installing a centralizer downhole in a well through a self-
actuating mechanism based
on expanding, dissolving and/or degrading, and/or reacting engineered
materials.
[0050] It is another and/or alternative object of the present invention to
provide a centralizing
device that can be placed/attached to the outside diameter of a well insertion
structure, such as a
tube or other structure, that is designed to be inserted into a wellbore, a
cavity, a tube or the like.
[0051] It is another and/or alternative object of the present invention to
provide a well insertion
structure that includes one or more slats, wings, bows, leaves, ribbons,
extensions, and/or ribs,
which one or more slats, wings, bows, leaves, ribbons, extensions, and/or ribs
function as radial
extensions that are positioned on the outer surface of the body of the well
insertion structure.
[0052] It is another and/or alternative object of the present invention to
provide a well insertion
structure that can be inserted into a wellbore, a cavity, a tube or the like
without obstruction by or
damage to the one or more slats, wings, bows, leaves, ribbons, extensions,
and/or ribs on the well
insertion structure.
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[0053] It is another and/or alternative object of the present invention to
provide a well insertion
structure that when positioned in a desired location in a wellbore, a cavity,
a tube or the like, the
one or more slats, wings, bows, leaves, ribbons, extensions, and/or ribs can
be caused to move to
a partially or fully deployed position.
[0054] It is another and/or alternative object of the present invention to
provide a well insertion
structure that includes one or more expandable, degradable metals that can be
used to cause one
or more of the slats, wings, bows, leaves, ribbons, extensions, and/or ribs to
partially or fully move
to the fully deployed position.
[0055] It is another and/or alternative object of the present invention to
provide a well insertion
structure that includes one or more slats, wings, bows, leaves, ribbons,
extensions, and/or ribs that,
when in the partially or fully open or expanded position, result in the one or
more slats, wings,
bows, leaves, ribbons, extensions, and/or ribs engaging the inner wall of the
wellbore, a cavity, a
tube or the like.
[0056] Other objects, advantages, and novel features of the present
invention will become
apparent from the following detailed description of the invention when
considered in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] Referring particularly to the drawings for the purposes of
illustration only and not
limitation:
[0058] FIG. 1 is a side view of an annular centralizer with expanding bow
elements in an
unexpanded configuration;
[0059] FIG. 2 is a side view of an annular centralizer with expanding bow
elements in an
expanded configuration;
[0060] FIG. 3 is a side cut-away view of one bow element that is formed of
a structural material
and an expandable structural material wherein the expanded material has not
been caused to be
expanded;
[0061] FIG. 4 is a side cut-away view of the bow element of FIG. 3 wherein the
expanded
material has been caused to be expanded to thereby cause the bow element to
bow;
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[0062] FIG. 5 is a side cut-away view of another bow element that is formed
of a structural
material and an expandable structural material wherein the expanded material
has not been caused
to be expanded;
[0063] FIG. 6 is a side cut-away view of the bow element of FIG. 5 wherein the
expanded
material has been caused to be expanded to thereby cause the bow element to
bow;
[0064] FIG. 7 is a side cut-away view of another bow element that is formed
of a structural
material and an expandable structural material wherein the expanded material
has not been caused
to be expanded;
[0065] FIG. 8 is a side cut-away view of the bow element of FIG. 7 wherein the
expanded
material has been caused to be expanded to thereby cause the bow element to
bow;
[0066] FIG. 9 is a side cut-away view of another bow element that is formed
of a structural
material and an expandable structural material and a degradable material
wherein the expanded
material has been caused to be expanded to thereby cause the bow element to
bow and wherein
the degradable material has not been caused to degrade;
[0067] FIG. 10 is a side cut-away view of the bow element of FIG. 9 wherein
the degradable
material is caused to degrade after the expanded material has been caused to
be expand to thereby
cause the bow element to move back to the unbowed position;
[0068] FIG. 11 is a side view of an annular centralizer with expanding bow
elements in an
unexpanded configuration wherein the bows are retained in an unbowed position
by a degradable
sleeve;
[0069] FIG. 12 is a side view of the annular centralizer of FIG. 11 in the
expanded position
wherein the degradable sleeve is dissolved and/or degraded to allow the bow
elements to move to
the bow position;
[0070] FIG. 13 is an illustration of core particles reacting under
controlled stimulus, at which
point the core particle will expand, expanding the fracture to enhance oil and
gas recovery;
[0071] FIGS. 14a and 14b illustrate a non-limiting method of engineering a
force delivery
system for expanding into fracture opening, namely constraint by a semi-
permeable or
impermeable matrix;
[0072] FIGS. 15a and 15b are schematics of shape memory alloy syntactic, as
well as actual
syntactic metal;
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[0073] Fig. 16 illustrates a typical cast microstructure with grain
boundaries (500) separating
grains (510);
[0074] Fig. 17 illustrates a detailed grain boundary (500) between two
grains (500) wherein
there is one non-soluble grain boundary addition (520) in a majority of grain
boundary composition
(530) wherein the grain boundary addition, the grain boundary composition, and
the grain all have
different galvanic potentials and different exposed surface areas;
[0075] Fig. 18 illustrates a detailed grain boundary (500) between two
grains (510) wherein
there are two non-soluble grain boundary additions (520 and 540) in a majority
of grain boundary
composition (530) wherein the grain boundary additions, the grain boundary
composition, and the
grain all have different galvanic potentials and different exposed surface
areas;
[0076] Figs. 19-21 show a typical cast microstructure with galvanically-
active in situ formed
intermetallic phase wetted to the magnesium matrix; and,
[0077] Fig. 22 shows a typical phase diagram to create in situ formed
particles of an
intermetallic Mg(M) where M is any element on the periodic table or any
compound in a
magnesium matrix and wherein M has a melting point that is greater than the
melting point of Mg.
DESCRIPTION OF THE INVENTION
[0078] The present invention relates to methods and constructions for
centering components
within a well, particularly an oil or gas well, more particularly to
centralizers for use in drilling
and completion operations, and still more particularly to centralizer devices
which employ
interventionless mechanisms to deploy and retract a tube, liner, casing, etc.
in a drilling or well
operation.
[0079] The present invention uses materials that have been developed to
react and/or respond
to wellbore conditions. These materials can be used to create various
responses in a wellbore, such
as dissolution, structural degradation, shape change, expansion, change in
viscosity, reaction
(heating or even explosion), changed magnetic or electrical properties, and/or
others of such
materials. These responses can be triggered by a change in temperature from
the surface to a
particular location in the wellbore, change in pH about the material,
controlling salinity about the
region of the material, addition or presence of a chemical (e.g., CO2, etc.)
to react with the material,
and/or electrical stimulation (e.g., introducing an electrical current,
current pulse, etc.) to the
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material, among others. These materials can be used in conjunction with a
centralizer to activate
and/or deactivate the centralizer.
[0080] When structural expandable materials are used with a centralizer,
these expandable
structural materials can be used to apply forces to the bow structure of a
centralizer, thereby
causing such bow structures to deploy once the centralizer is placed in a
desired position in the
wellbore. Similarly, when a degradable structural material is used with the
centralizer, such as,
but not limited to, a ring, sleeve, spring, bolt, rivet, bracket, pin, clip,
etc., such degradable
structural material can be used to retain, compress and/or constrain a
centralizer utilizing spring-
loaded wings or bows. In such a configuration, when the degradable structural
material is caused
to dissolve and/or degrade (thereby removing or weakening the degradable
structural material) the
spring-loaded wings or bows will be allowed to actuate and deploy of on the
centralizing device.
By combining degradable materials on a centralizing device, a novel
centralizing device can be
created that can be automatically deployed and/or retracted in a controlled
manner in a wellbore.
As can also be appreciated, after the centralizing device has been deployed,
the centralizing device
can be caused to be disabled by the degradable structural material. For
example, a degradable
structural material can be in the form of a retaining pin that can be designed
to dissolve and/or
degrade to thereby cause the pin to fail, which pin failure causes the spring
force on the wings or
bows to be reduced or lost. As can be appreciated, many other or additional
components of the
centralizing device can be formed of a degradable structural material to cause
the centralizing
device to be activated or deactivated. As can be appreciated, one type of
degradable structural
material can be used to cause the activation of the centralizing device, and a
different degradable
structural material can be used to disable or deactivate the centralizing
device; however, this is not
required.
[0081] Referring now to FIG. 1, there is illustrated a centralizer 200 in a
non-deployed position
or unexpanded position. The centralizer includes first and second end portions
210, 220 that are
connected together by a plurality of bendable ribs 300. As defined herein, the
bendable ribs are
one type of well bore wall engagement member that can be included on the
centralizer. The end
portions each have a cylinder shape having a cavity 212, 222 that is
configured to fit about a pipe.
The ribs having a generally rectangular shape and are spaced from one another.
FIG. 2 illustrates
the centralizer in the deployed or expanded position. The ribs in the
centralizer can be caused to
controllably deploy using an expandable material. As can be appreciated, the
centralizer can have
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other configurations wherein a portion of the centralizer moves from a non-
deployed to a deployed
position. As illustrated in FIGS. 1 and 2, the maximum outer perimeter of the
centralizer in FIG.
2 is greater in size to the maximum outer perimeter of the centralizer in FIG.
1. The increase in
the size of the outer perimeter of the centralizer in FIG. 2 is the result of
the outward bowing of
the ribs 300. The amount of bowing of the ribs caused by the expandable
material is non-limiting.
In one non-limiting embodiment, the increase in the size of the outer
perimeter of the centralizer
is a result of the one or more well bore wall engagement members on the
centralizer (e.g., slat,
wing, bow, leave, ribbon, extension, rib, etc.) moving from the non-deployed
position to the
deployed position is at least about 0.1 inches, typically at least about 0.25
inches, and more
typically at least about 0.75 inches. In one specific non-limiting aspect of
the invention, the
increase in the size of the outer perimeter of the centralizer as a result of
the one or more well bore
wall engagement members on the centralizer moving from the non-deployed
position to the
deployed position is about 0.1-20 inches (and all values and ranges
therebetween), and typically
0.25-10 inches. In another specific non-limiting aspect of the invention, the
percent increase in
the size of the outer perimeter of the centralizer as a result of the one or
more well bore wall
engagement members on the centralizer moving from the non-deployed position to
the deployed
position is about 2-300% (and all values and ranges therebetween), and
typically 5-100%. As can
be appreciated, the amount of bowing of the ribs caused by the expandable
material can be
controlled by various factors (e.g., amount of expandable material used, the
thickness of the
bendable material used to form the ribs, the type of material used to form the
bendable material
used to form the ribs, the type of material used to form the expandable
material, the degree to
which the expandable material is caused to expand, the configuration of the
ribs, the use of slots
or other structures in the bendable material used to form the ribs, etc.).
[0082] Referring now to FIGS. 3 and 4, there is illustrated a cross-section
of one non-limiting
configuration of rib 300. As illustrated in FIGS. 3 and 4, the rib is formed
of a bendable material
310 such as a metal and includes a layer of expandable material 320. The
expandable material can
be a) mechanically connected to the bendable material (e.g., friction fit,
screw, rivet, bolt, etc.), b)
connected by an adhesive, c) connected by welding to the bendable material, d)
connected by
lamination to the bendable material and/or e) cast to the bendable material.
When the expandable
material is caused to expand, the expandable material applies a force to the
bendable material and
causes the bendable material to bend or bow as illustrated in FIG. 4. The
bending of the ribs of
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the centralizer results in the centralizing moving to the deployed position
and centralizing a pipe
in a well bore.
[0083] Referring now to FIGS. 5 and 6, cross section of another non-
limiting rib 300 is
illustrated. The rib is formed of a bendable material 310 (such as a metal)
and includes a layer of
expandable material 320. The bendable material includes one or more notches or
depressions 330
that are filled with the expandable material. The expandable material can be
a) mechanically
connected to the bendable material (e.g., friction fit, screw, rivet, bolt,
etc.), b) connected by an
adhesive, c) connected by welding to the bendable material, d) connected by
lamination to the
bendable material and/or e) cast to the bendable material. As illustrated by
the arrows in FIGS. 5
and 6, when the expandable material is caused to expand, the expandable
material applies a force
to the bendable material and causes the bendable material to bend or bow as
illustrated in FIG. 6.
The bending of the ribs of the centralizer results in the centralizing move to
the deployed position
and centralizing a pipe in a well bore.
[0084] Referring now to FIGS. 7 and 8, cross section of another non-
limiting rib 300 is
illustrated. The rib is formed of a bendable material 310 (such as a metal)
and includes two regions
of expandable material 340, 342. The bendable material includes one or more
notches or
depressions 350, 352 located at each end portion of the rib. The one or more
notches or depressions
are filled with the expandable material. The expandable material can be a)
mechanically connected
to the bendable material (e.g., friction fit, screw, rivet, bolt, etc.), b)
connected by an adhesive, c)
connected by welding to the bendable material, d) connected by lamination to
the bendable
material and/or e) cast to the bendable material. As illustrated by the arrows
in FIG. 8, when the
expandable material is caused to expand, the expandable material applies a
force to the bendable
material and causes the bendable material to bend or bow. The bending of the
ribs of the centralizer
results in the centralizing move to the deployed position and centralizing a
pipe in a well bore.
[0085] Referring now to FIGS. 9 and 10, the rib 300 can optionally include
a degradable metal
360, 362 that is located adjacent to expandable material 370, 372 that is
located in notches or
depressions 380, 382. After the rib has been caused to bend by the expansion
of the expandable
material as illustrated in FIG. 9, the rib can be allowed to flex or move
partially or fully to the
unbent position by reducing the bending force on the bendable material that is
caused by the
expansion of the expandable material. Such reduction in force as illustrated
by the arrow in FIG.
can be accomplished by causing the degradable metal to dissolve and/or degrade
as illustrated
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in FIG. 10. The partial or full removal of the degradable metal from the rib
results in the bending
force being applied by the expanded expandable material to be reduced or
eliminated, thereby
allowing the rib to unbend or bend partially or fully back to its position
prior to the expansion of
the expandable material. The ribs can be formed of a memory metal to
facilitate in the movement
of the rib back to the unbent position; however, this is not required. The
expandable material and
the degradable metal can be a) mechanically connected to the bendable material
(e.g., friction fit,
screw, rivet, bolt, etc.), b) connected by an adhesive, c) connected by
welding to the bendable
material, d) connected by lamination to the bendable material and/or e) cast
to the bendable
material.
[0086] The non-limiting embodiments illustrated in FIGS. 3-10 merely
illustrate a few of the
many configurations that can be used to cause the well bore wall engagement
members on the
centralizer (e.g., slat, wing, bow, leave, ribbon, extension, rib, etc.) to
bend and optionally unbend.
[0087] Referring now to FIGS 11 and 12, there is illustrated another type
of centralizer 200.
The ribs 300 of the centralizer are configured to move to a bent state when no
constraining force
is applied to the ribs. The ribs are maintained in an unbent state by use of a
retaining member 390.
As such, the ribs are biased in a bent state, but are retained in the unbent
state by the retaining
member. As can be appreciated, the ribs may not be biased in a bent state, but
can be activated
(e.g., temperature change, pH change, chemistry change, electric stimulation,
etc.) to move to the
bent state by some activation stimulus after the retaining member has been
partially or fully
dissolved and/or degraded. As can be appreciated, such activation can occur
prior to, during, or
after the retaining member has been partially or fully dissolved and/or
degraded. As also can also
or alternatively be appreciated, the ribs can be caused to be moved to the
bent state by use of an
expandable material as illustrated in FIGS. 3-9; however, this is not
required. As illustrated in Fig.
6a, the retaining member 400 partially or fully encircles all or a portion of
the ribs. As can be
appreciated, other retaining member configurations can be used to maintain the
ribs in an unbent
position. The retaining member is made of a degradable metal. When the
degradable metal
partially or fully dissolves and/or degrades, the retaining force of the ribs
is reduced or eliminated,
thereby enabling the ribs to move from the non-deployed to the deployed
position.
[0088] Generally, the expandable material is typically configured to expand
less than 5 vol.%
in the well bore prior to being activated, typically expand less than 2 vol.%
in the well bore prior
to being activated, more typically expand less than 1 vol.% in the well bore
prior to being activated,
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and still more typically expand less than 0.5 vol.% in the well bore prior to
being activated.
Likewise, the degradable material is typically configured to degrade less than
5 vol.% in the well
bore prior to being activated, typically degrade less than 2 vol.% in the well
bore prior to being
activated, more typically degrade less than 1 vol.% in the well bore prior to
being activated, and
still more typically degrade less than 0.5 vol.% in the well bore prior to
being activated. The
activation of the expandable or the degradable material can be accomplished by
one or more events
selected from the group consisting of a) change in temperature about the
expandable material or
the degradable material from the surface of the well bore to a particular
location in the well bore,
b) change in pH about the expandable material or the degradable material, c)
change in salinity
about the expandable material or the degradable material, d) exposure of the
expandable material
or the degradable material to an activation element or compound, e) electrical
stimulation of the
expandable material or the degradable material, 0 exposure of the expandable
material or the
degradable material to a certain sound frequency, and/or g) exposure of the
expandable material
or the degradable material to a certain electromagnetic frequency.
[0089] Expandable materials that can be used in a centralizer.
[0090] Non-limiting examples of expandable materials that can be used in a
centralizer are set
forth below:
[0091] Example 1
[0092] A high temperature resistant and tough thermoplastic polysulfone
with 25% volumetric
loading of expanding Fe micro powder showed an unconstrained volumetric
expansion of 50% is
possible in a solution of 2% KCl at 190 C over a period of 50 hours.
[0093] Example 2
[0094] A 30% volumetric loading of expandable metal CaO powder in epoxy binder
milled
and sieved to 8/16 mesh size showed a 24% volumetric expansion while under
3,000 psig fracture
load stress when exposed to a solution of 2% KC1, 0.5M NaCO3 at 60-80 C in a
period of 1 hour.
[0095] Example 3
[0096] A 30% volumetric loading of expandable metal CaO powder in 6,6 nylon
binder under
2,500 psig fracture load stress when exposed to a solution of 2% KCl, 0.5M
NaCO3 at 60-80 C in
a period of 1 hour.
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[0097] The high force reactive expandables that are used in the centralizer
are engineered to
act as a force delivery system to cause the centralizer to move to a partially
or fully deployed
position. The deployment of the high force reactive expandables can be at
least partially
controlled. Such control can be accomplished by coating, encapsulating,
microstructure placement
and alignment and/or otherwise shielding the expandable core particle with a
dissolving/triggerable surface coating that will dissolve and/or degrade under
specific formation
conditions. The volumetric expansion of the expandable core particle in such
an aspect of the
invention can then be constrained to deliver force.
[0098] FIGS. 13 and 14 illustrate non-limiting methods for controlling the
volumetric
expansion of the expandable core particle. The core particles can be designed
to react under
controlled stimulus, at which point the core will expand. One non-limiting
feature of the invention
is the controlling of the timing/trigger, and/or amount and/or speed of the
expanding reaction.
Control/trigger coatings can also be used (e.g., temperature activated
coatings, chemically
activated engineered response coatings, etc.). Control of the protective layer
thickness and/or
composition can be used to dictate where and under what conditions the
reactive composite core
particle will be exposed to formation fluids. Once exposed, the expandable
materials will expand
volumetrically and, with properly engineered constraint, direct the volumetric
expansion as a
normal force to cause the centralizer to move to a partially or fully deployed
position.
[0099] Referring to FIG. 13, there is illustrated an expandable material 10
that includes a
protective layer or surface coating 20, an expandable core 30 which can
include, but is not limited
to, an expanding metal, structural filler, and activator in a diluent/binder
to control mechanical
properties. The protective layer is generally formulated to dissolve and/or
degrade when exposed
to a controlled external stimulus (e.g., temperature and/or pH, chemicals,
etc.). The protective
layer is used to control activation of the expanding of the expandable core
30, which upon
expansion becomes expanded core 40. Protective layer 20 can be comprised of
one or more of,
but not limited to, polyester, polyether, polyamine, polyamide, polyacetal,
polyvinyl,
polyureathane, epoxy, polysiloxane, polycarbosilane, polysilane, and
polysulfone. Protective
layer 20 can range in thickness from, but not limited to, 0.1-1 mm and any
value or range
therebetween, and generally range from 10 [tm to 100 tim and any value or
range therebetween.
Composition of the expandable core 30 can include an expanding material that
can be, but is not
limited to, Ca, Li, CaO, Li2O, Na2O, Fe, Al, Si, Mg, K2O and Zn. The
expandable material can
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range in volumetric percentage of expandable core 30 of, but not limited to, 5-
60% and any value
or range therebetween, and generally range from 20-40% and any value or range
therebetween.
Composition of the expandable core 30 may or may not include a structural
filler that can be, but
is not limited to, fumed silica, silica, glass fibers, carbon fibers, carbon
nanotubes and other finely
divided inorganic material. Structural filler can range in volumetric
percentage of expandable core
30 of, but not limited to, 1-30% and any value or range therebetween, and
generally range from 5-
20% and any value or range therebetween. Composition of expandable core 30 may
or may not
include an activator that can be, but is not limited to, peroxide, metal
chloride, or galvanically-
active material. Composition of expandable core 30 can include a
diluent/binder that can be, but
is not limited to, polyacetals, polysulfones, polyurea, epoxys, silanes,
carbosilanes, silicone,
polyarylate, and polyimide. Binder can range in volumetric percentage of
expandable core 30 of,
but not limited to, 50-90% and any value or range therebetween, and generally
range from 50-70%
and any value or range therebetween. Expandable core 30 expands into expanded
core 40 in the
range of 5-50% volumetric expansion and any value or range therebetween, and
generally in the
range of 5-20% and any value or range therebetween.
[00100] Referring now to FIGS. 14a and 14b, a non-limiting method of
engineering force
delivery system to cause the centralizer to move to a partially or fully
deployed position is
illustrated, namely constraint by a semi-permeable or impermeable sleeve (FIG.
14a).
Constraining sleeve translates triggered expansion into a uniaxial force (FIG.
14b). The protective
layer 20 (in the form of a plug) is formulated to dissolve and/or degrade or
become permeable
when exposed to controlled external stimulus (temperature, pH, certain
chemicals, etc.) to cause
the protective layer to dissolve and/or degrade or otherwise breakdown,
thereby controlling
activation of expanding of the expandable core 30. Upon expansion to expanded
core 40
constraining sleeve 50 directs expansion forces parallel to constraining
sleeve.
[00101] The protective layer 20 (when used) can be comprised of one or more
of, but not limited
to, polyester, polyether, polyamine, polyamide, polyacetal, polyvinyl,
polyureathane, epoxy,
polysiloxane, polycarbosilane, polysilane, and polysulfone. Protective layer
20 can range in
thickness from, but is not limited to, 0.1-1 mm, and generally range from 10-
100 tm. Composition
of expandable core 30 can include an expanding material that can be, but is
not limited to, Ca, Li,
CaO, Li2O, Na2O, Fe, Al, Si, Mg, K20 and Zn. The expandable material can range
in volumetric
percentage of expandable core 30 of, but is not limited to, 5-60%, and
generally range from 20-
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40%. The composition of expandable core 30 may or may not include a structural
filler that can
be, but is not limited to, fumed silica, silica, glass fibers, carbon fibers,
carbon nanotubes and other
finely divided inorganic material. The structural filler can range in
volumetric percentage of
expandable core 30 of, but is not limited to, 1-30%, and generally range from
5-20%. The
composition of expandable core 30 may or may not include an activator that can
be, but is not
limited to, peroxide, metal chloride, or galvanically active material. The
composition of
expandable core 30 can include a diluent/binder that can be, but is not
limited to, polyacetals,
polysulfones, polyurea, epoxies, silanes, carbosilanes, silicone, polyarylate,
and polyimide. The
binder can range in volumetric percentage of expandable core 30 of, but is not
limited to, 50-90%,
and generally range from 50-70%. Expandable core 30 is configured to expand
into expanded
core 40 in the range of 5-50% volumetric expansion, and generally in the range
of 5-20%. The
constraining sleeve 50 can include, but is not limited to, one or more high
temperature-high
strength materials such as polycarbonate, polysulfones, epoxies, polyimides,
inert metals (e.g., Cu
with leachable salts), etc. Constraining layer 50 can range in thickness from,
but not limited to 0.1
inn to 1 mm, and generally range from 10-100 Inn. The configuration of the
constraining sleeve
50 is non-limiting, as other shape configurations are applicable for imparting
directional
expansion. Generally, the constraining sleeve is designed to not rupture
during the expansion of
expandable core 30; however, this is not required. In one non-limiting
arrangement, the
constraining sleeve is designed to not rupture and may or may not deform
during the expansion of
expandable core 30. The constraining sleeve can include one or more side
openings; however, this
is not required. The one or more side opening can be used as an alternative or
in addition to the
one or more end openings in the constraining sleeve. The one or more side
openings (when used)
can optionally include a protective coating that partially or fully covers the
side opening.
[00102] FIGS. 15a and 15b illustrate the construction of shape memory
expandables derived
from metal- or plastic-coated hollow sphere 60 or syntactic 100. Shape memory
expandables can
include, but are not limited to, a hollow sphere core 70 and a plastic or
metal coating or composite
80. The shape memory composites 60 and 100 are compressed under temperature
promoting
plastic yield and then cooled while compressed, locking in potential
mechanical force to produce
shape memory expandables. Under the external stimulus of temperature above
glass transition
temperatures, the shape memory composites return to their uncompressed states
exerting up to 30-
70 Ksi forces and any value or range therebetween. Hollow sphere core 70 can
be comprised of,
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but is not limited to, glass (borosilicate, aluminosilicate, etc.), metal
(magnesium, zinc, etc.), or
plastic (phenolic, nylon, etc.), which range in sizes from 10 nm to 5 mm and
any value or range
therebetween, and generally range from 10-100 vm. Coating or composite matrix
80 can be
comprised of one or more of, but not limited to, metal (titanium, aluminum,
magnesium, etc.), or
plastic (epoxy, polysulfone, polyimides, polycarbonate, polyether, polyester,
polyamine,
polyvinyl, etc.), which range in composite volume percentages from 1-70% and
any value or range
therebetween. Actual compressed and non-compressed syntactics are illustrated
and, in this case,
the compression is reversed using the shape memory effects delivering forces
as high as 30-70 Ksi.
Advantages of the shape memory alloy include low density, very high actuation
force, and/or very
controllable actuation.
[00103] Expandable Chemistries
[00104] In still another non-limiting aspect of the invention, a feature in
the expandable design
of the high force reactive expandables is the active expandable material.
Active expandable
material having reactive mechanical or chemical changes occurring in the
temperature range of at
least 25 C (e.g., 30-350 C, 30-250 C, etc. and all values and ranges
therebetween) and having a
volumetric expansion of over 10% (e.g., 20-400%, 30-250%, etc. and all values
and ranges
therebetween) can be utilized in the present invention. Table 1 lists some non-
limiting specific
reactions that are suitable for use in the structural expandable materials and
for the expandable
propp ants:
[00105] Table 1
[00106] CaO 4 CaCO3 119% expansion
[00107] Fe 4 Fe2O3 115% expansion
[00108] Si 4 SiO2 88% expansion
[00109] Zn 4 ZnO 60% expansion
[00110] Al 4 Al2O3 29% expansion
[00111] The formation of hydroxides and/or carbonates can potentially result
in larger
expansion percentages.
[00112] In still another non-limiting aspect of the invention, there is
provided a method to
control the rate and/or completion of the oxidation reaction through 1)
control over active particle
surface area, 2) binder/polymer permeability control, 3) the addition of
catalysis (e.g., AlC13 - used
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to activate iron surfaces), and/or 4) control over water
permeability/transport to the metal surface.
Ultrafine and near nanomaterials, as well as metallic flakes (which expand
primarily in one
direction) can be used to tailor the performance and response of these
expandable materials.
Mechanical properties such as modulus, creep strength, and/or fracture
strength can also or
alternatively be controlled through the addition of fillers and diluents
(e.g., oxides, etc.) and semi-
permeable engineering polymers having controlled moisture solubility.
[00113] Degradable materials that can be used in a centralizer.
[00114] Non-limiting examples of degradable materials that can be used in a
centralizer are set
forth below.
[00115] Example 1
[00116] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 800 C and at least 200 C below the melting point
of nickel.
About 7 wt.% of nickel was added to the melt and dispersed. The melt was cast
into a steel mold.
The degradable metal exhibited a tensile strength of about 14 Ksi, an
elongation of about 3%, and
shear strength of 11 Ksi. The degradable metal dissolved and/or degraded at a
rate of about 75
mg/cm2-min in a 3% KC1 solution at 90 C. The material dissolved and/or
degraded at a rate of 1
mg/cm2-hr in a 3% KCl solution at 21 C. The material dissolved and/or degraded
at a rate of
325mg/cm2-hr. in a 3% KCl solution at 90 C.
[00117] Example 2
[00118] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 800 C and at least 200 C below the melting point
of copper.
About 10 wt.% of copper alloyed to the melt and dispersed. The melt was cast
into a steel mold.
The degradable metal exhibited a tensile yield strength of about 14 Ksi, an
elongation of about
3%, and shear strength of 11 Ksi. The degradable metal dissolved and/or
degraded at a rate of
about 50 mg/cm2-hr. in a 3% KCl solution at 90 C. The material dissolved
and/or degraded at a
rate of 0.6 mg/cm2-hr. in a 3% KC1 solution at 21 C.
[00119] Example 3
[00120] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 700 C. About 16 wt.% of 75um iron particles were
added to the
melt and dispersed. The melt was cast into a steel mold. The degradable metal
exhibited a tensile
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strength of about 26 Ksi, and an elongation of about 3%. The degradable metal
dissolved and/or
degraded at a rate of about 2.5 mg/cm2-min in a 3% KC1 solution at 20 C. The
material dissolved
and/or degraded at a rate of 60 mg/cm2-hr in a 3% KCl solution at 65 C. The
material dissolved
and/or degraded at a rate of 325mg/cm2-hr. in a 3% KC1 solution at 90 C.
[00121] Example 4
[00122] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 700 C. About 2 wt.% 75um iron particles were
added to the melt
and dispersed. The melt was cast into steel molds. The material exhibited a
tensile strength of 26
Ksi, and an elongation of 4%. The material dissolved and/or degraded at a rate
of 0.2 mg/cm2-min
in a 3% KC1 solution at 20 C. The material dissolved and/or degraded at a rate
of lmg/cm2-hr in
a 3% KC1 solution at 65 C. The material dissolved and/or degraded at a rate of
10mg/cm2-hr in a
3% KC1 solution at 90 C.
[00123] Example 5
[00124] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 700 C. About 2 wt.% nano iron particles and
about 2 wt.% nano
graphite particles were added to the composite using ultrasonic mixing. The
melt was cast into
steel molds. The material dissolved and/or degraded at a rate of 2 mg/cm2-min
in a 3% KC1
solution at 20 C. The material dissolved and/or degraded at a rate of 20
mg/cm2-hr in a 3% KC1
solution at 65 C. The material dissolved and/or degraded at a rate of 100
mg/cm2-hr in a 3% KC1
solution at 90 C.
[00125] Example 6
[00126] A magnesium alloy that includes 9 wt.% aluminum, 0.7 wt.% zinc, 0.3
wt.% nickel,
0.2 wt.% manganese, and 2 wt.% calcium was added to the molten magnesium
alloy. The
magnesium alloy dissolved and/or degraded at a rate of 91 mg/cm2-hr. in the 3%
KCl solution at
90 C. The magnesium alloy also dissolved and/or degraded at a rate of 34
mg/cm2-hr. in the 0.1%
KC1 solution at 90 C, a rate of 26 mg/cm2-hr. in the 0.1% KC1 solution at 75
C, a rate of 14
mg/cm2-hr. in the 0.1% KC1 solution at 60 C, and a rate of 5 mg/cm2-hr. in the
0.1% KCl solution
at 45 C.
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[00127] Example 7
[00128] 1.5-2 wt.% zinc, 1.5-2 wt.% nickel, 3-6 wt.% gadolinium, 3-6 wt.%
yttrium, and 0.5-
0.8% zirconium were added to the molten magnesium. The dissolution rate in 3%
KCl brine
solution at 90 C as 62-80 mg/cm2-hr.
[00129] Example 8
[00130] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and
90 wt.%
magnesium. About 16 wt.% of 75um iron particles were added to the melt and
dispersed. The
melt was cast into a steel mold. The iron particles did not fully melt during
the mixing and casting
processes. The degradable metal dissolved and/or degraded at a rate of about
2.5 mg/cm2-min in a
3% KC1 solution at 20 C. The material dissolved and/or degraded at a rate of
60 mg/cm2-hr in a
3% KCl solution at 65 C. The material dissolved and/or degraded at a rate of
325mg/cm2-hr. in a
3% KC1 solution at 90 C. The dissolving and/or degrading rate of the
degradable metal for each
these test was generally constant. The iron particles were less than 1 [irn,
but were not
nanoparticles. However, the iron particles could be nanoparticles, and such
addition would change
the dissolving and/or degrading rate of the degradable metal.
[00131] Example 9
[00132] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 700 C. About 2 wt.% 75um iron particles were
added to the melt
and dispersed. The iron particles did not fully melt during the mixing and
casting processes. The
material dissolved and/or degraded at a rate of 0.2 mg/cm2-min in a 3% KCl
solution at 20 C. The
material dissolved and/or degraded at a rate of lmg/cm2-hr in a 3% KCl
solution at 65 C. The
material dissolved and/or degraded at a rate of 10mg/cm2-hr in a 3% KCl
solution at 90 C. The
dissolving and/or degrading rate of the degradable metal for each these test
was generally constant.
The iron particles were less than 1 Inn, but were not nanoparticles. However,
the iron particles
could be nanoparticles, and such addition would change the dissolving and/or
degrading rate of
the degradable metal.
[00133] Example 10
[00134] An AZ91D magnesium alloy having 9 wt.% aluminum, 1 wt.% zinc and 90
wt.%
magnesium was melted to above 700 C. About 2 wt.% nano iron particles and
about 2 wt.% nano
graphite particles were added to the composite using ultrasonic mixing. The
melt was cast into
steel molds. The iron particles and graphite particles did not fully melt
during the mixing and
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casting processes. The material dissolved and/or degraded at a rate of 2
mg/cm2-min in a 3% KC1
solution at 20 C. The material dissolved and/or degraded at a rate of 20
mg/cm2-hr in a 3% KCI
solution at 65 C. The material dissolved and/or degraded at a rate of 100
mg/cm2-hr in a 3% KCl
solution at 90 C. The dissolving and/or degrading rate of the degradable metal
for each these test
was generally constant.
[00135] The dissolvable or degradable metal generally includes a base metal or
base metal alloy
having discrete particles disbursed in the base metal or base metal alloy. The
discrete particles are
generally uniformly dispersed through the base metal or base metal alloy using
techniques such
as, but not limited to, thixomolding, stir casting, mechanical agitation,
electrowetting, ultrasonic
dispersion and/or combinations of these methods; however, this is not
required. The degradable
metal can be designed to corrode at the grains in the degradable metal, at the
grain boundaries of
the degradable metal, and/or the location of the particle additions in the
degradable metal. The
particle size, particle morphology and particle porosity of the particles can
be used to affect the
rate of corrosion of the degradable metal. The particles can optionally have a
surface area of
0.001m2/g-200m2/g (and all values and ranges therebetween). The base metal of
the degradable
metal can include magnesium, zinc, titanium, aluminum, iron, or any
combination or alloys
thereof. The particles can include, but is not limited to, beryllium,
magnesium, aluminum, zinc,
cadmium, iron, tin, copper, titanium, lead, nickel, carbon, calcium, boron
carbide, and any
combinations and/or alloys thereof. In one non-limiting specific embodiment,
the degradable
metal includes a magnesium and/or magnesium alloy as the base metal or base
metal alloy, and
nanoparticle additions. In another non-limiting specific embodiment, the
degradable metal
includes aluminum and/or aluminum alloy as the base metal or base metal alloy,
and nanoparticle
additions. The particles in the degradable metal are generally less than about
1 1AM in size (e.g.,
0.00001-0.999 lun and all values and ranges therebetween), typically less than
about 0.5 [Am, more
typically less than about 0.1 pm, and typically less than about 0.05 vm, still
more typically less
than 0.005 vm, and yet still more typically no greater than 0.001 p.m
(nanoparticle size). The total
content of the particles in the degradable metal is generally about 0.01-70
wt.% (and all values and
ranges therebetween), typically about 0.05-49.99 wt.%, more typically about
0.1-40 wt.%, still
more typically about 0.1-30 wt.%, and even more typically about 0.5-20 wt.%.
When more than
one type of particle is added in the degradable metal, the content of the
different types of particles
can be the same or different. When more than one type of particle is added in
the degradable
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metal, the shape of the different types of particles can be the same or
different. When more than
one type of particle is added in the degradable metal, the size of the
different types of particles can
be the same or different. After the mixing process is completed, the molten
magnesium or
magnesium alloy and the particles that are mixed in the molten magnesium or
magnesium alloy
are cooled to form a solid component. Such a formation in the melt is called
in situ particle
formation as illustrated in FIGS. 19-21. Such a process can be used to achieve
a specific galvanic
corrosion rate in the entire magnesium composite and/or along the grain
boundaries of the
magnesium composite. The final magnesium composite can also be enhanced by
heat treatment
as well as deformation processing (such as extrusion, forging, or rolling) to
further improve the
strength of the final composite over the as-cast material; however, this is
not required. The
deformation processing can be used to achieve strengthening of the magnesium
composite by
reducing the grain size of the magnesium composite. Achievement of in situ
particle size control
can be achieved by mechanical agitation of the melt, ultrasonic processing of
the melt, controlling
cooling rates, and/or by performing heat treatments. In situ particle size can
also or alternatively
be modified by secondary processing such as rolling, forging, extrusion and/or
other deformation
techniques. A smaller particle size can be used to increase the dissolution
rate of the magnesium
composite. An increase in the weight percent of the in situ formed particles
or phases in the
magnesium composite can also or alternatively be used to increase the
dissolution rate of the
magnesium composite. A phase diagram for forming in situ formed particles or
phases in the
magnesium composite is illustrated in FIG. 22.
[00136] The degradable metal can be designed to corrode at the grains in the
degradable metal,
at the grain boundaries of the degradable metal, and/or the location of the
particle additions in the
degradable metal e depending on selecting where the particle additions fall on
the galvanic chart.
For example, if it is desired to promote galvanic corrosion only along the
grain boundaries (500)
of the grains (510) as illustrated in FIGS. 16-18, a degradable metal can be
selected such that one
galvanic potential exists in the base metal or base metal alloy where its
major grain boundary alloy
composition (530) will be more anodic as compared to the matrix grains (i.e.,
grains that form in
the base metal or base metal alloy) located in the major grain boundary, and
then a particle addition
(520) will be selected which is more cathodic as compared to the major grain
boundary alloy
composition. This combination will cause corrosion of the material along the
grain boundaries,
thereby removing the more anodic major grain boundary alloy (530) at a rate
proportional to the
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CA 03040185 2019-04-10
WO 2018/085102 PCT/US2017/058400
exposed surface area of the cathodic particle additions (520) to the anodic
major grain boundary
alloy (530).
[00137] If a slower corrosion rate of the degradable metal is desired, two or
more particle
additions can be added to the degradable metal to be deposited at the grain
boundary as illustrated
in FIG. 18. If the second particle (540) is selected to be the most anodic in
the degradable metal,
the second particle will first be corroded, thereby generally protecting the
remaining components
of the degradable metal based on the exposed surface area and galvanic
potential difference
between second particle and the surface area and galvanic potential of the
most cathodic system
component. When the exposed surface area of the second particle (540) is
removed from the
system, the system reverts to the two previous embodiments described above
until more particles
of second particle (540) are exposed. This arrangement creates a mechanism to
retard corrosion
rate with minor additions of the second particle component.
[00138] It will thus be seen that the objects set forth above, among those
made apparent from
the preceding description, are efficiently attained, and since certain changes
may be made in the
constructions set forth without departing from the spirit and scope of the
invention, it is intended
that all matter contained in the above description and shown in the
accompanying drawings shall
be interpreted as illustrative and not in a limiting sense. The invention has
been described with
reference to preferred and alternate embodiments. Modifications and
alterations will become
apparent to those skilled in the art upon reading and understanding the
detailed discussion of the
invention provided herein. This invention is intended to include all such
modifications and
alterations insofar as they come within the scope of the present invention. It
is also to be
understood that the following claims are intended to cover all of the generic
and specific features
of the invention herein described and all statements of the scope of the
invention, which, as a
matter of language, might be said to fall there between. The invention has
been described with
reference to the preferred embodiments. These and other modifications of the
preferred
embodiments as well as other embodiments of the invention will be obvious from
the disclosure
herein, whereby the foregoing descriptive matter is to be interpreted merely
as illustrative of the
invention and not as a limitation. It is intended to include all such
modifications and alterations
insofar as they come within the scope of the appended claims.
34
