Note: Descriptions are shown in the official language in which they were submitted.
CA 02901560 2015-08-26
"FLOW RESISTANT PACKING ELEMENT SYSTEM FOR
COMPOSITE PLUG"
FIELD
Embodiments disclosed herein generally relate to packing systems
used on composite plugs, and more particularly related to a packing element
having
at least one element co-molded into the packing material.
BACKGROUND
Packing element systems used on composite plugs are typically
designed as individual components comprised of a rubber packing element and a
back-up extrusion resistant component. For example, Fig. 1 illustrates a
composite
plug 10 in partial cross-section. The plug 10 has a mandrel 12 with cones 14
and
backup systems 16 arranged on both sides of a packing element 18. Outside the
inclined cones 14, the plug 10 has slips 20. As shown here, the slips 20 can
be a
conventional wicker-type slip typically composed of cast iron.
The backup systems 16 have several elements, namely a wedge ring
16a composed of a composite, a solid backup ring 16b composed of
Polytetrafluoroethylene (PTFE), and a slotted ring 16c composed of a
composite.
When deployed downhole, the plug 10 is activated by a wireline setting tool
(not
shown), which uses conventional techniques of pulling against the mandrel 12
while
simultaneously pushing against a push ring 13. As a result, the element system
(i.e., packing element 18, cones 14, backup systems 16, and slips 20) is
compressed along the axis of the mandrel 12. In particular, the slips 20 ride
up the
cones 14, the cones 14 move along the mandrel 12 toward one another, and the
packing element 18 compresses and extends outward to engage a surrounding
casing wall.
During the compression and extension of the packing element 18, the
backup systems 16 control the extrusion of the packing element 18 so that the
material does not overly extrude axially, which would weaken any resultant
seal.
The slips 20 are pushed outward in the process to engage the wall of the
casing,
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CA 02901560 2015-08-26
which both maintains the plug 10 in place in the casing and keeps the packing
element 18 contained.
As will be appreciated, the plug 10 and most of its components are
preferably composed of millable materials because the plug 10 is milled out of
the
casing once operations are done, as noted previously. As many as fifty such
plugs
can be used in one well and must be milled out at the end of operations.
Therefore, having reliable plugs 10 composed of entirely (or mostly) of
millable
material is of particular interest to operators. As noted above, the solid
backup
rings 16b of the backup systems 16 are typically compose of PTFE or similar
10 material. Such a material can cause problems during mill up of the tool
10, leaving
a ring of material, tending to gum up, etc.
To deploy the plug 10 downhole, operators may need to pump the
plug 10 along the wellbore. For instance, the plug 10 may be pumped down a
horizontal section of a wellbore at extremely high pump rates that create a
high fluid
velocity across the plug 10. The high fluid velocity, which can be in excess
of 50
ft./sec., may cause the element system (i.e., packing element 18, backup
systems
16, slips 20, etc.) to pre-set while running in the wellbore. For example,
should the
plug 10 be stalled for whatever reason in the casing during run-in, the high
velocity
of fluid used to pump the plug 10 may flare out components of the backup
system
16, expanding it like a sail and causing pre-setting of the element system 30.
As will be appreciated, pre-setting of the plug 10 can be catastrophic
and may require operators to use coil tubing to drill up the pre-set plug 10,
which
can be very costly. Even though there is a risk of pre-setting, operators
still want to
run the plug 10 in the hole at higher rates because this reduces the rig time
costs.
In other situations, operators want to run the plug 10 at higher rates due to
the
extended reach of the well.
In addition, as the composite plugs are pumped downhole, the slips 20
have the potential to flare out due to high fluid velocities past them. The
slips 20
can also incur physical damage while tripping downhole or mishandling of the
composite plug. One solution to these issues has been to increase the break
load
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on the upper slip 20, adding pins to the upper cone 14 and/or using yield
bands.
Still, even these mechanical fastening means can be prone to damage during run-
in.
To prevent pre-setting, the element system (i.e., packing element 18,
backup systems 16, slips 20, etc.) of the plugs 10 have also been designed
with
different geometries. Adhesives have been used to glue components together, or
the components have been wrapped with a shrink fit. However, pre-setting still
occurs, and the conventional element system has created limitations on the
speed
that a plug 10 can be run in the hole.
In other related aspects of plugs with packing elements, it is known in
the art to use other types of anti-extrusion devices. For example, U.S. Pat.
No.
8,167,033 discloses anti-extrusion rings that have hard segments surrounded by
an
elastic matrix. The hard segments expand to form a near solid ring of rigid
material
within the elastomeric matrix to prevent extrusion of the packing element.
Additionally, it is known in the art to embed slip type components in
the packing element of a plug. For example, U.S. Pat. No. 2,194,331 discloses
a
plug having a packing element with embedded metal pieces that help securely
engage in the casing.
The subject matter of the present disclosure is directed to overcoming,
or at least reducing the effects of, one or more of the problems set forth
above.
SUMMARY
An element system for a downhole tool includes a packer with at least
one co-molded element. The packer positions on the downhole tool. For example,
the packer can be a sleeve disposed on a mandrel of the downhole tool adjacent
and activating element. The packer is composed of packing material and is
compressible on the downhole tool. The at least one element is co-molded
directly
into the packing material at at least one end of the packer. The at least one
co-
molded element at least partially limits extrusion of the packing material
axially past
the at least one element beyond the at least one end of the packer.
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In one embodiment, the at least one element includes at least one
backup ring, which can define a plurality slots longitudinally therein and
disposed
about of the at least one backup ring. In fact, at least two backup rings can
be used
next to each other, and the slots of the at least two backup rings can be
offset from
one another. In another embodiment, the at least one co-molded element can
include first and second backup rings molded into the packing material at
opposing
ends of the packer.
In one arrangement, at least a portion of the at least one end of the
packer at least partially covers an exterior of the at least one backup ring.
The at
least one backup ring can include an endwall exposed beyond the packing
material.
In another embodiment, the at least one co-molded element includes
a first slip co-molded directly into the packing material at the at least one
end of the
packer. A second slip can be co-molded directly into the packing material at
an
opposite end of the packer.
A method of manufacturing a packing element for a downhole tool
involves positioning at least one element in a mold; molding a packer of
packing
material in the mold; and adapting the at least one element to at least
partially limit
extrusion of the packing material axially past the at least one element beyond
at
least one end of the packer by co-molding the at least one element directly
into the
packing material at the at least one end of the packer.
To position the at least one element in the mold, at least one backup
ring can be positioned in the mold with a plurality slots disposed around a
circumference of the at least one backup element. In an example, at least two
backup rings can be positioned in the mold with the slots of the at least two
backup
rings being offset from one another. Backup rings can be molded directly into
the
packing material at opposing ends of the packer.
When molding the at least one element directly into the packing
material at the at least one end of the packer, at least a portion of the at
least one
end of the packer can at least partially cover an exterior of the at least one
element.
An endwall of the at least one element can be exposed beyond the packing
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material. At least one slip can also position in the mold to be molded with
the
packing material.
The foregoing summary is not intended to summarize each potential
embodiment or every aspect of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a downhole tool in partial cross-section having a
packing element system according to the prior art;
Figures 2A-2B illustrate downhole tools in partial cross-section having
packing element systems according to the present disclosure;
Figure 3A illustrates a perspective view of one end of the disclosed
element system in a molded state;
Figure 3B illustrates a perspective view of the end of the disclosed
element system in diagrammatic disassembly;
Figure 4A illustrates an end view of one end of the disclosed element
system;
Figures 4B-4D illustrates cross-sectional views of the end of the
disclosed element system at different orientations;
Figure 5A illustrates an end view of one end of another arrangement
of the disclosed element system;
Figures 5B-5D illustrates cross-sectional views of the end of the
disclosed element system in Fig. 5A at different orientations;
Figure 6 illustrates a downhole tool in partial cross-section having yet
another packing element system according to the present disclosure;
Figures 7A-7B illustrates cross-sectional and side views of the
element system of Fig. 6;
Figure 8 illustrates a downhole tool in partial cross-section having yet
another packing element system according to the present disclosure;
Figures 9A-9B illustrate partial cross-sectionals of additional packing
element systems according to the present disclosure; and
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Figure 10 diagrams a molding process for the disclosed element
system.
DETAILED DESCRIPTION
Figs. 2A-2B illustrate downhole tools 10 in partial cross-section having
packing element systems 30 according to the present disclosure. The downhole
tool 10 can be a composite plug as shown, but it could also be a packer, a
liner
hanger, an anchoring device, or other downhole tool. The plug 10 has a mandrel
12
having cones 14 arranged on both sides of the element system 30. Outside the
inclined cones 14, the plug 10 has slips 20, which may be conventional wicker-
type
slips or other type of slips having inserts or buttons.
The composite plug 10 is preferably composed mostly of non-metallic
components according to procedures and details as disclosed, for example, in
U.S.
Pat. No. 7,124,831. This makes the plug 10 easy to mill out after use.
When deployed downhole, the plug 10 is activated by a wireline
setting tool (not shown), which uses conventional techniques of pulling
against the
mandrel 12 while simultaneously pushing against the push ring 13. The element
system 30 is compressed axially between activating elements (e.g., the push
ring
13 at the uphole end and the mandrel's shoulder 11 at the downhole end). As a
result, the slips 20 ride up the cones 14, the cones 14 move along the mandrel
12
toward one another, and the packing element 32 compresses and extends outward
to engage a surrounding casing wall. The slips 20 are pushed outward in the
process to engage the wall of casing, which both maintains the plug 10 in
place in
the casing and keeps the element system 30 contained.
The force used to set the plug 10 may be as high as 30,000 lbf. and
could even be as high as 85,000 lbf. These values are only meant to be
examples
and could vary for the size of the plug 10. In any event, once set, the plug
10
isolates upper and lower portions of the casing so that fracture treatment or
other
operations can be performed. When used during fracture operations, for
example,
the plug 10 may isolate pressures of 10,000 psi or so uphole of the plug 10,
while
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pressure is kept from downhole locations.
As will be appreciated, any slipping or loosening of the plug 10 can
compromise operations. Therefore, it is important that the slips 20
sufficiently grip
the inside of the casing. At the same time, however, the plug 10 and most of
its
components are preferably composed of millable materials because the plug 10
is
milled out of the casing once operations are done, as noted previously. As
many as
fifty such plugs 10 in the form of plugs can be used in one well and must be
milled
out at the end of operations. Therefore, having reliable plugs 10 composed of
entirely (or mostly) of millable material is of particular interest to
operators.
The plug 10 in Fig. 2A has a symmetrically-arranged element system
30 and may be configured for use as a bridge plug to isolate pressures above
and
below the plug 10 when set in casing. By contrast, the plug 10 in Fig. 2B has
an
asymmetrically-arranged element system 30 and may be configured for use as a
fracture plug to isolate pressure from above when set in casing. In
this
asymmetrical arrangement, molded components of the element system 30 are used
for the downhole end of the plug 10, while conventional cone 14 and extrusion
rings
16 are used for the uphole end. Although not shown, a reverse arrangement
could
be used depending on the needs of a particular implementation.
Due to the configuration of the element system 30 as disclosed herein,
the overall length of the plug 10 or portions thereof can be reduced in length
by
about 6-in, or more. This shortening is not strictly depicted in the figures.
Fig. 3A illustrates a perspective view of one end of the disclosed
element system 30 as molded for the plug 10 of Fig. 2B. Additionally, Fig. 3B
illustrates a perspective view of the end of the disclosed element system 30
diagrammatically disassembled.
The element system 30 includes a molded packing element or packer
32 and includes anti-extrusion or backup elements 40 and 50. As best shown in
Fig. 3A, the molded packer 32 is a sleeve, which is composed of an elastomer
material that is compressible. The packer 32 is co-molded with the backup
elements 40, 50 and encompasses them. In other words, the elastomer material
of
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the packer 32 is molded into the interstices of the backup elements 40,
50¨i.e., into
the small openings, spaces, gaps, etc. around, between, in, etc. the elements
40,
50. In turn, the backup elements 40 and 50 interstitially molded with packer
32
control the extrusion of the packing element 32. An end or cover 34 of the
packing
packer 32 may extend molded (at least partially or entirely) over the backup
elements 40 and 50.
As diagrammed in Fig. 3B, the backup elements 40 and 50 can
include one or more back-up or anti-extrusion rings, which can be composed of
a
composite (non-metallic) material or any other suitable material. For
higher
temperature and pressure ratings, at least two slotted rings 40 and 50 can be
used.
The slots 44, 54 are defined longitudinally and are spaced around the
circumference of the rings 40, 50. The slots 44, 54 can be staggered to
prevent
extrusion of the compressed packer's material through the slots 44, 54 during
application of pressures, such as pressures during a fracture operation. As
will be
appreciated, the size and number of the slots 44, 55 can be configured for a
particular implementation.
For a conventional sized plug used in standard casing, the slots 44, 55
may be expected to be about 1/8-in, wide, although this may vary depending on
the
implementation. The width of the slots 44, 55 could be further reduced while
still
allowing for compression molding of the elastomer material of the packer 32
therebetween during the compression molding process to form the element system
30.
The first (inner) slotted ring 40 is a thin conical shape with a number of
expandable petals separated by the slots 44. This inner ring 40 is embedded
closer
into the end of the element system 30. By contrast, the second (outer) slotted
ring
50 has a thick cylindrical shape with a conical recess and with a number of
expandable segments separated by the slots 54. This outer ring 50 fits
adjacent the
inner ring 40 so that the conical recess fits next to the conical shape of the
inner
ring 40. The thick, expandable segments of the outer ring 50 resist expanding
outward as the element system 30 is run downhole on the tool 100 at high
velocities
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and pressures. This can help prevent premature setting of the element system
30
during deployment.
As already hinted to above, the element system 30 is not assembled
as individual components. Instead, the backup rings 40 and 50 are placed in a
rubber mold prior to compression molding the packer 32. Once the compression
molding process is complete, the backup rings 40 and 50 are contained or co-
molded within the packer 32. After the compression molding, the element system
30 may be cured and finished according to standard practice.
The backup rings 40 and 50 may be at least partially or entirely
covered by the end of the packer 32. For example, a thin film or layer 34 of
the
elastomer of the packer 32 may cover the outside of the backup rings 40 and
50,
giving the element system 30 a streamline profile, although this is not
strictly
necessary.
As shown in Fig. 3A, only one end of the packer 32 is shown having
the embedded back-up rings 40 and 50, while the other end may or may not have
such embedded rings 40 and 50 as in Figs. 2A-2B. As shown on the plug 10 in
Fig. 2A, both ends of the packer 32 have backup rings 40 and 50 embedded
therein. If only one end of the packer 32 has the embedded rings 40 and 50,
the
other end can be used with conventional backup components on the plug 10, such
as those components depicted above with reference to Fig. 2B.
Further details of the element system 30 are discussed with reference
to Figs. 4A-4D. As shown in Fig. 4A, an end view shows one end of the
disclosed
element system 30. Figs. 4B-4D illustrate cross-sectional views of the end of
the
disclosed element system 30 at different orientations.
In Fig. 4A, the outer backup ring 50 has an internal diameter 52 that
fits on the mandrel (12) of the plug (10). The outer ring 50 is shown with its
endwall
56 and lip 58 exposed. These fit against a cone (14) of the plug (10). See
e.g.,
Figs. 2A-2B. The several slots 54 of the outer ring 50 are disposed around the
outer circumference of the ring 50, and the material of the packer 32 is
molded into
the slots 54. Additionally, the molded end 34 of the packer 32 can cover the
outer
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circumference of the ring 50. Shown in dashed lines, the slots 44 of the inner
backup ring 40 are offset from the outer ring's slots 54.
In the cross-section of Fig. 4B, the co-molding of the packer 32 and
backup rings 40, 50 (i.e., molding under, over, between, etc.) is shown at an
orientation lacking alignment with any of the slots 44, 54. By contrast in the
cross-
section of Fig. 4C, the co-molding of the packer 32 and the backup rings 40
and 50
is shown at an orientation aligned with the outer ring's slots 54, while the
cross-
section in Fig. 4D shows the co-molding at an orientation aligned with the
inner
ring's slots 44.
The segments of the outer ring 50 are wedged shape, defining a
portion of the conical recess for fitting against the inner ring 40 and
defining a
cylindrical outer surface for completing the shape of the packer 32. The
thickness
of the inner ring 40 can be modified to alter its strength to meet the
requirements of
an implementation. As shown in Figs. 4B-4D for example, the wedge profile of
the
inner ring 40 can make it stronger. Other variations are possible.
The materials of the inner and outer rings 40 and 50 may be the same
or different. In particular, the inner ring 40 and the outer ring 50 can
preferably both
be composed of a composite material. Overall, the inner ring 40 may be
intended to
perform most of the anti-extrusion function for the element system 30.
In an alternative arrangement shown in comparable Figs. 5A-5D, the
element system 30 can also include a wedge ring 60 disposed adjacent the inner
backup ring 40. This wedge ring 60 is co-molded together with the backup rings
40
and 50 in the elastomer of the packer 32. The wedge ring 60 includes an inner
diameter 62 that fits on the mandrel (12). A wedged edge of the ring 60 may be
oriented toward the inner ring 40. The wedge ring 60 can also be composed of
composite material and can be a solid ring. During operations, the wedge ring
60
can help compress the packer 32 during the setting process.
Fig. 6 illustrates a downhole tool 10 in partial cross-section having yet
another element system 30 according to the present disclosure. The downhole
tool
10 shown here can be a fracture plug used during a fracture operation, such as
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CA 02901560 2015-08-26
plug and perf operation of casing.
The element system 30 includes a downhole slip 20, a cone 14, a
packer 32, one or more backup rings 50, and uphole slip 70. When the plug 10
is
deployed downhole in the casing, the uphole slip 70 only needs to hold back
the
elastomer of the packer 32 until a frac ball is deployed on the ball seat of
the
mandrel 12. In this element system 30, therefore, an upper cone is eliminated,
and
the uphole slip 70 is co-molded with the elastomer of the packer 32. In the
end, this
can make the plug 10 shorter, thus yielding a faster mill-up time. The co-
molding of
the slip 70 also helps prevent the uphole slip 70 from flaring out and
breaking during
run-in and damage incurred due to mishandling of plug 10.
As shown in Figs. 7A-7B, the one or more backup rings 50 are co-
molded and incorporated on the downhole side of the packer 32. Only one backup
ring 50 is shown, but it will be appreciated that additional rings (e.g.,
backup ring 40
and/or wedge ring 60) disclosed previously can be used. The one or more backup
rings 50 can define slots as before through which the elastomer of the packer
32
can fill. Also, a layer 34 of elastomer may be molded over the outside of the
backup
rings 50 to further streamline the element system 30, as shown in Figs. 7A-7B.
By contrast, the uphole slip 70 with buttons 74 is co-molded and
incorporated on the uphole side of the packer 32. The uphole slip 70 can
thereby
act as an extrusion barrier. As this arrangement shows, the downhole backup
ring
50 and the uphole slip 70 are co-molded with the elastomer to yield a single
co-
molded element 30 that is then positioned on the mandrel (12) of the plug (10)
(See
Fig. 6). Once assembled, the disclosed element system 30 has the uphole slip
70
encapsulated with the elastomer, making the system 30 more robust and
streamlined for run-in.
The uphole slip 70 is formed as a ring having external holes 72 for
inserts 74 and having a number of slits or divisions 76, making separable
segments
or arcuate members. The elastomer of the packer 32 can mold in the slits 76
and
may not necessarily be molded over the outside of the slip 70, although it
could.
The slits 76 may not pass through the entire length of the slip 70 so that
inside
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edges around the back end of the slip 70 can remain connected.
An alternative system shown in Fig. 8 may have the uphole slip 70 co-
molded with the packer 32, but may use a conventional backup system 16 at the
downhole end. The downhole tool 10 shown here can be a fracture plug used
during a fracture operation, such as a plug and perf operation of casing.
The element system 30 includes a packer 32, backup system 16, and
slips 20 and 70. In this element assembly 30, the conventional arrangement of
slip
20, cone 14, and backup system 16 is used on the downhole end of the plug 10.
An
upper cone is eliminated, and the uphole slip 70 is co-molded with the
elastomer of
the packer 32.
Another element system 30 shown in Fig. 9A can have one or more
backup rings 80 co-molded along with the uphole slip 70 with the packer 32.
The
backup rings 80 can provide extrusion resistance for higher pressures at the
uphole
end of the packer 32. The backup rings 80 can be similar to those rings 40,
50, 60,
etc. discussed previously. Yet another element system 30 shown in Fig. 9B can
have uphole and downhole slips 70 co-molded with the packer 32 and may not
directly use separate anti-extrusion rings (not shown), although it could have
backup rings as disclosed herein.
As can be seen in the above examples, the packer 32 can be co-
molded with one or more of: an upper slip 70; a lower slip 70; upper anti-
extrusion
ring(s) 40, 50, 60, and/or 80; and lower anti-extrusion ring(s) 40, 50, 60,
and/or 80.
Being able to co-mold these components with the packer 32 allows the plug 10
to
be shorter (e.g., about 15% of the length can be eliminated over current
plugs).
This has the benefit of reducing the amount of time required to mill up the
plug 10.
As mentioned above, components (e.g., 40, 50, 60, 70, and/or 80) of
the elements system 30 are co-molded with the packing element 32 by being
placed
in a mold prior to compression molding the packer 32. Fig. 10 merely diagrams
some of the features of a molding system 100 to mold the disclosed element
system
10. In general, the molding system 100 includes a mandrel 120 about which mold
parts 110a-b fit. The mandrel 120 can be one component or can be composed of
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several components to facilitate assembly and removal. There are typically
more
than one mold part 110a-b, and each has a mold cavity 112 for containing
molded
elements.
The components (e.g., 40, 50, 60, 70, and/or 80) of the elements
system 30 are installed on the mandrel 120 and contained in the mold parts
110a-b.
Features (not shown) for injection molding, compression molding, etc. of the
elastomer material of the packer 32 are then used to co-molded these element
components with the packing element 32. Once the molding process is complete,
the components (e.g., 40, 50, 60, 70, and/or 80) are contained or co-molded
within
the packer 32. After the compression molding, the element system 30 may be
cured and finished according to standard practice and then installed on a tool
mandrel (12) or the like.
To mold the components of the element system 30, various surfaces
of the system 30 are prepped before compression molding so they can bond with
the elastomer of the packer 32. To prepare the surfaces, bonding agents can be
applied, surface treatment may be performed, holes or roughness can be added,
or
other methods may be used. For example, surfaces of the inner ring 40 and/or
outer ring 50 on the element system 30 as in Figs. 3A-3B, 4A-4C, etc. can be
prepped with a bonding agent before compression molding so they can bond with
the elastomer of the packer 32.
The bonding process can use a primer as an overcoat adhesive for
bonding vulcanized and unvulcanized rubber compounds to rigid substrates. The
bonding process can also use an adhesive to bond rubber compounds to a primed
substrate or can use a non-conductive, one coat adhesive. Types of agents for
the
bonding process can be composed of polymers, organic compounds, and mineral
fillers in an organic solvent and can include Chemlok 205 Primer, 233X-LS
Adhesive, and 258XN Adhesive, for example. (CHEMLOK is a registered
trademark of Lord Corporation.)
It would be expected that more bonding of the elastomer to the
surfaces and interstices of the components would produce better results.
Instead, it
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may be preferred that the surfaces and interstices of the backup rings 40, 50,
60,
and/or 80 be only partially prepped for bonding with the elastomer. The same
preference can be applied to the slips 70 discussed previously.
If extensive preparation is done to produce strong bonding, for
example, the inner ring 40 may simply remain a rigid body inside the elastomer
as
the packer 32 is compressed. Rather than expanding out and preventing
extrusion,
the inner ring 40 stays somewhat fixed and allows the elastomer to extrude
over it.
Only the outer ring 50 may expand out to prevent extrusion. Since this is not
desirable, it may be preferred, for example, that the surfaces of the rings 40
and 50
are selectively treated for bonding with the elastomer of the packer 32.
A variation of manufacturing the co-molded element/back-up rings
involves molding the components and elastomer separately and then bonding them
together as if co-molded. For example, the back-up (or slip) rings 40, 50, 60,
80,
and/or 70 are molded first in elastomer, and the remainder of elastomer is
formed in
a second mold. The two pieces are then bonded together.
Co-molding the components (i.e., rings 40, 50, 60, 80, and/or slip 70)
into the packer 32 (by molding together or by separate molding then bonding)
creates an element system 30 that has significantly higher flow resistance and
is
less prone to pre-setting. In fact, the performance during run in is expected
to
increase by more than 50%. In contrast to the conventional type of element,
the
disclosed element system 30 does not have back-up rings that will tend to
flare out
and create a sail effect at high flow rates, which causes pre-set or other
catastrophic incidents. With the molded element system 30 of the present
disclosure, the components 40, 50, 60, 70, and/or 80 are encapsulated into the
elastomer during the molding process. Overall, the co-molded element system 30
can reduce the cost of the plug 10 and shorten the length.
Flow test data for the co-molded element system (30) indicates
favorable performance during simulated pump-down and run-in testing. For
example, a composite plug (10) with a co-molded element system (30) for 5-1/2
casing was tested. The plug (10) had a 4.375-in OD and was inserted in the 5-
1/2
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casing, which has a 4.670-in ID. Building up to a flow rate from 222.5 to 500-
gal/min at ambient temperature in intervals of 30-minutes, the co-molded
element
system (30) of the present disclosure in simulated run-in and pump-down
testing
showed no signs of pressure loss and showed no damage after the test. The test
conditions simulated run-in at equivalent line speeds ranging from 250 to 562-
ft/min
and pump-down at equivalent fluid velocities ranging from about 34 to 77-
ft/sec. By
comparison, a more conventional arrangement of an element system on a plug may
tend to swab at lower flow rates (e.g., 350-gal/min), causing load against the
lower
Teflon ring and pressing it against the lower pedals. As noted above, this can
be
problematic during run-in and pump-down operations at high rates and may cause
premature setting.
The foregoing description of preferred and other embodiments is not
intended to limit or restrict the scope or applicability of the inventive
concepts
conceived of by the Applicants. It will be appreciated with the benefit of the
present
disclosure that features described above in accordance with any embodiment or
aspect of the disclosed subject matter can be utilized, either alone or in
combination, with any other described feature, in any other embodiment or
aspect
of the disclosed subject matter.
