Note: Descriptions are shown in the official language in which they were submitted.
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Bonded Segmented Slips
-by-
Nauman Mhaskar, Shawn J. Treadaway, Matthew Stage, & Jonathan A. Young
BACKGROUND OF THE DISCLOSURE
[0002] Slips are used for various downhole tools, such as bridge plugs and
packers.
The slips can have inserts or buttons to grip the inner wall of a casing or
tubular.
Examples of downhole tools with slips and inserts are disclosed in U.S. Pat.
Nos.
6,976,534 and 8,047,279.
[0003] For example, Figure 1A illustrates a downhole tool 10 having slip
assemblies
20 according to one type in the prior art. Figure 1B illustrates a detailed
view of the
prior art slip assembly of Fig. 1A. The tool 10 is a bridge plug composed
mainly of
composite material. The bridge plug 10 has a mandrel 12 on which the slip
assemblies
20, cones 14, and extrusion rings 16 fit on either side of a sealing element
18.
[0004] As shown, the slip assemblies 20 each comprise a number of
independent
segments 22 disposed about the mandrel 12. The segments 22 are composed of non-
metallic material, such as composite, and use inserts 24 to engage with the
casing to
stop the plug 10 from moving during its operation. The inserts 24 are
typically made
from cast or forged metal, which is then machined and heat-treated to the
proper
engineering specifications according to conventional practices. When the
bridge plug
is being set, the slip segments 22 are pushed toward the ramped surfaces of
the
cones 14 so that the segments 22 move away from the mandrel 12 and engage
against
a surrounding tubular or casing wall.
[0005] To hold the various segments 22 together during run-in of the bride
plug, bands
26 are disposed in grooves around the top and bottom ends of the segments 22.
The
bands 26 hold the segments 22 inward together around the mandrel 12 and yield
when
the segments move away from the mandrel 12 by pushing against the cones 14.
The
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bands 26 can be composed of metal, plastic, or the like. Care must be taken
when
running-in the tool that the bands 26 do not break, which would allow the
segments 22
to fall free of the mandrel 12 and hinder operation of the plug 10.
[0006] Rather than using bands to hold the segments together, the slip
assemblies 20
for a downhole tool can having various segments integrally connected together.
For
example, Figure 2A illustrates a detailed view of another type of slip
assembly 30
according to the prior art. Here, the slip assembly 30 is shown relative to a
cone 14 for
use on a downhole tool, such as a bridge plug discussed previously. The
assembly has
a number of segments that dispose about the tool's mandrel (not shown). Rather
than
being independent segments requiring securement by a separate band or the
like, the
segments 32 have interconnecting portions or joints 36 integrally formed
between the
segments.
[0007] The slip assembly 30 can be composed of composite or other material
by
molding or the like, and the joints can be machined in assembly 30. When the
assembly 30 is pushed against the ramped surface of the cone 14, the segments
32
break at the joints 36 so that the segments 32 can then act to independently
wedge
between the cone 14 and the surrounding casing wall (not shown).
[0008] Rather than such an extensively machined notch, the slip assembly 30
in
Figure 2B has a similar arrangement of integrally connected segments 32, but
these
segments are connected at their ends by an integral end ring portion 38. In
any event,
this assembly 30 can operate similar to that discussed above in Figure 2A.
[0009] As can be seen above, non-metallic slip segments 22 used in downhole
tools
10, such as composite fracture plugs, are held together by independent yield
bands
disposed around the segments 22 or by a notch or other interconnecting portion
between each segment 22. Although these assemblies may be effective, there are
still
drawbacks.
[0010] The yield bands can be composed of metal to hold the composite slip
segments together. This introduces metallic components to a downhole tool,
which is
undesirable for fracture plugs and the like due to longer mill-up time. Yield
bands
composed of non-metallic material may not have the required mechanical
properties to
hold the slip segments together while tripping the tool 10 downhole.
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[0011] The notch introduces inconsistent results due to variations in
material
properties, manufacturing processes, etc. In addition, the process in which
the notch
fractures or breaks during setting of the tool can compromise structural
integrity of the
composite slip segments and the inserts 24 held therein.
[0012] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Fig. 1A illustrates a downhole tool having slip assemblies according
to one type
in the prior art.
[0014] Fig. 1B illustrates a detailed view of the prior art slip assembly
of Fig. 1A.
[0015] Fig. 2A illustrates a detailed view of another type of slip assembly
according to
the prior art.
[0016] Fig. 2B illustrates a detailed view of a similar prior art slip
assembly to that
shown in Fig. 2A.
[0017] Fig. 3A illustrates a downhole tool having slip assemblies according
to the
present disclosure.
[0018] Fig. 3B illustrates a detailed side view of the slip assembly in
Fig. 3A.
[0019] Fig. 3C illustrates a detailed cross-sectional view of the slip
assembly in Fig.
3A.
[0020] Fig. 4 illustrates a detailed side view of another slip assembly
according to the
present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0021] Figure 3A illustrates a downhole tool 10 having slip assemblies 50
according to
the present disclosure. The downhole tool 10 can be a bridge plug as shown,
but it
could also be a packer, a liner hanger, an anchoring device, or other downhole
tool.
[0022] The tool 10 has a mandrel 12 having cones 14 and backup rings 16
arranged
on both sides of a packing element 18. Outside the inclined cones 14, the tool
10 has
slip segments 52. Together, the slip segments 52 along with the cones 14 can
be
referred to as the slip assemblies 50, or in other instances, just the slip
segments 52
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may be referred to as the slip assemblies 50. In either case, either reference
may be
used interchangeably throughout the present disclosure.
[0023] As shown herein, the slip segments 52 have inserts or buttons 54. As
a bridge
plug, the tool 10is preferably composed mostly of non-metallic components
according to
procedures and details as disclosed, for example, in U.S. Pat. No. 7,124,831,
which is
incorporated herein by reference in its entirety. This makes the tool 10 easy
to mill out
after use.
[0024] 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 upper components against the slip assembly 50. As
a
result, the slip segments 52 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. The backup elements 16 control the
extrusion of
the packing element 18. The slip segments 52 are pushed outward in the process
to
engage the wall of the casing, which both maintains the plug 10 in place in
the casing
and keeps the packing element 18 contained. The metallic inserts 54 in the non-
metallic slip segments 52 allow the assemblies 50 to sufficiently grip the
inside of the
casing.
[0025] The force used to set the plug 10 may be as low as 30,000 lbf. and
could be as
high as 85,000 lbf. These values are only meant to be examples and could vary
for the
size of the tool. In any event, once set, the plug 10 isolates upper and lower
portions of
the casing so that frac and other operations can be completed uphole of the
plug 10,
while pressure is kept from downhole locations. When used during frac
operations, for
example, the plug 10 may isolate pressures of 10,000 psi or so.
[0026] As shown in Figures 3B-3C, the segments 52 of the assemblies 50 are
each
independent segments. Rather than being independently held by yield bands or
interconnected by integrally formed joints, the segments 52 are held by a bond
between
each longitudinal side of the segments 52. The bonded slip segments 52 can
separate
from one another when expanded by the cones 14 to get more consistent results
while
not degrading the mechanical integrity of the slip segments 52.
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[0027] The slip segments 52 can be bonded using a bonding material, such as
a
thermoplastic resin, a thermoset resin, an elastomer, an epoxy adhesive, and a
bonding
agent manufactured using ceramic, graphite, metallic agent, or a combination
of these.
Some examples include high temperature ceramic and graphite adhesives and high
performance epoxies, such as those available from Aremco. Additional examples
include metal filled epoxies, such as Duralco TM 4540, which is an active
aluminum filled
epoxy available from Cotronics Corporation, or include a high-temperature
adhesive,
such as Durabond 950, which is a metallic ceramic composite available from
Cotronics
Corporation. The surface area over which the bonding agent is applied can be
controlled for a particular implementation. Thus, more or less of the
longitudinal sides
of the segments 52 can be bonded to other segments 52. This provides greater
control
of the required force to break the bond itself, which can be tailored as
desired.
[0028] Again, bonding the slip segments 52 together with thermoplastic or
thermoset
resins or a bonding agent manufactured out of ceramics, metallic agents,
etc... results
in a tighter control over break strength of the slip segments 52. The bonds 56
are
independent of the mechanical properties of the slip segments 52. This allows
the
material properties of the bonds 56 to be different from the material of the
slip segments
52. In this sense, the bond 56 can be configured to have an appropriate break
strength
without compromising the integrity of the segments 52 when the bond 56 breaks.
The
bonding agent can be designed to fracture and break apart a predetermined
stress, thus
allowing the slip segments 52 to retain their structural integrity.
[0029] To form a slip assembly 50 as disclosed herein, a plurality of
independent
segments 52 are formed using standard practices, such as molding, machining,
etc. As
noted above, the segments 52 can be made of a non-metallic material and can
have
one or more inserts 54 disposed in the outward surface of the segments 52.
[0030] The segments 52 are then disposed side-by-side about a mandrel 12 of
a
downhole tool 10 so that one end of the segments 52 are adjacent the ramped
end of a
cone 14 on the mandrel 12. Each of the adjacent sides of the segments 52 are
bonded
with a bonding material that affixes the independent segments 52 as a unit
together
around the mandrel 12. As noted above, the bonding material can be a
thermoplastic
resin, a thermoset resin, an elastomer, an epoxy adhesive, a bonding agent
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manufactured using ceramic agent, a bonding agent manufactured using a
metallic
agent, and a bonding agent manufactured using a combination of ceramic and
metallic
agent.
[0031] Depending on the bonding material and how it can be applied, bonding
the
adjacent sides of the segments 52 with the bonding material can be done by
applying
the bonding material to the adjacent sides of the segments 52 before or after
they are
disposed side-by-side about the mandrel 12. For example, the bonding material
can be
applied to one or more sides of the segments 52, and the segments 52 can then
be
placed in or on a fixture so that the bonding material cures to affix the
sides together.
Once set, the affixed segments 52 can be disposed as a unit on the mandrel 12
of the
tool 10. Alternatively, the segments 52 with the bonding material already
applied can be
placed around the mandrel 12 and held by a fixture until cured in place on the
mandrel
12 of the tool 10.
[0032] In yet another alternative, the segments 52 can be disposed in place
about the
mandrel 10, and the bonding material can be applied to the exposed sides
between the
gaps or separations between the segments 52 to affix the sides together. As
will be
appreciated, temporary fixtures may be used to hold the segments 52 in place
while the
bonding material cures or otherwise hardens. Once the slip assembly 50 is
assembled
separately (i.e. bonded using a fixture), the assembly 50 can then be placed
on the
mandrel. (Finally, the backup elements 16 of Fig. 3A used to control the
extrusion of
the packing element 18 can also be bonded together in the same way as done
with slip
segments 52.)
[0033] Figure 4 shows another slip assembly 50 according to the present
disclosure.
The segments 52 of the assemblies 50 are each independent segments. Here,
yield
bands 60 are disposed around the segments 52 to hold them against the tool's
mandrel.
The bands 60 can fit in external slots (not visible) defined in the outer
surfaces of the
segments 50 both above and below the inserts 54. The yield bands 60 are
composed
of band segments 62 bonded together with bonds 64 to form the ring structure
of the
bands 60. In general, each band 60 can having one or more band segments 62
that
form at least a portion of a ring. Ends of the band segments 62 are bonded
together
with the bonding material to form the band 60.
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[0034] The band segments 62 can be composed of metal. In this case, use of
the
bonds 64 between segments 62 can still reduce the overall metallic content of
the tool.
This will also provide for faster mill up times because the segments 62 will
break up
easier than a solid ring during milling. Alternatively, the band segments 62
can be
composed of a non-metallic material. Although such material may be millable or
the
like, it need not necessarily have a required yield strength. Instead, the
characteristics
of the material used for the bonds 64 can be particularly configured to
provide the
needed breaking or yield to the bands 60 when the slip segments 52 are pushed
against the cone 14.
[0035] The bands 60 can fit in lateral slots on the outside surfaces of the
segments 52.
The bands 60 can be fully or partially constructed and then disposed about the
segments, or the bands 60 can be constructed on the segments 52 disposed in
its
circular arrangement.
[0036] In addition to or instead of bonding the slip segments 52 to one
another,
Figures 5A-5C show alternative arrangements where the slip segments 52 are
bonded
to a component of the downhole tool. In Figure 5A, the slip segments 52 are
bonded to
the mandrel 12 using bonding material 70. Each of the slip segments 52 can be
separately bonded to the mandrel 12 and may have free gaps 55 between their
long
sides. In Figure 5B, ends of the slip segments 52 are bonded to a setting
shoulder 13
(e.g., ring or mule-shoe) of the tool using bonding material 72. In Figure 5C,
the other
ends of the slip segments 52 are bonded to the cone 14 of the tool using
bonding
material 74. The bonding of the slip segments 52 in each of these can be
combined
together in any desired manner, and the slip segments 52 can be bonded to one
another.
[0037] As can be seen in Figures 5A-5C, bonding the slip segments 52 to the
mandrel
12, setting shoulder 13 (e.g., ring or mule-shoe), cone 14, or any combination
of these
together can provide a means of slip retention on the tool. Of course, if
desired, the
sides of the segments 52 can also be bonded in a manner similar to previous
embodiments.
[0038] Finally, as shown in Figure 6, a slip assembly 50 of the present
disclosure can
include a number of metallic slip segments 52. Each segment 52 can comprise
several
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smaller pieces 58 that are bonded together by bonding material 57 to form a
unitary slip
segment 52. In turn, these segments 52 can be bonded together side-by-side
using
another bonding material 56 to form one complete slip assembly 57. The bonding
material 56 used along the sides of the segments 52 may be relatively weaker
than the
bonding material 57 used for the segment's pieces 58. This arrangement would
also
reduce mill-up time because the slip segments 52 comprised of bonded pieces 58
are
expected to break up easier than single homogenous segments.
[0039] For the embodiments disclosed herein, additional components may be
used in
conjunction with the bonding to retain the slip segments 52 in place
especially during
run-in. For example, pins (not shown) may be used to pin the slip segments 52
to the
mandrel 12. Alternatively, solid bands (not shown) or other external feature
may be
used on the segments 52 and may even be glued in place to hold the segments 52
to
the mandrel 12. As will be appreciated, these and other additional components
can be
used to enhance retention of the segments 52 or at least to provide a failsafe
during
run-in of the tool 10.
[0040] Embodiments disclosed herein have illustrated the cones 14 as has
having flat
ramps so that the segments 52 have comparably configured ramped ends. As will
be
appreciated, this geometry is not strictly necessary because the cones 14 and
segments' ends can have any suitable geometry (e.g., conical, flat ramp,
etc.).
Moreover, any number of slip segments 52 can be used depending on the
implementation.
[0041] 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.
[0042] In exchange for disclosing the inventive concepts contained herein,
the
Applicants desire all patent rights afforded by the appended claims.
Therefore, it is
intended that the appended claims include all modifications and alterations to
the full
extent that they come within the scope of the following claims or the
equivalents thereof.
