Note: Descriptions are shown in the official language in which they were submitted.
SLOTTED BACKUP RING ASSEMBLY
FIELD OF THE INVENTION
[0001/2] The field of the invention is sealing systems for subterranean tools
against tubular or open hole or cased hole and more particularly backup rings
that are disposed at opposed ends of a sealing element assembly to contain the
sealing element against axial extrusion.
BACKGROUND OF THE INVENTION
[0003] In the unconventional drilling and completion industry, oil and
gas
deposits are often produced from tight reservoir formations through the use of
fracturing and frack packing methods. To frack a well involves the high
pressure and high velocity introduction of water and particulate media,
typically a sand or proppant, into the near wellbore to create flow paths or
conduits for the trapped deposits to flow to surface, the sand or proppant
holding the earthen conduits open. Often, wells have multiples of these
production zones. Within each production zone it is often desirable to have
multiple frack zones. For these operations, it is necessary to provide a seal
known as a frack packer, between the outer surface of a tubular string and the
surrounding casing or borehole wall, below the zone being fractured, to
prevent the pumped fluid and proppant from travelling further down the
borehole into other production zones. Therefore, there is a need for multiple
packers to provide isolation both above and below the multiple frack zones.
[0004] A packer typically consists of a cylindrical elastomeric element
that is compressed axially, or set, from one end or both by gages within a
backup system that cause the elastomer to expand radially and form a seal in
the annular space. Gages are compressed axially with various setting
mechanisms, including mechanical tools from surface, hydraulic pistons,
atmospheric chambers, etc. Setting typically requires a fixed end for the
gages
to push against. These fixed ends are often permanent features of a mandrel
1
Date Recue/Date Received 2021-08-03
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
but can include a dynamic backup system. When compressed, the elastomeric
seal has a tendency to extrude past the gages. Therefore, anti-extrusion
backups have become common in the art. However, typical elastomeric seals
maintain the tendency to extrude through even the smallest gaps in an anti-
extrusion backup system.
100051 In cased-hole applications, anchoring of compression set packers
is
a common feature in the completion architecture. Anchoring is provided by
wedge-shaped slips with teeth that ride up ramps or cones and bite into the
casing before a packer is set. These systems are not part of the backup system
nor are they designed to provide anti-extrusion. Often they are used in the
setting of the packer to center the assembly which lowers the amount of axial
force needed to fully set the elastomer seal. Once set, anchoring systems are
also useful for the life of the packer to provide a uniform extrusion gap,
maintain location and help support the weight of a bottom-hole assembly in
the case of coiled tubing frack jobs. Anchors also prevent tube movement in
jointed strings resulting from the cooling of the string by the frack fluid.
Movement of the packers can cause them to leak and lose seal.
100061 In open-hole frack pack applications it is rarer for the packer to
have anchoring mechanisms, as the anchor teeth create point load locations
that can overstress the formation, causing localized flow paths around the
packer through the near well-bore. However, without anchors, movement from
the base pipe tubing can further energize the elastomeric seal. Energizing the
seal from tube movement tends to overstress the near wellbore as well, leading
to additional overstressing of the wellbore, allowing communication around
the packer, loss of production, and potential loss of well control to surface.
However, the art of anchoring has been reintroduced in new reservoirs in
deep-water open-hole fracking operations. The current state of the art in open-
hole frack pack operations requires a choice between losing sealing due to
anchor contact induced fractures, packer movement, or over-energizing of the
elastomeric element.
[0007] Extrusion barriers involving tapers to urge their movement to
block
an extrusion path for a sealing element have been in use for a long time as
evidenced by US 4204690. Some designs have employed tapered surfaces to
urge the anti-extrusion ring into position by wedging them outwardly as in US
2
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
6598672 or in some cases inwardly as in US 8701787. Other designs simply
wrap thin metal rings at the extremities of the sealing element that are
designed to contact the surrounding tubular to create the anti-extrusion
barrier.
Some examples of these designs are US 8479809; US 7708080; US
2012/0018143 and US 2013/0147120. Of more general interest in the area of
extrusion barriers are US 9140094 and WO 2013/128222.
100081 These solid rings used in the past against the ends of the sealing
element assembly still had issues with preventing axial extrusion and provided
a great deal of resistance in the setting process. Accordingly, a backup ring
with axial slots having rounded ends was developed where the slots go part
way down the cylindrical portion of the backup ring assembly and the cross-
sectional shape of the cylindrical portion is tapered down in a direction
toward
the free end of the cylindrical portion. The face opposite the contact face
with
the sealing element is abutted to a sloping surface to allow the backup ring
to
ride up radially away from the mandrel during the setting. The tapered
segment flexes toward the surrounding tubular during setting movement and
the remainder of the cylindrical portion then arrives to contact the
surrounding
tubular. The non-slotted portion of the cylindrical shape acts as a barrier
against the surrounding tubular. A seal on an adjacent wedge ring that is
against the mandrel ultimately stops axial extrusion along the mandrel.
100091 In some applications the gap across which the seal is expected to
function is quite large placing such applications beyond the limits of the
design in US 6598672. There is a need for an extended reach design that can
withstand the pressure differentials. This need is addressed with a wedge
shaped extrusion ring assembly that, depending on the gap to be spanned is
pushed on opposing ramps along a pedestal ring for extended reach when
contacted by an outer support ring. To fixate the extrusion ring in the
extended
position an outer support rim also moves into contact with the extrusion ring
in its extended position on the pedestal ring. In the extended reach
configuration of the extrusion ring, the backup ring moves part way toward the
surrounding tubular or borehole. In shorter reach applications the extrusion
ring can move out to the surrounding tubular or borehole wall on one side of
the pedestal ring and the outer support ring is eliminated. The backup ring is
wedged against the surrounding borehole wall to allow it to act as an anchor
3
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
for the plug that has the sealing system. In the extended reach configuration
the reaction forces from the extrusion ring are directed into the abutting
backup ring and into the setting system so that the backup ring is prevented
from being squeezed out of its wedged position against the pedestal ring. The
present invention is focused on the extrusion ring abutting the ends of the
sealing element and the various features and movement of that ring to provide
reliable barrier against extrusion along the borehole wan. These and other
aspects of the present invention will be more readily apparent to those
skilled
in the art from a review of the description of the preferred embodiment and
the
associated drawings while understanding that the full scope of the invention
is
to be found in the appended claims.
SUMMARY OF THE INVENTION
100101 A sealing element is flanked by wedge-shaped extrusion ring
assemblies. The extrusion rings are continuous for 360 degrees and are slotted
from the outside dimension and alternatively from the inside dimension to
allow the diameter to increase to the surround tubular or open hole. The
extrusion rings climb a ramp on an adjacent pedestal ring on the way out to
the
borehole wall. Depending on the dimension of the gap to be spanned the
extrusion ring slides a variable distance up the pedestal ring ramp. An
optional
anchor ring is initially forced up an opposite ramp of the pedestal ring. If
the
sealing gap is short the anchor ring can be eliminated. For larger gaps the
anchor ring moves out far enough toward the borehole wall to contact the
extrusion ring located on an opposing ramp of the pedestal ring so that
reaction forces are directed to keep the anchor ring wedged in position for
support of the extrusion ring assembly.
100111 A unique backup ring against ends of a sealing element features
axial slots extending part way along a cylindrical segment of the backup ring.
The slots end in rounded openings to relieve stress and a part of the
cylindrical
shape of the backup ring is solid. The slotted end of the cylindrical portion
is
tapered in section toward the end overlapping the sealing element. The face of
the backup ring away from the sealing element is tapered and rides on an
adjacent tapered surface away from the mandrel during the setting. The
tapered seal end of the backup ring bends to reach the surrounding tubular
before the balance of the cylindrical portion reaches the surrounding tubular.
4
Extrusion along the mandrel is stopped by a mandrel seal on an adjacent
wedge ring. The mandrel end of the backup ring has a peripheral stiffener to
lend rigidity.
[0011a] An extrusion barrier assembly for a mandrel mounted sealing
element assembly of a borehole isolation device comprises: at least one
extrusion barrier ring surrounding the mandrel and initially abutting and
radially overlapping at least one end of the sealing element assembly, said
extrusion barrier ring comprising: a cylindrically shaped segment having a
first axial end and a second axial end, and which initially overlaps the
sealing
element assembly and features at least one axially oriented slot, said at
least
one axially oriented slot, including any opening through a thickness of the
cylindrically shaped segment that is an extension of the slot, being shorter
than
an axial length of said cylindrically shaped segment; and a frustoconical
segment extending from the first axial end of the cylindrically shaped
segment, the cylindrically shaped segment having a first cross sectional
thickness at the first axial end and a second cross sectional thickness at the
second end, the thickness continuously diminishing from the first end to the
second end.
[0011b] An extrusion barrier assembly for a mandrel mounted sealing
element assembly of a borehole isolation device comprises: at least one
extrusion barrier ring surrounding the mandrel and initially abutting and
radially overlapping at least one end of the sealing element assembly, said
extrusion barrier ring comprising a cylindrically shaped segment which
initially overlaps the sealing element assembly and a frustoconical segment
extending from the cylindrically shaped segment, the cylindrically shaped
segment being continuously tapered in cross-section axially along said
cylindrically shaped segment, said barrier further including at least one
slot,
said at least one slot, including any opening through a thickness of the
cylindrically shaped segment that is an extension of the slot, being shorter
than
an axial length of said cylindrically shaped segment.
[00110 A treatment method using a borehole isolation device comprising
an extrusion barrier assembly for a mandrel mounted sealing element
assembly comprises: providing at least one extrusion barrier ring surrounding
the mandrel and initially abutting and radially overlapping at least
Date Recue/Date Received 2021-08-03
one end of the sealing element assembly, said extrusion barrier ring
comprising a cylindrically shaped segment which initially overlaps the sealing
element assembly and features at least one axially oriented slot, said at
least
one axially oriented slot, including any opening through a thickness of the
cylindrically shaped segment that is an extension of the slot, being shorter
than
an axial length of said cylindrically shaped segment said cylindrically shaped
segment having a continuously tapering cross section along its axial length
and a frustoconical segment extending from the cylindrically shaped segment;
and performing a treatment against said sealing element assembly into at least
one formation adjacent the borehole.
[0011d] A treatment method using a borehole isolation device comprising
an extrusion barrier assembly for a mandrel mounted sealing element
assembly comprises: providing at least one extrusion barrier ring surrounding
the mandrel and initially abutting and radially overlapping at least one end
of
the sealing element assembly, said extrusion barrier ring comprising a
cylindrically shaped segment which initially overlaps the sealing element
assembly, said cylindrically shaped segment further including at least one
slot,
said at least one slot, including any opening through a thickness of the
cylindrically shaped segment that is an extension of the slot, being shorter
than
an axial length than said cylindrically shaped segment, the cylindrically
shaped segment being continuously tapered in cross-section axially along said
cylindrically shaped segment and a frustoconical segment extending from the
cylindrically shaped segment; and performing a treatment against said sealing
element assembly into at least one formation adjacent the borehole.
5a
Date Recue/Date Received 2021-08-03
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. la is a prior art perspective view of split extrusion rings
keyed
together with splits opposed at 180 degrees shown in the run in condition;
[0013] FIG. lb is the view of FIG. la in the expanded condition showing
the size increase for the split in the adjacent rings;
[0014] FIG. 2 is a section view in the run in position for a long reach
embodiment;
[0015] FIG. 3 is the view of FIG. 2 in the set position;
[0016] FIG. 4a is a perspective view of the extrusion ring in the run in
position;
[0017] FIG. 4b is the view of FIG. 4a in the set position;
[0018] FIG. 5 is a side view of a backup ring that is located next to a
sealing element;
[0019] FIG. 6 is a perspective view of an optional anchoring ring shown
in
the run in condition;
[0020] FIG. 7 is a section view of a short reach embodiment in the run
in
position;
[0021] FIG. 8 is the view of FIG. 7 in the set position;
[0022] FIG. 9 is a perspective view of FIG. 3;
[0023] FIG. 10 is a section view of the backup showing its axial slots;
[0024] FIG. 11 is a perspective view of the ring of FIG. 10;
[0025] FIG. 12 is a section view of a sealing assembly with the backup
ring of FIG. 10 in the run in position;
[0026] FIG. 13 is the view of FIG. 12 during the setting;
[0027] FIG. 14 is the view of FIG. 13 after the setting is complete;
[0028] FIG. 15 is a detailed view of circle D in FIG. 14;
[0029] FIG. 16 is an outside view of the assembly shown in FIG. 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] To appreciate the benefits of the present invention it is
necessary to
review the state of the art in compression set element extrusion barriers. The
sealing element design is typically one or more rubber sleeves that are
axially
5b
Date Recue/Date Received 2021-08-03
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
compressed against a surrounding tubular. Extrusion barriers can be one or
more layers of flexible thin sheet located at an end of a sealing assembly. As
the sealing element deforms due to axial compression the extrusion barrier
rings such as item 64 in US 5311938 bends with the end of sealing element
and makes contact with the opposing wall to bridge the sealing gap with the
idea that the rubber is prevented from extruding axially. While serviceable
this
design has issues in releasing which sometimes led to the packer getting stuck
even when the sealing element extended and relaxed but the extrusion ring did
not relax.
100311 FIG. 1 a shows another extrusion barrier ring assembly using a
pair
of split rings 10 and 12 that have splits 14 and 16 respectively. The rings 10
and 12 are keyed to prevent relative rotation to keep the splits 14 and 16
spaced 180 degrees apart. When the sealing element is axially compressed
these rings are moved out radially on a ring with a taper to contact the
surrounding tubular as the gaps 14 and 16 get substantially larger. The
enlarged gaps still created issues for rubber extrusion for the sealing
element
particularly in high pressure high temperature applications. With pressure
differentials of over 10,000 PSI extrusion past assemblies shown in FIGS. la
and lb was still a significant concern.
100321 The present invention addresses this concern in high temperature
and high pressure applications by the creation and application of a 360
expandable ring design featuring alternating inner and outer radially oriented
slits. For low and medium reach the expandable ring rides up a wedge ring
until the surrounding tubular or the open hole borehole is contacted. In high
reach application an outer expandable ring of a similar design rides on an
opposite side of a wedge ring until forced into supporting contact of the
principal expandable ring pushing the principal expandable ring against the
surrounding borehole or tubular. The expandable rings can be made of Teflon
or another flexible material that is sufficiently resilient while resistant to
high
temperatures and well fluids.
100331 FIG. 2 shows the basic layout for a long reach application.
Sealing
element 20 can optionally have a filler ring 22 in the center. The assemblies
on
opposed ends of the element 20 are preferably mirror image and so they will
be described only for one side with the understanding that the opposed side is
6
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
an identical mirror image. An extrusion barrier in the form of an expanding
ring 24 is attached to the element 20 and is sufficiently flexible to move
with
it. FIG. 5 shows a section view of the bonded expanding ring 24. Ring 24
prevents the sealing element from escaping the cut slots of ring 34 and better
conformability to the casing inside diameter or the borehole wall 54. It could
be made of non-metallic material or very ductile metallic material.
100341 It has sides 26, 28 and 30 against seal 20 and a ramp surface 32.
Inner expandable ring 34 rides on ramp 32 on one side and ramp 36 of ramp
ring 38. Ring 38 has another ramp 40 opposite ramp 36 on which rides outer
expandable ring 42. Ramp 44 on outer expandable ring 42 rides on ramp 40 of
ring 38. On the other side ramp 46 rides on ramp 48 of setting ring 50. The
setting sequence results from relative movement between rings 50 and 52.
Usually one is moving while the other is stationary. FIG. 3 shows the result
of
the relative movement. The element 20 is up against the borehole wall or
surrounding tubular 54 as is the adjacent ring 24. Ring 38 has shifted toward
element 20 by going under ring 24 that is continuously supported for 360
degrees by expandable ring 34. Inner expandable ring 34 has moved against
the borehole wall or tubular 54 by sliding along opposed ramp surfaces 32 and
36. The outer expandable ring 42 has moved out on ramps 40 and 48 until its
surface 56 engages surface 58 of inner expandable ring 34 to wedge it against
the borehole wall or tubular 54. The new relative position of rings 50 and 52
can be releasably locked to hold the FIG. 3 set position until it is time to
retrieve the packer. The abutting of rings 42 and 34 allows ring 34 to travel
further out radially than in the FIG. 8 embodiment which is otherwise the
same except outer expandable ring 42 is not shown because the required radial
movement in FIG. 8 is much less than in FIG. 3. As a result in FIG. 8 the
inner
expandable ring 34 simply rides out on ramps 36 and 32 until contact is made
with the borehole wall or tubular 54. Ring 38 abuts ring 50 and does not go
under ring 24 as in FIG. 3. The reach in FIG. 8 is much shorter than in FIG.
3.
100351 FIGS. 4a and 4b show ring 34 in the run in and the set positions
respectively. An outer face 60 continues along a tapered surface 62 to
internal
surface 64 seen as the inner parallel surface of a trapezoidal section in FIG.
3
and a continuous line in perspective in the views of FIG. 4. Slots 66
circumferentially alternate with slots 68 and are radially oriented to
preferably
7
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
align with the center of ring 34. Slots 66 start at the outer face 60 and
slots 68
start at the surface 64. Slots 68 end in a transverse segment 70 and slots 66
end
in a transverse segment 72. The transverse segments are there to limit stress
as
the slots 66 and 68 open up as the sealing element 20 is set against the
borehole wall or tubular 54. Outer expandable ring 42 is shown in perspective
in FIG. 6 and essentially has a similar slot configuration as described in
FIGS.
4a and 4b with the section profile being different as shown in FIGS. 2 and 3.
However it is the same continuous 360 degree design for the ring 42 as the
ring 34 with alternating slots with transverse end portions that start from
opposing ends of the ring structure. Specifically, slots 80 and 82 start
respectively at outer face 84 and inner dimension 86 seen as a ring in FIG. 6
and as a flat in section in FIG. 2. The slots extend radially and preferably
in
alignment with the center of ring 42. Alternatively the slots can extend
axially
but radially is preferred. At the respective ends of slots 80 and 82 are
transverse ends 88 and 90. As ring 42 expands from the FIG. 2 to the FIG. 3
position, the slots 80 and 82 open up to allow the diameter to increase until
surface 56 hits surface 58 of inner expandable ring 34 as shown in FIG. 3.
100361 Rings 34 and 40 can be Teflon, metallic, composite to name a few
examples. The shape can be created with lasers or wire EDM fabrication
methods. Although in FIGS. 2 and 3 a single inner ring 34 and outer ring 40
are illustrated multiple pairs of such rings that function in the same way can
be
used. In the case of FIGS. 7 and 8 multiple pairs of expandable ring 36 and
ramp ring 38 can be used and they can operate in the same manner as
illustrated for a single such pair of rings as shown in FIGS. 7 and 8. The 360
degree design for rings 34 and 42 combined with solid expandable ring 24,
which prevents the rubber element 20 from escaping through cut slots in ring
34 and improves conformance to tubular or borehole inside diameter
dramatically reduces extrusion of seal 20 even though the slots expand for the
lamer set position. The 360 degree feature of the rings 34, 42 and 24, if
used,
limit the extrusion gaps and allow a given sealing system 20 to be serviceable
in higher pressure differential applications without extrusion risk. The
design
is modular so that it is simple to switch between the FIG. 2 and FIG. 7
configurations for different applications. The ring 42 backing up the ring 34
wedges ring 34 in the FIG. 3 set position wedges in ring 34 to hold it in
8
CA 03069867 2020-01-13
WO 2019/014482
PCT/US2018/041880
position against high differential pressures that can exceed 10,000 PSI. The
slot ends can be a transverse slot or an enlarged rounded end or other shape
that limit stress concentration at the ends of the radial slots.
100371 A preferred design for backup ring 24' is shown in FIGS. 10 and
Ii. It features a cylindrically shaped component 100 that transitions to a
tapered segment 102 that ends at an enlarged end 104 that turns inwardly
toward mandrel 105 shown in FIG 8. The cylindrically shaped component is
tapered to its minimum thickness at end 106. An array of slots 108 start at
end
106 and extend generally axially to rounded ends 110 that are there to reduce
stress concentration at the ends of slots 108, The slots 108 are preferably
equally spaced and of uniform width. and length. The preferred length is less
than half of the axial length of the cylindrically shaped component 100. The
tapered section allows greater flexibility near end 106 during the setting as
shown in FIG. 13 such that end 106 and some of the adjacent cylindrically
shaped segment 100 that has slots 108 makes initial contact with the
surrounding borehole wall 112, As the setting movement continues the
cylindrically shaped component 100 continues to make contact with the
borehole wall 112 past the rounded ends 110 of slots 108 so that a slot free
segment of the cylindrically shaped component then makes contact with the
borehole wall 112. The slots 108 make the end 106 more flexible to allow
early initial movement toward the borehole wall 112 with reduced radial
pushing force so that the end 106 is preferably already in contact with the
borehole wall 112 before the internal pressure of the sealing assembly 20 get
very high as it is axially compressed to be radially extended against the
surrounding borehole wall 112. On thither axial compression of the sealing
assembly 20 the non-slotted portion of the cylindrically shaped segment 100
makes contact with borehole wall 112 to close off axial slots 108 as potential
extrusion paths. As that happens the tapered segment 102 is backed up by ring
34 that has a tapered surface 62 that conforms to the angle of the tapered
segment 102. Enlarged end 104 serves as a stiffening rib near the mandrel 105
but is driven away from mandrel 105 in the set position of FIGS. 14 and 15.
There is a path for the material of seal assembly 29 to pass under wedge ring
38 until that path is closed with a seal 114 against mandrel 105 in groove
116.
9
During the setting the enlarged end 104 contacts wedge ring 38 and rides up
inclined surface 36 of wedge ring 38.
[0038] Backup ring 24' performs markedly better than backup ring 24 in
high
pressure and high temperature applications. One of the reasons is that there
are
slots 108 and a tapered section near end 106. This allows early movement of
end
106 against the borehole wall 112 with the onset of application of the
compressive setting force. The slotted portion of the cylindrically shaped
segment
100 can establish itself against the borehole wall 112 before the internal
pressure
on the sealing element assembly 20 increases significantly so that extrusion
into
the slots 108 can start. While the seal material fills the slots 108 those
slots get
closed off quickly before the internal pressure in the seal material 20
increases
appreciably as the set position is achieved. The contact of the non-slotted
portion
of the cylindrically shaped component 100 with the borehole wall provided
strength due to absence of slots 108 and closure at the rounded slot ends 110
against axial extrusion along the borehole wall 105. At the same time the seal
114
in groove 116 in wedge ring 38 prevents extrusion along mandrel 105 even
though some small part of the seal assembly 20 does move axially under the
wedge ring 38 as shown in FIGS. 14 and 15. FIG. 16 shows the arrangement can
be symmetrical about opposed ends of the sealing element assembly 20.
[0039] The teachings of the present disclosure may be used in a variety
of
well operations. These operations may involve using one or more treatment
agents to treat a formation, the fluids resident in a formation, a wellbore,
and / or
equipment in the wellbore, such as production tubing. The treatment agents may
be in the form of liquids, gases, solids, semi-solids, and mixtures thereof.
Illustrative treatment agents include, but are not limited to, fracturing
fluids,
acids, steam, water, brine, anti-corrosion agents, cement, permeability
modifiers,
drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc.
Illustrative
well operations include, but are not limited to, hydraulic fracturing,
stimulation,
tracer injection, cleaning, acidizing, steam injection, water flooding,
cementing,
etc.
[0040] The above description is illustrative of the preferred embodiment
and
many modifications may be made by those skilled in the art without departing
from the invention whose scope is to be determined from the literal and
equivalent scope of the claims below.
Date Recue/Date Received 2021-08-03
