Note: Descriptions are shown in the official language in which they were submitted.
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DRILLABLE BRIDGE PLUG
BACKGROUND OF INVENTION
Field of the Invention
Embodiments disclosed herein relate generally to methods and apparatus for
drilling and
completing well bores. More specifically, embodiments disclosed herein relate
to methods
and apparatus for a drillable bridge plug.
Background Art
In drilling, completing, or reworking wells, it often becomes necessary to
isolate
particular zones within the well. In some applications, downhole tools, known
as
temporary or permanent bridge plugs, are inserted into the well to isolate
zones. The
purpose of the bridge plug is to isolate some portion of the well from another
portion of
the well. In some instances, perforations in the well in one section need to
be isolated
from perforations in another section of the well. In other situations, there
may be a need to
use a bridge plug to isolate the bottom of the well from the wellhead.
Drillable bridge plugs generally include a mandrel, a sealing element disposed
around the
mandrel, a plurality of backup rings disposed around the mandrel and adjacent
the sealing
element, an upper slip assembly and a lower slip assembly disposed around the
mandrel,
and an upper cone and a lower cone disposed around the mandrel adjacent the
upper and
lower slip assemblies, respectively. Figure 1 shows a section view of a well
10 with a
wellbore 12 having a bridge plug 15 disposed within a wellbore casing 20. The
bridge
plug 15 is typically attached to a setting tool and run into the hole on wire
line or tubing
(not shown), and then actuated with, for example, a hydraulic system. As
illustrated in
Figure I, the wellbore is sealed above and below the bridge plug so that oil
migrating into
the wellbore through perforations 23 will be directed to the surface of the
well.
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The drillable bridge plug may be set by wireline, coil tubing, or a
conventional drill string.
The plug may be placed in engagement with the lower end of a setting tool that
includes a
latch down mechanism and a ram. The plug is then lowered through the casing to
the
desired depth and oriented to the desired orientation. When setting the plug,
a setting tool
pulls upwardly on the mandrel, thereby pushing the upper and lower cones along
the
mandrel. This forces the upper and lower slip assemblies, backup rings, and
the sealing
element radially outward, thereby engaging the segmented slip assemblies with
the inside
wall of the casing. It has been found that once the plug is set, the slip
assemblies may not
be uniformly disposed around the inside wall of the casing. This non-uniform
positions of
the segmented slip assemblies results in uneven stress distribution on the
segmented slip
assemblies and the adjacent cones. An uneven stress distribution may limit the
axial load
capacities of the slip assemblies and casing, and reduce the collapse strength
of the
adjacent cones.
Further, due to the makeup or engagement of the backup rings adjacent the
sealing
element sealing element, the backup rings may provide an extrusion path for
the sealing
element. Extrusion of the sealing element causes loosening of the seal against
the casing
wall, and may therefore cause the downhole tool to leak.
Additionally, it has been found that downhole tools may leak at high pressures
unless they
include a means for increasing the seal energization, such as a pressure
responsive self-
energizing feature. Leakage occurs because even when a high setting force is
used to set
the downhole tool seals, once the setting force is removed, the ratchet system
of the lock
ring will retreat slightly before being arrested by the locking effect created
when the sets
of ratchet teeth mate firmly at the respective bases and apexes of each. This
may cause a
loosening of the seal. Downhole tools are also particularly prone to leak if
fluid pressures
on the packers are cycled from one direction to the other.
When it is desired to remove one or more of these bridge plugs from a
wellbore, it is often
simpler and less expensive to mill or drill them out rather than to implement
a complex
retrieving operation. In milling, a milling cutter is used to grind the tool,
or at least the
outer components thereof, out of the well bore. In drilling, a drill bit or
mill is used to cut
and grind up the components of the bridge plug to remove it from the wellbore.
It has
been found that when drilling up a bridge plug, lower components of the bridge
plug may
no longer engage the mandrel. Thus, as the drill rotates to drill up the plug,
the lower
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components spin or rotate within the well. This spinning or rotation of the
lower
components during drilling of the plug increases the time required to drill up
the plug.
Accordingly, there exists a need for a bridge plug that effectively seals a
wellbore.
Additionally, there exists a need for a bridge plug that may sustain a greater
load capacity
and increases the collapse strength of components of the bridge plug. Further,
a bridge
plug that is easier to drill up is also desired.
SUMMARY OF INVENTION
In one aspect, embodiments disclosed herein relate to a downhole tool for
isolating zones
in a well, the tool including a mandrel, a sealing element disposed around the
mandrel, an
upper cone disposed around the mandrel proximate an upper end of the sealing
element, an
upper slip assembly disposed around the mandrel adjacent a sloped surface of
the upper
cone, a lower cone disposed around the mandrel proximate a lower end of the
sealing
element, a lower slip assembly disposed around the mandrel adjacent a sloped
surface of
the lower cone, two element end rings, a first element end ring disposed
adjacent the upper
end of the sealing element and a second element end ring disposed adjacent the
lower end
of the sealing element, and two element barrier assemblies, each assembly
disposed
adjacent one of the two element end rings.
In another aspect, embodiments disclosed herein relate to a downhole tool for
isolating
zones in a well, the tool including a mandrel, a sealing element disposed
around the
mandrel, two slip assemblies disposed around the mandrel, wherein an upper
slip
assembly is disposed proximate an upper end of the sealing element and a lower
slip
assembly is disposed proximate a lower end of the sealing element, an upper
cone
disposed around the mandrel between the first slip assembly and the upper end
of the
sealing element, and a lower cone disposed around the mandrel between the
first slip
assembly and the lower end of the sealing element, wherein the mandrel
includes a central
bore and wherein a movable bridge is disposed between two stops in the central
bore.
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78543-339
In another aspect, embodiments disclosed herein relate to a downhole tool for
isolating zones
in a well, the tool comprising: a mandrel; a sealing element disposed around
the mandrel; an
upper cone disposed around the mandrel proximate an upper end of the sealing
element; an
upper slip assembly disposed around the mandrel adjacent a sloped surface of
the upper cone;
a lower cone disposed around the mandrel proximate a lower end of the sealing
element; a
lower slip assembly disposed around the mandrel adjacent a sloped surface of
the lower cone;
two element end rings, a first element end ring disposed adjacent the upper
end of the sealing
element and a second element end ring disposed adjacent the lower end of the
sealing
element; and two element barrier assemblies, each assembly disposed adjacent
one of the two
element end rings, wherein at least a portion of the element end rings is
disposed radially
inward of the sealing element.
In another aspect, embodiments disclosed herein relate to a downhole tool for
isolating zones
in a well, the tool comprising: a mandrel; a sealing element disposed around
the mandrel; two
slip assemblies disposed around the mandrel, wherein an upper slip assembly is
disposed
proximate an upper end of the sealing element and a lower slip assembly is
disposed
proximate a lower end of the sealing element; an upper cone disposed around
the mandrel
between the first slip assembly and the upper end of the sealing element; and
a lower cone
disposed around the mandrel between the first slip assembly and the lower end
of the sealing
element, wherein the mandrel comprises a central bore and wherein a sealed
movable bridge
is disposed between two stops in the central bore and configured to move
upwardly and
downwardly in response to a pressure differential.
Other aspects and advantages of the invention will be apparent from the
following description
and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows a section view of a prior art plug assembly as set in a
wellbore.
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Figure 2A is a perspective view of a bridge plug in accordance with
embodiments
disclosed herein.
Figure 2B is a cross-sectional view of a bridge plug in accordance with
embodiments
disclosed herein.
Figure 2C is a cross-sectional view of a bridge plug in accordance with
embodiments
disclosed herein.
Figures 3A and 3B show a sealing element in accordance with embodiments
disclosed
herein.
Figure 4 is a perspective view of a barrier ring in accordance with
embodiments disclosed
herein.
Figures 5A and 5B show perspective views of an upper cone and a lower cone,
respectively, in accordance with embodiments disclosed herein.
Figure 6 shows a partial cross-sectional view of a bridge plug in accordance
with
embodiments disclosed herein.
Figure 7 is a perspective view of a mandrel of a bridge plug in accordance
with
embodiments disclosed herein.
Figure 8 is a perspective view of a slip assembly in accordance with
embodiments
disclosed herein.
Figure 9 is a perspective view of an upper gage ring in accordance with
embodiments
disclosed herein.
Figure 10 is a perspective view of a lower gage ring in accordance with
embodiments
disclosed herein.
Figure 11 is a partial cross-sectional view of an assembled slip assembly,
upper cone, and
element barrier assembly in accordance with embodiments disclosed herein.
Figure 12 is a cross-sectional view of a bridge plug in an unexpanded
condition in
accordance with embodiments disclosed herein.
Figure 13 is a cross-sectional view of the bridge plug of Figure 12 in an
expanded
condition in accordance with embodiments disclosed herein.
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Figure 14 is a partial cross-sectional view of a bridge plug in accordance
with
embodiments disclosed herein.
Figure 15 is a cross-sectional view of a sealing element in accordance with
embodiments
disclosed herein.
Figure 16 is a multi-angle view of a frangible backup ring in accordance with
embodiments disclosed herein.
Figure 17 is a multi-angle view of a barrier ring in accordance with
embodiments
disclosed herein.
DETAILED DESCRIPTION
In one aspect, embodiments disclosed herein relate generally to a downhole
tool for
isolating zones in a well. In certain aspects, embodiments disclosed herein
relate to a
downhole tool for isolating zones in a well that provides efficient sealing of
the well. In
another aspect, embodiments disclosed herein relate to a downhole tool for
isolating zones
in a well that may be more quickly drilled or milled up. In certain aspects,
embodiments
disclosed herein relate to bridge plugs and frac plugs.
Like elements in the various figures are denoted by like reference numerals
for
consistency.
Referring now to Figures 2A and 2B, a bridge plug 100 in accordance with one
embodiment of the present disclosure is shown in an unexpanded condition, or
after
having been run downhole but prior to setting it in the wellbore. The
tmexpanded
condition is defined as the state in which the bridge plug 100 is run
downhole, but before a
force is applied to axially move components of the plug 100 and radially
expand certain
components of the plug 100 to engage a casing wall. As shown, bridge plug 100
includes
a mandrel 101 having a central axis 122, about which other components of the
plug 100
are mounted. The mandrel 101 includes an upper end A and a lower end B,
wherein the
upper end A and lower end B of the mandrel 101 include a threaded connection
(not
shown), for example, a taper thread. The lower end B of the mandrel 101 also
includes a
plurality of tongues 120 disposed around the lower circumference of the
mandrel 101.
In one embodiment, mandrel 101 includes a bridge 103 integrally formed with
the mandrel
101. As shown in Figure 2B, the bridge 103 is formed between two internal
bores 105,
CA 02648116 2008-12-30
107 formed in the mandrel 101 and disposed proximate an upper cone 110 when
the
bridge plug 100 is assembled. In this embodiment, upper internal bore 105 has
a diameter
greater that lower internal bore 107. Pressure applied from above the bridge
plug 100
provides a collapse pressure on the mandrel, whereas pressure applied from
below the
bridge plug 100 provides a burst pressure on the mandrel 101.
In an alternate embodiment, as shown in Figure 2C, mandrel 101 is formed with
a single
bore 109 having a substantially constant diameter along the length of the
mandrel 101. In
this embodiment, an upper stop block 115 is disposed in the bore 109. In one
embodiment, the upper stop block 115 is a solid cylindrical component
sealingly engaged
with an inner wall of the mandrel and disposed proximate an upper end of the
sealing
element 114. Alternatively, the upper stop block 115 may be a hollow
cylindrical
component, or a cylindrical component with a bore therethrough, sealingly
engaged with
the inner wall of the mandrel. A movable bridge 111 is disposed in the bore
109 below the
upper stop block 115. A sealing element 113, for example, an elastomeric ring
or o-ring,
is disposed around the moveable bridge 111, such that the sealing element 113
and the
outer surface of the moveable bridge 111 provide a seal against the inner wall
of the
mandrel 101. A lower stop block 117 is disposed below the moveable bridge 111.
As
shown, lower stop block 117 is formed by a change in the inner diameter of the
mandrel
101. As such, in this embodiment, lower stop block 117 is a bearing shoulder.
In alternate
embodiment, upper stop block 115 may be a similar bearing shoulder, while
lower stop
block 117 is a solid cylindrical component or a cylindrical component with a
bore
therethrough, sealingly engaged with the inner wall of the mandrel.
When a pressure differential is applied to the bridge plug 100, the movable
plug 111
moves upward or downward in the mandrel 101 between the upper and lower stop
blocks
115, 117. Thus, the movable plug 111 acts like a piston moving within a piston
housing,
i.e., the mandrel 101. Movement of the movable plug 111 with respect to the
applied
pressure may reduce the differential pressure across the cross-section of the
mandrel 101
proximate a sealing element 114 or may provide a burst pressure on the mandrel
101.
Sealing element 114 is disposed around the mandrel 101. The sealing element
114 seals
an annulus between the bridge plug 100 and the casing wall (not shown). The
sealing
element 114 may be formed of any material known in the art, for example,
elastomer or
rubber. Two element end rings 124, 126 are disposed around the mandrel 101 and
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proximate either end of sealing element 114, radially inward of the sealing
element 114, as
shown in greater detail in Figures 3A and 3B. In one embodiment, sealing
element 114 is
bonded to an outer circumferential area of the element end rings 124, 126 by
any method
know in the art. Alternatively, the sealing element 114 is molded with the
element end
rings 124, 126. The element end rings 124, 126 may be solid rings or small
tubular pieces
formed from any material known in the art, for example, a plastic or composite
material.
The element end rings 124, 126 have at least one groove or opening 128 formed
on an
axial face and configured to receive a tab (not shown) formed on the end of an
upper cone
110 and a lower cone 112, respectively, as discussed in greater detail below.
One of
ordinary skill in the art will appreciate that the number and location of the
grooves 128
formed in the element end rings 124, 126 corresponds to the number and
location of the
tabs (not shown) formed on the upper and lower cones 110, 112.
Bridge plug 100 further includes two element barrier assemblies 116, each
disposed
adjacent an end of the sealing element 114 and configured to prevent or reduce
extrusion
of the sealing element 114 when the plug 100 is set. Each element barrier
assembly 116
includes two barrier rings. As shown in Figure 4, a barrier ring 318 in
accordance with
embodiments disclosed herein, is a cap-like component that has a cylindrical
body 330
with a first face 332. First face 332 has a circular opening therein such that
the barrier ring
318 is configured to slide over the mandrel 101 into position adjacent the
sealing element
114 and the element end ring 124, 126. At least one slot 334 is formed in the
first face
332 and configured to align with the groves 128 formed in the element end
rings 124, 126
and to receive the tabs formed on the upper and lower cones 110, 112. One of
ordinary
skill in the art will appreciate that the number and location of the slots 334
formed in the
first face 332 of the barrier ring 318 corresponds to the number and location
of the grooves
128 formed in the element end rings 124, 126 and the number and location of
the tabs (not
shown) formed on the upper and lower cones 110, 112.
Barrier rings 318 may be formed from any material known in the art. In one
embodiment,
barrier rings 318 may be formed from an alloy material, for example, aluminum
alloy. A
plurality of slits 336 are disposed on the cylindrical body 330 of the barrier
ring 318, each
slit 336 extending from a second end 338 of the barrier ring 318 to a location
behind the
front face 332, thereby forming a plurality of flanges 340. When assembled,
the two
barrier rings 318 of the backup assembly (116 in Figure 2B) are aligned such
that the slits
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336 of the first barrier ring are rotationally offset from the slits 336 of
the second barrier
ring. Thus, when the bridge plug (100 in Figure 2B) is set, and the components
of the
bridge plug are compressed, the flanges 340 of the first and second barrier
rings radially
expand against the inner wall of the casing and create a circumferential
barrier that
prevents the sealing element (114 in Figure 2B) from extruding.
Referring back to Figures 2A and 2B, bridge plug 100 further includes upper
and lower
cones 110, 112 disposed around the mandrel 101 and adjacent element barrier
assemblies
116. The upper cone 110 may be held in place on the mandrel 101 by one or more
shear
screws (not shown). In some embodiments, an axial locking apparatus (not
shown), for
example lock rings, are disposed between the mandrel 101 and the upper cone
110, and
between the mandrel 101 and the lower cone 112. Additionally, at least one
rotational
locking apparatus (not shown), for example keys, may be disposed between the
mandrel
101 and the each of the upper cone 110 and the lower cone 112, thereby
securing the
mandrel 101 in place in the bridge plug 100 during the drilling or milling
operation used to
remove the bridge plug. An upper slip assembly 106 and a lower slip assembly
108 are
disposed around the mandrel 101 and adjacent the upper and lower cones 110,
112,
respectively. The bridge plug 100 further includes an upper gage ring 102
disposed
around the mandrel 101 and adjacent the upper slip assembly 106, and a lower
gage ring
104 disposed around the mandrel 101 and adjacent the lower slip assembly 108.
Referring now to Figures 5A and 5B, upper and lower cones 110, 112 have a
sloped outer
surface 442, such that when assembled on the mandrel, the outer diameter of
the cone 110,
112 increases in an axial direction toward the sealing element (114 in Figure
2B). Upper
and lower cones 110, 112 include at least one tab 444 formed on a first face
446. The at
least one tab 444 is configured to fit in a slot (334 in Figure 4) formed in a
first face (332)
of the barrier rings (318) of the element barrier assembly (116 in Figure 2B)
and to engage
the grooves (128 in Figure 3B) in the element end rings (124, 126). One of
ordinary skill
in the art will appreciate that the number and location of tabs 444
corresponds to the
number and location of the slots (334) formed in the first face (332) of the
barrier ring
(318) and the number and location of the grooves (128) formed in the element
end rings
(124, 126).
Briefly referring back to Figure 2B, the engaged tabs (444 in Figure 6) of the
upper and
lower cones 110, 112 rotationally lock the upper and lower cones 110, 112,
with the upper
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CA 02648116 2008-12-30
and lower element barrier assemblies 116 and the element end rings 124, 126.
Thus,
during a drilling/milling process, i.e. drilling/milling the bridge plug out
of the casing, the
cones 110, 112, element barrier assemblies 116, and sealing element 114 are
more easily
and quickly drilled out, because the components do not spin relative to one
another.
Referring back to Figures 5A and 5B, upper and lower cones 110, 112 are formed
of a
metal alloy, for example, aluminum alloy. In certain embodiments, upper and
lower cones
110, 112 may be formed from a metal alloy and plated with another material.
For
example, in one embodiment, upper and lower cones 110, 112 may be copper
plated. The
present inventors have advantageously found that copper plated cones 110, 112
reduce the
friction between components moving along the sloped surface 442 of the cones
110, 112,
for example, the slip assemblies (106, 108 in Figure 2B), thereby providing a
more
efficient and better-sealing bridge plug (100).
As shown in Figure 6, lower cone 112 has a first inside diameter D1 and a
second inside
diameter D2, such that a bearing shoulder 448 is formed between the first
inside diameter
D1 and the second inside diameter D2. The bearing shoulder 448 corresponds to
a
matching change in the outside diameter of the mandrel 101, such that during a
drilling or
milling process, the mandrel 101 stays in position within the bridge plug 100.
In other
words, the bearing shoulder 448 prevents the mandrel from falling out of the
bridge plug
100 during a drilling or milling process.
Briefly referring back to Figure 5B, lower cone 112 includes at least one
axial slot 450
disposed on an inner surface. At least one key slot (154 in Figure 7) is also
formed on an
outer diameter of the mandrel 101. When the lower cone 112 is disposed around
the
mandrel 101, the axial slot 450 and the key slot 154 are aligned and a
rotational locking
key (not shown) is inserted into the matching slots of the lower cone 112 and
the mandrel
101. Thus, when inserted, the rotational locking key rotationally lock the
lower cone 112
and the mandrel 101 during a drilling/milling process, thereby preventing the
relative
moment of one from another. One of ordinary skill in the art will appreciate
that the key
and key slots may be of any shape known in the art, for example, the key and
corresponding key slot may have square cross-sections or any other shape cross-
section.
Further, one of ordinary skill in the art will appreciate that the rotational
locking key may
be formed of any material known in the art, for example, a metal alloy.
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Referring generally to Figures 2A and 2B, upper and lower slip assemblies 106,
108 are
disposed adjacent upper and lower cones 110 and 112. Upper and lower gage
rings 102
and 104 are disposed adjacent to and engage upper and lower slip assemblies
106, 108.
Referring now to Figure 8, in one embodiment, upper and lower slip assemblies
include a
frangible anchor device 555. Frangible anchor device 555 is a cylindrical
component
having a first end 559 and a second end 561. A plurality of castellations 557
is formed on
the first end 559. The plurality of castellations 557 is configured to engage
a
corresponding plurality of castellations 662, 664 on upper and lower gage
rings 102, 104,
respectively (see Figures 9 and 10).
The second end 561 of the frangible anchor device 555 has a conical inner
surface 565
configured to engage the sloped outer surfaces 442 of the upper and lower
cones 110, 112
(see Figures 5A and 5B). Further, at least two axial slots 563 are formed in
the second end
561 that extend from the second end 561 to a location proximate the
castellations 557 of
the first end 559. The axial slots 563 are spaced circumferentially around the
frangible
anchor device 555 so as to control the desired break-up force of the frangible
anchor
device 555. A plurality of teeth 571, sharp threads, or other configurations
known in the
art are formed on an outer surface of frangible anchor device 555 and are
configured to
grip or bite into a casing wall. In one embodiment, frangible anchor device
555, including
teeth, is formed of a single material, for example, cast iron.
In alternate embodiments, as shown in Figure 11, slip assemblies 106, 108
include slips
567 disposed on an outer surface of a slip base 569. Slips 567 may be
configured as teeth,
sharp threads, or any other device know to one of ordinary skill in the art
for gripping or
biting into a casing wall. In certain embodiments, slip base 569 may be formed
from a
readily drillable material, while slips 567 are formed from a harder material.
For example,
in one embodiment, the slip base 569 is formed from a low yield cast aluminum
and the
slips 567 are formed from cast iron. One of ordinary skill in the art will
appreciate that
other materials may be used and that in certain embodiments the slip base 569
and the
slips 567 may be formed from the same material without departing from the
scope of
embodiments disclosed herein.
Figure 11 shows a partial perspective view of an assembly of the upper slip
assembly 106,
upper cone 110, and element barrier assembly 116. As shown, the conical inner
surface
565 of slip base 569 is disposed adjacent the sloped surface 442 of the upper
cone 110.
CA 02648116 2008-12-30
Slips 567 are disposed on an outer surface of the slip base 569. Tabs 444
formed on a
lower end of upper cone 110 are inserted through slots 334 in each of the two
barrier rings
318 that form element barrier assembly 116. As shown, the slip assembly 106
may
provide additional support for the sealing element (114 in Figure 2), thereby
limiting
extrusion of the sealing element.
Referring now to Figure 9, the upper gage ring 102 includes a plurality of
castellations 662
on a lower end. As discussed above, the plurality of castellations 662 are
configured to
engage the plurality of castellations 557 of the upper and lower slip
assemblies 106, 108,
for example, the frangible anchor device 555 (see Figure 8). The upper gage
ring 102
further includes an internal thread (not shown) configured to thread with an
external thread
of an axial lock ring (125 in Figure 2B) disposed around the mandrel (101 in
Figure 2).
Referring generally to Figure 2B, the axial lock ring 125 is a cylindrical
component that
has an axial cut or slit along its length, an external thread, and an internal
thread. As
discussed above, the external thread engages the internal thread (not shown)
of the upper
gage ring 102. The internal thread of the axial lock ring 125 engages an
external thread of
the mandrel 101. When assembled, the upper gage ring 102 houses the axial lock
ring.
Referring now to Figure 10, the lower gage ring 104 includes a plurality of
castellations
664 on an upper end 668. As discussed above, the plurality of castellations
664 are
configured to engage the plurality of castellations 557 of the upper and lower
slip
assemblies 106, 108, for example, frangible anchor device 555 (see Figure 8).
A box
thread (not shown) is formed in a lower end 670 of the lower gage ring 104 and
configured
to engage a pin thread on an upper end of a second mandrel when using multiple
plugs. In
one embodiment, the box thread may be a taper thread. A box thread (not shown)
is also
formed in the upper end 668 of the lower gage ring 104 and configured to
engage a pin
thread on the lower end B of the mandrel 101 (see Figure 2B). During a
drilling/milling
process, the lower gage ring 104 will be released and fall down the well,
landing on a top
of a lower plug. Due to the turning of the bit, the lower gage ring 104 will
rotate as it falls
and make up or threadedly engage the mandrel of the lower plug.
Referring generally to Figures 2-11, after the drillable bridge plug 100 is
disposed in the
well in its desired location, the bridge plug 100 is activated or set using an
adapter kit.
The plug 100 may be configured to be set by wireline, coil tubing, or
conventional drill
string. The adapter kit mechanically pulls on the mandrel 101 while
simultaneously
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CA 02648116 2008-12-30
pushing on the upper gage ring 102, thereby moving the upper gage ring 102 and
the
mandrel 101 in opposite directions. The upper gage ring 102 pushes the axial
lock ring,
the upper slip assembly 106, the upper cone 110, and the element barrier
assembly 116
toward an upper end of the sealing element 114, and the mandrel pulls the
lower gage ring
104, the lower slip assembly 108, the lower cone 112, the rotational locking
key, and the
lower element barrier assembly 116 toward a lower end of the sealing element
114. As a
result, the push and pull effect of upper gage ring 102 and the mandrel 101
compresses the
sealing element 114.
Compression of the sealing element 114 expands the sealing element into
contact with the
inside wall of the casing, thereby shortening the overall length of the
sealing element 114.
As the bridge plug components are compressed, and the sealing element 114
expands, the
adjacent element barrier assemblies 116 expand into engagement with the casing
wall. As
the push and pull forces increase, the rate of deformation of the sealing
element 114 and
the element barrier assemblies 116 decreases. Once the rate of deformation of
the sealing
element is negligible, the upper and lower cones 110, 112 cease to move
towards the
sealing element 114. As the activating forces reach a preset value, the
castellations 662,
664 of the upper and lower cones 110, 112 engaged with the castellations 557
of the upper
and lower slip assemblies 106, 108 breaks the slip assemblies 106, 108 into
desired
segments and simultaneously guide the segments radially outward until the
slips 557
engage the casing wall. After the activating forces reach the preset value,
the adapter kit is
released from the bridge plug 100, and the plug is set.
Referring now to Figure 12, a bridge plug 1100 in an unexpanded condition is
shown in
accordance with an embodiment of the present disclosure. Figure 13 shows the
bridge
plug 1100 in an expanded condition. Bridge plug 1100 includes a mandrel 1101,
a sealing
element 1114, element barrier assemblies 1116 disposed adjacent the sealing
element
1114, an upper and lower slip assembly 1106, 1108, upper and lower cones 1110,
1112, a
locking device 1172, and a bottom sub 1174.
The mandrel 1101 may be formed as discussed above with reference to Figure 2.
For
example, mandrel 1101 may include a fixed bridge, as shown in Figure 2B, or a
movable
bridge, as shown in Figure 2C. A ratchet thread 1176 is disposed on an outer
surface of an
upper end A of mandrel 1101 and configured to engage locking device 1172.
Upper end
A of mandrel 1101 includes a threaded connection 1178 configured to engage a
threaded
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CA 02648116 2008-12-30
connection in a lower end of a mandrel when multiple plugs are used. As
discussed
above, the mandrel 1101 may be formed from any material known in the art, for
example
an aluminum alloy.
As shown in greater detail in Figure 14, the locking device 1172 includes an
upper gage
ring, or lock ring housing, 1102, and an axial lock ring 1125. When a setting
load or force
is applied to the bridge plug 1100, the axial lock ring 1125 may move or
ratchet over the
ratchet thread 1176 disposed on an outer surface of the upper end A of mandrel
1101. Due
to the configuration of the mating threads of the axial lock ring 1125 and the
ratchet thread
1176, after the load is removed, the axial lock ring 1125 does not move or
return upward.
Thus, the locking device 1172 traps the energy stored in the sealing element
1114 from the
setting load.
Further, when pressure is applied from below the bridge plug 1100, the mandrel
1101 may
move slightly upward, thus causing the ratchet thread 1176 to ratchet through
the axial
lock ring 1125, thereby further pressurizing the sealing element 1114.
Movement of the
mandrel 1101 does not separate the locking device 1172 from the upper slip
assembly
1106 due to an interlocking profile between the locking device 1172 and slip
base 1569 (or
frangible anchoring device, not independently illustrated) of the upper slip
assembly 1106,
described in greater detail below.
Referring now to Figures 12 and 15, sealing element 1114 is disposed around
mandrel
1101. Two element end rings 1124, 1126 are disposed around the mandrel 1101
and
proximate either end of the sealing element 1114, with at least a portion of
each of the
element end rings 1124, 1126 disposed radially inward of the sealing element
114. In one
embodiment, sealing element 1114 is bonded to an outer circumferential area of
the
element end rings 1124, 1126 by any method know in the art. Alternatively, the
sealing
element 1114 is molded with the element end rings 1124, 1126. The element end
rings
1124, 1126 formed from any material known in the art, for example, plastic,
phenolic
resin, or composite material.
The element end rings 1124, 1126 have at least one groove or opening 1128
formed on an
axial face and configured to receive a tab (not shown) formed on the end of an
upper cone
1110 and a lower cone 1112, respectively, as discussed above in reference to
Figures 2-11.
One of ordinary skill in the art will appreciate that the number and location
of the grooves
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CA 02648116 2008-12-30
1128 formed in the element end rings 1124, 1126 corresponds to the number and
location
of the tabs (not shown) formed on the upper and lower cones 1110, 1112.
As shown in Figure 15, element end rings 1124, 1126 further include at least
one
protrusion 1180 disposed on an angled face 1182 proximate the outer
circumferential edge
of the element end rings 1124, 1126. The protrusions 1180 are configured to be
inserted
into corresponding openings (1184 in Figure 17) in a barrier ring (1318 in
Figure 17),
discussed in greater detail below. In certain embodiment, the protrusions 1180
may be
bonded to or molded with the element end rings 1124, 1126.
The element barrier assemblies 1116 are disposed adjacent the element end
rings 1124,
1126 and sealing element 1114. Element barrier assembly 1116 includes a
frangible
backup ring 1319 and a barrier ring 1318, as shown in Figures 16 and 17,
respectively.
Frangible ring 1319 may be formed from any material known in the art, for
example,
plastic, phenolic resin, or composite material. Additionally, frangible ring
1319 may be
formed with slits or cuts 1321 at predetermined locations, such that when the
frangible
ring 1319 breaks during setting of the bridge plug 1100, the frangible ring
1319 segments
at predetermined locations, i.e., at the cuts 1321.
The barrier ring 1318 is a cap-like component that has a cylindrical body 1330
with a first
face 1332. First face 1332 has a circular opening therein such that the
barrier ring 1318 is
configured to slide over the mandrel 1101 into a position adjacent the sealing
element
1114 and the element end ring 1124, 1126. At least one slot 1334 is formed in
the first
face 1332 and configured to align with the grooves 1128 formed in the element
end rings
1124, 1126 and configured to receive the tabs formed on the upper and lower
cones 1110,
1112. One of ordinary skill in the art will appreciate that the number and
location of the
slots 1334 formed in the first face 1332 of the barrier ring 1318 corresponds
to the number
and location of grooves 1128 formed in the element end rings 1124, 1126 and
the number
and location of tabs (not shown) formed on the upper and lower cones 1110,
1112.
Further, a plurality of openings 1184 are formed in the first face 1332 of the
barrier ring
1318 and configured to receive the protrusions 1180 of the element end ring
1124, 1126.
Thus, the protrusions 1180 rotationally lock the element barrier assembly 1116
with the
sealing element 1114. One of ordinary skill in the art will appreciate that
the number and
location of the openings 1184 formed in the first face 1332 of the barrier
ring 1318
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CA 02648116 2008-12-30
corresponds to the number and location of protrusions formed in the element
end rings
1124,1126.
A plurality of slits (not shown) are disposed on the cylindrical body 1330 of
the barrier
ring 1318, each slit extending from a second end 1338 of the barrier ring 1318
to a
location behind the front face 1332, thereby forming a plurality of flanges
(not shown).
When the setting load is applied to the bridge plug 1100, the frangible backup
rings 1319
break into segments. The segments expand and contact the casing. The space
between the
segments in contact with the casing is substantially even, because the
protrusions 1180 of
the element end rings 1124, 1136 guide the segmented frangible backup rings
1319 into
position. When the setting load is applied to the bridge plug 1100, the
barrier rings 1318
expand and the flanges of the barrier rings 318 disposed on each end of the
sealing
element 1114 radially expand against the inner wall of the casing. The
expanded flanges
cover any space between the segments of the frangible backup rings 319,
thereby creating
a circumferential barrier that prevents the sealing element 1114 from
extruding.
Referring back to Figures 12 and 14, upper and lower slip assemblies 1106,
1108 are
configured to anchor the bridge plug 1100 to the casing and withstand
substantially high
loads as pressure is applied to the bridge plug 1100. Upper and lower slip
assemblies
1106, 1108 include slip bases 1569, slips 1567, and slip retaining rings 1587.
Upper and
lower slip assemblies 1106, 1108 are disposed adjacent upper and lower cones
1110, 1112,
respectively, such that conical inner surfaces of the slip base 1569 are
configured to
engage a sloped surface 1442 of the cones 1110, 1112.
Slip base 1569 of upper slip assembly 1106 includes a locking profile 1599 on
an upper
face of the slip base 1569. Locking profile 1599 is configured to engage the
upper slip
base 1569 with the upper gage ring 1102. Thus, upper gage ring 1102 includes a
corresponding locking profile 1597 on a lower face. For example locking
profiles 1599,
1597 may be interlocking L-shaped protrusions, as shown in View D of Figure
14. As
discussed above, these locking profiles 1597, 1599 secure the slip base 1569
to the upper
gage ring 1102 during pressure differentials across the bridge plug 1100,
thereby
maintaining energization of the sealing element 1114. Further, L-shaped
protrusions are
less likely to break off than typical T-shaped connections and more likely to
be efficiently
drilled up during a drilling/milling process.
CA 02648116 2008-12-30
Slips 1567 may be configured as teeth, sharp threads, or any other device know
to one of
ordinary skill in the art for gripping or biting into a casing wall. In one
embodiment, slips
1567 may include a locking profile that allows assembly of the slips 1567 to
the slip base
1569 without additional fasteners or adhesives. The locking profile includes a
protrusion
portion 1589 disposed on an inner diameter of the slip 1567 and configured to
be inserted
into the slip base 1569, thereby securing the slip 1567 to the slip base 1569.
Protrusion
portion 1589 may be, for example, a hook shaped or L-shaped protrusion, to
provide a
secure attachment of the slip 1567 to the slip base 1569. One of ordinary
skill in the art
will appreciate that protrusions with different shapes and/or profiles may be
used without
departing from the scope of embodiments disclosed herein.
Slip base 1569 may be formed from a readily drillable material, while slips
1567 are
formed from a harder material. For example, in one embodiment, the slip base
1569 is
formed from a low yield cast aluminum and the slips 1567 are formed from cast
iron.
Alternatively, slip base 1569 may be formed from 6061-T6 aluminum alloy while
slips
1567 are formed from induction heat treated ductile iron. One of ordinary
skill in the art
will appreciate that other materials may be used and that in certain
embodiments the slip
base and the slips may be formed from the same material without departing from
the scope
of embodiments disclosed herein.
Slip retaining rings 1587 are disposed around the slip base 1569 to secure the
slip base
1569 to the bridge plug 1100 prior to setting. The slip retaining rings 1587
typically shear
at approximately 16,000-18,000 lbs, thereby activating the slip assemblies
1106, 1108.
After activation, the slip assemblies 1106, 1108 radially expand into contact
with the
casing wall. Once the slips 1567 contact the casing wall, a portion of the
load applied to
the sealing element 1114 is used to overcome the drag between the teeth of the
slips 1567
and the casing wall.
While select embodiments of the present disclosure describe certain features
of a bridge
plug, one of ordinary skill in the art will appreciate that features discussed
with respect to
one embodiment may be used on alternative embodiments discussed herein.
Further, one
of ordinary skill in the art will appreciate that certain features described
in the present
disclosure may be applicable to both bridge plugs and frac plugs, and that use
of the term
bridge plug herein is not intended to limit the scope of embodiments to solely
bridge
plugs.
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CA 02648116 2008-12-30
Advantageously, embodiments disclosed herein provide one or more barrier rings
that
creates a circumferential barrier ring with a bridge plug is set to prevent or
reduce the
amount of extrusion of the sealing element of a bridge plug. Further,
anchoring devices in
accordance with embodiments of the present disclosure provide a more even
stress
distribution on a cone and/or the casing wall.
Advantageously, a bridge plug in accordance with embodiments of the present
disclosure
includes a segmented anchoring device such that the circumferential length of
the
segments is shorter as compared to conventional anchoring devices. As such,
when
actuated, the entire circumferential length of these anchoring segments may
penetrate the
casing wall, resulting in maximum contact surface between the anchoring
segments and
the casing wall, i.e. minimum uniform stress distribution between the
anchoring device
and the adjacent cone. Therefore, damage to the anchoring device and the cone
may be
prevented or reduced.
Further, embodiments disclosed herein advantageously provide a bridge plug
that provides
more efficient and quicker drilling/milling processes. Because components of
the a bridge
plug in accordance with the present disclosure are rotationally locked with
one another,
spinning of the components during drilling/milling processes is eliminated,
thereby
resulting in faster drilling/milling times.
Still further, a bearing shoulder provided in a lower cone of a bridge plug in
accordance
with the present disclosure allows a mandrel to stay engaged for a longer
amount of time
during a drilling/milling process than a conventional bridge plug. The bearing
shoulder
may allow for retention of the mandrel until the bearing shoulder is drilled
up. Thus, the
portion of the plug that remains in the well after the drilling/milling
process is reduced.
While the invention has been described with respect to a limited number of
embodiments,
those skilled in the art, having benefit of this disclosure, will appreciate
that other
embodiments can be devised which do not depart from the scope of the invention
as
disclosed herein. Accordingly, the scope of the invention should be limited
only by the
attached claims.
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