Note: Descriptions are shown in the official language in which they were submitted.
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LIh 'TIC f2 'TI~/A~i~E
A~~CGfZ~U~ THE IV'E TIf~
Field ~~ the Irwerati~ra
The present invention gcr~eraily relates to down hole tools for use in a
hydrocarbon welibore. I~lore particularly, the present invention per:ains to
packers
used for seating fluid flow within a weiibore. Itrlore particularly still, the
present
invention relates to a slip system for use in a downhole tool, such as a
retrievable
packer.
corr~pressed and extruded into en~gager~ent with the surrounding casing
string. In
this way, the annular region between the production string grad the casing is
sealed
to fluid flow. This, in turn, servws to direct the flow c>f production fluids
up the
production tubing and to the surface.
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Typically9 a plurality of slips are disposed radially around the outer
diameter of a
tubular mandrel. The slips have ~~ tail that is connected i:o a slip ring. The
slip ring,
in turn, is slideably placed around the outer diameter of a central mandrel in
the
packer. Movement of the slip rind through hydraulic or I~ydro-mechanical
actuation
drives the slip ring axially towards the cones. Movement: of the slip ring
causes the
respective slips to be driven along the beveled surfaces of the cones, and
thereby
moved radialiy outward into engagement with the surrounding tubular.
It can be seen from iigre ~ that the geometry of the pockEas 32 is
configured to mate with that of the shank land the tail portion 1of the slip
~0. In
36 this respect, each pocket has a base opening 3for receiving thE; tail
portion '1
2
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of the slip 10. Similarly, each pocket 2 has a neck opE:ning 3extending up
from
the base portion 3for receiving the shank 16 of the slip 10.
in some instances, the slip 10 will include a guide rail 0. Typically, a pair
of guide rails 20 is disposed on either side of the slip body 1. The guide
rails 20 are
slideable along siots (not shown) in a cage body (also r7ot shown) associated
with
the cones. The guide rails 0 assist in directing the slips 10 into engagement
with
the surrounding tubular body when the slip system is set.
In certain applications, it is desirable to be able to retrieve a packer from
the weflbore. in order to retrieve the packer, the slip system for the packer
must be
released from the surrounding casing. This, in turn, means that the slip ring
30 must
be moved away from the cones, and the slips 10 moved downward ov of the
respective beveled surfaces of the> cones. In some instances, reBease of the
slip
system requires extreme mechanical force, such as the application of many
thousands of pounds of tensile force imparted by pulling upp on the packer
mandrel
(not shown in Figure 1 ). In order to release the slip system, this mechanical
tensile
force is directed through the shank portion 16 of the slips 10 and associated
neck
portion 36 of the pockets 32.
It can be seen from the view of Figure 1 that the shank 1~i has a limited
width. i~lhere extreme and sudden tensile force is generated during release of
the
packer, a great deal of tensile force must be borne by the trim amount of
material in
the shank 16. Further, because of the perpendicular geometry of the tail
portion 14
of the slip 10, a great deal of sheae° stress must be borne by the tail
14 at the points
of contact with the base portion 34. of the pockets 32. If the shank 16 or
tail 14 of the
slip 10 are unable to withstand the generated tensile and shear forces, the
slip 10
will break, leaving the packer frictionally set within the welibore. This, in
turn,
reduires expensive milling and circulation operations to remove the packer.
In order to overcome the problem described above created by the
geometry of the slips 10, the manufacturer might choose to increase the
thickness of
the slip system. it can be seen from the exemplary arrangement in Figure 1
that
both the slip 10 and the slip ring 30 have a defined thickness °6.99
~~~,ever, it is
desirable by the operator of the well to have a thin slip system, so as to
retain a
3
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larger bore within the packer . A larger bore means more area through which
production fluids may flow in a prc'duction tubing, and a cheater diameter for
running
tools down the wellbore.
The manufacturer might also consider increasing the width of the shank
16. However, increasing the width of the shank 16 produces a reciprocal
reduction
of material in the slip ring, i.e., ~fJ, at the neck opening 6. in addition,
significant
shear load is still borne at the perpendicular point where the slip shank 16
meets the
tail 14.. Thus, an overall increase in tensile strength within the slip system
is not
necessarily gained.
There is a need, therefore, for a slip system in a retrievably set tool, such
as a retrievable packer, that is able to withstand extrerrre tensile forces
applied
during packer release. Further, there is a need for such a slip system that
retains a
thin geometry. Still further, there is a need for such a slip system that is
capable of
setting a packer within casing strings having a wide range of weight grades
such that
a multitude of packer/slip system sues is not needed in product inventory.
IJNINI~ Y OF THE INVENTIO
The present invention provides an improved slip system that is able to
withstand greater tensile forces during packer release without an increase in
thickness of material. The slip system c~mprises (1 ) a plurality of slips;
(2) a tubular
slip ring for holding the individual slips at an end; and (3) a tubular cone
body having
beveled surfaces for receiving the individual slips when the slip system is
actuated.
Of significance is the geometry of the individual slips. Fach slip has a first
end that defines a tail. The slip has a second opposite end that defines a
slip body.
The slip body has an outer surl'ac~: for engaging a surrounding tubular
string, such
as a string of casing, or liner. i~iuralities of teeth are placed along the
slip body to
assist in creating a frictional engag~:r~ent with the surrounding tubular
:string. The tail
and the slip body are integral, meaning that the intermediate shank portion of
prior
art slips is essentially removed. Instead, a dovetail geometry is provided
within the
tail, creating an increased tail width at the end o~ the tail opposite the
slip body.
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To aid in the positioning ofi the slips within their respective cone body
pockets,
the bodies of the slips and the pockets have mating beveled side edges. The
sides
of the bodies of the slips are beveled to face upwardly, while the sides of
the pockets
are beveled to face downwardly. ~J~lith this arrangement, the guide rails 20
and slots
of slip systems of the prior art are no longer needed.
The slip ring comprises a tubular body having a plurality of pockets. Each
pocket is substantially equidistantly spaced in radial array around the slip
ring.
Further, each pocket is dimensioned to receive the dovetailed configuration of
the tail
on the respective slips.
To further aid in the positioning of the slips within their respective slip
ring
pockets, the tails of the slips and tl~e pockets have mating beveled side
edges. The
sides of the tails of the slips are beveled to face upwardly, white the sides
of the
pockets are beveled to face downwardly. At the lower end, the lower edge of
the
tails of the slips are beveled to face downwardly, while the sower edge of the
pockets
are beveled to face upwardly. "ith this arrangement, an additional downward
radial
force is placed into the tail of slips during retrieval in addition to that
created by the
cone pocket geometry. Additionally, the pocket geomet~y~ limits the outward
radial
travel of the slips preventing them from becoming disengaged from the slip
ring.
BRIEF ~ESCRIPTI~N ~F TFIE RAIIIIINGS
So that the manner in wriich the above recited features of the present
invention can be understood in detail, a more particular description oi~ the
invention,
briefly summarized above, may be had by reference tc~ the appended drawings
(Figures 2-7). It is to be noted, however, that the appended drawing s
(Figures 2-7)
illustrate only typical embodiment; of this invention and are therefore not to
be
considered limiting of its scope.
Figure 1 provides a perspective view of a slip system of the prior art. A slip
ring and an exemplary slip are provided. (The tubular body providing the cones
is
not shown.) An exemplary slip is shown exploded away from the slip ring fior
clarification.
5
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Figure 2 presents a perspective view of a slip system of the present
invention,
in ~ne embodiment. A tubular slip ring is seen f~r holding individual slips. A
single
exemplary slip is shown within cne of the pockets of the slip ring. Finally; a
tubular
cone body having beveled surfaces for receiving the respective slips is shown.
Figure 3A presents a cross-sectional view of the slip system of Figure 2. The
system has been cut longitudinally along line 3A-3A.
Figure 3B presents a second cross-sectional view of the slip s5rstem of Figure
2. Mere, the slip system is shown through line 3B-3B.
Figure 4~ is a perspective view of an individual slip of the slip system in
the
present invention, in one embodiment. The outer surface of the slip is seen.
Figure 5 shows another perspective view of the individual slip of Figure 3. In
this view, the inner surface of the slip is seen.
Figure 6 provides a cross~sectior~al view of a packer as might employ the slip
system of Figure 2. This is a hydraulically actuated packeir. The packer is
seen in its
run-in position.
Figure 7 provides another cross-sectional view of the packer of Figure 5. In
this view, the packer is being actuated. Fluid injected under pressure causes
a
setting piston to act against upper and lower slip systems, and an
intermediate
sealing element. The packer is seen set against a surrounding string of
casing.
~0 Figure $ presents yet another cross-sectional view of the packer of Figure
6.
Here, the packer is being released from frictional and sealed engagement with
a
surrounding tulaular body.
Figure 9 presents an alternafie embodiment of a slip system. The alternate
slip system employs a modified slip design. The alternate slip system is shown
in
perspective view.
Figure 10 presents the modified slip cf Figure g, in perspective view.
6
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DETAILED DESCRIPTION OF THIE PREFERRED EMBODIMENT
The present invention provides a slip system 1 G0 for frictionally engaging a
temporarily set body, such as a packer or a whipstock, within a wellbore. An
improved slip system 100 of the present invention, in one embodiment, is shown
in
Figure 2. The slip system 100 comprises (1 ) a plurality of slips 110; (~) a
tubular slip
ring 130 for holding the individual slips 110 at an end; arid (3) a tubular
cone body
140 having beveled surfaces 142 for receiving the individual slips 110 when
the slip
system 100 is actuated.
Figures 3A and 3B present cross-sectional views of the slip system 100 of
Figure 2. In Figure 3A, the slip ;system 100 has been cut longitudinally along
line
3a~-3A. In Figure 3B, the slip system 100 is sl°~own through line 3B-
3B. From these
cross-sectional views, the tubular nature of the slip ring 130 and the cone
body 140
are seen.
~f signif;cance in the slip system 100 of the present invention is the
geometry
of the individual slips 110. Figure 4 provides a perspective view of ar,
individual slip
110 of the slip system 100 in the present invention, in one embodiment. The
outer
surface of the slip 110 is seen. Figure ~ shows another perspective view of
the
individual slip 110 of Figure . In this view, the inner surface of the slip
110 is
shown. From Figures 4 and 5 it is seen that each slip 110 has a first end that
defines a tail 114. The slip 110 has a second opposite end that defines a slip
body
112. The slip body 112 has an outer surface for engaging a surrounding tubular
string, such as a string of casing, or liner (not shown). h'luralities of
teeth, such as
wickers 11 ~, are preferably placed along the slip body 112 to assist in
creating a
frictional engagement with a surrounding tubular' string (not shown).
'~5 The tail 114 and the slip body 112 are integral, meaning that the
intermediate
shank portion of prior art slips is essentially removed. Instead, a dovetail
geometry
is provided within the tail 114., creating an increasing tail width at the end
o~~~ the tail
114 opposite the slip body 112. In this manner, the overall width of the slip
110 is
increased, thereby increasing its ability to withstand tensile forces without
a
reciprocal increase in thickness. Further, tensile forces in the tail portion
114 are
borne along an angle, thereby increasing the tensile strength of the slip 110.
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Referring again to Figure 2, the slip system 100 of the present invention also
includes a slip ring 130. The slip ring 130 comprise~~ a tubular body having a
plurality of pockets 132. Each pocket 132 is substantially equidistantly
spaced in
radial array around the slip ring 130. Further, each pocket 132 is dimensioned
to
receive the dovetailed configuration of the tail 114 on the respective slips
110. Thus,
the pockets '632 each employ a mating dovetail configuration.
To further aid in the positioning of the slips 110 within their respective
slip ring
pockets 132, the tails 114 of the slips 110 and the pockets 132 preferably
have
elating beveled sides. The sides 111 of the tails 11 ~. of the slips 110 are
beveled to
face outwardly (shown in FIGS. fi~ and 5), while the sides °i31 of the
pockets 132 are
beveled to face inwardly. The end 117 of each tail 114 of the slips 110 is
beveied to
face inwardly (shown in FICaS. 4 and 5~, while each edge 137 of the pockets
132 that
receives the ends 11 ~ is beveled to face outwardly. Enough play is afforded
in the
mating configuration of the pockets 132 to allow the slips 110 to slide and
move
radially outward to engage a surrouinding casing.
In order to demonstrate the operation of the slip system 100 of the present
invention, it is helpful to refer to a retrievable downhole to~Ji in which the
system 100
might be deployed. Examples of such a tool are retrievable packers and
whipstocks.
The slip system 100 may be set either hydraulically or me~;hanically using any
known
2Q actuation means. For purposes of clarity, an exemp6ary retrievable packer
200 is
shown in Figure 0. Figure ~ presents a cross-sectional view of a packer 200 as
might receive the slip system 100 of Figure 2. The exemplary packer 200 is a
hydraulically actuated packer 200. The packer 200 is seen in Figure in its run-
in
position.
The packer 200 generally defines an elongated tubular tool Have an upper
end 2000 and a Power end 2006. The packer 200 includes a sealing element 230
disposed intermediate the upper 2001 and cower 20flL ends. The sealing element
230 is seen in cross section in Figure ~. The sealing element 230, of course,
is
fabricated from a pliable and compressible material that is capable of being
extruded
into sealing engagement with surrounding casing (shown at 250 in Figure ~6)
when
the packer 200 is actuated.
0
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The packer 200 also comprises an elongated packer mandrel 210. The
packer mandrel 210 extends from the upper end 200U to the lower end 200L of
the
packer 200. The packer mandrE:l 210 defines an elongated tubular body. The
packer mandrel 210 has an inner diameter defining a bore 205, and an outer
diameter. In the arrangement for the packer 200 of Figure 6, a!I operational
parts,
including the sealing element 230, are disposed along the outer diameter of
the
packer mandrel 210.
The upper end of the packer mandrel 210 includes a threaded connection
212U. The threads connect to a lower joint of production tubing, an injection
tubing,
or some other working string {not shown}. The lower end of the packer mandrel
210
also preferably includes a threaded connection 212L. The lower connection 212L
may be left open, or may be attached to a tailpipe, a bottom sub, or even
another
packer for isolating an area of interest.
As noted, a sealing element 230 is circumferentially disposed around the
packer mandrel 210. A pair of gauge rings 232U, 232L i:;~ placed above and
below
the sealing element 230, respectively. The upper gauge ring 232U provides a
shoulder above the sealing element 230, while the lower gauge ring 232L
provides a
shoulder below the sealing element 230. Thus, compression of the sealing
element
230 is accomplished by moving the upper 23tJ and lower 2Lo gauge rings
relatively towards one another.
An elongated housing 240 is disposed below the lower gauge ring 22L. The
housing 240 defines an elongated tubular body concentrically pieced around the
packer mandrel 210. The upper er~d of the housing 240 is threadedly connected
to
the lower end of the lower gauge ring 232L. An annular region 242 is retained
between the concentrically arranged packer mandrel 210 and the surrounding
housing 240.
one or more ports 215Uj 15L are placed within the packer mandrel 210.
The ports 215 serve as setting ports, and provide fluid communication between
the
bore 205 of the packer mandrel 210 and the annular region 242 within the
housing
body 240. As will be described further below, the channel of fluid
communication
created by the setting ports 215U, 215L allows hydraulic pressure to be
applied to
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the seating element 230 and slip systems 2200, 220L around the packer mandrel
210. More specifically, upper setting ports 215U serve to actuate the sealing
element 230 and upper slip system 220U, while lower setting ports 215L serve
in
actuating the lower slip system 2~~L.
A pair of subs 2140, 214L is also provided around the packer mandrei 210.
First, a top sub 214U is provided proximate to the upper end 212U of the
packer
mandrel 210. Second, a bottom sub 214L is provided above the lower end 212L of
the packer 210. The top sub 2140 is threadedly connecaed to the ~>acker
mandrel
210, such that it has no relative movement with the packer mandrel 210.
Likewise,
the bottom sub 214L is conrsected to the packer mandrel 210. However, the
connection between the bottom sub 214L and the packer mandrel 212L is
temporary. To this end, a shear ring 213 is provided between the bottom sub
214L
and the packer mandrel 212L. ~s will be described more fully below, the shear
ring
213 retains the connection between the bottom sub 214L and the packer mandrel
210 until it is desired to release the packer 200 from the surrounding
wefibore.
/~s noted earlier, a pair of slips 2200, 220L is provided with the packer 200
of
Figure 5. First, an upper slip sysi:em 2201) is provided above the sealing
element
230. More specifically, the upper sealing element 2200 is disposed between the
top
sub 2140 and the upper gauge ring 232U. The lower slip system 232L is placed
below the sealing element 230. More specifically, the lower slip system 220U
is
disposed between the elongated outer housing 240 and the bottom sub 214L,.
The lower slip system 220L may be a known slip system, such as slip system
5shown in Figure 1. It can be seen that the slip system 220L includes slips
224L
disposed within a slip ring 222L. The slips include teeth 25L on an outer
surface
thereof. The slips 224L also have an inner surface configured to ride along a
beveled surface 22L of a lower cone body 229L.
because of the extraordinary tensile forces running through the packer 200
during release, the upper slip system 2200 must be a slip system such as slip
system 100 shown in :cigure 2. Visible in Figure '6, in cross section, are
~0 components of a slip system 22U in accordance with the slip system 100 oi~
Figure
2. Thus, there is a slip 2240 (analogous to slip 110 of Figure 2); there is a
slip ring
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2220 (analogous to slip ring 130 in Figure 2); there is an upper cone 22~U
(analogous to tubular cone body °!40 in Figure 2); and there are
beveled surfaces
2290 (analogous to the outwardly Leveled surfaces 14.2 seen in Figure 2).
Figure 6 presents the packer 200 in its run-in position. In this view, the
sealing element 230 and the slips 2200, 220L have not been set. However, in
Figure 7, it can be seen that the packer 200 has been actuated. Figure 7
provides
a cross-sectional view of the packer of Figure 5, but with the packer 200
having
been actuated. To this end, the sealing element 230 has now been compressed
between the upper 232U and IOwE;r 232iu. gauge rings. The sealing element 230
is
1 t~ seen extruded into sealed engagement with a surrounding casing 250.
Actuation of the sealing element 230 has been accomplished by injection of
hydraulic fluid, under pressure, through upper setting ports 15U. l3etails
concerning actuation of the packer 200 in order to effectuate sealing are not
important for purposes of the present invention. It is noted, however, that a
setting
piston 260 is provided around the t,acker mandrel 210. More specifically, the
setting
piston 260 is nested concentrically between the packer mandrel 210 and the
surrounding housing 240. The setting piston 250 acts in response to hydraulic
pressure provided through the lower setting ports 215L. The setting piston 260
moves downwardiy against the lower cone system 220i_. At the same time,
hydrostatic and formation pressures act fiogether against ithe housing 240.
Relative
movement between the housing 240 and the setting piston 260 is permitted.
Relative upward movement of the housing 240 relative ta;a the packer mandrel
210
and setting piston 260 serves to compress the sealing element 230 and to also
set
the upper slip system 2200.
As noted, the packer 200 is designed to be retrievable from within the casing
250. The packer 200 is released by a straight pull of the production tubing
(or other
working string) above the packer 200 and from the surface. because the packer
200
withstands extremely high forces during operation, extraordinary tensile force
is
reduired to release the packer 200. For this reason, the improved slip system
100 of
the present invention is necessary to serve as the upper slip system 220U in
the
packer 200.
11
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Figure $ presents yet another cross-sectional view of the packer 200 of
Figure ~. I-lere, the packer 200 is being released from frictional and sealed
engagement with the surrounding ~tubuiar body 250. It can be seen that the
lower
shear ring 213 has broken, releasing the packer mandrel 210 from the bottom
sub
214t_. This allows the packer mandrel 210 to move upward relative to the
seating
element 230 and the upper 22019 and lower 220L slip systems. Again, the
details as
to how the various components of the packer 200 are released are not
important; it is
sufficient to note that split rings 21~ engage shoulders along the components
of the
packer 200, allowing the packer 200 and its radially diaposed components to be
removed from the wellbore.
Figure 9 presents an alternate embodiment of a slip system 100'. The slip
system 100' employs a modified slip design,, shown at 110' in Figure 10. The
modified slip design utilizes slips 110' which have teeth 113' with a finer
pitch, and
which cover the majority of the slip surface. This more evenly distributes the
loads
placed into the slip system 100' during operation of the retrievably set tool,
such as
packer 200 of Figures 6A-6. Additionally, a small section 11' at the front of
each
slip 110' does not contain teeth. In one arrangement, the surface of this flat
section
11 J' is 0.010" below that of the teeth 113'. This seines to limit the depth
that the
teeth bite into the casing.
The tail of the slip 110' has a similar dovetail georrretry as the previous
embodiment shown in Figures ~ and 5; however, the sides 111' of the slip tail
114'
are not beveled, nor are the sides '131' of the mating pockets 132' on the
slip ring
130'. ~uring retrieval, this ser~~es to eliminate any radial force in the slip
ring 130'
which can cause deflection or deformation of the slip ring 130'. These changes
allow the slip system 100' to withstand significantly higher working (pads
while
maintaining retrievability.
liVhile the foregoing is directed to embodiments o~f the present invention,
other
and further embodiments of the invention may be devised without departing from
the
basic scope thereof, and the scope thereof is determined by the claims that
follow
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