U.S. patent application number 12/925141 was filed with the patent office on 2011-04-21 for ultra-short slip and packing element system.
Invention is credited to Gregg W. Stout.
Application Number | 20110088891 12/925141 |
Document ID | / |
Family ID | 43878409 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110088891 |
Kind Code |
A1 |
Stout; Gregg W. |
April 21, 2011 |
Ultra-short slip and packing element system
Abstract
A packer device, with a commercial name called "Frac Disc"
includes an interior packer mandrel and radially surrounding cone,
slip and seal system that seals and engages the surrounding casing
or other tubular member. The cones expand the slip system and the
slips compress and expand the seal system, simultaneously. The slip
system provides a means for supporting the seal system when
pressure is applied from above or below the packer. The close
proximity of the seal and slip system in combination with a
separating packer body provides for a very short packer, or a
"minimum material packer", that offers lower cost, higher
performance, and if required, faster mill-out.
Inventors: |
Stout; Gregg W.;
(Montgomery, TX) |
Family ID: |
43878409 |
Appl. No.: |
12/925141 |
Filed: |
October 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61279019 |
Oct 15, 2009 |
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Current U.S.
Class: |
166/120 |
Current CPC
Class: |
E21B 33/129 20130101;
E21B 33/1204 20130101 |
Class at
Publication: |
166/120 |
International
Class: |
E21B 33/12 20060101
E21B033/12 |
Claims
1) A tool for sealing along a section of a wall of a subterranean
well and carriable into said well on a conduit, and moveable from a
run-in position to a set position by a setting tool manipulatable
on said conduit, said well tool comprising: (1) a plurality of
anchoring elements shiftable from a first retracted position when
said well tool is in a run-in position to a second expanded
position after manipulation of said setting tool; (2) seal means
contained within said anchoring elements for sealing engagement
along the wall of the well; and (3) cone means activatably
receiving said anchoring elements in a retracted position during
the run-in position and, upon manipulation of said setting tool,
urging said anchoring elements in a direction toward the wall of
the subterranean well, said anchoring elements being shiftable to
said second expanded position, said seal means sealingly engaging
said well wall, and said cone means urging said anchoring means in
a direction toward the wall of said well, all in concert and
substantially concurrently with one another.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related in subject matter to application
Ser. No. 12/653,155 filed Dec. 9, 2009 entitled "Subterranean Well
Ultra-Short Slip and Packing Element System", Gregg W. Stout,
inventor.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to downhole tools for oil and gas
wells and similar applications and more particularly to improved
well packers.
[0004] 2. Description of Prior Art
[0005] Well packers are used to form an annular barrier between
well tubing or casing, to create fluid barriers, or plugs, within
tubing or casing, or the control or direct fluid within tubing or
casing. Packers may be used to protect tubulars' from well
pressures, protect tubulars' from corrosive fluids or gases,
provide zonal isolation, or direct acid and frac slurries into
formations.
[0006] Typical well packers consist of a packer mandrel. Radially
mounted on the packer mandrel is a locking or release mechanism, a
packing element system with gage rings, and a slip/cone system.
These packers tend to be 2 feet or longer depending on the packer
design. The packing system is typically an elastomeric packing
element with various types of backup devices such as gage rings.
The packing system is typically expanded outward, between the gage
rings to contact the I.D. of the casing by a longitudinal
compression force generated by a setting tool or hydraulic piston.
This force expands the elastomer and any backup material to create
a seal between the packer mandrel and casing I.D. This same
longitudinal force acts through the sealing system and acts on the
slip system. The slip system is typically an upper and lower cone
that slides under slip segments and expands the slip segments
outwardly until teeth on the O.D. of a series of slip segments
engage the I.D. of the casing. Teeth or buttons on the O.D. of the
slip segments penetrate the I.D. of the casing, to secure the
packer in the casing, so the packer will not move up or down as
pressure above or below the packer is applied. A locking system
typically secures the seal and slip systems in there outward
engaged position in order to maintain compression force in the
elastomer and, in turn, compression force on the slip system.
Certain part configurations allow the locking mechanism to
disengage to allow retrieval of the packer. The presence of the
release mechanism usually classifies the packer as a "retrievable
packer" and the absence of the release mechanism classifies the
packer as a "permanent packer".
[0007] Problems with prior art packers, in some cases, can be the
excessive length of the packers since all of the above combined
systems require length. It would advantageous to have a packer that
is much shorter in that reduced material would certainly lower
material and manufacturing costs. It would be advantageous to have
a very short packer, so if packer removal is required, milling time
would be greatly reduced. Some of the drillable frac plugs on the
market are the Halliburton "Obsidian Frac Plug", the Smith Services
"D2 Bridge Plug", the Owen Type "A" Frac Plug, the Weatherford
"FracGuard", and the BJ Services "Phython". By comparison, all of
these plug designs are very long in comparison to the current
invention. Also, a very short packer would reduce cost and simplify
the task of creating a "Pass-through" packer. "Pass-through"
packers are used for intelligent well completions and allow the
passage of, for example and not limited to, hydraulic control
lines, fiber optic lines, and electrical lines.
[0008] Both retrievable and permanent packers are sometimes drilled
or milled out of the casing. If the packer is being used as a "Frac
Plug", a Halliburton trademark, it is commonly milled out after the
frac is completed. Typical packers, as described above, tend to
have mill-out problems because the packer parts tend to spin within
the engaged slips. The mill operation becomes very inefficient
because the packer parts spin with the rotation of the milling
tool. Some packer designs exist, for example the BJ Services U.S.
Pat. No. 6,708,770, to reduce this spinning tendency. It would be
advantageous to have a packer design that would offer alternative
features to prevent spinning of parts while milling out. It would
also be advantageous if this same design feature would provide a
means to equally distribute the slip segments around the packer
body to evenly distribute the load on the I.D. of the casing
[0009] Another problem is that the slip system is loaded through
the packing element system without a fully supported packing
element to prevent extrusion. Extrusion of the packing element
system reduces stored energy in the slip system thus allowing the
slip system to disengage, especially during pressure reversals, the
casing and in turn cause packer slippage and seal failure. Typical
packers have a seal system that has elastomers backed up by
anti-extrusion devices and the anti-extrusion devices are backed up
by gage rings. The gage rings typically have a built-in extrusion
gap between the O.D. of the gage ring and the I.D. of the casing to
provide running clearance for the packer. The built-in extrusion
gap can be a problem and is commonly the primary mode of seal
system failure at higher temperatures and pressures. This is
because the elastomers and backup devices tend to move into the
extrusion gaps. When this movement occurs, the stored energy is
lost in the seal system and the seal engagement is jeopardized to
the point of seal failure. It would be an advantage to remove the
majority of the extrusion gap to prevent the seal from extruding or
moving. Attempts have been made to reduce the extrusion gap by use
of expandable-metal packers, for example, the Baker expandable
packer U.S. Pat. No. 7,134,504 B2, US 2005/0217869, and U.S. Pat.
No. 6,959,759 B2, or the Weatherford Lamb metal sealing element
patent # US 2005/023100 A1.
[0010] Typical retrievable packers have slip systems that, when
expanded, contact the I.D. of the casing at 45 degree or 60 degree
increments around the I.D. of the casing. Each slip segment has a
width and there is typically a space between each slip segment. The
space between each slip segment creates a surface area where no
slip tooth engagement occurs. The total slip contact with the I.D.
of the casing may, for example, only be 50% of the surface area on
the inside of the casing. If pressure is applied across the packer,
the slips are driven outward into the casing. It is a problem in
that due to the incremental contact on the I.D. of the casing, high
non-uniform stresses in the casing wall can cause deformation or
even failure of the casing wall. It would be very desirable to have
a slip system that approaches a full 360 degree contact in the I.D.
of the casing to minimize damage to the casing. Also, with slip
engagement approaching 360 degrees, there is more slip tooth
engagement due to increased radial surface contact area, thereby
providing the opportunity to reduce length of the slip. Reduced
length of the slip then reduces the overall length of the
packer.
[0011] Typical permanent packers have slip systems that "break".
Slips that "break" approach the 360 degrees of contact. These slips
are usually made by manufacturing a ring, cutting slots in the ring
to create break points, and then treating the teeth on the O.D. of
the ring for hardness purposes. When longitudinal load is applied
to a cone, the cone moves under the slip ring and the ring tends to
break at the slots to create slip segments. History has shown that
the slip segments, break unevenly or don't break at all, break at
different forces, and engage the I.D. of the casing in irregular
patterns. These breaking problems can reduce the performance and
reliability of the packer. It would be advantageous to have slips
that approach the 360 degrees of contact and are not required to
break, don't require a variable force to break, and evenly
distribute themselves around the I.D. of the casing.
SUMMARY OF THE INVENTION
[0012] This invention provides an improved packer for cased wells
or for a tubular member positioned inside of casing. The invention
includes a number of features that overcome the above mentioned
problems. A very short and simple packer design, with features that
increase overall packer reliability, is created by effectively
combining synergies of the cone, slip and seal elements to work in
unison.
[0013] This packer can be set on standard electric wireline or with
hydraulic setting tools conveyed on jointed pipe or coiled
tubing.
[0014] The packer can be ready modified to serve several
applications: 1) A hydraulic setting cylinder can be added so the
packer can be run as part of the casing or tubing; 2) the packer
can utilize a fixed frangible disc or a flapper device to serve as
a bridge plug, frac plug, or a preferred title, a "Frac Disc". The
materials of the packer can be optimized to reduce mill-out time.
Mill-out time is greatly reduced due to the very short length of
the packer, around 4'', so expensive composite materials aren't
necessarily required, 3) a seal bore can easily be attached to the
packer body, 4) since the slip system creates a metal-to-metal
interface with the I.D. of the casing, the packer can readily be
adapted to a high pressure and temperature well environment, 5) the
packer can address applications as simple as low cost plug and
abandonment to highly complex applications in hostile environment
wells, and 6) the packer, due to it's short length, is ideal for
incorporating "control line pass-thru" for intelligent well
completions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic view of the present invention in the
"running position".
[0016] FIG. 2 is a schematic view of the present invention in the
"set position".
[0017] FIG. 3 is a cross-sectional end view of the packer mandrel
and slip segments of the present invention in the fully expanded
"set position".
[0018] FIG. 4 shows three views of a slip segment that demonstrates
an alternate to teeth.
[0019] FIG. 5 is a schematic view of the present invention, less
the upper slip segments, in the "set position".
[0020] FIG. 6 is a schematic of the present invention in the set
position, further simplified with use of a packer cup rather than a
compressed packing element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] With reference to FIG. 1, a schematic of the present
invention shows a 180 degree lengthwise cross-section of the
packer. A mandrel 1 has a running thread 16 with a tension or shear
parting point, or connection, 17 located below the running thread.
The mandrel 1 may be shortened by more than one means at point 17,
i.e., any type of shear, tension, or locking device that can be
separated in a fashion to shorten the mandrel. A setting tool (not
shown) is made up to running thread 16 in order to convey the
packer into the well. A millable, frangible or disintegrable disc
14 is a fluid barrier and is part of mandrel 1 or can be attached
and sealed to mandrel 1 in some fashion. Cone surface 3 is shown of
the O.D. of mandrel 1. Slip segments 4 are expandable by sliding up
coned surfaces at 2 and 3. Seal 5, commonly known as a packing
element, is located between slip segments 4 and extrusion barriers
6. Seal 5 is compressed and expanded between slip segments 4.
[0022] The slip segments 4 have gaps between them that increase in
size as the slip segments travel up the cones 2 and 3. The
extrusion barriers 6 are segmented and attached to the slip
segments 4 so that the gaps between the slip segments 4 are always
bridged to prevent extrusion of Seal 5 as the slip segments 4
travel outward to meet the I.D. of the casing. As an alternative,
the extrusion barriers 6 may be manufactured as part of the slip
segments 4 so that the slip segments 4 themselves bridge the gaps
between the slip segments as the slip segments expand outward.
Shear pins 7 secure the slip segments 4 in the retracted position
while the packer is run into the well.
[0023] The slip segments 4 have dovetail shaped runners 12 that
slide in dovetail grooves 11 at cone surfaces 3 and 2. The runners
12 and grooves 11 may be of any profile and serve to retain the
slip segments to both mandrel 1 and cone 8. Furthermore, the
runners and grooves provide a means to equally space the slip
segments 4 around the perimeter of the plug. Additionally, the
runners and grooves provide a means to rotationally lock the slip
segments 4, the mandrel 1, the cone 8, and the lock ring 9 together
during milling operations. When the slip segments engage the inner
casing wall, all components become rotationally locked together to
help prevent spinning of the packer parts. The lock ring 9 threads
are arranged in a manner so if right-hand rotation during milling
rotates lock ring 9 to the right, the lock ring 9 rotates down
thread 10, until it bottoms out at the end of thread 10. Once
bottomed out, it 9 becomes rotationally locked to the mandrel 1,
rotationally locked to the cone 8, which is rotationally locked to
slip segment 4, while the teeth 19 of slip segment 4 are penetrated
into the inner casing wall.
[0024] The slip segments 4 are positioned almost 360 degrees around
the O.D. of the mandrel 1. Each slip segment has a series of teeth
19, or some other casing penetrating profiles such as hard inserts
positioned on the O.D. of the slip segments as shown in FIG. 4.
[0025] In FIG. 4 the slip segment 4 is shown without teeth 19, but
instead inserts or coating 25. Inserts or coating 25 may be ceramic
balls, carbide balls, other geometries made of carbide or ceramic,
proppant or sand, or other materials. Inserts or coatings 25 may be
of any pattern on the O.D. of slip segment 4 and can be either a
structured or random pattern. Sand or proppant, for example 20-40
or larger sizes, gravel pack sand or fracturing proppant made by
Santrol or Hexion, or Carboceramics, can be used in or on the
surface of slip segment 4 and can be attached to the surface with
bonding materials or imbedded into the base material. Those in the
gravel pack or frac pack business know that sand or proppant can
stick downhole tools in the well, so it would be obvious that sand
or proppant can be used on packer slips to hold tools in place
relative to pipe or casing. The objective of using inserts or
coatings 25 is to improve millability of the slip segments whereby
the base material of the slip segments are easily machined and the
inserts or coating 25 are hard enough to penetrate the casing I.D.
Another objective to inserts or coating 25 is to minimize casing
damage on the I.D. of the casing. Teeth marks from slips can
increase susceptibility of the casing to corrosion and other
failure mechanisms, especially in chrome based materials. The
teeth, inserts, or coatings are sufficiently hard to penetrate the
inside of the casing wall in order to grip the wall and prevent the
packer from moving relative to the casing.
[0026] The slip segments have an O.D. that is machined to be almost
equal to the I.D. of the casing. The slip segments are machined to
minimize any gaps between the O.D. of the slip segments and the
I.D. of the casing. Similarly, the angles on the I.D. of the slip
segments are machined to almost match the O.D. of the cone surfaces
2 and 3 when the slip is fully expanded, in order to minimize gaps
between the parts.
[0027] The cone 8 has a surface 2. The setting tool (not shown)
pushes against surface 18 while pulling on threads 16 during the
setting operation. The cone 8 has an internal thread that engages
body lock ring 9. Body lock ring 9 can ratchet freely toward the
slip segments 4 but engages and prevents movement away from the
slip segments 4 by engaging the threads 10 on the top O.D. of the
mandrel 1. Lugs 13 engage slots 15 if plugs stack during milling so
the relative plugs don't spin during milling.
[0028] FIG. 2 shows the packer in the "set position". In operation,
also see FIG. 1, the setting tool (not shown) pushes on cone 8, at
or near surface 18, and simultaneously pulls on thread 16 of
mandrel 1. Cone 8 moves toward the slip segments 4 and seal 5 and
in the process expands the slip segments 4 up cones 2 and 3 and
compresses Seal 5 between slip segments 4 and extrusion barriers 6.
Expansion of slip segments 4 and seal 5 continues until sufficient
contact is made with the I.D. of the casing to achieve slip tooth
19 penetration in the inner wall of the casing.
[0029] At this point the teeth of the slip segments have nearly
closed any seal 5 extrusion gaps between the O.D. of the slip
segments 4 and the I.D. of the casing. Extrusion gaps have been
minimized nearly 360 degrees around the packer. Additionally, slip
load has been nearly evenly distributed around the I.D. of the
casing to minimize distortion of the casing. Slip segment 4
distribution around the O.D. of the mandrel 1 is more uniform due
to the rails 12 and grooves 11 keeping the slip segments equally
spaced around the packer. Also, extrusion gaps have been closed
where the I.D. of the slip segments contact the surfaces of the
cones at 20 and 21. At this point, the extrusion gaps between the
slip segments 4 are bridged with the extrusion barriers 6.
In the set position, FIG. 2, the lock ring 9 has traveled over
thread 10. Thread 10 is designed to prevent reverse movement of
lock ring 9, so that lock ring 9 holds cone 8 in a firm position
under slip segment 4 while maintaining compression on seal 5 and
keeping the slip segments 4 expanded into the I.D. of the casing.
Once sufficient load is applied to cone 8 and thread 16 of mandrel
1, in order the drive teeth 19 into the I.D. of the casing and
create an adequate seal with seal 5, the upper portion of mandrel 1
with thread 16, disconnects at point 17. The upper portion 22 of
mandrel 1 comes out of the hole with the setting tool (not shown)
and leaves a short section of mandrel 1 in the well.
[0030] Obviously, with the outer packer components 4,5, and 8
compressed closely together in combination with the short section
of mandrel 1, the remaining portion of the plug is not only very
short, but requires less material and length to mill out. The
amount of material to mill out is minimized by taking as much
material out of the packer components as possible, while still
maintaining enough strength to hold well pressure differentials.
For example, notice on mandrel 1 that the I.D. is bored out and at
the lower end of mandrel 1 below the angled surface 3, material has
been removed at location 23. As a result, the packer becomes a
minimum material packer by removing material that is not needed to
structurally maintain a pressure differential in the well bore.
Also, to enhance millability of the packer, highly millable
materials may be used, such as cast iron, or some other easily
machinable material.
[0031] FIG. 3 shows a cross-sectional end view of the slip segments
4 in the expanded position. In the expanded and set position, gaps
exist between each slip segment 4. An extrusion barrier 6 is
attached to the slip segment 4 by an attachment means, such as
drive-loc pins 24. The extrusion barriers 6 cover the gaps between
each slip segment 4 to form a seal 5 backup surface to prevent seal
5 extrusion past the slip segments 4. Since the teeth 19 of the
slip segments penetrate the inside of the casing wall, any
extrusion gaps are closed off on the outside of the slip segments
4. Since the I.D. of the slip segments 4 closely matched the O.D.
of the tapered surfaces 2 and 3, the extrusion gaps on the inside
of the slip segments 4 are reduced to a minimum. This described
geometry forms a near metal-to-metal seal backup system in the
packer which is very desirable for high pressure and temperature
well conditions.
[0032] FIG. 5 shows a similar packer, or Frac Disc, to FIG. 1. The
FIG. 5 packer has the same features mentioned above except it does
not have an upper set of slip segments 4, therefore, it would
normally be used in situations where the packer is only required to
hold pressure from above. This version would be a lower cost
version than the one shown in FIG. 1 and cone 8 could be replaced
with lock ring housing 26. In order to further simplify the packer
design, the extrusion rings 6 could be eliminated and the packing
element, or seal 5, could have a backup built into the seal system
5. In low pressure applications, or in cases where a positive seal
with the I.D. of the casing is not needed, extrusion backup 6 and
other backups in the packing element could be eliminated.
[0033] FIG. 6 shows a similar packer, or Frac Disc, to FIG. 1. The
FIG. 6 packer has many of the same features mentioned above except
it does not have the upper set of slip segments 4, or the packing
element 5, or the anti-extrusion devices 6. The cone 8 is replaced
with cup retainer 27 and the packing element 5 is replaced with the
packing cup 28. Obviously the packing cup 28 only holds pressure
from above generated from pressure operations occurring above the
cup. This design allows opportunities to further minimize the
material left in the well for milling out, for example, by
eliminating the upper slip segments 4 and leaving a shorter mandrel
1 by moving separation point 17 downward.
* * * * *