U.S. patent application number 13/314986 was filed with the patent office on 2013-06-13 for continuous backup assembly for high pressure seals.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. The applicant listed for this patent is Edward J. O'Malley. Invention is credited to Edward J. O'Malley.
Application Number | 20130147120 13/314986 |
Document ID | / |
Family ID | 48571272 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130147120 |
Kind Code |
A1 |
O'Malley; Edward J. |
June 13, 2013 |
Continuous Backup Assembly for High Pressure Seals
Abstract
An extrusion barrier assembly for high pressure and temperature
applications for a sealing element incorporates a backing member
between the sealing element and a multi-row petal type backup ring
assembly. The surface irregularities of the offset petals are
distributed through the backing member so that stress concentration
locations at the petal transitions between rows are diffused
through the backing member to avoid or minimize the tendency of the
petals to stress crack at row to row transitions. The backing
member is formed from spirally wound strip of sheet material that
can be coated to promote relative sliding of overlapping layers.
The assembly can be temporarily bonded to retain its shape with
adhesive that releases under expected well conditions when the
packer or bridge plug is set.
Inventors: |
O'Malley; Edward J.;
(Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
O'Malley; Edward J. |
Houston |
TX |
US |
|
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
48571272 |
Appl. No.: |
13/314986 |
Filed: |
December 8, 2011 |
Current U.S.
Class: |
277/336 |
Current CPC
Class: |
E21B 33/1216
20130101 |
Class at
Publication: |
277/336 |
International
Class: |
E21B 33/12 20060101
E21B033/12 |
Claims
1. An extrusion barrier assembly for a subterranean seal,
comprising: a seal element having a longitudinal axis; a backup
ring assembly located adjacent at least one end of said seal
element; a backup member disposed between said backup ring assembly
and said seal element and formed from an elongated strip rolled
into overlapping layers.
2. The assembly of claim 1, wherein: said strip is spirally wound
so that adjacent layers are offset from each other.
3. The assembly of claim 1, wherein: said layers slide relatively
upon compressive loading of said seal element along the
longitudinal axis of said element.
4. The assembly of claim 1, wherein: said layers are initially
secured to each other with an adhesive.
5. The assembly of claim 1, wherein: said layers have a coating in
between that reduces friction to promote relative sliding between
said layers.
6. The assembly of claim 1, wherein: said backup member conforms to
the shape of said petal backup ring at a contact location.
7. The assembly of claim 1, wherein: said petal backup ring
provides structural support for said backup member.
8. The assembly of claim 1, wherein: said strip is continuous
throughout said layers.
9. The assembly of claim 1, wherein: said backup member has a
frusto-conical shape.
10. The assembly of claim 9, wherein: said shape comprising an axis
and a taper slope angle of 5-60.degree. with respect to said
axis.
11. The assembly of claim 1, wherein: spaced petal pairs in one row
of said petal backup ring are backed by another petal in an
adjacent row to define step transitions at adjacent edges of said
spaced petals; said backup member spanning said step transitions of
said spaced petal pairs to reduce stress at said step transitions
from compressive loading in a direction of said longitudinal axis
of said sealing element.
12. The assembly of claim 2, wherein: said layers slide relatively
upon compressive loading of said seal element along the
longitudinal axis of said element.
13. The assembly of claim 12, wherein: said strip is continuous
throughout said layers.
14. The assembly of claim 13, wherein: said backup member has a
frusto-conical shape.
15. The assembly of claim 14, wherein: spaced petal pairs in one
row of said petal backup ring are backed by another petal in an
adjacent row to define step transitions at adjacent edges of said
spaced petals; said backup member spanning said step transitions of
said spaced petal pairs to reduce stress at said step transitions
from compressive loading in a direction of said longitudinal axis
of said sealing element.
16. The assembly of claim 15, wherein: said layers are initially
secured to each other with an adhesive.
17. The assembly of claim 16, wherein: said layers have a coating
in between that reduces friction to promote relative sliding
between said layers.
18. The assembly of claim 17, wherein: said backup member conforms
to the shape of said petal backup ring at a contact location.
19. The assembly of claim 18, wherein: said petal backup ring
provides structural support for said backup member.
20. The assembly of claim 19, wherein: said shape comprising a axis
and a taper slope angle of 5-60.degree. with respect to said
axis.
21. The assembly of claim 1, wherein: said backup ring assembly
comprises a petal backup ring assembly further comprising at least
two rows of circumferentially offset petals and located adjacent at
least one end of said seal element.
22. The assembly of claim 1, wherein: said backup ring assembly
comprises at least one ring with abrupt surface transitions.
23. The assembly of claim 1, wherein: said backup ring assembly
comprises a plurality of split rings with circumferentially spaced
splits.
Description
FIELD OF THE INVENTION
[0001] The field of the invention is anti-extrusion assemblies for
subterranean seals in high differential pressure and high
temperature environments and more particularly to intermediate
structures between a sealing element and a backup ring assembly to
control stress at said backup ring assembly.
BACKGROUND OF THE INVENTION
[0002] High pressure elastomer seals often require the use of a
backup system to prevent extrusion failure of the seal material.
Backup systems may be comprised of multiple components with
different design intents. Petal backups are employed as means of
mechanically reinforcing an elastomer seal against applied
pressures. Petal backups are so named due to their resemblance to a
flower--typically a thin metallic cup-shape with slots cut into the
sidewalls to reduce the amount of for required to expand the part
during setting. One such design is shown in FIG. 1.
[0003] In use, when the petal backups expand are set, a gap is
generated between adjacent petals, which would cause seal failure
if only one backup were present. As a result, petal backups are
staggered and stacked, so that when the complete backup system is
assembled the gaps of one backup are against the centers of the
petals of the next backup. A disadvantage to this approach is that
a discontinuous surface will exist within a set seal stack, and as
temperature and pressure increase, that discontinuous surface
becomes an increasingly risky potential failure point.
[0004] High expansion packers are used in through tubing
applications where the packer or plug is then set in casing below
the tubing through which it was delivered. Some designs provided
cup shaped backup ring stacks that has staggered slots as between
layers as an extrusion barrier in expansion ranges up to 25%. U.S.
Pat. No. 6,827,150 is an illustration of one such design. Others
are U.S. Pat. No. 7,128,145; US Publication 2004/0149429 and
2005/0115720. Other high expansion packer designs are U.S. Re
32,831; U.S. Pat. Nos. 6,311,778; 6,318,461 and 6,164,375.
[0005] Another design is revealed in US Publication 2008/0251250
where a series of overlapping petals 310 are initially retained by
a band 314. The petals are connected to tubular 312 that is
expanded. The band breaks with expansion of the tubular. The petals
can be in a single row but are stated to be preferably in multiple
rows. The main issue with this design is the dependency for sealing
on petal overlap which can be problematic if the petals do not all
move out radially in a uniform fashion.
[0006] In extreme pressure differential applications the surface
irregularity presented with the offset gaps among the petal layers
becomes a stress concentration location and the end result can be
cracking where a gap in the innermost row that is up against the
sealing element is backed by the middle of another petal in an
adjacent row. Once the petal ring assembly develops stress cracks
the seal can be lost as portions of the sealing element begin to
flow and extrude through such newly formed cracks. Situations where
there are high temperatures aggravate these types of potential
failures.
[0007] To help limit the risk, a new backup is proposed. In the
simplest embodiment, the backup would be constructed from a spool
of sheet material that would be wrapped onto a mandrel of the
desired shape. Material type and thickness would be determined by
the application. In operation, the helically wrapped backup would
be part of a seal stack that might include one or more elastic
elements, non-elastic elements, and other metallic backup
components included for strength. In use, the layers of the backup
should slide relative to one another fairly easily until
compressive forces become large, allowing the part to conform to a
desired shape. Because the layers are fairly thin, a smooth surface
remains in the load path against the seal, limiting non-uniform
loading of the seal, and ultimately reducing the risk of failure.
Applying a coating on the sheet material as the part is wrapped may
ease the force required to set the backup. A temporary adhesive
might also be useful to hold the wrapped component together until
use. The adhesive is chosen in such a way that a slight application
of force or exposure to wellbore fluid would disable it. Shear or
other temporary mechanical means might also be used.
[0008] Those skilled in the art will more readily understand these
and other aspects of the invention from a review of the description
of the preferred embodiment and the associated drawings while
recognizing that the full scope of the invention is to be
determined from the appended claims.
SUMMARY OF THE INVENTION
[0009] An extrusion barrier assembly for high pressure and
temperature applications for a sealing element incorporates a
backing member between the sealing element and a multi-row petal
type backup ring assembly. The surface irregularities of the offset
petals are distributed through the backing member so that stress
concentration locations at the petal transitions between rows are
diffused through the backing member to avoid or minimize the
tendency of the petals to stress crack at row to row transitions.
The backing member is formed from spirally wound strip of sheet
material that can be coated to promote relative sliding of
overlapping layers. The assembly can be temporarily bonded to
retain its shape with adhesive that releases under expected well
conditions when the packer or bridge plug is set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an elevation view in section of a prior art petal
type multi-layer backup ring assembly that can be used with the
present invention;
[0011] FIG. 2 shows a mandrel on which the backing member of the
present invention is produced;
[0012] FIG. 3 shows a roll of sheet material before it is wrapped
onto the mandrel of FIG. 2;
[0013] FIG. 4 shows the sheet material of FIG. 3 wrapped around the
mandrel of FIG. 2;
[0014] FIG. 5 is a section view along lines 5-5 in FIG. 4 with the
mandrel removed;
[0015] FIG. 6 shows the backing member of the present invention on
a sealing element with the petal type backing member removed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Mandrel 10 has a taper 12 and a cylindrical portion 14 that
is used to support the mandrel 10 as the sheet 16 comes off the
roll 18 and is spirally wound beginning with the cylindrical
portion 14 and then continuing to the taper 12. The spiral winding
leaves a potion 20 of the previous winding exposed as another
winding is made. As a result when the mandrel 10 is removed and
portions wound on the cylindrical portion 14 are trimmed off the
resulting shape shown in section is a chevron shape or a
frusto-conical shape illustrated in FIG. 5. As shown in FIG. 6 the
backup member 22 conforms to the shape of the end of the sealing
element 24. With the petal type backup assembly 26 shown in FIG. 1
and fitted over the backup member 22 an applied axial force causes
the overlapping layers such as 28 and 30 to slide over each other
as they get axially compressed in the direction of arrow 34 while
growing radially in the direction of arrow 32 against the
surrounding tubular or wellbore surface for a sealing contact.
[0017] The backup member 22 is not intended to be structural and is
combined with the petal ring assembly 26 for the strength of the
assembly 26 combined with a layered petal assembly having the
ability to be axially compressed and to extend radially while
serving as an extrusion barrier. The addition of backup member 22
that is a thin multi-layer spiral structure preferably shaped to
conform to the end of the sealing element 24 serves the purpose of
distributing compressive loading when the assembly is set about the
petal ring assembly 26. Referring to FIG. 1 petals 36 and 38 of one
row of petals are backed by petal 40 in the adjacent row so as to
create two ledge surfaces 42 and 44 that move apart during
compressive loading to allow the ring assembly 26 to flatten out
while growing radially and still not have open gaps between the
petals. While there are no open gaps such as between petals 36 and
38 there are step transitions 42 and 44 that under high
differential pressure loading will be lines of stress
concentration. Cracking can occur at or adjacent transitions 42 and
44 and the presence of backup member 22 that overlays these step
transitions 42 and 44 reduces the localized stresses at these
locations by being flexible enough to distribute loading over a
ring of petal shapes in ring assembly 26.
[0018] The petal ring assembly 26 of FIG. 1 is a preferred barrier
to be used with the backup member 22 of the present invention and
other barrier configurations with comparable performance can be
used in conjunction with backup member 22. Any stack of ring
members with circumferentially offset splits are contemplated such
as split rings that have offset gaps, for example. Even a single
ring with abrupt surface transitions can be used instead of the
FIG. 1 design with the backup member 22.
[0019] The initial shape shown in FIG. 5 can be maintained by
addition of adhesive as the shape is formed on the mandrel 10. The
adhesive can hold the shape intact as the mandrel is removed to
produce the chevron shape shown in FIG. 5. Once the backups 22 and
26 are assembled to the sealing element 24 and run to a
subterranean location it is desirable for the adhesive to release
to allow sliding among the windings to promote the setting process
where movement in the directions of arrows 32 and 34 are
contemplated. Normally the high temperatures, on the order of
450.degree. F., anticipated in the high pressure applications of
over 10,000 PSI for the present invention should be an aid in the
breakdown of the adhesive. Also beneficial to relative sliding
between winding as occurs when the backup member 22 is forced to
move in the directions of arrows 32 and 34 can be a coating on one
or both sides of the strip to reduce friction and promote relative
sliding movement that occurs when the backup member is flattened
and moves in the directions of arrows 32 and 34. The nature of the
material selected for the strip 16 can provide a desired low
coefficient of friction or/and a coating can be added or both.
Softer metals that can tolerate the well conditions such as brass
provide an added load spreading benefit. Coatings such as PTFE or
other materials compatible with the well fluids and operating
temperatures can also be used. The chevron shape promotes the
relative sliding that allows the overall shape to move under
compressive loading in directions of arrows 32 and 34. The strip 16
can be metallic, composite or other material that can be fabricated
in thin continuous strip for rolling on a mandrel. The taper angle
of taper 12 can vary between 5-60.degree. measured from the axis of
the mandrel 10.
[0020] The above description is illustrative of the preferred
embodiment and many modifications may be made by those skilled in
the art without departing from the invention whose scope is to be
determined from the literal and equivalent scope of the claims
below:
* * * * *