U.S. patent application number 09/990383 was filed with the patent office on 2003-05-29 for composite packer cup.
Invention is credited to Serafin, Witold P..
Application Number | 20030098153 09/990383 |
Document ID | / |
Family ID | 25536093 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030098153 |
Kind Code |
A1 |
Serafin, Witold P. |
May 29, 2003 |
Composite packer cup
Abstract
A packer cup for use in a packer assembly is disclosed. The cup
has an outer layer, an intermediate reinforcing layer of meshed
metal plies and an inner layer. The intermediate layer acts as a
continuous, but flexible reinforcement to allow expansion and
contraction of the cup as it is forced into the wellbore and to
resist extrusion of the elastomers under pressure. The cup outer
layer is preferably abrasion resistant and the inner layer is
preferably chemical resistant. The layers are vulcanized into a
unitary cup capable of resisting outer wear and tear as a result of
insertion into the wellbore and internal chemical deterioration as
a result of the harsh downhole environment.
Inventors: |
Serafin, Witold P.;
(Calgary, CA) |
Correspondence
Address: |
Sean W. Goodwin
Goodwin Berlin McKay
The Burns Building
237 - 8th Avenue S.E., Suite 360
Calgary
AB
T2G 5C3
CA
|
Family ID: |
25536093 |
Appl. No.: |
09/990383 |
Filed: |
November 23, 2001 |
Current U.S.
Class: |
166/202 ;
166/177.4 |
Current CPC
Class: |
E21B 33/126
20130101 |
Class at
Publication: |
166/202 ;
166/177.4 |
International
Class: |
E21B 033/12 |
Claims
The embodiments of the invention is which an exclusive property or
priviledge is claimed are defined as follows:
1. An improved packer cup comprising: an annular base ring for
mounting to a packer assembly which is positioned in a wellbore
casing to isolate a higher pressure zone from a lower pressure
zone; an annular cup extending from the annular base ring toward
the higher pressure zone and having an elastomeric inner layer, and
an elastomeric outer layer; and an annularly extending flexible
intermediate layer of reinforcing plies of material disposed
between the inner and outer layers, and mounted at a lower end to
the base ring, the inner, outer and intermediate layers being
bonded together to form a unitary, flexible structure.
2. The improved packer cup as described in claim 1 wherein the
inner elastomeric layer is fabricated from a chemically impervious
elastomer.
3. The improved packer cup as described in claim 2 wherein the
chemically impervious elastomer is Viton.TM..
4. The packer cup as described in claim 1 wherein the outer layer
is fabricated from an abrasion resistant elastomer.
5. The packer cup as described in claim 4 wherein the abrasion
resistant elastomer is Nitrile.TM..
6. The packer cup as described in claim 1 wherein the inner layer
is fabricated from Viton.TM. and the outer layer is fabricated from
Nitrile.TM..
7. The packer cup as described in claim 1 wherein the intermediate
layer is formed of multiple, biased interwoven layers of
reinforcing plies having upper and lower ends, the lower ends being
fixed circumferentially to the annular base ring.
8. The packer cup as described in claim 7 wherein the reinforcing
fibers are metal wire.
9. The packer cup as described in claim 7 wherein the reinforcing
fibers are aircraft cable.
10. An improved packer cup for a packer assembly, the cup isolating
a higher pressure zone from a lower pressure zone in the wellbore
casing wherein an inside of the cup is exposed to corrosive
chemicals and hydrocarbons and an outside to mechanical abrasion,
the improvement comprising: an annular base ring; an annular cup
extending from the base ring and toward the zone of higher pressure
and having, an elastomeric chemically impervious inner layer, and
an elastomeric abrasion resistant outer layer; and an annularly
extending flexible interwoven fiber intermediate layer, disposed
between the inner and outer layers, and fixed at a lower end to the
base ring, the inner, outer and intermediate layers being bonded
together to form a unitary, flexible structure.
11. The packer cup as described in claim 10 wherein the inner layer
is fabricated from Viton.TM..
12. The packer cup of claim 10 wherein the outer layer is
fabricated from Nitrile.TM..
13. The packer cup as described in claim 10 wherein the inner layer
is fabricated from Viton.TM. and the outer layer is fabricated from
Nitrile.TM..
14. The packer cup as described in claim 10 wherein the reinforcing
plies are metal cables.
15. The packer cup as described in claim 13 wherein the reinforcing
plies are metal cables.
16. A cup-type packer assembly for positioning in a wellbore casing
comprising: a mandrel for positioning in the casing and forming an
annulus therebetween; and at least one packer cup, each cup having
an annular base ring sealing engaged concentrically about the
mandrel and an annular body for sealing against the wellbore casing
for isolating a zone of higher pressure from a zone of lower
pressure in the wellbore casing, the annular body comprising an
elastomeric inner layer, an elastomeric outer layer; and an
annularly extending flexible intermediate layer of interwoven
reinforcing plies disposed between the inner and outer layers, the
plies being mounted at a lower end to the base ring, the inner,
outer and intermediate layers being bonded together to form a
unitary, flexible structure.
17. The cup-type packer assembly of claim 13 wherein the packer is
used for chemical stimulation at a zone in the wellbore casing and
wherein, for each cup: the inner elastomeric layer is fabricated
from a chemically impervious elastomer; and the outer layer is
fabricated from an abrasion resistant elastomer.
18. The cup-type packer assembly of claim 16 further comprising:
one or more uphole cups mounted at an uphole end of the mandrel,
each cup's annular body extending downhole from its base ring; and
one or more downhole cups mounted at a downhole end of the mandrel,
each cup's annular body extending uphole from its base ring, the
uphole and downhole cups' outer layers being resistant to abrasion
during positioning of the packer in the wellbore casing and the
uphole and downhole cups' inner layers being resistant to chemicals
during higher pressure wellbore stimulation.
19. The packer cup as described in claim 16 wherein the inner layer
is fabricated from Viton.TM..
20. The packer cup of claim 16 wherein the outer layer is
fabricated from Nitrile.TM..
21. The packer cup as described in claim 16 wherein the inner layer
is fabricated from Viton.TM. and the outer layer is fabricated from
Nitrile.TM..
22. The packer cup as described in claim 16 wherein the reinforcing
plies are metal cables.
23. The packer cup as described in claim 21 wherein the reinforcing
plies are metal cables.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to packer cups and more
specifically to packer cups used as seals in packer cup assemblies
acting to isolate zones within a formation by sealing a portion of
the wellbore.
BACKGROUND OF THE INVENTION
[0002] Packer cups are known for use in hook wall packers and other
assemblies designed to isolate zones within a wellbore or to
separate high and low pressure zones within a wellbore. Typically,
this type of operation is performed for reservoir stimulations such
as to stimulate a delimited portion of the well with the
introduction of acidic solutions to enhance reservoir flow. Often
the acidic solutions will further contain solvents, surfactants and
anti-foaming agents all designed to aid in leaching substances,
such as calcium carbonate and asphaltenes from the formation,
resulting in the opening of pores to increase production. These
constituents, dissolved in the highly acidic solution challenge the
materials of construction of the assemblies, particularly the
packer cups.
[0003] Historically, to access a zone in a wellbore, it was
necessary to first "kill" the well by pumping a fluid into the well
until sufficient hydrostatic pressure was obtained to overcome the
pressure of the formation and prevent fluids from being blown out
of the well. The wellhead was removed and the necessary treating
apparatus tied into the production tubing. Following treatment the
well was swabbed to re-instate production.
[0004] A number of assemblies have been designed to replace the
historical process of killing the well, accessing and treating the
well and swabbing to reinstate production. U.S. Pat. No. 3,380,304
to Cummins describes one of the earliest assemblies wherein a
hollow high pressure mandrel, slidingly engaged within a high
pressure casing was provided. The casing was adapted to seal
against the wellhead and the mandrel adapted to seal to the top of
the production tubing below the wellhead. Thus, the mandrel could
be extended or retracted and fluids provided to the formation, all
the while protecting the wellhead from high pressure. Seal means,
between the outer surface of the mandrel and the interior of the
production tubing, were required to pump sand-laden fracturing
fluids out through the assembly described.
[0005] Mechanical packers and inflatable packers are known which
can be positioned in a well and actuated to seal a zone in a
wellbore. Other assemblies, such as hook wall, or cup-type packers
are also known are inserted into the wellbore in their actuated
state.
[0006] The cup-type packers are inexpensive compared to inflatable
or mechanically actuated packers. The cup-type packers use
elastomeric sealing cups fabricated from elastomeric materials
having metal reinforcing fingers embedded in the elastomer. The cup
is mounted on a pipe or mandrel for insertion into the well. To
effect a downhole wellbore seal, the cups are generally oversized
compared to the inner diameter of the well casing so as to bear
against the casing wall. The contact of the seal, against the
casing, is further enhanced by the resultant force of differential
pressure across the seal. Typically, as described in U.S. Pat. No.
4,424,865 to Payton Jr., the reinforcing metal elements are
fabricated as fingers which extend upwardly into the elastomeric
body from a metal base plate. The fingers expand radially outward,
rotating from the metal base as a result of increases in
temperature and pressure, forcing the cup into engagement with the
casing side wall.
[0007] Conventional packer cups have a number of shortcomings.
Firstly, as the cups are always "actuated" and in contact with the
wellbore, the exterior of the cup is subjected to sustained
mechanical abrasion against the casing side wall during insertion
and removal from the wellbore. Typically, installation requires
travel through a long bore which can result in removal of the
exterior portion of the elastomer to the point where the seal is
compromised.
[0008] Secondly, packer cups are fabricated from synthetic rubber
materials that have limited mechanical properties under elevated
temperature and that are susceptible to repeated exposure to
aggressive wellbore fluids. Further, the interior of the packer cup
is subjected to highly acidic, organo-solvent based wellbore
fracturing fluids which are highly corrosive and also destructive
to most synthetic rubbers, eventually resulting in a breach of the
elastomeric material, often failing due to extrusion of the
elastomer through in the spaces between the reinforcing
elements.
[0009] Conventional packer cups are a compromise between chemical
resistance, mechanical abrasion resistance and structural
properties.
SUMMARY OF THE INVENTION
[0010] The packer cup of the present invention comprises, in a
broad aspect, an inner chemically impervious elastomeric layer, an
outer abrasion resistant elastomeric layer and an internal
interwoven fiber-reinforced flexible layer, preferably metal. All
three layers are formed into a unitary composite packer cup capable
of withstanding repeated mechanical insertion and removal from the
wellbore casing as well as exposure to harsh wellbore fluids.
Further, the composite inner layer provides additional
reinforcement throughout the entire cup structure, for strength to
resist extrusion and withstand elevated pressures and temperature
commonly found downhole.
[0011] Preferably the chemically impervious inner layer is
Viton.TM. and the outer abrasion resistant layer is Nitrile.TM..
The inner layer is an interwoven mesh of high strength fibers such
as aircraft cable attached to an annular base ring. The cup has a
body formed of the three layers which is shaped to flare upwardly
and outwardly from the base ring and has an annular flange
extending outwardly from the body adjacent an open first end for
engaging the casing.
[0012] When the layers are bonded, preferably by vulcanizing, into
a unitary structure, the cup can be used in a packer assembly for
isolating a zone of high pressure containing harsh chemicals. The
base ring is sealing engaged with a mandrel for threading into
production tubing and the annular flange extends outwardly into an
annulus formed between the production tubing and the casing for
sealing engaging the casing. The open first end is oriented to face
towards the zone of higher pressure so that the differential
pressure across the cup can act to further seal the cup against the
casing.
[0013] A plurality of cups may be used in each packer assembly, the
cups being oriented to isolate the zone of interest. For isolating
zones intermediate ends of the production tubing, the cups may be
positioned uphole and downhole, with open ends facing or for other
purposes such as isolating the wellhead from high pressure or
cleaning perforations at the downhole end of a production string
they may all be oriented uphole or downhole as the case may be.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a packer cup of the present
invention;
[0015] FIG. 2 is a cross-sectional view of a packer cup according
to FIG. 1, showing the inner and outer elastomeric layers
surrounding an intermediate interwoven, flexible fiber reinforcing
layer;
[0016] FIG. 3 is cross-sectional view of packer cups of the present
invention installed in a packer assembly, the upper edge of the cup
sealingly engaging the casing wall and the lower edge sealingly
engaging the tubing string;
[0017] FIG. 4 is a schematic cross-sectional view of a packer
assembly of FIG. 3, having packer cups isolating a zone of high
pressure intermediate the production tubing;
[0018] FIG. 5 is a schematic cross-sectional view of a packer
assembly having packer cups isolating a downhole zone of high
pressure; and
[0019] FIG. 6 is a schematic cross-sectional view of a packer
assembly having packer cups isolating an uphole zone of high
pressure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Having reference to FIGS. 1 and 2, a packer cup 10 of the
present invention is shown. The packer cup 10 comprises a base ring
11 from which an annular body 12 extends and which enables mounting
of the cup to a tool or assembly 20 (FIGS. 3-6). The cup body 12
has an open first end 13 having an annular lip 21 and which has a
radial extent which is larger in diameter than the open second end
14. The second end 14 is attached to the base ring 11. Typically,
the radial extent of the open first end 13 is slightly larger in
diameter than an inner diameter of a wellbore casing string 30 into
which the packer cup 10 is to be placed. As shown in FIG. 3, the
smaller open second end 14 is sized to snugly fit the base ring 11,
which is fit into a packer cup assembly 20 for insertion into a
production tubing string 32.
[0021] As shown in FIG. 2, the packer cup 10 comprises three
layers, an inner layer 15, an outer layer 16 and an intermediate
layer 17, disposed therebetween. The three layers 15, 16, 17 are
bonded together, such as by vulcanizing, to form the unitary packer
cup body 12.
[0022] In a preferred embodiment of the invention, the inner and
outer layers 15,16 are fabricated from elastomers which are
specifically selected for the contrary environments.
[0023] The inner layer 15 is an elastomer. There are many
elastomers which may be selected for chemical and temperature
resistance.. Viton.TM. is such a chemically impervious synthetic
elastomer. Viton.TM. is typically impervious to the corrosive
nature of the wellbore fluids used in stimulation and fracturing.
However, by comparison to other elastomers, Viton.TM. is relatively
mechanically weak and not particularly resistant to abrasion.
[0024] The outer layer 16 is fabricated from a mechanically strong
and tough elastomer. There are many elastomers which may be
selected to toughness and temperature resistance. Once such
elastomer is a synthetic such as Nitrile.TM.. Nitrile.TM., which is
relatively impervious to hydrocarbons and very mechanically strong
such as for resisting abrasion. Nitrile.TM. does not have the
chemical resistant properties of Viton.TM..
[0025] As shown in FIG. 2, the intermediate layer 17 comprises a
mesh of biased or helical, interwoven high strength reinforcing
plies 18, such as wire or more preferably aircraft cable, attached
at a lower end 19 to the base ring 11. The mesh 18, is typically a
helically wound assembly so that the cup's annular body can flex
radially and expand and contract slightly with the inner and outer
15, 16 elastomeric layers. The plies 18 provide a substantially
continuous structural reinforcement throughout a substantial
portion of the body 12 of the packer cup 10. Examples of the
manufacture and use of such mesh is known to persons in the art of
inflatable packers. It is known to vary the thickness and number of
cables, and helical build angle to affect their flexibility.
Opposing helical winds of cable plies result in a criss-cross
pattern which assists in avoiding extrusion of the inner layer 15
therethrough. An example of the selection of some of these
parameters is set forth in inflatable packer U.S. Pat. No.
5,778,982 the entirety of which is incorporated herein.
[0026] In a preferred method of fabrication, the intermediate layer
17 is first attached to the base ring 11 such as by brazing and
then is embedded within the inner 15 and outer layers 16. The
packer cup 10, so assembled, is then vulcanized to bond the layers
15,16,17 into a unitary structure, capable of withstanding
differential wellbore pressures across the cup, which can in the
range of 15,000 psi or greater without suffering extrusion
failure.
[0027] Having reference again to FIGS. 2 and 3, the cup's body 12
has an annular lip 21 formed adjacent the first open end 13 for
engaging the inner wall 31 of the casing string 30. Further, the
body 12 is tapered at the second end 14, about the annular ring 11
to allow insertion into the packer assembly 20.
[0028] As shown in FIGS. 3-6, packer cups 10 are mounted to packer
assemblies 20 having a mandrel 33 for threading into or otherwise
suitably connection to a production tubing string 32, which is
lowered into the wellbore casing string 30. The annular ring 11 of
the cup 10 is sealingly engaged against the mandrel 33 while the
annular lip 21 protrudes radially outward therefrom into an annulus
34 formed between the mandrel 33 and the casing 30. The protruding
lips 21 of the packer assemblies 20 are squeezed into the casing 30
mechanically, by an insertion and rotation of the production tubing
32. Once in position, the annular lips 21 seal against the inner
wall 31 of the casing string 30.
[0029] The cups 10 are preferably oriented having the first open
end 13 directed toward a zone of higher pressure 35 and away from a
zone of lower pressure 36 so that the differential pressure across
the cup 10 further acts to drive the annular lip 21 of the cup 10
to seal against the inner wall 31 of the casing 30.
[0030] FIG. 4 illustrates one embodiment of a packer assembly 20
having uphole and downhole packer cups 40, 41 which act to isolate
an intermediate zone of higher pressure 35 between the cups 40,41.
This configuration of packer assembly 20 is typically used in high
pressure acid stimulation of delimited portions of the formation 43
and is used to penetrate through a plurality of wellbore casing
perforations 45 to dissolve blockages and increase reservoir flow.
In such an embodiment, the outer layer 16 of the cups 40,41 is
subjected to abrasion during insertion while the inner layer 15 of
each cup 40,41 is exposed to corrosive stimulation fluids 44.
[0031] Similarly, FIGS. 5 and 6 illustrate alternate and simple
embodiments of assemblies employing the invention, each utilizing a
single set of packer cups 10 in a packer assembly 20 for isolating
a downhole or uphole zone of higher pressure, respectively.
* * * * *