GB2382364A

GB2382364A - Packer cup

Info

Publication number: GB2382364A
Application number: GB0225807A
Authority: GB
Inventors: Witold P Serafin
Original assignee: POLAR COMPLETIONS ENGINEERING
Current assignee: POLAR COMPLETIONS ENGINEERING
Priority date: 2001-11-23
Filing date: 2002-11-05
Publication date: 2003-05-28
Also published as: US20030098153A1; GB0225807D0; CA2408309A1

Abstract

A packer cup 10 for isolating a high pressure zone from a lower pressure zone comprises a base ring 11 from which an annular body 12 extends. An intermediate section 17 formed from interwoven high strength reinforcing plies 18, such as wires or cables, is attached to the base ring 11. The packer cup 10 comprises an inner and outer layer 15, 16 bonded onto either side of the intermediate section 17. The inner and outer layers 15, 16 are formed from an elastomeric or rubber material to form a unitary and flexible structure. The intermediate layer 17 acts as an continuous, but flexible reinforcement to allow the expansion and contraction of the packer cup 10. The intermediate section 17 further prevents the inner and outer elastomeric layers 15, 16 from extruding whilst under pressure.

Description

1 "COMPOSITE PACKER CUP"

3 FIELD OF THE INVENTION

4 The present invention relates to packer cups and more specifically 5 to packer cups used as seals in packer cup assemblies acting to isolate zones 6 within a fornication by sealing a portion of the wellbore.

8 BACKGROUND OF THE INVENTION

9 Packer cups are known for use in hook wall packers and other 10 assemblies designed to isolate zones within a wellbore or to separate high and 11 low pressure zones within a wellbore. Typically, this type of operation is 12 performed for reservoir stimulations such as to stimulate a delimited portion of the 13 well with the introduction of acidic solutions to enhance reservoir flow. Often the

14 acidic solutions will further contain solvents, surfactants and antifoaming agents 15 all designed to aid in leaching substances, such as calcium carbonate and 16 asphaltenes from the formation, resulting in the opening of pores to increase 17 production. These constituents, dissolved in the highly acidic solution challenge 18 the materials of construction of the assemblies, particularly the packer cups.

19 Historically, to access a zone in a wellbore, it was necessary to first 20 "kill" the well by pumping a fluid into the well until sufficient hydrostatic pressure 21 was obtained to overcome the pressure of the formation and prevent fluids from 22 being blown out of the well. The welihead was removed and the necessary 23 treating apparatus tied into the production tubing. Following treatment the well 24 was swabbed to re-instate production.

1 A number of assemblies have been designed to replace the 2 historical process of killing the well, accessing and treating the well and swabbing 3 to reinstate production. US Patent 3,380,304 to Cummins describes one of the 4 earliest assemblies wherein a hollow high pressure mandrel, slidingly engaged 5 within a high pressure casing was provided. The casing was adapted to seal 6 against the welihead and the mandrel adapted to seal to the top of the production 7 tubing below the welihead. Thus, the mandrel could be extended or retracted and 8 fluids provided to the formation, all the while protecting the welihead from high 9 pressure. Seal means, between the outer surface of the mandrel and the interior 10 of the production tubing, were required to pump sand-laden fracturing fluids out 11 through the assembly described.

12 Mechanical packers and inflatable packers are known which can be 13 positioned in a well and actuated to seal a zone in a wellbore. Other assemblies, 14 such as hook wall, or cup-type packers are also known are inserted into the 15 wellbore in their actuated state.

16 The cup-type packers are inexpensive compared to inflatable or 17 mechanically actuated packers. The cup-type packers use elastomeric sealing 18 cups fabricated from elastomeric materials having metal reinforcing fingers 19 embedded in the elastomer. The cup is mounted on a pipe or mandrel for 20 insertion into the well. To effect a downhole wellbore seal, the cups are generally 21 oversized compared to the inner diameter of the well casing so as to bear against 22 the casing wall. The contact of the seal, against the casing, is further enhanced 23 by the resultant force of differential pressure across the seal. Typically, as 24 described in US Patent 4,424,865 to Payton Jr., the reinforcing metal elements 25 are fabricated as fingers which extend upwardly into the elastomeric body from a

1 metal base plate. The fingers expand radially outward, rotating from the metal 2 base as a result of increases in temperature and pressure, forcing the cup into 3 engagement with the casing side wall.

4 Conventional packer cups have a number of shortcomings. Firstly, 5 as the cups are always "actuated" and in contact with the wellbore, the exterior of 6 the cup is subjected to sustained mechanical abrasion against the casing side 7 wall during insertion and removal from the wellbore. Typically, installation 8 requires travel through a long bore which can result in removal of the exterior 9 portion of the elastomer to the point where the seal is compromised.

10 Secondly, packer cups are fabricated from synthetic rubber 11 materials that have limited mechanical properties under elevated temperature 12 and that are susceptible to repeated exposure to aggressive wellbore fluids.

13 Further, the interior of the packer cup is subjected to highly acidic, organo-solvent 14 based wellbore fracturing fluids which are highly corrosive and also destructive to 15 most synthetic rubbers, eventually resulting in a breach of the elastomeric 16 material, often failing due to extrusion of the elastomer through in the spaces 17 between the reinforcing elements.

18 Conventional packer cups are a compromise between chemical 19 resistance, mechanical abrasion resistance and structural properties.

1 SUMMARY OF THE INVENTION

2 The packer cup of the present invention comprises, in a broad 3 aspect, an inner chemically impervious elastomeric layer, an outer abrasion 4 resistant elastomeric layer and an internal interwoven fiber-reinforced flexible 5 layer, preferably metal. All three layers are formed into a unitary composite 6 packer cup capable of withstanding repeated mechanical insertion and removal 7 from the wellbore casing as well as exposure to harsh wellbore fluids. Further, 8 the composite inner layer provides additional reinforcement throughout the entire 9 cup structure, for strength to resist extrusion and withstand elevated pressures 10 and temperature commonly found downhole.

11 Preferably the chemically impervious inner layer is VitonrM and the 12 outer abrasion resistant layer is Nitrile_. The inner layer is an interwoven mesh 13 of high strength fibers such as aircraft cable attached to an annular base ring.

14 The cup has a body formed of the three layers which is shaped to flare upwardly 15 and outwardly from the base ring and has an annular flange extending outwardly 16 from the body adjacent an open first end for engaging the casing.

17 When the layers are bonded, preferably by vulcanizing, into a 18 unitary structure, the cup can be used in a packer assembly for isolating a zone 19 of high pressure containing harsh chemicals. The base ring is sealing engaged 20 with a mandrel for threading into production tubing and the annular flange 21 extends outwardly into an annulus formed between the production tubing and the 22 casing for sealing engaging the casing. The open first end is oriented to face 23 towards the zone of higher pressure so that the differential pressure across the 24 cup can act to further seal the cup against the casing.

1 A plurality of cups may be used in each packer assembly, the cups 2 being oriented to isolate the zone of interest. For isolating zones intermediate 3 ends of the production tubing, the cups may be positioned uphole and downhole, 4 with open ends facing or for other purposes such as isolating the welihead from 5 high pressure or cleaning perforations at the downhole end of a production string 6 they may all be oriented uphole or downhole as the case may be.

8 BRIEF DESCRIPTION OF THE DRAWINGS

9 Figure 1 is a perspective view of a packer cup of the present 1 0 invention; 11 Figure 2 is a cross-sectional view of a packer cup according to Fig. 12 1, showing the inner and outer elastomeric layers surrounding an intermediate 13 interwoven, flexible fiber reinforcing layer; 14 Figure 3 is cross-sectional view of packer cups of the present 15 invention installed in a packer assembly, the annular lip of the cup sealingly 16 engaging the casing wall and the base ring sealingly engaging the tubing string; 17 Figure 4 is a schematic cross-sectional view of a packer assembly 18 of Figure 3, having packer cups isolating a zone of high pressure intermediate the 19 production tubing; 20 Figure 5 is a schematic cross-sectional view of a packer assembly 21 having packer cups isolating a downhole zone of high pressure; and 22 Figure 6 is a schematic cross-sectional view of a packer assembly 23 having packer cups isolating an uphole zone of high pressure.

1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

2 Having reference to Figs. 1 and 2, a packer cup 10 of the present 3 invention is shown. The packer cup 10 comprises a base ring 11 from which an 4 annular body 12 extends and which enables mounting of the cup to a tool or 5 assembly 20 (Figs. 3-6). The cup body 12 has an open first end 13 having an 6 annular lip 21 and which has a radial extent which is larger in diameter than the 7 open second end 14. The second end 14 is attached to the base ring 11.

8 Typically, the radial extent of the open first end 13 is slightly larger in diameter 9 than an inner diameter of a wellbore casing string 30 into which the packer cup 10 10 is to be placed. As shown in Fig. 3, the smaller open second end 14 is sized to 11 snugly fit the base ring 11, which is fit into a packer cup assembly 20 for insertion 12 into a production tubing string 32.

13 As shown in Fig. 2, the packer cup 10 comprises three layers, an 14 inner layer 15, an outer layer 16 and an intermediate layer 17, disposed 15 therebetween. The three layers 15, 16, 17 are bonded together, such as by 16 vulcanizing, to form the unitary packer cup body 12.

17 In a preferred embodiment of the invention, the inner and outer 18 layers 15,16 are fabricated from elastomers which are specifically selected for the 19 contrary environments.

20 The inner layer 15 is an elastomer. There are many elastomers 21 which may be selected for chemical and temperature resistance.. Viton_ is such 22 a chemically impervious synthetic elastomer. Viton_ is typically impervious to the 23 corrosive nature of the wellbore fluids used in stimulation and fracturing.

24 However, by comparison to other elastomers, Viton_ is relatively mechanically 25 weak and not particularly resistant to abrasion.

l 1 The outer layer 16 is fabricated from a mechanically strong and 2 tough elastomer. There are many elastomers which may be selected to 3 toughness and temperature resistance. Once such elastomer is a synthetic such 4 as NitrilerM. Nitrile_, which is relatively impervious to hydrocarbons and very 5 mechanically strong such as for resisting abrasion. Nitrile_ does not have the 6 chemical resistant properties of Viton.

7 As shown in Fig. 2, the intermediate layer 17 comprises a mesh of 8 biased or helical, interwoven high strength reinforcing plies 18, such as wire or 9 more preferably aircraft cable, attached at a lower end 19 to the base ring 11.

10 The mesh 18, is typically a helically wound assembly so that the cup's annular 11 body can flex radially and expand and contract slightly with the inner and outer 12 15, 16 elastomeric layers. The plies 18 provide a substantially continuous 13 structural reinforcement throughout a substantial portion of the body 12 of the 14 packer cup 10. Examples of the manufacture and use of such mesh is known to 15 persons in the art of inflatable packers. It is known to vary the thickness and 16 number of cables, and helical build angle to affect their flexibility. Opposing 17 helical winds of cable plies result in a cries-cross pattern which assists in avoiding 18 extrusion of the inner layer 15 therethrough. An example of the selection of some 19 of these parameters is set forth in inflatable packer US Patent 5,778,982 the 20 entirety of which is incorporated herein.

21 In a preferred method of fabrication, the intermediate layer 17 is first 22 attached to the base ring 11 such as by brazing and then is embedded within the 23 inner 15 and outer layers 16. The packer cup 10, so assembled, is then 24 vulcanized to bond the layers 15,16,17 into a unitary structure, capable of

1 withstanding differential wellbore pressures across the cup, which can in the 2 range of 15,000 psi or greater without suffering extrusion failure.

3 Having reference again to Figs. 2 and 3, the cup's body 12 has an 4 annular lip 21 formed adjacent the first open end 13 for engaging the inner wall 5 31 of the casing string 30. Further, the body 12 is tapered at the second end 14, 6 about the annular ring 11 to allow insertion into the packer assembly 20.

7 As shown in Figs. 3 - 6, packer cups 10 are mounted to packer 8 assemblies 20 having a mandrel 33 for threading into or otherwise suitably 9 connection to a production tubing string 32, which is lowered into the wellbore 10 casing string 30. The annular ring 11 of the cup 10 is sealingly engaged against 11 the mandrel 33 while the annular lip 21 protrudes radially outward therefrom into 12 an annulus 34 formed between the mandrel 33 and the casing 30. The protruding 1 3 lips 21 of the packer assemblies 20 are squeezed into the casing 30 14 mechanically, by an insertion and rotation of the production tubing 32. Once in 1 5 position, the annular lips 21 seal against the inner wall 31 of the casing string 30.

16 The cups 10 are preferably oriented having the first open end 13 17 directed toward a zone of higher pressure 35 and away from a zone of lower 18 pressure 36 so that the differential pressure across the cup 10 further acts to 19 drive the annular lip 21 of the cup 10 to seal against the inner wall 31 of the 20 casing 30.

21 Fig. 4 illustrates one embodiment of a packer assembly 20 having 22 uphole and downhole packer cups 40, 41 which act to isolate an intermediate 23 zone of higher pressure 35 between the cups 40,41. This configuration of packer 24 assembly 20 is typically used in high pressure acid stimulation of delimited 25 portions of the formation 43 and is used to penetrate through a plurality of

1 wellbore casing perforations 45 to dissolve blockages and increase reservoir 2 flow. In such an embodiment, the outer layer 16 of the cups 40,41 is subjected to 3 abrasion during insertion while the inner layer 15 of each cup 40,41 is exposed to 4 corrosive stimulation fluids 44.

5 Similarly, Figs 5 and 6 illustrate alternate and simple embodiments 6 of assemblies employing the invention, each utilizing a single set of packer cups 7 10 in a packer assembly 20 for isolating a downhole or uphole zone of higher 8 pressure, respectively.

Claims

1 THE EMBODIMENTS OF THE INVENTION IN WHICH AN

2 EXCLUSIVE PROPERTY OR PRIVILEDGE IS CLAIMED ARE DEFINED AS

3 FOLLOWS:

5 1. An improved packer cup comprising: 6 an annular base ring for mounting to a packer assembly which is 7 positioned in a wellbore casing to isolate a higher pressure zone from a lower 8 pressure zone; 9 an annular cup extending from the annular base ring toward the 10 higher pressure zone and having 11 an elastomeric inner layer, and 12 an elastomeric outer layer; and 13 an annularly extending flexible intermediate layer of reinforcing plies 14 of material disposed between the inner and outer layers, and mounted at a lower 15 end to the base ring, the inner, outer and intermediate layers being bonded 16 together to form a unitary, flexible structure.

18 2. The improved packer cup as described in claim 1 wherein 19 the inner elastomeric layer is fabricated from a chemically impervious elastomer.

21 3. The improved packer cup as described in claim 2 wherein 22 the chemically impervious elastomer is Viton_.

24 4. The packer cup as described in claim 1 wherein the outer 25 layer is fabricated from an abrasion resistant elastomer.

1 5. The packer cup as described in claim 4 wherein the abrasion 2 resistant elastomer is Nitrile_.

4 6. The packer cup as described in claim 1 wherein the inner 5 layer is fabricated from Viton_ and the outer layer is fabricated from NitrilelM.

7 7. The packer cup as described in claim 1 wherein the 8 intermediate layer is formed of multiple, biased interwoven layers of reinforcing 9 plies having upper and lower ends, the lower ends being fixed circumferentially to 10 the annular base ring.

12 8. The packer cup as described in claim 7 wherein the 13 reinforcing fibers are metal wire.

15 9. The packer cup as described in claim 7 wherein the 16 reinforcing fibers are aircraft cable.

l 1 10. An improved packer cup for a packer assembly, the cup 2 isolating a higher pressure zone from a lower pressure zone in the wellbore 3 casing wherein an inside of the cup is exposed to corrosive chemicals and 4 hydrocarbons and an outside to mechanical abrasion, the improvement 5 comprising: 6 - an annular base ring; 7 - an annular cup extending from the base ring and toward the 8 zone of higher pressure and having, 9 an elastomeric chemically impervious inner layer, and 10 an elastomeric abrasion resistant outer layer; and 11 an annularly extending flexible interwoven fiber intermediate 12 layer, disposed between the inner and outer layers, and fixed at a lower end to 13 the base ring, the inner, outer and intermediate layers being bonded together to 14 form a unitary, flexible structure.

16 11. The packer cup as described in claim 10 wherein the inner 17 layer is fabricated from Viton_.

19 - 12. The packer cup of claim 10 wherein the outer layer is 20 fabricated from Nitrile_.

22 13. The packer cup as described in claim 10 wherein the inner 23 layer is fabricated from Viton_ and the outer layer is fabricated from Nitrile.

1 14. The packer cup as described in claim 10 wherein the 2 reinforcing plies are metal cables.

4 15. The packer cup as described in claim 13 wherein the 5 reinforcing plies are metal cables.

7 16. A cup-type packer assembly for positioning in a wellbore 8 casing comprising: 9 a mandrel for positioning in the casing and forming an annulus 10 therebetween; and 11 at least one packer cup, each cup having an annular base ring 12 sealing engaged concentrically about the mandrel and an annular body for 13 sealing against the wellbore casing for isolating a zone of higher pressure from a 14 zone of lower pressure in the wellbore casing, the annular body comprising an 15 elastomeric inner layer, an elastomeric outer layer; and an annularly extending 16 flexible intermediate layer of interwoven reinforcing plies disposed between the 17 inner and outer layers, the plies being mounted at a lower end to the base ring, 18 the inner, outer and intermediate layers being bonded together to form a unitary, 19 flexible structure.

1 17. The cup-type packer assembly of claim 13 wherein the 2 packer is used for chemical stimulation at a zone in the wellbore casing and 3 wherein, for each cup: 4 the inner elastomeric layer is fabricated from a chemically 5 impervious elastomer; and 6 the outer layer is fabricated from an abrasion resistant elastomer.

8 18. The cup-type packer assembly of claim 16 further 9 comprising: 10 one or more uphole cups mounted at an uphole end of the mandrel, 11 each cup's annular body extending downhole from its base ring; and 12 one or more downhole cups mounted at a downhole end of the 13 mandrel, each cup's annular body extending uphole from its base ring, the uphole 14 and downhole cups' outer layers being resistant to abrasion during positioning of 15 the packer in the wellbore casing and the uphole and downhole cups' inner layers 16 being resistant to chemicals during higher pressure wellbore stimulation.

18 19. The packer cup as described in claim 16 wherein the inner 19 layer is fabricated from Viton_.

21 20. The packer cup of claim 16 wherein the outer layer is 22 fabricated from NitrilelM.

24 21. The packer cup as described in claim 16 wherein the inner 25 layer is fabricated from Viton_ and the outer layer is fabricated from NitrilerM.

1 22. The packer cup as described in claim 16 wherein the 2 reinforcing plies are metal cables.

4 23. The packer cup as described in claim 21 wherein the 5 reinforcing plies are metal cables.

24. An improved packer cup constructed and arranged substantially as described in relation to Figs. 1 and 2 of the accompanying drawings