GB2469870A - Support assembly for a downhole tool - Google Patents

Abstract

A downhole apparatus 14 and a support assembly 18 therefor is described. The downhole apparatus, such as a packer, has a radially expanding portion 26 comprising a swellable elastomeric material selected to increase in volume on exposure to at least one predetermined fluid. The expanding portion may be a ring. The support assembly is operable to be deployed from a first retracted position (fig 2) to a second expanded condition (fig 11) in which it at least partially covers an end of the radially expanding portion of the apparatus. The support assembly comprises an inner surface 32 arranged to face the radially expanding portion, wherein at least a portion of this surface is concave.

Description

1 lmrovements to swellable aiaratus 3 The present invention relates to downhole apparatus for use in hydrocarbon wells, and 4 more particularly to downhole apparatus for use with swellable materials, such as are used in the hydrocarbon exploration and production industries. The invention also relates to a 6 downhole tool incorporating the apparatus, and a method of use. Embodiments of the 7 invention relate to isolation and sealing applications which use swellable wellbore packers.

9 BackQround to the invention 11 In the field of hydrocarbon exploration and production, various tools are used to provide 12 fluid seals between two components in a wellbore. Annular barriers have been designed 13 for preventing undesirable flow of wellbore fluids in the annulus between a wellbore tubular 14 and the inner surface of a surrounding tubular or the borehole wall. In many cases, the annular barriers provide a fluid seal capable of holding a significant pressure differential 16 across its length. In one application, a welibore packer is formed on the outer surface of a 17 completion string which is run into an outer casing in a first condition having a particular 18 outer diameter. When the packer is in its desired downhole location, it is inflated or 19 expanded into contact with the inner surface of the outer casing to create a seal in the 1 annulus. Similar wellbore packers have been designed for use in openhole environments, 2 to create a seal between a tubular and the surrounding wall of the wellbore.

4 Conventional packers are actuated by mechanical or hydraulic systems. A force or pressure is applied from surface to radially move a mechanical packer element into 6 contact with the surrounding surface. In an inflatable packer, fluid is delivered from 7 surface to inflate a chamber defined by a bladder around the tubular body.

9 More recently, wellbore packers have been developed which include a mantle of swellable material formed around the tubular. The swellable material is selected to increase in 11 volume on exposure to at least one predetermined fluid, which may be a hydrocarbon fluid 12 or an aqueous fluid or brine. The swellable packer may be run to a downhole location in 13 its unexpanded state, where it is exposed to a wellbore fluid and caused to increase in 14 volume. The design, dimensions and swelling characteristics are selected such that the swellable packer element expands to create a fluid seal in the annulus to isolate one 16 wellbore section from another. Swellable packers have several advantages over 17 conventional packers, including passive actuation, simplicity of construction, and 18 robustness in long term isolation applications.

In addition, swellable packers may be designed for compliant expansion of the swellable 21 mantle into contact with a surrounding surface, such that the force imparted on the surface 22 prevents damage to a rock formation or sandface, while still creating an annular barrier or 23 seal. Swellable packers therefore lend themselves well to open hole completions in loose 24 or weak formations.

26 The materials selected to form a swellable element in a swellable packer vary depending 27 on the specific application. Swellable materials are elastomeric (i.e. they display 28 mechanical and physical properties of an elastomer or natural rubber). Where the 29 swellable mantle is designed to swell in hydrocarbons, it may comprise a material such as an ethylene propylene diene monomer (EPDM) rubber. Where the swellable mantle is 31 required to swell in aqueous fluids or brines, the material may for example comprise an N- 32 vinyl carboxylic acid amide-based crosslinked resin and a water swellable urethane in an 33 ethylene propylene rubber matrix. Suitable materials for swellable packers are described 34 in GB 2411918 orW020051012686. In addition, swellable elastomeric materials designed to increase in volume in both hydrocarbon fluids and aqueous fluids are described in the 1 applicant's co-pending International patent publication numbers W02008/1 55564 and 2 W02008/1 55565.

4 Applications of swellable tools are limited by a number of factors including their capacity for increasing in volume, their ability to create a seal, and their mechanical and physical 6 properties when in their unexpanded and expanded states. A swellable packer may be 7 exposed to high pressure differentials during use. The integrity of the annular seal created 8 by a well packer is paramount, and a tendency of the swellable material to extrude, deform 9 or flow under forces created by the pressure differential results in a potential failure mode between the apparatus and the surrounding surface. In practice therefore, swellable tools 11 and in particular swellable packers, will be designed to take account of the limitations of 12 the material. For example, a swellable packer may be run with an outer diameter only 13 slightly smaller than the inner diameter of the surrounding surface, in order to limit the 14 percentage volume increase of the swellable material during expansion. In addition, swellable packers may be formed with packer elements of significant length, greater than 16 those of equivalent mechanical or hydraulic isolation tools, in order to increase the 17 pressure rating and/or reduce the chances of breaching the seal at high differential 18 pressures.

International patent publication numberWO 2006/121340 describes an expandable end 21 ring for a swellable packer which is said to anchor the packer material to the tubular more 22 effectively. However, the arrangement of WO 2006/121340 does not address the 23 problems of extrusion of the swellable material in use.

The applicant's co-pending International patent publication number WO 2008/062186 26 describes a support structure suitable for use with a swellable packer, which is operable to 27 be deployed from a first unexpanded condition to a second expanded condition by the 28 swelling of the packer. By providing a support structure which substantially covers the end 29 of the swellable mantle, extrusion of the swellable material is mitigated. This permits packers to be produced with a required pressure rating which are shorter in length than 31 conventional swellable packers. Furthermore, packers can be formed with reduced outer 32 diameter, as the mechanical strength of the elastomeric material is less critical. The 33 packer can therefore be engineered to have a larger expansion factor while maintaining 34 shear strength and differential pressure rating. The arrangement of WO 2008/062186 therefore allows a swellable packer to be used over a wider range of operating 1 parameters. Although the arrangement of WO 2008/062186 is suitable for use in many 2 wellbore applications, in certain conditions its effectiveness and/or practicality are limited.

4 It is one aim of an aspect of the invention to provide a support assembly for a swellable material in a downhole apparatus, which is improved with respect to previously proposed 6 support assemblies.

8 Other aims and objects will become apparent from reading the following description.

1 Sum mary of the Invention 3 According to a first aspect of the invention there is provided a downhole apparatus having 4 a radially expanding portion comprising a swellable elastomeric material selected to increase in volume on exposure to at least one predetermined fluid and a support 6 assembly operable to be deployed from a first retracted position to a second expanded 7 condition in which it at least partially covers an end of the radially expanding portion; 8 wherein the support assembly comprises an inner surface arranged to face the radially 9 expanding portion, and at least a portion of the inner surface is concave.

11 Elastomeric in this context means having the physical or mechanical properties of a 12 rubber, and elastomeric material includes synthetic polymer materials and natural rubbers.

14 According to a second aspect of the invention there is provided a support assembly for a downhole apparatus having a radially expanding portion, wherein the radially expanding 16 portion comprises a swellable elastomeric material selected to increase in volume on 17 exposure to at least one predetermined fluid, wherein the support assembly is operable to 18 be deployed from a first retracted position to a second expanded condition in which it at 19 least partially covers an end of a radially expanding portion of the apparatus; wherein the support assembly comprises an inner surface arranged to face the radially expanding 21 portion, and at least a portion of the inner surface is concave.

23 By providing a support assembly with a partially or fully concave inner surface, the support 24 assembly is improved with respect to prior art designs. A larger volume of swellable material can be accommodated beneath the support assembly per unit axial length of the 26 support assembly. Thus the volume of swellable elastomeric material that can be 27 accommodated between the support assembly and the body of the apparatus is increased 28 with respect to the prior art, providing a more robust sealing element.

Efficiently maximising the volume of rubber may in some embodiments allow a reduced 31 radial profile of the support assembly and downhole apparatus, i.e. a sufficient volume can 32 be accommodated beneath a support assembly of reduced outer diameter. The concave 33 shape also allows the support assembly to be formed over a shorter axial length of the 34 tool, compared with support devices proposed in the prior art. This reduces the additional length of the apparatus, or alternatively allows the length of the main swellable part of the 1 apparatus to be maintained. This is a particular advantage in certain applications, 2 including fracturing (or "fracing") applications.

4 The concave surface may be in the form of a curved bowl and/or may have a parabolic shape. The inventors have appreciated that such a concave shape provides an efficient 6 transfer of swelling forces -which have radial and longitudinal components -to the 7 support assembly for deployment to the expanded condition. This allows the support 8 assembly to be deployed more easily, and in some cases further, than support devices 9 proposed in the prior art. Thus the deployment of the support assembly has a reduced impact on the normal swelling profile and swell time of the apparatus. In particular the 11 inventors have appreciated that the concave shape provides an efficient harnessing of 12 longitudinal forces -for example due to down weight, pulling force, or differential pressures 13 -which are directed to further deploy of the support assembly. This improves the 14 operation of the support assembly by increasing its anti-extrusion and immobilisation capabilities, resulting in a more reliable annular seal.

17 The support assembly may be configured to be deployed to its second expanded condition 18 by pivoting or otherwise deforming a main support component, which may be a main 19 support ring. The support assembly may comprise an inner portion, positioned adjacent a body of the apparatus (which may be a tubular such as a base pipe, or may be a 21 cylindrical mandrel) and a distal edge which moves outwardly with respect to the body of 22 the apparatus. The support assembly preferably extends radially and longitudinally of the 23 apparatus, and may therefore define an annular volume between the body of the 24 apparatus and an inner surface of the support assembly. Advantageously, the volume of swellable elastomeric material adjacent a pivot or deformation point of the support 26 assembly is increased compared with the prior art.

28 In a preferred embodiment of the invention, the apparatus comprises a first annular 29 volume of swellable elastomeric material disposed between the support assembly and a body of the apparatus, which may be an elastomeric ring member formed from a swellable 31 material. The elastomeric ring member may form a part of the radially expanding portion 32 of the apparatus. The apparatus may comprise a second annular volume of swellable 33 elastomeric material, which may be disposed on the body adjacent the first annular 34 volume. The second annular volume of swellable elastomeric material may for example form a majority of the swellable mantle of a wellbore packer. Thus the radially expanding 1 portion may be of compound construction, consisting of the first and second volumes of 2 swellable elastomeric material in combination.

4 At an opposing end of the apparatus, a similar support assembly and! or volume of swellable material may be provided to complete the opposing end of the wellbore packer.

7 Using first and second annular volumes of swellable material may offer certain 8 manufacturing and!or operational advantages. For example, the first and second annular 9 volumes may be formed sequentially. In a preferred embodiment of the invention, the second annular volume is disposed on the body of the apparatus, and over at least a part 11 of the first annular volume. The first annular volume may comprise a ring member, with a 12 part sloping surface portion. Preferably the sloping surface portion is concave.

14 The interface between the first and second volumes of swellable elastomeric material may be configured to provide one or more exhaust paths for gases, which may otherwise 16 become trapped under layers of rubber used to form the first and!or annular volumes. In 17 particular, air may become trapped during the location of several layers of elastomer 18 material during manufacturing process. Other gases, formed as by-products of the 19 manufacturing process, may also become trapped.

21 An additional advantage of the compound structure comprising two volumes of swellable 22 material is that different materials with different chemical or mechanical properties may be 23 used to form the compound radially expanded portions. For example, the materials of the 24 first and second annular volumes may be selected to differ in one or more of the following characteristics: fluid penetration, fluid absorption, swelling co-efficient, swelling coefficient, 26 swelling rate, elongation coefficient, hardness, resilience, elasticity, tensile strength, shear 27 strength, elastic modulus, and density. In one embodiment, the first volume is an 28 elastomeric material selected to be relatively hard and relatively highly cross-linked, 29 compared to the elastomer of the swellable mantle. This may reduce the tendency of the ring member to extrude before and after swelling.

32 It will be appreciated that embodiments of the second aspect of the invention may 33 comprise preferred and/or optional features defined above with respect to the 34 incorporation of the assembly within a downhole apparatus.

1 According to a third aspect of the invention there is provided a downhole apparatus having 2 a radially expanding portion comprising a swellable elastomeric material selected to 3 increase in volume on exposure to at least one predetermined fluid and a support 4 assembly, wherein the support assembly comprises a main support component operable to be deployed from a first retracted position to a second expanded condition in which it at 6 least partially covers an end of the radial expanding portion; and further comprises an 7 energising member disposed between the radially expanding portion and the main support 8 component.

In this context "disposed between" means that the radially expanding portion and the main 11 support component are positioned on either side of the energising member, but does not 12 necessarily mean "adjacent to" or "in abutment with", unless the context requires 13 otherwise. In embodiments of the invention, there may be additional components located 14 between the radially expanding portion and the energising member, and/or the main support component and the energising member.

17 Use of an energising member serves to improve the deployment of the support device 18 and/or the expansion of the radially expanding portion. Preferably, the energising member 19 directs a compression load to the radially expanding member, which may then be distributed as a radial expansion force. The energising member may therefore direct 21 compressive axial forces from the support member and transfer them to the radial 22 expanding portion. The radial expanding portion may in turn act on the main support 23 component to further deploy it to an expanded condition.

Preferably, the energising member comprises an abutment surface, which may face the 26 radially expanding portion. At least a portion of the abutment surface abuts a face or nose 27 of the radial expanding portion. The abutment surface may be oriented in a plane 28 perpendicular to the axis of the downhole apparatus, or may be inclined to such a plane in 29 other embodiments. Preferably the energising member is a ring, which may function as a piston in use.

32 Preferably, the energising member is operable to direct an axial force, such as a force due 33 to a pressure differential and/or weight on the base pipe, to the energising member to 34 energise a seal.

1 Preferably the energising member is an energising ring moveable on a body of the 2 apparatus.

4 The support assembly, preferably a main support component thereof, may comprise a pivot which permits movement of a flared portion of the support assembly with respect to a 6 body of the apparatus. The pivot may be radially displaced from the body of the 7 apparatus, to create a lever effect in the support assembly. Movement of a part of the 8 support assembly radially outward of the pivot may therefore generate a compressive 9 force on the energising member.

11 Embodiments of the third aspect of the invention may comprise preferred and/or optional 12 features of the first or second aspect of the invention or vice versa.

14 According to a fourth aspect of the invention, there is provided a method of forming a seal in a wellbore, the method comprising the steps of: 16 providing a downhole apparatus in a wellbore, the apparatus having a radially expanding 17 portion comprising a swellable elastomeric material selected to increase in volume on 18 exposure to at least one predetermined fluid; 19 exposing the downhole apparatus to at least one predetermined fluid to swell the swellable elastomeric material and create a seal in the wellbore; 21 deploying a support assembly to an expanded position in which it at least partially covers 22 an end of the radially expanding portion; 23 partially energising the seal by directing a force from the support assembly to the radially 24 expanding portion via an energising member.

26 The method preferably involves deploying the support assembly by swelling of the 27 swellable elastomeric material.

29 Preferably the force from the support assembly to the radially expanding portion is a compressive force. The compressive force may result, at least in part, from the 31 deployment of the support assembly. In a preferred embodiment, the support assembly 32 pivots or otherwise deforms by swelling of the swellable elastomeric material, and an inner 33 part of the support assembly directs a compressive axial force through the energising 34 member. The energising member preferably imparts a force on the swellable elastomeric material via an abutment surface. The swellable elastomeric material may direct the force 1 from the support assembly radially outward, to enhance the seal with a surface 2 surrounding the apparatus. In a preferred embodiment, the force is directed to further 3 deploy the support assembly to an expanded position.

Embodiments of the fourth aspect of the invention may comprise preferred and/or optional 6 features of any of the first to third aspects of the invention or vice versa.

8 According to a fifth aspect of the invention there is provided a downhole apparatus 9 comprising a swellable elastomeric material selected to increase in volume on exposure to at least one predetermined fluid, the apparatus comprising a body, a ring member located 11 on the body. and a volume of swellable elastomeric material disposed over the body 12 proximal to at least a part of the ring member; 13 wherein a gas exhaust path is provided between the ring member and the volume of 14 swellable elastomeric material.

16 Preferably the volume of swellable elastomeric material is formed from multiple layers, 17 which may be wrapped around the body. The multiple layers may be layers of uncured 18 elastomer material. However, in alternative embodiments, the layers may be of partially, 19 substantially, or fully cured elastomeric materials.

21 By providing an exhaust path, gases, including air or gases formed as by-products from 22 the manufacturing process, are able to pass out of the volume and out to the surface.

23 These gases may otherwise become trapped between layers of the swellable material 24 leaving cavities in the formed body. Such cavities reduce the integral strength of the swellable body and/or create a potential failure mode. Gas pockets also affect the 26 passage of fluids through the swellable body and therefore affect the swelling 27 characteristics of the tool.

29 Preferably the apparatus comprises ar-i outer layer of swellable material disposed over the gas exhaust path.

32 The ring member may comprise a swellable elastic material, and may therefore form part 33 of a compound radially expanding member. The swellable elastomer material of the ring 34 member may be selected to have identical, or substantially the same, chemical and mechanical properties as the swellable elastomeric material selected for the volume.

1 Alternatively, the material of the ring member may be selected to differ in one or more of 2 the following characteristics: fluid penetration, fluid absorption, swelling coefficient, 3 swelling co-efficient, swelling rate, elongation coefficient, hardness, resilience, elasticity, 4 tensile strength, shear strength, elastic modulus and density. In one embodiment, the elastomer of the ring member is selected to be relatively hard and relatively highly cross- 6 linked, compared to the elastomer of the swellable mantle. This may reduce the tendency 7 of the ring member to extrude before and after swelling.

9 In alternative embodiments of this aspect of the invention, the ring member is formed from, or partially formed from, a non-swellable material such as an elastomer, plastic, metal, 11 ceramic or composite material.

13 According to a sixth aspect of the invention there is provided a method of forming a 14 downhole apparatus comprising a swellable elastomeric material selected to increase in volume on exposure to at least one predetermined fluid, the method comprising: 16 providing a ring member located on a body; 17 forming a volume of swellable elastomeric material adjacent at least a part of the ring 18 member; 19 providing an exhaust path between the ring member and the volume of swellable elastomeric material for gases during the formation of the volume of swellable elastomeric 21 material.

23 The method may comprise the additional step of forming multiple layers of a swellable 24 elastomeric material to provide a swellable mantle.

26 The volume of swellable elastomeric material may be formed over at least a part of the 27 ring member. The ring member may have a sloping surface portion. Successive layers of 28 the swellable elastomeric material may be formed over successively greater parts of the 29 ring member.

31 The method may include the subsequent step of curing (or re-curing) the multiple layers on 32 the body, while maintaining the exhaust path.

34 The method may comprise a subsequent step of forming an outer layer of swellable elastomeric material over the exhaust path.

2 Embodiments of the sixth aspect of the invention may comprise preferred and/or optional 3 features of any of the first to fifth aspects of the invention or vice versa.

According to a seventh aspect of the invention, there is provided a wellbore packer 6 comprising the apparatus of any of the first, third or fifth aspects of the invention.

1 There will now be described, by way of example only, various embodiments of the 2 invention with reference to the drawings, of which: 4 Figure 1 is a longitudinal section through a wellbore packer incorporating a support assembly in accordance with an embodiment of the invention; 7 Figure 2 is a longitudinal section of a detail of Figure 1; 9 Figure 3 is a longitudinal section and part side view part of a support assembly according to the embodiment of Figure 1; 12 Figure 4A is a part section through a main support ring of Figure 3, showing some inside 13 surface features; Figure 4B is an end view showing an inside surface of the main support ring of the 16 embodiment of Figure 3; 18 Figure 5A is a side view of a containing layer used with the embodiment of Figure 3; Figure 5B is an end view of the containing layer of Figure 5A; 22 Figure 6 is a detailed side view of a containing layer according to an alternative 23 embodiment of the invention; Figures 7A and 7B are respectively side and end views of a first intermediate layer of the 26 embodiment of Figure 3; 28 Figures 8A and 8B are respectively side and end views of a second intermediate layer of 29 the embodiment of Figure 3; 31 Figure 9 is a longitudinal section of a ring member used in the embodiment of Figure 3; 33 Figures 1OA to 100 show schematically a manufacturing method according to an 34 embodiment of the invention; 1 Figure 11 schematically shows the wellbore packer and support assembly in an expanded 2 condition in a wellbore; 4 Figure 12 is a sectional view through a detail of a support assembly in accordance with an alternative embodiment of the invention; 7 Figure 13 is a sectional view through a ring member in accordance with a further 8 alternative embodiment of the invention; Figure 14 is a sectional view through a detail of a support assembly in accordance with a 11 further alternative embodiment of the invention; and 13 Figure 15 is a sectional view through a detail of a support assembly in accordance with a 14 further alternative embodiment of the invention.

16 Detailed descrirtion 18 Referring firstly to Figure 1, there is shown in longitudinal section a downhole apparatus in 19 the form of a wellbore packer, generally depicted at 10. The wellbore packer 10 is formed on a base pipe 12, and comprises a mantle 14 and pair of end rings 16. A support 21 assembly 18 is provided between the mantle 14 and each of the end rings 16 at opposing 22 ends of the packer 10. The end rings 16 are secured to the base pipe 12, in this case by 23 screws which extend radially through the end rings 16 and into abutment with the base 24 pipe body 12.

26 The mantle 14 is formed from a swellable elastomeric material selected to increase in 27 volume on exposure to a predetermined triggering fluid. Such materials are known in the 28 art, for example from GB 2411918 and WO 2005/012686. In this embodiment, the 29 swellable elastomeric material is an ethylene propylene diene monomer (EPDM) rubber selected to swell in hydrocarbon fluids, but alternative embodiments may comprise 31 materials which swell in aqueous fluids, or which swell in both hydrocarbon and aqueous 32 fluids. In Figure 1, the apparatus is shown in a run-in configuration. The mantle 14 is in 33 an unswollen condition, and its outer diameter (00) is approximately flush with the 00 of 34 the end rings 16.

1 Figure 2 is an enlarged view of a portion 20 of the wellbore packer 10. The drawing shows 2 a longitudinal section of a part of the support assembly 18, an end ring 16, and the mantle 3 14. The construction of the apparatus 10 and the support assembly 18 is described herein 4 with reference to Figures 3 to 11, which show parts of the apparatus in more detail. The support assembly 18 is shown before location on a base pipe 12 in Figure 3. The upper 6 half of Figure 3 shows the assembly in section, and the lower half shows the assembly 7 from an external side view.

9 The support assembly 18 comprises a main support ring 22, an energising ring 24, and an elastomeric ring member 26, each defining throughbores sized to accommodate the base 11 pipe 12. The main support ring 22 (shown most clearly in Figures 4A and 4B) is formed 12 from a metal such as steel, and comprises a neck portion 28 and a flared portion 30. The 13 neck portion 28 is received in a corresponding recess 31 in the end ring 19, and abuts the 14 end wall of the recess. The flared portion 30 extends radially and longitudinally on the base pipe 12 to define an internal volume (when assembled) which accommodates a part 16 of the elastomeric ring member 26. The main support ring 22 comprises a concave inner 17 surface 32 which defines a cup, and the outer surface 34 is angled to define a conical part 18 34a and a cylindrical part 34b.

The main support ring 22 is provided with circumferentially spaced slots 36 which extend 21 from an outer edge 35 (distal the base pipe), through the flared portion 30 to a 22 predetermined depth, to define leaves 38 in the flared portion 30. The slots 36 facilitate 23 deployment of the support assembly 18, allowing opening of the slots 36 by pivoting or 24 deformation of the leaves 38. The slots 36 may for example be formed by water jet cutting or wire cutting.

27 The main support ring 22 also defines a pivot formation 39, which is in the form of a 28 circular edge that abuts the end ring 16. The operation of the pivot 39 will be described 29 below.

31 The support assembly 18 comprises a containment layer 40, a first intermediate layer 42, 32 and a second intermediate layer 44. The containment layer 40, shown in more detail in 33 Figures 5A and SB, is formed from a layer of Cl 01 copper foil in a press-forming process.

34 The layer 40 has an extended neck portion 46 and a flared portion 48 provided with a cup-like shape corresponding to the concave shape of inner surface 32 of the main support 1 ring 22. Slots 50 are circumferentially spaced in the flared portion 48 to define leaves 52.

2 The spacing of the slots 50 is selected to correspond to the spacing of the slots 36, 3 although when the support assembly 18 is assembled, the slots are offset with respect to 4 one another.

6 The extended neck portion 46 has an inner section 54 which is disposed between the main 7 support ring 22 and the base pipe in use, and an outer section 55 which is forged to 8 extend over and around the neck portion 28 of the main support ring 22, as is most clearly 9 shown in Figure 2. The containment layer 40 is therefore held in place in the assembly 18 by the main support ring 22.

12 In an alternative embodiment of the invention, shown in Figure 6, a containment layer 40' 13 is used. The containment layer 40' is similar in shape and function to the containment 14 layer 40, although its extended neck portion 46' differs in that it is provided with slots 56.

The slots 56 facilitate flaring of the extended neck portion around the neck portion 28 of 16 the main support ring 22.

18 The first intermediate layer 42, shown most clearly in Figures 7A and 7B, is formed from a 19 layer of ClOl copper foil in a press-forming process, and is disposed between the containment layer 40 and the main support 22, adjacent the containment layer 40. The 21 layer 42 is flared in a cup-like shape corresponding to the concave shape of inner surface 22 32 of the main support ring 22. Slots 58 define leaves 60, and again the spacing of the 23 slots 58 is selected to correspond to the spacing of the slots 36. When the support 24 assembly 18 is assembled, the slots 58 are offset with respect to the slots 36 and the slots 50. Thus the slots 36, 50 and 58 are phased such that they are out of alignment, and any 26 path through the slots from an internal volume to the exterior of the assembly is highly 27 convoluted.

29 The second intermediate layer 44, shown most clearly in Figures 8A and 8B, is similar to layer 42 and will be understood from Figures 7A and 7B. However, the second 31 intermediate layer differs in that it is formed from annealed stainless steel. The layer 44 is 32 disposed between the layer 42 and the inner surface 32 of the main support ring 22. Slots 33 62, formed by water jet or wire cutting, define leaves 64, with the same angular spacing as 34 the slots in the main support ring 22, and layers 40 and 42. The slots 62 are offset with 1 the slots in the other layers to define a highly convoluted path from the internal volume 2 defined by the assembly to a volume outside of the main support ring.

4 The elastomeric ring member 26, shown in isolation in Figure 9, is pre-moulded from a swellable elastomeric material, which in this case is the same as the swellable elastomeric 6 material used to form mantle 14. The ring member 26 is disposed on and bonded to the 7 base pipe 12 and has an outer end 64 which generally faces the support assembly 18, and 8 an inner end 66 which generally faces the mantle 14. The outer end 64 has a convex 9 shape which corresponds to the concave shape of the layers 40, 42, 44 and the surface 32, and a planar nose 68. The inner end 66 has a shape corresponding to the shape of 11 the end of the mantle 14, and in this case is concave, sloping downwards from its 00 to its 12 innermost edge 70. The effects of the shape of the inner end 66 will be described in more 13 detail below. The elastomeric ring member 26, together with the mantle 14, forms a 14 radially expanding portion of the wellbore packer 10.

16 The energising ring 24 is disposed on the base pipe 12 between the elastomeric ring 17 member 26 and the main support ring 22. The energising ring 24 is formed from a 18 material which is harder than the elastomeric ring member 26 and the mantle 14, such as 19 steel. In this embodiment, the energising ring 24 is immediately adjacent the containment layer 40 and provides an abutment surface 72 which faces the nose 68 of the elastomeric 21 ring member 26. In this embodiment the abutment surface 72 is planar, although 22 variations such as concave, convex, or part-conical surfaces are within the scope of the 23 invention. An opposing surface 74 of the ring 24 has a convex shape which corresponds 24 to the concave shape of the layers 40,42,44 and the surface 32. The ring 24 has a leading edge 76 which extends into the space defined by the innermost part of layer 20 26 and the base pipe 12. The ring 24 is axially moveable on the base pipe 12.

28 The wellbore packer 10 is manufactured as follows, with reference to Figures 1OA to 1OC 29 of the drawings.

31 The support assembly 18, consisting of main support ring 22, energising ring 24, 32 elastomeric ring member 26 and layers 40, 42, and 44 is assembled on a base pipe 12.

33 The elastomeric ring member 26 is bonded to the base pipe by a suitable adhesive. End 34 ring 16 is secured to the base pipe by threaded screws (not shown) to axially restrain the support assembly 18. The innermost edge 70 of the elastomeric ring member has an OD 1 equal to the thickness of one calendared sheet 80a of uncured elastomeric material, which 2 is wrapped on and bonded to the base pipe 12. A second calendared sheet 80b, slightly 3 wider than the first so that it extends over a greater axial length, is wrapped over the first 4 layer and a part of the ring member 26. Third layer 80c, fourth layer 80d and successive layers are formed over the previous layers, each extending further over the inner section 6 66 of the ring member 26.

8 During lay-up of the elastomer layers on the base pipe 12 air, which may otherwise be 9 trapped between the layers, is able to pass through the gas exhaust path 82 provided between the ring member 26 and the edges of the layers of elastomer 80. Layers are 11 successively built up to form the mantle 84, which is then cured. A final layer 86 of 12 elastomer is provided over the mantle and the cylindrical part of the main support ring 22, 13 as shown in Figure 2.

The inventors have appreciated that an appropriate shape of ring member allows the 16 layers to be sequentially laid up, with each extending over a larger part of the ring 17 member. This facilitates the exhaust of air and gas from between the layers to outside of 18 the packer. Providing a concave surface on the facing section of the ring member is 19 particularly advantageous, although a part-conical surface may also be used in other embodiments. In further variations, the layers of elastomer may have chamfered or curved 21 edges to conform more closely to the profile of the ring member.

23 Use of the wellbore packer 10 will now be described with reference to Figures 2 and 11 of 24 the drawings. Figure 2 shows the packer in an unswollen condition before exposure to a triggering fluid. The support assembly 18 is in a retracted position, with the OD of the tool 26 suitable for run-in to a wellbore location. The outer layer 86 of swellable material provides 27 a lower friction coating for the support assembly 18 and protects it from snagging on 28 obstructions in the wellbore during run-in, and from high velocity and potentially viscous 29 fluids that may be pumped past the packer.

31 Figure 11 shows the wellbore packer 10 in a downhole location in a wellbore 90 in a 32 formation 92. In this embodiment the packer is shown in an openhole bore, but use in 33 cased hole operations is within the scope of the invention. In the wellbore 90 the packer is 34 exposed to a triggering fluid, which may be a fluid naturally present in the well, or may be a fluid injected and! or circulated in the well. The fluid diffuses into the mantle 14 and 1 causes an increase in volume. The elastomeric ring member 26, also formed from a 2 swellable material, increases in volume and directs an outward radial force against the 3 flared portion 30 of the main support ring 22, above the energising ring 24 and the pivot 39 4 via the layers 40, 42, and 44. The force is sufficient to pivot and deform the main support ring 22 above the pivot 39, opening the slots 36 to deploy and expand the support 6 assembly. Similarly the slots in the layers 40, 42 and 44 open to allow the leaves to be 7 deployed to accommodate expansion of the ring member 26. Together the layers 40, 42, 8 44 and the main support ring 22 cover the end of the radially expanding portion formed by 9 the ring member 26 and the mantle 14. The packer and the support assembly swell into contact with the surrounding surface of the wellbore to create a seal.

12 By providing a concave inner surface to the support assembly, a larger volume of 13 swellable material can be accommodated beneath the support assembly per unit axial 14 length of the support assembly. This results in an increased swell volume and more effective deployment. In addition, the axial length of the support assembly can be reduced 16 compared with support assemblies described in the prior art. The parabolic bowl shape of 17 the support assembly also provides an efficient transfer of radial and longitudinal swelling 18 forces to the support assembly to enhance its deployment.

The support assembly 18 functions to mitigate the effects of forces on the swellable 21 material which may otherwise adversely affect the seal. The support assembly 18 is 22 operable to expand to the full extent of the wellbore cross section, and contains and 23 supports the expanded packer over the whole wellbore. The support assembly 18 24 provides an extrusion barrier, mitigating or eliminating extrusion of the swellable material which may otherwise be caused by shear forces in the swellable material due to pressure 26 differential across the seal and! or axial forces on the base pipe. The slots of the 27 respective layers are offset with respect to one another to provide a convoluted path which 28 reduces the likelihood of extrusion.

Forces on the support assembly due to continued expansion or axial forces on the base 31 pipe tend to further deploy the support assembly. The pivoting movement of the main 32 support ring 22 about pivot 39 leverages a compressive force through the layers 40, 42, 33 44 to the energising ring 24, as depicted by arrow 94. The energising ring 24 is axially 34 moveable on the base pipe, and its movement transfers the compressive force to the nose 78 of the ring member 26, as depicted by arrows 96. The compressive force is distributed 1 through the ring member 26 and has a radial component 98 which boosts the seal. Thus 2 axial forces due to pressure differentials and! or weight on base pipe tend to be redirected 3 through the support assembly and the energising ring, back to the sealing components to 4 energise and boost the seal. The concave shape and energising member is particularly effective at capturing longitudinal forces in the elastomer and utilising them to enhance the 6 seal.

8 An additional feature of the assembly is that the flared portion 30 may be deformed against 9 the surrounding surface of the openhole. By continued deployment, the relatively thin outer edge 99 of the flared portion 30 is deformed to provide a bearing surface which 11 conforms to the openhole surface. This provides effective containment of the volume of 12 swellable material.

14 Awellbore packer 100 having a support assembly 118 according to an alternative embodiment of the invention is shown in Figure 12. The support assembly 118 is similar 16 to support assembly 18, with like parts depicted by like reference numerals incremented by 17 100, and its operation will be understood from the foregoing description. The support 18 assembly 118 is located on a base pipe 12 adjacent an end ring 16. However, the 19 configuration differs in that the support assembly does not include an elastomeric ring member. Instead, the mantle 114 itself is shaped to fit within the volume defined by the 21 support assembly 118. This embodiment illustrates that the radially expanding portion 22 need not be a compound portion formed from a mantle and an elastomeric ring member.

23 Expansion of the mantle 114 causes deployment of the support assembly 118, and the 24 energising ring 124 boosts the seal. Intermediate layers are disposed between the main support ring 122 and a containment layer, but are not shown in this drawing. A further 26 difference of this embodiment is that the containment layer 140 extends beyond the edge 27 102 of the flared portion 130 of the main support member 122. The containment layer 140 28 is longer to ensure that as the main support ring flares outwards, the containment layers 29 form a feathered edge at point 102, creating a softer interface between the edge 102 of the support member 122 and the adjacent swellable material 114.

32 Figure 13 shows an alternative ring member 126 that may be used with embodiments of 33 the invention. The ring member 126 is similar in form and function to the ring member 26 34 described with reference to Figure 9. However, ring member 126 differs in that is provided with an inlay 150 of a non-swellable elastomeric material. The inlay 150 is in the form of 1 an annular ring, located around the outer surface of the main body 152 of swellable 2 elastomeric material in the ring. The inlay is disposed at a lip 154 which is positioned 3 adjacent an edge 102 of the main support ring 22 or 122 and the layers of the assembly.

The inlay 150 is formed from a non-swellable elastomeric material, and therefore does not 6 swell on exposure to a triggering fluid. However, the elastomeric properties allow the inlay 7 150 to be stretched to accommodate expansion of the swellable elastomeric material 8 forming the main body 152 of the ring.

Because the inlay 150 is formed from a non swellable elastomeric material, it does not 11 lose mechanical properties such as hardness and shear, and therefore has a reduced 12 tendency to extrude over the edge 102 of the support ring. This improves the anti- 13 extrusion properties of the assembly.

Figure 14 shows a main support ring 222 according to an alternative embodiment of the 16 invention. The main support ring 222 is similar to support ring 22, and its operation will be 17 understood from the foregoing description. Like parts are designated by like reference 18 numerals, incremented by 200. Support ring 222 differs in that it is provided with a 19 weakened formation 224, located between the neck 228 and the flared portion 230. In this embodiment, the weakened formation is located on the neck 228 at the junction 229 21 between the neck and the flared portion 230.

23 One function of the weakened formation 224 is to allow operation of the support assembly 24 in a situation in which the swellable elastomeric material cannot be compressed by the energising member (not shown). Forces on the flared portion 230 from the swellable 26 elastomeric material will tend to cause the main support ring 222 to pivot around the pivot 27 239. If however the energising member is immovable against the volume of elastomeric 28 material, for example due to loading within the elastomeric material, the neck 228 of the 29 main support ring 222 will not be able to travel on the base pipe, limiting the deployment of the support assembly. Stresses will build up in the main support ring 222, and may 31 become large enough to shear the neck 228 from the flared portion 230 at the weakened 32 formation 224. This allows the flared portion 230 to be further deployed without being 33 restricted by the incompressibility of the elastomeric material. The embodiment therefore 34 provides a frangible main support ring 222.

1 In addition, the weakened portion 224 provides an alternative pivot point for deployment of 2 the main support ring due to axial and/or radial forces experienced from the swellable 3 elastomer. This arrangement allows use of the ring with different end ring structures, 4 which may not necessarily provide a suitable abutment for the pivot 39 as described with reference to Figure 11.

7 Figure 15 shows a further alternative main support ring 322, which is similar to the main 8 support ring 222, having a neck 328 and a flared portion 330. As with the embodiment of 9 Figure 13, a weakened formation 324 is provided. The main support ring 322 differs in that pivot ring, equivalent to the pivot 39, is omitted. Thus there is no pivot which abuts a 11 part of the end ring in this embodiment. Providing a weakened formation 324 at the 12 interface 329 between the neck portion and the flared portion facilitates pivoting of the 13 flared portion and therefore deployment of the support assembly of this embodiment.

Because the pivot is located at the base of the main support ring 322, the compressive 16 force directed through the main support ring to the elastomeric material is negligible. Thus 17 this embodiment provides no substantial energising effect on the seal, and is most suited 18 for use in an embodiment which omits an energising member from the assembly.

The present invention provides in one of its aspects a support assembly for use with well 21 packers or other expanding downhole apparatus. One of the advantages of the invention 22 is the ability to provide a seal in the annulus of high pressure integrity per unit length of 23 expanding member. This permits operation under high pressure or weight conditions, or 24 alternatively allows a reduction in the length or number of packers used in a particular application having a required pressure rating.

27 The invention also allows an expanding apparatus to be used over a range of operating 28 parameters. For example, by providing support to the expanding portion it may be 29 acceptable to expand the apparatus to a greater degree. This facilitates use in a wide range of bore diameters, 32 In one aspect, a concave shape of support assembly maximises the volume of elastomeric 33 material beneath the support assembly in a manner that is efficient in terms of the length 34 and radius of the assembly. The shape also efficiently transfers forces from the elastomeric material to deploy the support assembly and maintain the seal.

2 In another aspect, a means is provided for energising the seal. A further aspect provides 3 an exhaust gas path which allows an improved swellable elastomeric component to be 4 formed.

6 Variations and modifications to the above described embodiments may be made within the 7 scope of the invention herein intended. For example, although in the described 8 embodiments described particular configurations of layers, it will be appreciated that other 9 configurations, including the addition or omission of layers, are within the scope of the invention. In addition, it will be apparent that multiple elastomeric volumes or inlays may 11 be used with the present invention. The multiple volumes may be selected to have 12 different characteristics, such as hardness or swell rates, in order to affect the distribution 13 of forces in the radial expanding portion.

The materials used to form the components of the support assembly may be varied 16 according to the required application and performance. For example, the assembly may 17 include components formed from materials selected from steels, plastics, epoxy resins, 18 elastomers or natural rubbers of varying hardness, aluminium alloys, tin plate, coppers, 19 brass, other metals, KEVLAR � or other composites, carbon fibre and others. Any of a number of suitable manufacturing techniques may be used, including press forming and 21 machining.

23 Combinations of features other than those expressly claimed are within the scope of the 24 invention, and it will be understood that features of certain embodiments may be incorporated in other specific embodiments of the invention.