GB2458557A

GB2458557A - A swellable packer with swellable support discs

Info

Publication number: GB2458557A
Application number: GB0904060A
Authority: GB
Inventors: Nitin Y Vaidya; Manual Marya; Frederick Lemme Sr
Original assignee: Schlumberger Holdings Ltd
Current assignee: Schlumberger Holdings Ltd
Priority date: 2008-03-28
Filing date: 2009-03-10
Publication date: 2009-09-30
Anticipated expiration: 2029-03-10
Also published as: GB0904060D0; US20090242189A1; GB2458557B

Abstract

A swell packer 10 includes a base tubular 12, a seal member 14 encircling the base tubular 12, the seal member 14 swelling radially to a seal equilibrium swell upon contact with a particular fluid. At least one disc 28a-d is positioned about the base tubular 12 substantially abutting an end of the seal member 14 but not physically connected to the seal member 14 in a manner that limits the equilibrium swell of the seal member 14 , the disc 28a-dswelling radially to a first equilibrium swell upon contact with a particular fluid. The disc 28a-d may be radially less swellable than the seal member 14. The disc 28a-d may include stiffening elements such as glass and carbon fibres.

Description

SWELL PACKER

BACKGROUND

The present invention relates in general to weilbore packers and more specifically to packers that swell when exposed to a particular fluid or condition in the weilbore.

It is often desired to utilize packers to form an annular seal in welibores.

Open-hole packers provide an annular seal between the earthen sidewall of the weilbore and a tubular. Cased hole packers provide an annular seal between an outer tubular and an internal tubular.

Common types of packers include inflatable packers, mechanical expandable packers, and swell packers. Inflatable packers typically carry a bladder that may be pressurized to expand outwardly to form the annular seal. Mechanical expandable packers have a flexible material expanding against the outer casing or wall of the formation when compressed in the axial direction of the well. Swell packers comprise a sealing material that increases in volume and expands radially outward when a particular fluid contacts the sealing material in the well. For example the sealing material may swell in response to exposure to a hydrocarbon fluid or to exposure to water in the well. The sealing material may be constructed of a rubber compound or other suitable swellable material.

One drawback of swell packers is that the sealing material may extrude, due to differential pressure for example. Anti-extrusion, or anchoring, devices in the form of end-rings have been utilized as a means of mediating this drawback. The end-rings typically include petals or the like that expand outwardly by the force of the swelling seal material. While the end-rings may provide a benefit in some installations, cased hole installations it is believed that they may deter sealing in other installations. For example, in open hole installations the ovality or eccentricity of the welibore varies along its length. The non-unifonnity in the cross-sectional shape arid dimensions of the welibore, means that the annular gap to be sealed may vary substantially from point to point, It also means that the dimension of the annular gap is often unknown.

SUMMARY

An example of an apparatus for supporting a radially swellable seal member of a swell packer includes a radially swellable disc positioned at an end of the seal member. The disc may have a modulus of elasticity greater than that of the seal

I

member. The disc may have an internal stiffening element. A stiffening element may be operationally connected to the disc opposite from the seal member. It may be that the disc is not physically connected to the seal member, in a manner such that the connection would limit the ability of the disc to expand to its equilibrium swell.

An example of an anti-extrusion device positionable at an end of a packer seal member that radially swells when contacted by a particular fluid to form an annular seal in a wellbore includes a first disc for positioning adjacent the seal member, the first disc expandable to a first equilibrium swell upon contact with the particular fluid; and a second disc positionable adjacent the first disc and opposite the seal member, the second disc expandable to a second equilibrium swell upon contact with the particular fluid, wherein the second equilibrium swell is less than the first equilibrium swell.

An example of a swell packer includes a base tubular; a seal member encircling the base tubular, the seal member swelling radially to a seal equilibrium swell upon contact with a particular fluid; and a disc positioned about the base tubular substantially abutting an end of the seal member but not physically connected to the seal member in a manner that limits the equilibrium swell of the seal member, the disc swelling radially to a first equilibrium swell upon contact with a particular fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a conceptual illustration of an example of a swell packer and anti-extrusion device of the present invention; Figure 2 is a conceptual illustration of an example of swell packer of the present invention expanded and concentrically aligned in a weilbore; Figure 3 is a conceptual illustration of an example of a swell packer of the present invention expanded and eccentrically positioned in a wellbore; and Figure 4 is an end view an example of a swell packer of the present invention activated in an open-hole welibore.

DETAILED DESCRIPTION

Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.

Figure 1 is a conceptual illustration of an example of a swell packer of the present invention, generally denoted by the numeral 10. Swell packer 10 includes a base tubular 12, swellable seal member 14, and an anti-extrusion device generally denoted by the numeral 16. Swell packer 10 has a longitudinal axis 18 shown by the dashed line.

Swell packer 10 is shown disposed in a wellbore 20 having a sidewall 22.

Open-hole refers to sidewall 22 being formed by the surrounding earthen formation.

Cased hole refers to the sidewall 22 being formed by a tubular. The tubular may be a casing, liner, tubing, production string, screen or in general any other tubular in which packer 10 is positioned.

Seal member 14 has opposing ends 24, 26 and encircles base tubular 12. Seal member 14 may be may be connected to base tubular 12 in various manners. Seal member 14 is formed of a material that swells when exposed to a particular fluid or condition in wellbore 20. For example, seal member 14 could swell in volume in response to a hydrocarbon, water, or other activating fluid or chemical. Seal material 14 may be of a rubber compound or other material. Seal member 14 may be constructed as a unitary member or in layers. To form an annular seal, seal member 14 must expand radially the distance of annular gap 34, which is the distance between the outer surface of seal member 14 and sidewall 22.

Anti-extrusion device 16 may be positioned about base tubular 12 at one or both of ends 24, 26 of seal member 14. Anti-extrusion device 16 includes one or more discs 28. Discs 28 are formed of a swellable material. Anti-extrusion device 16 is now described with reference to the left end of seal member 14, referred to herein as end 24. Anti-extrusion device 16 includes multiple discs identified as 28a, 28b, 28c, 28d, etc. from the end 24 of seal member 14 outward. Although four discs are illustrated in the Figures, device 16 may include more or fewer discs 28.

Adjacent discs 28 are in ftmctional connection with one another so as to cooperatively provide support to seal member 14 against extrusion without limiting the radial expansion of seal member 14. Adjacent discs 28 may physically abut one another or may be spaced apart by one or more elements. Anti-extrusion device 16 may include various non-swellable elements such as reinforcement members, components, and the like.

Each disc 28 may be constructed of a material having a different swellability and modulus of elasticity than its adjacent disc. Swellability" is utilized herein to denote the ability to increase in volume and extend radially outward from base tubular 12. In the illustrated example, discs 28 decrease in swellability as they move outward from an end of seal member 14. Thus, disc 28a has a greater swellability than disc 28b which has a greater swellability than disc 28c, and so forth. As the swellability decreases, the modulus of elasticity, or Young's Modulus, increases. Thus, the discs become more rigid or stiffer as they move outward from the end of seal member 14.

Discs 28 may be constructed of materials such as, but not limited to, swellable rubber compounds and non-elastomeric plastics. Examples include Rytonlelastomer blender, Xtel XE3200 polyphenylene sulfide alloy with 100 percent elongation at break and 450 psi tensile strength, PVDFfVito blends, and thermoplastic elastomers.

Refer now to Figure 2, wherein swell packer 10 is illustrated in the expanded position. In this example, swell packer 10 is concentrically aligned within wellbore 20. The longitudinal axis 36 (Figure 3) of this portion of wellbore 20 corresponds to longitudinal axis 18 of packer 10 and is therefore not visible in this view. Figure 2 illustrates an installation that is common to cased holes.

Upon contact with a selected fluid, seal member 14 and discs 28 of anti-extrusion device 16 swell and expand radially outward from base tubular 12 to their respective equilibrium swells or until contained by sidewall 22. Discs 28b, 28c, and 28d have each reached their respective equilibrium swell in Figure 2. Disc 28a may have reached its equilibrium swell or it contacted sidewall 22 prior to reaching equilibrium.

Disc 28a, being the disc adjacent to the end of seal member 14 has a swellability similar to the swellability of seal member 14. In some examples, disc 28a will have a swellability less that that of seal member 14 and thus have a higher modulus than seal member 14. Disc 28a is not physically connected to seal member 14 in a maimer that will limit seal member 14 from obtaining its equilibrium swell.

The rigidity and the swellability of disc 28a aids in preventing or limiting the extrusion of seal member 14, while not interfering with the ability of seal member 14 to contact and form a seal against sidewall 22. Each subsequent disc (28b, 28c, etc.) out from the end of seal member 14 deceases in swellability and increases in stiffness (higher modulus of elasticity), thus providing additional support against extrusion of seal member 14.

Anti-extrusion device 16 may include one or more elements to provide additional rigidity. For example, device 16 may include an external or first stiffening element 30, such as an expandable end-ring that is spaced apart from seal member 14 and abutting a disc 28. Anti-extrusion device 16 may include disc 28a abutting an end of seal member 14 and a first stiffening element 30, such as an end-ring, that is operationally connected to the end of disc 28a opposite of seal member 14. Stiffening element 30 may provide the support to disc 28a necessary to prevent or limit the extrusion of seal member 14 without materially limiting the ability of seal member 14 to expand radially. In one example, disc 28a may have a swellability and modulus of elasticity that is the same or substantially the same as seal member 14.

Device 16 may include internal or second stiffening elements 32. Examples of second stiffening elements 32 include without limitation, Kevlar, glass, and carbon incorporated into discs 28 for example as chopped fibers, fiber mats, and long fibers.

Refer now to Figures 3 and 4 illustrating swell packer 10 activated in an open-hole wellbore 20. Swell packer 10 is shown eccentrically positioned in wellbore 20, indicated by the misalignment of longitudinal axis 18 of base tubular 12 and longitudinal axis 36 of wellbore 20 (Figure 3).

As is comiTlon in open-hole wellbores, the cross-sectional dimensions of wellbore 20 is non-uniform along its length. The unpredictability of the welibore dimensions at the desired seal location creates difficulties in obtaining an effective seal. One difficulty is presented by the inability to determine the annular gap at the desired point of sealing. The inability to accurately identify the annular gap at the point of the seal may result in the mis-sizing of the traditional anti-extrusion devices, in particular the end-ring type devices. The mis-sizing of the traditional anti-extrusion devices may not only fail to operate as desired but may in fact prevent the seal member from sealing against the sidewall. For example, if a tradition end-ring is selected for an annular gap less than the actual annular gap to be sealed, the traditional end-ring may prevent the sealing element from expanding sufficiently to achieve the desired seal.

Anti-extrusion device 16 does not grip seal member 14 in a manner that will limit the radial expansion of seal member 14. As illustrated in Figure 4, seal member 14 is free to expand radially from base tubular 12 to seal against the contour of sidewall 22. Disc 28a swells radially to an extent to aid against extrusion of seal member 14 without limiting the radial expansion of seal member 14. As can be seen in the end-view of Figure 4, disc 28a may expand to sidewall 22 or may reach its equilibrium swell before reaching sidewall 22 without limiting the radial expansion of seal member 14.

Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.

Claims

CLAIMS1. An apparatus for supporting a radially swellable seal member of a swell packer, the apparatus comprising a radially swellable disc positioned at one end of the seal member.
2. The apparatus of claim 1, further including a stiffening element.
3. The apparatus of claim 2, wherein the stiffening element is operationally connected to the side of the disc opposite from the seal member.
4. The apparatus of claim 2 or claim 3, wherein the stiffening element is an end-ring.
5. The apparatus of any preceding claim, wherein the disc is not physically connected to the seal member.
6. The apparatus of any preceding claim, wherein the disc is radially less swellable than the seal member.
7. The apparatus of any preceding claim, wherein the disc includes internal stiffening elements.
8. The apparatus of claim 7, wherein the internal stiffening elements comprise Keviar, glass, and carbon incorporated into the disc.
9. The apparatus of claim 7, wherein the internal stiffening elements comprise Kevlar, glass, and carbon incorporated into the disc as chopped fibers, fiber mats, or long fibers.
10. An anti-extrusion device positionable at an end of a packer seal member that radially swells when contacted by a particular fluid to form an annular seal in a weilbore, the device comprising: a first disc for Positioning adjacent the seal member, the first disc being expandable to a first equilibrium swell upon contact with the particular fluid; and a second disc positionable adjacent the first disc and opposite the seal member, the second disc expandable to a second equilibrium swell upon contact with the particular fluid, wherein the second equilibrium swell is less than the first equilibrium swell.
11. The device of claim 14, further including a stiffening element.
12. A swell packer comprising: a base tubular; a seal member encircling the base tubular, the seal member swelling radially to a seal equilibrium swell upon contact with a particular fluid; and a radially swellable disc positioned about the base tubular substantially abutting one end of the seal member but not physically connected to the seal member in a maimer that limits the equilibrium swell of the seal member, the disc swelling radially to a first equilibrium swell upon contact with the particular fluid.
13. The swell packer of claim 12, further including a stiffening element operationally connected to the disc opposite the seal member.
14. The swell packer of claim 12, wherein the first swell equilibrium is less than the seal swell equilibrium, and the disc is more rigid at the first swell equilibrium than the seal member is at the seal swell equilibrium.
15. The swell packer of claim 14, further including a second disc positioned about the base tubular adjacent the disc opposite the seal member, the second disc swelling radially to a second equilibrium swell upon contact with a particular fluid, wherein the second equilibrium swell is less than the first equilibrium swell.
16. The swell packer of claim 15, further including an external stiffening element positioned between the firstmentioned disc and the second disc.