MULTI-PIECE PACKER ELEMENT CONTAINMENT SYSTEM AND METHOD

FOR MANUFACTURING THE SAME

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to packer devices used within a wellbore.

2. Description of the Related Art

[0002] Packers are used to create a fluid seal within a wellbore between a central work string, such as a production tubing string, and a surrounding tubular, such as a wellbore wall. A common packer design has a central mandrel with an elastomeric packer element surrounding the mandrel. The packer element is set by axially compressing it on the mandrel. As the packer element is compressed axially, the packer element is expanded radially outwardly and into contact with the surrounding surface. [0003] One problem with packer devices of this type is that of extrusion of the packer element axially along the space between the packer mandrel and the surrounding wellbore. This can occur as a result of high wellbore temperatures, pressures and/or caustic chemicals which act upon the packer element. Severe extrusion of the packer element can cause the seal to fail.

SUMMARY OF THE INVENTION

[0004] The invention provides methods and devices for containing a packer element in a set condition within a wellbore and for preventing or minimizing extrusion of the packer element after setting. An exemplary packer device is described which includes a plurality of defoπmable packer elements which radially surround a packer mandrel. One or more of the packer elements is contained against axial extrusion using a packer containment system. In a preferred embodiment, the packer containment system includes a flexible

metal backup ring, which partially encases the packer element by substantially covering at least one axial side and a portion of the exterior radial surface of the packer element. The packer containment system also includes a plurality of annular support rings, or "petal rings" which have petal-shaped radial protuberances with slots between them. The petal rings are arranged so that the petals of adjacent rings are radially offset. As a result, the slots of each ring are covered by a petal of an adjacent ring. Petal rings are preferred since they may be axially compressed with relatively small amount of force due to the presence of the slots. Because there are multiple support rings used, a strong containment barrier is provided when set which prevents extrusion of a packer element axially along the annular space between the packer device and the inner surface of the surrounding tubular member. BRIEF DESCRIPTION QF THE DRAWINGS

[0005] The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein:

[0006] Figure 1 is a side, partial cross-sectional view of an exemplary packer assembly in accordance with the present invention. [0007] Figure 2 is an enlarged cross-sectional view of a packer element containment system in accordance with the present invention.

[0008] Figure 3 is an enlarged cross-sectional view of the containment system shown in Figure 2, now in a set condition.

[0009] Figure 4 is an external isometric view of the containment system shown in Figures 2-3, in an unset condition.

[0010] Figure 5 is an external isometric view of the containment system shown in Figures 2-3, in a set condition. [0011] Figure 6 is an axial external view of an exemplary petal-type support ring used in the containment system shown in Figures 2-5.

[0012] Figure 7 is an external isometric view of the exemplary support ring shown in Figure 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0013] Figure 1 illustrates an exemplary packer assembly 10 which includes a central packer mandrel 12. The packer mandrel 12 can be incorporated into a production tubing string or other work string (not shown), in a manner known in the art. A flowbore 14 is defined within the mandrel 12. The outer radial surface of the mandrel 12 has an expanded diameter portion 16 which presents a stop shoulder 18. Radially surrounding the packer mandrel 12 and immediately below the stop shoulder 18 is a packer element portion, generally indicated at 20, the structure of which will be described in greater detail shortly. A setting sleeve 22 radially surrounds the packer mandrel 12 below the packer element portion 20. The setting sleeve 22 is axially moveable with respect to the mandrel 12 and presents a compression end 24. [0014] The exemplary packer element portion 20 depicted in Figure 1 includes an upper end cone 28 which surrounds the mandrel 12 and abuts the stop shoulder 18. The packer element portion 20 also includes an upper packer element 30 and an upper packer element containment assembly 32. A first spacer ring 34 separates the upper packer

element 30 from a central packer element 36. A second spacer ring 38 separates the central packer element 36 from a lower packer element 40 and a lower packer element containment assembly 42. A lower end cone 44 lies adjacent the containment assembly 42 and abuts the compression end 24 of the setting sleeve 22. [0015] It is noted that the upper packer element 30, central packer element 36 and lower packer element 40 are preferably formed of nitrile or another suitable elastomeric material.

It is noted that the packer elements 30, 36, 40 and spacer rings 34, 38, containment assemblies 32, 42 and end rings 28, 44 are not affixed to the mandrel 12 so that they may slide axially with respect to it. It is noted that, during the initial construction and run in of the packer assembly 10, the end rings 28, 44 are preferably affixed in place using frangible shear screws, as is known in the art

[0016] Figures 2 and 3 depict the upper packer element containment assembly 32 in greater detail. It is noted that the lower packer element containment assembly 42 preferably has the same structure and function as upper containment assembly 32. The upper containment assembly 32 includes a solid backup ring 46 which is substantially formed of a malleable metal of low yield and high ductility. The backup ring 46 includes a close-fitting radially reduced inner annular flange portion 48. A portion of the inner flange portion 48 is disposed beneath an axially-extending lip 50 of the end cone 28. An annular web portion 52 of the backup ring 46 extends radially outwardly from the flange portion 48. The web portion 52 lies axially adjacent the upper packer element 30. A leg portion 54 extends axially along the outer radial surface 56 of the packer element 30. The upper packer element 30 is partially encased by the web portion 52 and the leg portion 54. In

particular, the web portion 52 and leg portion 54 of the backup ring 46 help prevent axial extrusion of the element 30 axially toward the end ring 28.

[0017] Support rings 58, 60, 62 are located adjacent to the backup ring 46 and are preferably in an abutting relation to the backup ring 46. The support rings 58, 60, 62 are preferably each petal-type rings or, "petal rings" with a construction substantially as follows.

Figures 6 and 7 illustrate a single exemplary petal ring 58 apart from the other components of the containment assembly 32 and 42. It is noted, however, that the exemplary construction shown for the petal ring 58 can be representative of the same construction for rings 60, 62 as well as each of the rings used in the containment assembly 42. The ring 58 has a cross-sectional, substantially flat plate-form annular body 64 that is disposed angularly outwardly with respect to the ring's axis 66 at an angle 68, which is depicted graphically in Figure 7. Thus, the ring 58 has a generally conical form. The angle 68 may vary depending upon the particular project and design in which the assembly 10 will be used. Preferably, however, the angle 68 is from about 35° to about 45°. Most preferably, the angle 68 is about 40°. The body 64 of the ring 58 includes a plurality of slots 70 which partially divide portions of the body 64 into petal portions 72. The presence of the slots 70 permits the ring 58 to be deformed or bent more easily during the setting process. The petal rings 58, 60, 62 are preferably formed of metal and most preferably formed of a malleable metal with low yield and high ductility. [0018] In the embodiment of the containment assembly 32 depicted in Figures 2-5, there are three petal rings 58, 60, 62. However, there may be fewer than or more than three rings, as desired. A greater number of rings will result in a higher containment force for the packer element 30. When assembled, the petals 72 of adjacent rings 58, 60, 62 are offset

from one another, as depicted in Figure 4 so that a petal 72 of one ring will overlap and cover the slot 70 of an adjacent ring. This will help form a solid barrier against extrusion by blocking the gaps provided by the slots 70.

[0019| In operation, the packer assembly 10 is set by moving the setting sleeve 22 axially with respect to the mandrel 12 so that the compression end 24 is urged against the end cone 44. This results in the components 42, 40, 38, 36, 34, 32, 30 and 28 being compressed against the stop shoulder 18. The setting sleeve 22 may be actuated by one of any number of methods known in the art, including the use of a setting tool (not shown) or hydraulically. As the components are compressed, the packer elements 30, 36, and 40 are expanded radially outwardly as Figure 3 shows, so that the packer elements 30, 36, 40 are set against the external wall 80 of a surrounding tubular.

[0020] When the packer assembly 10 is set in the manner described, the upper and lower packer element containment assemblies 32, 42 become actuated to prevent axial extrusion of the upper and lower packer elements 30, 40, respectively. Figures 2 and 3 illustrate the operation of the containment assembly 32 moving from unset (Figure 2) to set (Figure 3) positions. The web and leg portions 52, 54 portions of the backup ring 46 will flex, so that they remain in an encasing relation to the packer element 30 and physically block potential extrusion of the element 30 axially toward the end cone 28. In addition, the petal rings 58, 60, 62 are compressed axially to the conditions depicted in Figures 3 and 5. The slots 70 of the rings 58, 60, 62 are expanded, allowing the rings to be axially flattened.

When axially flattened, the angle 68 of the rings 58, 60, 62 is increased to approximately

90° (see Figure 3). The support rings 58, 60, 62 do not, themselves, necessarily contact the surrounding surface 80 (see Figure 3) when in the set position. The support rings 58,

60, 62 form a structural axial barrier to help preserve containment of the packer element 30 by preventing the backup ring 46 from deforming, which might permit extrusion of the packer element 30. The containment assemblies 32, 42 require a relatively small amount of setting force is required, but provide increased resistance to shear forces. [0021] The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to those skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.