Patent Application
20090218107
1. Field of the Invention
The invention relates generally to devices and methods for setting packers within a wellbore. In more particular aspects, the invention relates to the setting of swellable packers.
2. Description of the Related Art
Packers are used to create a fluid seal within a wellbore. One type of packer is an external casing packer. External casing packers are packer devices that are incorporated into a string of casing and used to secure the string of casing within an open borehole pending completion of a cementing operation which will permanently secure the casing string within the wellbore. External casing packers are intended to be permanently set and remain in the bore hole following cementing.
Typically, an external casing packer includes a central mandrel having a central axial passage the is the same diameter as the interior casing diameter. The packer device is located on the external diameter of the mandrel. The packer is actuated between an unset position and a set position. In the set position, the packer is expanded radially and makes sealing contact with the surrounding wellbore wall. Examples of conventional external casing packers are found in U.S. Pat. No. 5,201,369 issued to Berzin et al., which is owned by the assignee of the present invention and is herein incorporated by reference.
The invention provides a new type of external casing packer wherein the packer element is fashioned from materials that physically expand (“swell”) in response to contact by an appropriate swelling fluid. In preferred embodiments, the packer element is fashioned of a swellable elastomer, and the swelling fluid is an oil or water-based fluid that is effective to swell the particular elastomer used.
In a related aspect, the invention provides a mechanism for activating and radially expanding the packer element into sealing engagement with the surrounding borehole wall. In a preferred embodiment, the activating mechanism includes one or more fluid reservoirs which are mounted upon the exterior surface of the packer mandrel. In preferred embodiments, the fluid reservoir(s) are provided with one or more fluid injection nozzles which are operably associated with the packer element to provide fluid transmission from the reservoir(s) into portions of the packer element. The fluid reservoir(s) contain amounts of oil or water-based fluids that are sufficient to cause swelling of the packer element and radial expansion of the packer element into sealing engagement with the surrounding wellbore wall. In currently preferred embodiments, as well, the reservoir(s) contain a piston that is in contact with the fluid and moveable within the reservoir. In operation, external pressure within the annulus surrounding the casing string will urge the piston of each reservoir against the fluid contained therein and cause the fluid to flow out of the injection nozzles and into the packer element.
For detailed understanding of the invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference characters designate like or similar elements throughout the several figures of the drawings.
An external casing packer device 26 in accordance with the present invention is incorporated into the casing string 14. Construction and operation of the packer device 26 is better understood with further reference to
A packer element 36 radially surrounds the mandrel 28 and is secured thereto. The packer element 36 is formed of a swellable material. In preferred embodiments, the packer element 36 is fashioned of a swellable elastomer. Swellable elastomers are known materials that physically expand, or swell, in response to contact with certain swelling fluids. Swelling of the elastomer occurs due to absorption of the appropriate swelling fluid by the elastomer. Currently, there are two basic swellable elastomers: elastomers that are swellable in response to water-based fluids, and elastomers that are swellable in response to oil-based fluids.
A plurality of packer activation devices 40 are also mounted upon the outer radial surface of the mandrel 28. Although there are a plurality of activation devices 40 shown, there may in fact, be only a single activation device 40, if desired.
The nozzle 44 includes a plurality of fluid openings 48. The openings 48 may be variously shaped, sized and spaced to ensure optimal disposition of the swelling fluid 46 within the packer element 36. The activation devices 40 may be secured to the mandrel 28 by straps (not shown), welding, connectors, or in other ways known in the art. When the activation devices 40 are secured to the mandrel 28, the nozzles 44 are disposed within the packer element 36. In a currently preferred embodiment, the nozzles 44 are disposed within the packer element 36 as the packer element 36 is formed onto the mandrel 28 by wrapping of several layers. As the layers of the element 36 are wrapped around the mandrel 28, the nozzles 44 are disposed between overlapping layers. In alternative embodiments, the nozzles 44 may be disposed within the packer element 36 by molding them into the element 36 as it is cast upon the mandrel 28 or by forming openings in the element 36 within which the nozzles 44 can reside.
A piston 50 is disposed within each reservoir 42 atop the swelling fluid 46. The piston 50 forms a fluid seal against the interior wall of the reservoir 42. An opening 52 is formed in the reservoir body 42, and the piston 50 is moveably disposed within the reservoir body 42 between the fluid 46 and the opening 52.
In operation, the packer device 26 is first incorporated into the casing string 14. The casing string 14 is run into the wellbore 10. Thereafter, fluid pressure is increased within the annulus 20. This may be accomplished by filling the annulus 20 with a fluid, such as drilling fluid or water, and then increasing fluid pressure within the annulus 20 from the surface using a pump (not shown) or hydrostatic pressure, in a manner known in the art. As fluid pressure rises in the annulus 20, it will act upon the piston 50 and urge the piston 50 against the swelling fluid 46 to cause the swelling fluid 46 to flow outwardly through the nozzles 44 and be absorbed into the packer element 36. The swelling fluid 46 will cause the packer element 36 to expand radially and thereby form a seal against the surrounding wall 10, as depicted in
Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.
