Patent Publication Number: US-2009218107-A1

Title: Reservoir Tool for Packer Setting

Description:
BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  is a side, partial cross-sectional view of an exemplary casing string within a wellbore containing a packer device constructed in accordance with the present invention. 
         FIG. 2  is a side, partial cross-sectional view of the packer device shown in  FIG. 1 , in an unactivated condition. 
         FIG. 3  is a side, partial cross-sectional view of the device shown in  FIGS. 1 and 2 , now in an activated condition. 
         FIG. 4  is a side, cross-sectional view of an exemplary activating mechanism used with the external casing packer of  FIGS. 1-3 , in accordance with the present invention 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically depicts an exemplary open bore hole  10  which has been drilled into the earth  12 . A string  14  of metallic casing sections  16 , of a type known in the art, is shown disposed within the open hole  10 . The casing string  14  defines an axial flowbore  18  along its length. An annulus  20  is defined between the exterior surface  22  of the casing string  14  and the interior wall  24  of the bore hole  10 . 
     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  FIGS. 2 and 3 . The packer device  26  includes a central packer mandrel  28  that is generally cylindrical and defines a central flowbore  30 . The mandrel  28  has first and second axial ends  32 ,  34  that have threaded connections to permit the mandrel  28  to be affixed to adjacent casing sections  16  and thereby incorporated into the casing string  14 . 
     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.  FIG. 4  depicts an exemplary packer activation device  40  in greater detail. The activation device  40  includes a fluid reservoir  42 . In the embodiment depicted, the reservoir  42  is substantially cylindrical in shape. However, other shapes may be used. A fluid distribution conduit with nozzle  44  extends downwardly from the lower end of the reservoir  42 . The reservoir  42  is filled with a swelling fluid  46 . In some preferred embodiments, the swelling fluid  46  comprises a water-based fluid such as fresh water. In other preferred embodiments, the swelling fluid  46  comprises an oil-based fluid, such as kerosene or diesel. The type swelling fluid  46  is determined by the type of swellable elastomer that is used to form the packer element  36 . 
     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  FIG. 3 . 
     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.