Abstract:
A two-stage packer and method for sealing an annulus in a wellbore is provided. The packer may be set by a force which will not cause a sealing element to buckle, collapse, or otherwise fail. In one aspect, the packer comprises a body having a sealing element and shoulder disposed there-around, and a slideable member slideably arranged on the body, the slideable member having a first surface disposable beneath the element to increase the inner diameter thereof and a second surface disposable against an end of the element to increase the outer diameter thereof. The method comprises running a body into the wellbore, the body comprising a sealing element and a slideable member slideably disposed there-around, wherein the slideable member comprises a first surface and a second surface; forcing the first surface beneath the element to increase the inner diameter thereof; and forcing the second surface against an end of the element to increase the outer diameter thereof.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to downhole packers. More particularly, the present invention relates to a two-stage, retrievable, expandable packer for sealing an annulus within a wellbore. 
     2. Background of the Related Art 
     Downhole packers are typically used to seal an annular area formed between two coaxially disposed tubulars within a wellbore. A packer may seal, for example, an annulus formed between production tubing disposed within wellbore casing. Alternatively, some packers seal an annulus between the outside of a tubular and an unlined borehole. Routine uses of packers include the protection of casing from pressure, both well and stimulation pressures, and protection of the wellbore casing from corrosive fluids. Other common uses may include the isolation of formations or of leaks within wellbore casing, squeezed perforation, or multiple producing zones of a well, thereby preventing migration of fluid or pressure between zones. Packers may also be used to hold kill fluids or treating fluids in the casing annulus. 
     Packers typically are either permanently set in a wellbore or retrievable. Permanent packers are installed in the wellbore with mechanical compression setting tools, fluid pressure devices, inflatable charges, or with cement or other materials pumped into an inflatable seal element. Due to the difficulty of removing permanent packers, retrievable packers to permit the deployment and retrieval of the packer from a particular wellbore location. Retrievable packers have a means for setting and then deactivating a sealing element, thereby permitting the device to be pulled back out of the wellbore. 
     Conventional packers typically comprise a sealing element between upper and lower retaining rings or elements. The sealing element is compressed to radially expand the sealing element outwardly into contact with the well casing therearound, thereby sealing the annulus. 
     One problem associated with conventional packers arises when a relatively large annular area between two tubulars is to be sealed. Conventional packers, because they rely solely on compressive forces applied to the ends of the sealing member, are sometimes ineffective in sealing these larger areas. If the annular area to be sealed is relatively large, the sealing element must be extensively compressed to fill the annulus. Often times, the element buckles due to the compressive forces, thereby effecting an incomplete seal or a seal that is prone to premature failure. Therefore, there is a need for an expandable packer that can be more effectively used in sealing annular areas between tubulars. 
     SUMMARY OF THE INVENTION 
     A packer for sealing an annulus in a wellbore is provided wherein the sealing element is actuated in a two-stage process. In one aspect, the packer comprises a body having a sealing element, a shoulder disposed there-around, and a slideable member arranged on the body. The slideable member has a first surface disposable beneath the element to increase the inner diameter thereof and a second surface disposable against an end of the element to compress the element against the shoulder to increase the outer diameter thereof. 
     In another aspect, the invention comprises a packer for sealing an annulus in a wellbore, comprising an annular body having at least one port disposed in an outer surface thereof; a shoulder disposed about the body; a slideable member slideably disposed about the body; and a sealing element disposed about the body between the shoulder and the slideable member whereby the element is expandable upon movement of the slideable member towards the shoulder. The slideable member has a first surface disposable beneath the element to increase the inner diameter thereof and a second surface disposable against an end of the element to compress the element and increase the outer diameter thereof. The ratchet mechanism retains the element in the compressed position to seal an annular area between the body and the inner surface of the tubular. 
     In still another aspect, a method for actuating a packer in a wellbore is provided. The method comprises running a body into the wellbore, the body comprising a sealing element a shoulder, and a slideable member slideably disposed there-around, wherein the slideable member comprise a first surface and a second surface; forcing the first surface beneath the element to increase the inner diameter thereof; and forcing the second surface against an end of the element to increase the outer diameter thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a partial section view of a down hole packer. 
     FIG. 1A is an enlarged section view of a ratchet housing. 
     FIG. 2 is a partial section view of a downhole packer disposed in a wellbore during a first stage of activation. 
     FIG. 2A is an enlarged section view of a containment ring. 
     FIG. 3 is a partial section view of a downhole two-stage packer after the first stage of activation. 
     FIG. 3A an enlarged section view of a mating engagement between a cylinder and a lower piston. 
     FIG. 4 is a partial section view of a downhole two-stage packer at the beginning of a second stage of activation. 
     FIG. 4A is an enlarged section view of a first section of a lower gauge ring. 
     FIG. 5 is a partial section view of a downhole two-stage packer after a second stage of activation. 
     FIG. 6 is a partial section view of a downhole two-stage packer during the release and recovery of the packer. 
     FIG. 6A is an enlarged section view of an ratcheting piston assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a partial section view of a two-stage down hole packer  100 . The packer  100  includes a body  102 , a lower piston  200 , a sealing element  300 , a shoulder  400 , a ratcheting piston assembly  500 , and a running ring  600 , each disposed about an outer surface of the body  102 . FIG. 1A is an enlarged section view showing portions of the ratcheting piston assembly in greater detail. The ratcheting piston assembly  500  includes a ratchet housing  510 , a slip ratchet  530 , containment rings  540 ,  541 , an upper piston  550 , a seal ring  570 , and a cylinder  580 . 
     For ease and clarity of description, the packer  100  will be further described in more detail as if disposed within a tubular  700  in a vertical position wherein the top of the packer is the left-hand corner of FIGS. 1-6. It is to be understood, however, that the packer  100  may be disposed in any orientation, whether vertical or horizontal. Furthermore, the packer  100  may be disposed in a borehole without a tubular casing there-around. 
     The body  102  is a tubular member having a longitudinal bore  103  there-through. The body  102  also includes a first port  105  that allows for fluid communication between the bore  103  and a first variable volume chamber  120  which is adjacent an upper surface of the lower piston  200 . The body  102  further includes a second port  107  that allows for fluid communication between the bore  103  and a second variable volume chamber  130 . The second chamber  130  will be described below in operation with the packer  100 . 
     The lower piston  200  is disposed about the body  102  with a first end adjacent the sealing element  300 . A plurality of shear pins  236  releasably retain the lower piston  200  in a first position relative to the body  102 . The lower piston  200  includes two annular grooves  231 ,  232  disposed therein to house elastomeric seals or the like to form a fluid barrier between the first chamber  120  and fluid in the wellbore. Referring to FIG. 1A, the lower piston  200  includes a sloped surface  233 . Also included in the lower piston is a recessed groove  234  disposed in an inner surface thereof that is engageable with a lock ring  250 . The piston  200  further includes a tapered shoulder  240  which contacts a similarly tapered inner surface  585  of the cylinder  580 . The engagement of the shoulders  240 ,  585  allows the lower piston  200  and the cylinder  580  to move together along body  102 . 
     As will be explained, the tapered surface  233  travels underneath an inner surface of the sealing element  300 . The tapered shoulder  240  engages the tapered shoulder  585  of the cylinder  580 , and the recessed groove  234  of the lower piston  200  engages the lock ring  250 . Thereafter, the lower piston  200  and the cylinder  580  move together along the body  102  as one unit. The lock ring  250  prevents movement of the lower piston  200  in an opposite direction. 
     The sealing element  300  is an annular member disposed about the body  102  between the lower piston  200  and the shoulder  400 . The sealing element  300  may have any number of configurations to effectively seal the annulus created between the body  102  and a tubular there-around. For example, the sealing element  300  may include grooves, ridges, indentations or protrusions designed to allow the sealing element  300  to conform to variations in the shape of the interior of the tubular. The sealing element  300  can be constructed of any expandable or otherwise malleable material which creates a set position and stabilizes the body  102  relative to the tubular and which a differential force between the bore  103  of the body  102  and the wellbore does not cause the sealing element  300  to relax or shrink over time due to tool movement or thermal fluctuations within the wellbore. For example, the sealing member  300  may be a metal, a plastic, an elastomer, or a combination thereof. 
     The shoulder  400  is an annular member disposed about a lower portion of the body  102 , and adjacent a lower portion of the sealing element  300 . In the preferred embodiment, the shoulder is a releasable shoulder and includes a first  402  and second section  404 . The first section  402  is offset from the second section  404  thereby forming a cavity  415  between an inner surface of the second section  404  and the outer surface of the body  102 . Referring to FIGS. 4 and 4A, the first section  402  of the shoulder  400  includes a plurality of shear pins  405  which releasably engage the shoulder  400  to the body  102 . The first section  402  further includes a recessed groove  410  disposed about an inner surface thereof. The recessed groove  410  houses a snap ring  420  disposed about the outer surface of the body  102 . The snap ring  420  is disposed about the body  102  within an annular groove (not shown) formed in the outer surface of the body  102  and extends within the recessed groove  410 . The snap ring  420  prevents the shoulder  400  from upward axial movement along the body which may be caused by contact between the packer  100  and the wellbore, as the packer  100  is run into the well. 
     Referring again to FIG. 1, the second section  404  of the shoulder  400  includes a substantially flat upper surface which abuts a lower surface of the sealing member  300 . The upper surface also includes a radial protrusion  407  which abuts the lower surface of the sealing element  300 . As the sealing element  300  moves radially outward from the body  102 , the radial protrusion  407  presses into the sealing element  300  thereby providing a seal between the sealing element  300  and the shoulder  400 . 
     The ratcheting piston assembly  500  includes the slip ratchet  530  and containment rings  540 ,  541  disposed about an upper end of the body  102 . An inner surface of the slip ratchet  530  includes teeth or serrations  532  to contact the outer surface of the body  102 . An outer surface of the slip ratchet  530  may be tapered to form a wedged or coned surface to complement a similar inner surface of the ratchet housing  510 . The containment rings  540 ,  541  are concentric rings disposed about the body  102 . An expandable member  542  is disposed about the body  102  between the two rings  540 ,  541 . The expandable member  542  is a spring-like member which applies an axial force against the containment rings  540 ,  541 . In particular, the expandable member  542  creates an axial force which drives the teeth  532  of the inner surface of the slip ratchet  530  into the outer surface of the body  102  thereby holding the ratcheting piston assembly  500  firmly against the body  102 . 
     The ratchet housing  510  is an annular member disposed about the slip ratchet  530  and containment rings  540 ,  541 . The ratchet housing  510  includes a first  502  and second section  504 . The first section  502  is offset from the second section  504 , thereby forming a substantially flat shoulder  501 . The first section  502  is disposed radially between the body  102  and the upper end of the cylinder  580 . The second section  504  is disposed radially about the slip ratchet  530  and a lower section of the upper piston  550 . The shoulder  501  is adjacent to and contacts the upper surface of the cylinder  580 . The ratchet housing  510  further includes an annular groove disposed about an outer surface of the first section  502  to house an elastomeric seal or the like to form a fluid barrier between the ratchet housing  510  and the cylinder  580 . 
     Referring to FIG. 2, the upper piston  550  is an annular member disposed about the body  102  adjacent the ratchet housing  510 . The upper piston  550  includes a first  552  and second section  554 . The first section  552  is offset from the second section  554  thereby forming a substantially flat shoulder  556 . The first section  552  is disposed radially between the body  102  and the second section  504  of the ratchet housing  510 . The second section  554  is disposed radially about the seal ring  570 . The shoulder  556  is adjacent to and contacts an upper surface of the second section  504  of the ratchet housing  510 . The upper piston  550  further includes an annular groove disposed about an outer surface of the first section  552  to house an elastomeric seal or the like to form a fluid barrier between the upper piston  550  and the ratchet housing  510 . The second port  107  is disposed within the outer surface of the body  102  adjacent the offset interface between the first  552  and second  554  sections of the upper piston  550 . 
     Referring again to FIG. 1, the cylinder  580  is disposed about the lower piston  200  between the ratchet housing  510  and the sealing element  300 . An upper surface of the cylinder  580  abuts the shoulder  501  of the ratchet housing  510 . The first chamber  120  is formed by an inner surface of the cylinder  580  and an outer surface of the body  102 . The lower piston  200  lies within a portion of the chamber  120 . The chamber  120  is in fluid communication with the bore  103  via the port  105  formed in the outer surface of the body  102 . Both the cylinder  580  and the lower piston  200  are longitudinally movable along the body  102 . 
     The cylinder  580  also includes a recessed groove  589  formed in an inner surface thereof. The recessed groove  589  houses the lock ring  250 . As stated above, the recessed groove  234  within the lower piston  200  is engageable with the lock ring  250  which extends radially from an inner surface of the cylinder  580 . After the lower piston  200  moves axially along the outer surface of the body  102  to a predetermined position, the lock ring  250  snaps into place within the recessed groove  234  of the lower piston  200 . Afterwards, the cylinder  580  and the lower piston  200  move along the housing together. 
     The cylinder  580  further includes a lower end having an axial protrusion or extension  581  which abuts an upper end of the sealing element  300 . As the sealing element  300  moves radially outward from the body  102 , the extension  581  presses into the sealing element  300  thereby providing a seal between the sealing element  300  and the cylinder  580 . Referring to FIG. 6, the cylinder  580  also includes a recessed groove or indentation  583  formed in an inner surface thereof toward a second end of the cylinder  580 . The indentation  583  engages a ridge or radial protrusion  505  extending from an outer surface of the ratchet housing. The radial protrusion  505  rests within the indentation  583 , engaging the ratchet housing  510  to the cylinder  580 . 
     Referring to FIGS. 2 and 2A, the running ring  600  is disposed about a split ring  610  at an upper end of the body  102 . For assembly purposes, the running ring  600  and the slip ring  610  are separate pieces. The running ring  600  and the split ring  610  prevent upward axial forces from moving the slideable components described herein once the packer  100  has been actuated within the wellbore. The split ring  610  is disposed about an annular groove disposed within the outer surface of the body  102 . The running ring  600  and the split ring  610  are releasably engaged to each other and the body  102  by a plurality of shear pins  620 . A stop ring  543  is also disposed about the body  102  within the first chamber  120 . The stop ring  543  prevents the ratcheting piston assembly  500  from over-travelling along the body  102  upon the operation and release of the packer  100 . The operation of the packer  100  and the interaction of the various components described above will be described in detail below. 
     FIG. 2 is a partial section view of a downhole packer  100  disposed in a wellbore during a first stage of activation. The packer  100  is first attached within a string of tubulars (not shown) and run down a wellbore  700  to a desired location. A fluid pressure is then supplied through the ports  105 ,  107 , and to the first and second chambers  120 ,  130 . The fluid pressure within the chambers  120 ,  130  is substantially equal to the pressure within the bore  103 . 
     Referring to FIGS. 1-2, once the fluid pressure reaches a predetermined value which exceeds the sum of the wellbore pressure and the shear strength of the pins, the pins  236  shear allowing the lower piston  200  to move axially along the body  102  from a first position to a second position before any other components of the packer  100  are set in motion. In this manner, the lower piston moves to a position underneath the inner surface of the sealing element  300  as shown in FIG.  3 . 
     FIG. 3 is a partial section view of the packer of FIG. 2 after the first stage of activation. As shown in FIGS. 3 and 3A, the lower piston  200  has traveled underneath the element  300  to its second position thereby moving the element  300  closer to the inner surface of the tubular  710  there-around. As the lower piston  200  reaches the second position, the lock ring  250  snaps into the annular groove  234 . Thereafter, the lower piston  200  and the cylinder  580  move along the body  102  as one unit. 
     FIG. 4 is a partial section view of the packer of FIG. 2 at the beginning of a second stage of activation. During the second stage of activation, the fluid pressure through second port  107  acting upon a piston surface formed on upper piston  550  reaches a predetermined value which sets the upper piston  550  in motion. Movement of the upper piston  550  away from the seal ring  570  enlarges the volume of the second chamber  130  which is illustrated in FIG.  4 . 
     The ratchet housing  510 , slip ratchet  530 , cylinder  580  and lower piston  200  move along the body  102  with the upper piston  550 . The slip ratchet  530  with teeth  532  on an inner surface thereof prevent the ratcheting piston assembly  500  from travelling back towards its initial position. In the preferred embodiment, the teeth  532  are angled opposite the direction of travel to grip the outer surface of the body to prevent axial movement. The expandable member  542  disposed between the containment rings  540 ,  541  acts to provide a spring-like axial force directly to the upper surface of the slip ratchet  530  thereby driving the teeth toward the surface of the body  102 . FIG. 6, described below, shows an expanded view of the containment rings  540 ,  541  and the slip ratchet  530 . 
     As the components  200 ,  510 ,  530 , and  580 , travel along the body  102 , the lower surface of the cylinder  580  transfers force against the upper surface of the sealing element  300 . Because the lower surface of the sealing element is held by the shoulder  400 , element  300  is compressed by the opposing forces and caused to expand radially as shown in FIG.  5 . 
     FIG. 5 is a partial section view of the packer of FIG. 2 after the second stage of activation. As shown, the sealing element  300  has been longitudinally compressed and fully expanded in the radial direction thereby effectively sealing the annulus there-around. The second chamber  130  has further increased in volume. Further, as mentioned above, the axial protrusion  581  disposed on the lower surface of the cylinder  580  and the similar axial protrusion  407  disposed on the upper surface of the shoulder  400  provide a fluid seal with the sealing member  300 . Consequently, the sealing element  300  provides a fluid-tight seal within the annulus. 
     In one aspect, the packer  100  is removable from a wellbore. FIG. 6 is a partial section view of the packer during the release and recovery of the packer. To release the activated packer  100 , upward forces are applied which exceed the shear value of the pins  405 . An upward axial force may be supplied from the surface of the well. Once the pins  405  release, the shoulder  400  travels axially along the body  102  from a first position to a second position. The release of the shoulder  400  relaxes the sealing element  300 . The ratcheting assembly  500  is also released and free to move axially along the body  102  between the stop ring  543  and the seal ring  570 . The stop ring  543  prevents the upper ratcheting assembly  550  from over-travelling along the body  102  in the direction of the sealing element  300 , as shown in FIG.  6 A. The stop ring  543  also prevents the cylinder  580  from further contacting the sealing element  300  and re-activating the packer  100 . 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope thereof is determined by the claims that follow.