Patent Publication Number: US-8109340-B2

Title: High-pressure/high temperature packer seal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to packer and sealing devices of the type used within a wellbore. 
     2. Description of the Related Art 
     There are generally two separate categories of designs for elastomeric wellbore packer seals: those that are set by axial compression and those that are set by moving the seal element radially outwardly with a ramp. Both of these designs are problematic when used at extreme wellbore depths wherein there are very high pressures and temperatures which tend to degrade elastomers. A compression set packer seal is compressed axially, which causes the seal element to expand radially until it contacts and seals against the inner radial surface of the surrounding casing or other tubular member. Compression set packers inherently require large volumes of elastomer, which is very expensive. In addition, it may be difficult or impossible to mold compression set packer elements from certain specialized elastomers that are resistant to high temperatures and pressures. Also at high pressures, the elastomeric seal element may become too soft to properly deploy anti-extrusion devices which prevent the elastomer from bleeding out along the axial space between the packer and the surrounding tubing. 
     Ramp set packer elements typically require the elastomeric sealing element to be bonded to a steel insert. But it is currently not feasible to bond elastomers that are greatly resistant to high temperatures and pressures to such inserts. Ramp set seals also have a tendency to leak when pressure is applied to the side with the smaller cross-section because the pressure pushes the seal element down the ramp. Even when a ratchet mechanism is used to try to retain the seal element on the ramp, there is still some inherent slippage that occurs. 
     SUMMARY OF THE INVENTION 
     The devices and methods of the present invention provide a packer design that overcomes a number of the problems of the prior art. A packer design in accordance with the present invention provides a reliable fluid seal which is highly resistant to degradation from high temperatures and pressures. In a preferred embodiment, a packer device is described which includes an elastomeric packer element which is seated upon an inner sleeve that surrounds a central inner mandrel. The inner sleeve and the inner mandrel are oriented at an angle of departure with respect to the central axis of the tool, thereby providing a ramp assembly which helps to set the packer device. An anchor ring and a retaining ring are located on opposite axial sides of the packer element. The retaining ring is secured to the sleeve, while the anchor ring is axially moveable with respect to the sleeve. 
     In operation, the packer device is incorporated into a production tubing string or other work string. A packer setting tool is incorporated into the production tubing string adjacent the packer device. The production tubing string is then deployed into a wellbore along with the setting tool. When a depth or location has been reached at which it is desired to set the packer device, the setting tool is actuated to move a setting sleeve axially. The setting sleeve contacts and moves the actuating ring of the packer device axially downwardly with respect to the central inner mandrel of the packer device. Downward movement of the actuating ring causes the retaining ring, inner sleeve, packer element and anchor ring components to be moved axially downwardly with respect to the inner mandrel. One the anchor ring is brought into contact with the surrounding tubular, downward movement of the anchor ring with respect to the surrounding tubular is halted, and a metal-to-metal barrier is formed between the anchor ring and the surrounding tubular. 
     As the setting sleeve continues to move axially downwardly, the sleeve and the actuating ring are moved further downwardly with respect to the inner mandrel. The packer element is axially compressed between the retaining ring and the anchor ring, thereby causing it to expand radially outwardly to form a resilient fluid seal against the surrounding tubular. 
     Eventually, downward movement of the setting sleeve will cause the actuating ring to be moved radially outwardly and into contact with the surrounding tubular. This contact creates a second metal-to-metal barrier between the packer device and the surrounding tubular. In preferred embodiments, the actuating ring is provided with at least one radially raised pip which can be crushed during setting of the packer device. 
     A number of alternative embodiments are described. In one alternative embodiment, the anchor ring is securely affixed to the inner sleeve. In other alternative embodiments, the actuating ring and/or the retaining ring is/are releasably secured to the inner sleeve. In still other alternative embodiments, multiple raised pips are provided on the actuating ring and/or the anchor ring. Further the outer radial surfaces of the actuating ring and/or the anchor ring may be coated with a metal or material that is softer than the material forming the rings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and other aspects of the invention will be readily appreciated by those of skill in the art and better understood with further reference to the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawings and wherein: 
         FIG. 1  is a side, cross-sectional view of an exemplary production tubing string having a packer device incorporated therein that is constructed in accordance with the present invention. 
         FIG. 2  is a side, one-quarter cross-sectional view of the packer device in an unset position. 
         FIG. 3  is a side, one-quarter cross-sectional view of the packer device shown in  FIG. 2 , now in a partially set position. 
         FIG. 4  is a side, one-quarter cross-sectional view of the packer device shown in  FIGS. 2 and 3 , now in a fully set position. 
         FIG. 5  depicts an alternative embodiment for a packer device in accordance with the present invention wherein the anchor ring is securely affixed to the inner sleeve. 
         FIG. 6  depicts a further alternative embodiment for a packer device in accordance with the present invention wherein the actuating ring and retaining ring are releasably secured to the inner sleeve. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an exemplary hydrocarbon production wellbore  10  that has been drilled through the earth  12  and has been lined with casing  14 . A production tubing string  16  is disposed within the casing  14 , having been run in from the surface (not shown) in a manner known in the art. A central flowbore  18  is defined along the length of the production tubing string  16 . The production tubing string  16  may be formed of a number of interconnected production tubing sections, or it may be formed of coiled tubing. A packer setting tool  20  is incorporated into the production tubing string  16 . The setting tool  20  operates to set a packer by axial movement of a setting sleeve  22 . The setting tool  20  may be actuated electrically, hydraulically, or in other ways known in the art. Two commercially available setting tools which would be suitable for use as the setting tool  20  are the Baker Hughes Model “E-4” Wireline Setting Tool and the “BH” Hydraulic Setting Tool, both of which are available commercially from Baker Hughes Incorporated of Houston, Tex. 
     A packer device  24 , constructed in accordance with the present invention, is also incorporated into the production tubing string  16  adjacent to the setting tool  20 . The packer device  24  is depicted in greater detail in  FIGS. 2 and 3 . The packer device  24  includes a central inner mandrel  26  which defines a central flowbore  28 . The inner mandrel  26  has a central axis along its length, which is depicted by the dashed line  30 . The inner mandrel  26  presents an outer radial surface  32  which is angled with respect to the central axis  30 . The angle of departure from the central axis  30  is illustrated by angle  34  in  FIG. 2 . In a currently preferred embodiment, the angle of departure  34  is 3 degrees. The inner mandrel  26  will typically be provided with threaded axial ends, as are known in the art, for incorporating the packer device  24  into the production tubing string  16 . 
     The packer device  24  also includes an upper metallic actuating ring  36  which radially surrounds the inner mandrel  26  and abuts the setting sleeve  22  of the setting tool  20 . The actuating ring  36  is affixed, at its lower end, to a substantially rigid retaining ring  38 . Preferably, the retaining ring  38  is metallic. The retaining ring  38  presents a radially outer surface  40  with a raised deformable pip  42 . 
     An inner sleeve  44  radially surrounds the inner mandrel  26  and is slidably moveable with respect to the inner mandrel  26 . The sleeve  44  has a radially outwardly projecting flange  46  which abuts a radially inwardly projecting flange  48  on the retaining ring  38 . The sleeve  44  also presents an outer ramp surface  50 . Annular fluid seals  52  are preferably disposed between the sleeve  44  and the inner mandrel  26 . 
     An elastomeric packer element  54  radially surrounds the sleeve  44  and is slidably moveable upon the ramp surface  50 . The packer element  54  includes axial end lips  56  and  58 . The upper lip  56  is mechanically interlocked with complimentary flange  60  on the retaining ring  38 . 
     A substantially rigid anchor ring  62  surrounds the sleeve  44  and the inner mandrel  26  and is slidably moveable with respect to the sleeve  44 . Typically, the anchor ring  62  is metallic. The anchor ring  62  has an inwardly directed flange  64  which is shaped and sized to be complimentary to the lip  58  of the packer element  54 . The lip  58  and flange  64  are mechanically interlocked to secure the anchor ring  62  and the packer element  54  together. The use of mechanical interlocks between the lips  56 ,  58  and the flanges  60 ,  64  eliminates the need to use bonding to secure the elastomer of the packer element  54  to a rigid component. 
     In operation, the packer device  24  and setting tool  20  are run into the wellbore  10  with the production tubing string  16 . The packer device  24  is in the unset position shown in  FIG. 2 . When a depth has been reached wherein it is desired to set the packer  24 , the setting tool  20  is actuated to move the setting sleeve  22  axially downwardly against the actuating ring  36  of the packer device  24 . The actuating ring  36  urges the retaining ring  38  and sleeve  44  axially downwardly with respect to the inner mandrel  26 . Due to the angle of departure  34  of the outer radial surface  32 , the packer device  24  is moved to the position depicted in  FIG. 3  wherein the anchor ring  62  is moved radially outwardly and into contact with the casing  14 . Downward axial movement of the anchor ring  62  with respect to the mandrel  26  is halted by this contact. The contact between the packer device  24  and the casing  14  helps to prevent extrusion of the elastomeric material forming the packer element  54  axially outwardly between the packer device  24  and the casing  14 . 
     As the setting sleeve  22  is further moved axially downwardly by the setting tool  20 , the actuating ring  36  and the sleeve  44  are also moved axially downwardly. Because downward axial movement of the anchor ring  62  has been stopped, downward movement of the retaining ring  38  will urge the packer element  54  against the anchor ring  62 . The packer element  54  is axially compressed between the retaining ring  38  and the anchor ring  62  and will be expanded radially outwardly, as depicted in  FIG. 4 . The packer element  54  will be brought into contact with the casing  14 , and forms a resilient fluid seal against the casing  14 . As the retaining ring  38  and sleeve  44  are moved axially downwardly, the sleeve  44  is permitted to slide downwardly upon the outer radial surface  32  of the inner mandrel  26 . The seals  52  provide a fluid seal between the sleeve  44  and the inner mandrel  26  so that any fluid path between the sleeve  44  and the inner mandrel  26  is closed off. As the packer element  54  is set by compression between the retaining ring  38  and the anchor ring  62 , the radial expansion of the packer element  54  will also energize the seals  52 . 
     As the setting sleeve  22  moves axially downwardly further still, the angle  34  of the outer radial surface  32  of the inner mandrel  26  will cause the retaining ring  38  to be brought into contact with the casing  14 . Initially, the raised pip  42  of the retaining ring  38  will make contact with the casing  14  (see  FIG. 4 ). Further downward pressure on the retaining ring  38  by the actuating ring  36  will cause the pip  42  to deform and flatten to cause the outer radial surface  40  of the retaining ring  38  to be brought into contact with the surrounding casing  14 . The pip  42  is an anti-extrusion mechanism for the elastomeric material making up the packer element  54 . Because the interior surface of the casing  14  is not perfectly cylindrical, the pip  42  will compensate by deforming more where the casing  14  is smaller (i.e., a smaller space between the casing  14  and the retaining ring  38 ) and deform less where the casing  14  is larger. This variable deformation allows the pip  42  to contact the interior diameter of the casing  14  around its complete circumference. The retaining ring  38  provides a second contact between the packer device  24  and the casing  14  which helps prevent axially extrusion of the elastomeric material of the packer element  54  outwardly between the packer device  24  and the casing  14 . 
     In the event that the packer device  24  is to be removed, the setting device  20  is actuated to move the setting sleeve  22  axially upwardly with respect to the packer device  24 , thereby reversing the axial compression of the packer element  54 . If the packer device  24  is intended to be removed, the setting sleeve  22  and the actuating ring  36  are preferably affixed together via complimentary latching fingers, collets, connecting pins, threading, or in other ways known in the art, so that upward movement of the setting sleeve  22  will also move the actuating ring  36  upwardly. As the actuating ring  36  is moved upwardly, it will cause the affixed retaining ring  38  to move upward also thereby helping to unset the packer element  54 . 
     Alternative constructions for packer assemblies in accordance with the present invention are depicted in  FIGS. 5 and 6 .  FIG. 5  depicts an alternative packer device  24   a  wherein the anchor ring  62  of packer device  24   a  is rigidly affixed to the sleeve  44  via one or more pins  66  or other connectors, of a type known in the art. Alternatively, the anchor ring  62  could be secured to the inner sleeve  44 ′ by means of threading, splining or in other ways known in the art. In addition, the radially outwardly extending flange  46  of the inner sleeve  44 ′ is not present, so that the retaining ring  38 ′ can slide axially with respect to the inner sleeve  44 ′. When the packer device  44   a  is constructed in this manner, downward movement of the setting sleeve  22  will cause the actuating ring  36 , retaining ring  38 ′, sleeve  44 , packer element  54  and anchor ring  62  to all move axially downwardly upon the outer radial surface  32  of the inner mandrel  26 . The anchor ring  62  will contact the casing  14 , as previously described, to form a first metal-to-metal seal between the packer device  24   a  and the casing  14 . Thereafter, further downward movement of the setting sleeve  22  will move the actuating ring  36  and retaining ring  38 ′ downwardly to axially compress the packer element  54  between the retaining ring  38 ′ and the anchor ring  62 . The packer element  54  will create a resilient seal against the casing  14 . The retaining ring  38 ′ will also be brought into contact the casing  14 , as previously described, and will form a second metal-to-metal seal between the packer device  24   a  and the casing  14 . 
       FIG. 6  illustrates a further alternative embodiment for a packer device  24   b , in accordance with the present invention. In  FIG. 6 , the actuating ring  36  and the retaining ring  38  are releasably secured to the inner sleeve  44  with the use of one or more shear members, such as shear screws  68 . Although both the actuating ring  36  and the retaining ring  38  are shown releasably affixed to the inner sleeve  44  in  FIG. 6 , those of skill in the art will understand that either the actuating ring  36  or the retaining ring  38  may be independently affixed to the sleeve  44  in a releasable manner without the other being so attached. The packer device  24   b  is operated in essentially the same manner as the packer device  24  described previously. However, the shear screws  68  preclude early movement of the actuating ring  36  or retaining ring  38  which might cause early setting or early partial setting of the packer device  24   b.    
     In other variations for a packer device constructed in accordance with the present invention, one or more metal back-up rings may be added as an extrusion barrier for the packer element  54 . Additionally, the surfaces of the retaining ring  38  and/or the anchor ring  62  which will contact the casing  14  may be plated with a softer metal, such as silver, or another material that is softer than the material used to form the rings  38 ,  62 . Rings  38  and  62  are preferably fashioned from a hardened metal, such as annealed AISI 8620. One advantage of plating is that the material used to plate the rings  38  and/or  62  will deform into any inconsistencies or gaps within the casing  14  surface in order to help prevent the elastomeric material making up the packer element  54  from bleeding between the packer device  24  and the casing  14 . Also, raised pips, such as pip  42 , may be formed on the anchor ring  62 , and multiple raised pips can be formed on both or either of the retaining ring  38  and the anchor ring  62 . 
     It should be understood that the angled outer radial surface  32  of the inner mandrel  26  and the sleeve  44  collectively provide a ramp assembly that will move the packer element  54 , the anchor ring  62  and the retaining ring  38  radially outwardly as they are moved axially with respect to the inner mandrel  26 . 
     Those of skill in the art will understand that the components of the various described packer devices  24 ,  24   a ,  24   b  may be inverted so that the packer element  54  and other components are moved axially upwardly with respect to the inner mandrel  26 . In this instance, the setting tool  20  may be located below the packer device  24 ,  24   a  or  24   b  in the production tubing string  16 . 
     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.