Abstract:
An expandable downhole sealing assembly in which an axial setting force is applied to radially compress and self-energize an expanding element such that stored radial forces in the expanding element effect and maintain a seal thereafter. The sealing assembly can be used to provide a seal between a casing and a mandrel in a well, among other applications.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional App. No. 61/791,983 filed Mar. 15, 2013, the entirety of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates generally to sealing assemblies used in the oil and gas industry, and more particularly, to expandable downhole sealing assemblies in which an axial setting force is applied to radially compress and self-energize an expanding element such that stored radial forces in the expanding element effect and maintain a seal thereafter. 
     Downhole packers are well known in the oil and gas industry for sealing an annulus between various weight casings and mandrels at different underground locations in an oil well, for example, to exploit different production zones. Conventional downhole packers include multi-element elastomeric packers (see  FIG. 7 ), packers including a single elastomeric element having metal or mesh back-ups (see  FIG. 8 ), and inflatable packers. Elastomeric sealing elements are generally restricted for use in applications up to about 450° F., while high temperature and pressure applications require flexible or expanded graphite. 
     Packers having elastomeric sealing elements typically require a large axial setting force to deform the sealing element radially outward to reach the interior of the casing. Typically, the greater the setting force the more energy transferred radially outward. Once set, internal stresses within the sealing element work against the packer as lost energy, thus an axial maintenance force is required to resist the elastomeric memory of the element. As a result, the packer is not “self-energizing,” and will leak at a pressure higher than its equilibrium internal pressure without any sign of extrusion. 
     Geothermal packers used in high temperature applications (e.g., up to about 650° F.) can include braided graphite packing elements or compressed flexible graphite elements. These packers also require large axial setting forces to deform the element to reach the interior of the casing. One problem associated with the use of flexible graphite elements is that they are fragile, and thus susceptible to damage when the tool is lowered into the well. To protect the flexible graphite elements from damage during installation, the elements are typically covered with an elastomeric shell, which not only increases the complexity of the assembly, but also introduces the problems associated with elastomeric memory as discussed above. 
     Inflatable packers utilize air or other fluid injected into an expandable element to expand the outer shell to reach the interior of the casing. In inflatable packers, the inflation pressure must be higher than the system pressure in order to maintain a positive seal. Thus, like the other conventional packers discussed above, inflatable packers are not self-energizing. Additionally, any axial movement of the packer or the anchoring stop will relax the packer and reduce the sealing force accordingly. Further, when the temperature increases after setting, the element tends to expand, which further deforms the back-up system to create more gland volume or room. Further, changes in internal pressure as a result of thermal cycling affect the sealability. 
     Accordingly, what is needed is a self-energizing packer that overcomes the disadvantages of prior art assemblies in that the packer is structurally simple, requires a minimum setting force, obviates the need for axial maintenance forces, and is suitable for use with elastomeric, thermoplastic and graphitic elements, among other advantages. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, a sealing assembly for use in the oil and gas industry is provided herein and generally includes a sealing ring (i.e., an “expanding element”) and a deflecting ring, wherein an axial setting force is applied to the deflecting ring to radially deflect and compress the sealing ring to force the axially aligned rings into an arrangement in which the sealing ring is radially outside of the deflecting ring. By radially compressing the sealing ring and causing it to deform, in contrast to conventional packers arrangements in which a sealing element is axially compressed, stored forces in the sealing ring work to effect and maintain the seal after the setting force is removed. 
     In another aspect, the sealability of the sealing ring is independent of the setting force. 
     In yet another aspect, the sealing ring is radially compressed between the deflecting element and the interior of the casing when expanded downhole. 
     In yet another aspect, the cross-section of the sealing ring increases in the axial direction and decreases in the radial direction from the unset to the set configurations. 
     In yet another aspect, the deflecting ring defines a ramped surface at one end thereof facing in the direction of the sealing ring and configured for radially displacing the sealing ring upon axial movement of the deflecting ring in the direction of the sealing ring. 
     In yet another aspect, the deflecting ring defines a first surface arranged at an angle to the interior wall of the casing, and a second surface arranged substantially parallel to the interior wall of the casing, wherein, upon axial movement of the deflecting ring in the direction of the sealing ring, at least a portion of the sealing ring is forced passed the first surface and comes to rest over the second surface such that a portion of the sealing ring and the deflecting ring overlap in the axial direction. 
     In yet another aspect, after the sealing assembly is set (i.e., “expanded”), the portion of the sealing ring axially overlapping the second surface of the deflecting ring is radially compressed to a greater degree than portions of the sealing ring axially overlapping the first surface. 
     In yet another aspect, a portion of the second surface of the deflecting ring is recessed radially inward to receive a portion of the deformed sealing ring therein when the sealing ring and the deflecting ring overlap in the axial direction. 
     In yet another aspect, the sealing ring is resiliently deformable and assumes a final shape after being set. 
     In yet another aspect, the sealing ring retains its radially compressed shape and set height after the setting force is removed. 
     In yet another aspect, the sealing ring is radially compressed such that its cross-section decreases when set. 
     In yet another aspect, the sealing ring includes at least one of elastomeric, thermoplastic, and graphitic materials. 
     In yet another aspect, axial system pressure in translated into radial force to self-energize the sealing ring. 
     In another aspect, the sealing ring is made from PTFE (e.g., virgin or filled), and is suitable for use in temperature applications from about −50° F. to about 650° F., as well as within harsh chemical environments. 
     To achieve the forgoing and other aspects and advantages, in a first embodiment the present invention provides a sealing assembly for sealing an annulus in a downhole application including a sealing ring and a deflecting ring axially aligned between axially opposed mesh back-ups, each of the sealing ring and the deflecting ring defining a first ramped end, the first ramped ends of the sealing ring and the deflecting ring arranged facing each other such that an axial set force applied to the deflecting ring deflects the sealing ring radially outward forcing the sealing ring into a side-by-side arrangement with the deflecting ring to fill and seal the annulus. 
     In a further embodiment, the sealing ring is deformable such that when the sealing ring is forced radially outward, the sealing ring extends axially and compresses radially. 
     In a further embodiment, the sealing ring has a larger cross-section before the axial set force is applied than after the axial set force is applied. 
     In a further embodiment, the deflecting ring defines a recess along the length thereof for receiving a portion of the sealing ring therein when the sealing assembly is in an expanded configuration. 
     In a further embodiment, each of the sealing ring and the deflecting ring define a second ramp spaced from their respective first ramped end, wherein the second ramp and the ramped end of each of the sealing ring and the deflecting ring are parallel such that when the set force is applied, the first ramped end of the sealing ring slides against and passes the second ramp of the deflecting ring, and the first ramped end of the deflecting ring slides against and passes the second ramp of the sealing ring, in the axial direction. 
     In a further embodiment, the sealing ring defines a second ramped end adjacent the mesh back-up at a 35 degree angle to the longitudinal axis of the sealing assembly, and the deflecting ring defines a second ramped end adjacent the mesh back-up at a 55 degree angle to the longitudinal axis of the sealing assembly. 
     In a further embodiment, the sealing assembly includes an o-ring retained against an inner wall of the deflecting ring. 
     In another embodiment, provided herein is a sealing assembly for sealing an annulus in a downhole application including a sealing ring and a deflecting ring axially aligned between axially spaced mesh back-ups, each of the sealing ring and the deflecting ring defining a first ramped end and a second ramp spaced from the first ramped end, the sealing ring and the deflecting ring arranged such that, when an axial set force is applied to the deflecting ring, the first ramped end of the deflecting ring slides against and passes the second ramp of the sealing ring and the first ramped end of the sealing ring slides against and passes the second ramp of the deflecting ring to deflect the sealing ring radially outward to force the sealing ring into an arrangement in which the sealing ring at least partially overlaps the deflecting ring to seal the annulus. 
     In a further embodiment, the sealing ring further defines a second ramped end at a 35 degree angle to a longitudinal axis of the sealing assembly, and the deflecting ring defines a second ramped end at a 55 degree angle to the longitudinal axis of the sealing assembly. 
     In yet another embodiment, provided herein is a sealing assembly for sealing an annulus in a downhole application including a deformable sealing ring and a rigid deflecting ring axially aligned between axially spaced mesh back-ups, each of the deformable sealing ring and the rigid deflecting ring defining a first ramped end, the first ramped ends of the deformable sealing ring and the rigid deflecting ring arranged facing each other such that an axial set force applied to the rigid deflecting ring deflects the deformable sealing ring radially outward relative to a longitudinal axis of the sealing assembly, axially lengthens the deformable sealing ring, and radially compresses the deformable sealing ring to force the deformable sealing ring into a side-by-side arrangement with the rigid deflecting ring to fill the annulus. 
     Additional features, aspects and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein. It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which: 
         FIG. 1  is an axial cross-section of a sealing assembly according to a first embodiment of the invention; 
         FIG. 2  is an axial cross-section of a geothermal sealing assembly according to an embodiment of the invention; 
         FIG. 3  is an axial cross-section of the sealing assembly of  FIG. 1  shown expanded downhole; 
         FIG. 4  is an axial cross-section of a downhole sealing assembly having a recessed formed in the deflecting element of the assembly, and shown expanded downhole; 
         FIG. 5  is a perspective view of another embodiment of a sealing assembly; 
         FIG. 6  is an axial cross-section of the sealing assembly of  FIG. 5 ; 
         FIG. 7  is an axial cross-section of a prior art sealing assembly; and 
         FIG. 8  is an axial cross-section of another prior art sealing assembly including multiple, spaced sealing elements. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as limited to the representative embodiments set forth herein. The exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention and enable one of ordinary skill in the art to make, use and practice the invention. Like reference numbers refer to like elements throughout the various drawings. 
     Referring to  FIG. 1 , a first embodiment of a sealing assembly (e.g., a “downhole packer”) suitable for use in downhole applications in the oil and gas industry is shown generally at reference numeral  10 . The sealing assembly  10 , shown prior to being set (i.e., in an “unexpanded” configuration), generally includes a deflecting ring  12  and a sealing ring  14  arranged between (i.e., sandwiched) axially opposed back-up systems  16 . The deflecting ring  12  is positioned on the “stroking” or dynamic side of the assembly  10 , and moves with a gauge ring to axially expand the sealing ring  14 , as described in detail below. An O-ring  18  may be retained in an annular slot along the interior wall of the deflecting ring  12  that functions to further effect a seal between the deflecting ring  12  and the outer wall of a cylindrical mandrel (see  FIG. 3 ). 
     The deflecting ring  12  can be made from any suitable material or combination of materials including, but not limited to, PTFE (filled or virgin), PPS, PEEK, elastomer, thermoplastic material or metal/alloy. The back-up systems  16  can be made from any material or combination of materials including, but not limited to, Sintermesh™, Unsintermesh™, wire mesh, graphoil with wire mesh, of the like, with the back-up systems being capable of expanding to close extrusion gaps between the gauge ring and the casing interior. The sealing ring  14 , also referred to herein as the “expanding element,” can be made from any material or combination of materials including, but not limited to, elastomeric, thermoplastic and graphitic materials. The sealing ring  14  may be a machined or molded elastomeric element suitable for use in applications up to about 450° F. Applications above about 450° F. may require thermoplastic PTFE compounds and/or graphitic elements. 
     The deflecting ring  12  is an annular ring defining a ramped surface  20  (i.e., a surface at an angle to the axial direction) at one end thereof facing in the direction of and in physical contact with a corresponding ramped surface  22  of the sealing ring  14 . During setting, the ramped surfaces  20 ,  22  of the components slide passed one another such that the angular relationship therebetween causes at least a portion of the deflecting ring  12  to slide beneath at least a portion of the sealing ring  14 , thereby deflecting at least a portion of the sealing element radially outward. As used herein, the term “axial” or “axial direction” is intended to mean in the direction along the axis of the well bore, casing, mandrel or sealing element. As used herein, the term “radial,” “radially” or “radial direction” is intended to mean in the direction from the center of the well bore, casing, mandrel or sealing element outward, or from the circumference of the well bore, casing or sealing element inward. 
     The deflecting ring  12  further defines a substantially flat surface  24  or “table” adjacent the ramped surface  20 , that at least partially slides beneath the sealing ring  14  when the sealing assembly  10  is in its expanded configuration. Surface  24  is arranged substantially parallel to the axial direction. Referring to  FIG. 4 , surface  24  may optionally include at least one shaped recess  26  positioned along the length thereof for receiving a portion of the deformed sealing ring  14  therein when the packer is expanded. The receipt of a portion of the sealing ring  14  in the recess  26  further resists relative axial movement between the sealing ring and the deflecting ring when the packer is expanded. 
     Referring to  FIGS. 3 and 4 , the sealing assembly  10  with and without the recess  26  is shown in the expanded configuration. When the axial set force is applied, the deflecting ring  12  moves axially in the direction of the sealing ring  14 , thus forcing the sealing ring radially outward. As the deflecting ring  12  continues to be forced in the direction of the sealing ring  14 , the space constraints between the casing  28  and the deflecting ring force the deformable sealing ring to radially compress and axially expand to fill the annulus (i.e., “gap”) between the deflecting ring and the interior wall of the casing. Because the sealing ring&#39;s starting radial cross-section is greater than the space between the deflecting ring  12  and the interior wall of the casing  28 , the sealing ring  14  is radially compressed or “squeezed,” with predetermined maximum and minimum compression based on the casing weight tolerance. At the same time, the back-up system  16  is activated and expanded until it reaches the interior wall of the casing  28 , assuring zero extrusion gaps. 
     When set, the sealing ring  14  and surface  26  overlap in the axial direction. In other words, when the sealing assembly is expanded, the sealing ring  14  and the deflecting ring  12  are side-by-side, with the sealing ring  14  radially outward of the deflecting ring  12 . The extent of overlap depends upon the starting thickness of the sealing ring  14 , the size of the annulus to be filled, the length of the second surface  26 , etc. Once set, because the sealing ring  14  is radially compressed, the elastic memory of the material wants to return to its original cross-section (i.e., wants to radially expand). This compressive strength acts on the deflecting ring  12  and the interior wall of the casing  28 , illustrated by the small force arrows  30 , to create a high contact load on the sealing ring  14 , thus providing a “self-energized” seal between the deflecting ring  12  and the interior of the casing  28 . 
     The seal achieved as a result of the radial compression of the sealing ring  14  and the O-ring  18  cooperate to achieve a high-pressure seal between the interior of the casing  28  and exterior of the mandrel  32 . Removing or relaxing the setting force and/or removing the anchoring system has no appreciable effect on the seal performance once set. Additionally, the low end of a thermal cycle will not cause an appreciable reduction of the sealing ring&#39;s  14  internal stress, and consistent sealability can be maintained similar to the original setting. 
     Referring to  FIG. 2 , an embodiment of a geothermal packer for high temperature applications is shown generally at reference numeral  34 . Because of the high temperatures in such applications, the sealing ring  14  may be made from thermoplastic PTFE compounds or graphitic elements. In this embodiment, the sealing ring  14  defines a tapered portion  36  having a ramped surface that tapers in thickness in the direction of the deflecting ring  12 . In use, when the axial set force is applied, the deflecting ring  12  moves in the direction of the sealing ring  14 , thereby deflecting the sealing ring  14  radially outward, and forcing the sealing ring  14  into the gap between the deflecting ring and the interior wall of the casing. 
     When set or “expanded,” the sealing ring  14  and the deflecting ring  12  overlap in the axial direction over the length of the tapered portion  36 . At the same time, the back-up system  16  is activated and expanded until it reaches the interior wall of the casing, assuring zero extrusion gaps. The compressive forces in the sealing ring  14  urge against the deflecting ring  12  and the interior wall of the casing to create a high contact load on the sealing ring  14 , thus achieving a seal between the deflecting ring and the interior wall of the casing. The back-up requirements in the geothermal packer may be relaxed due to the lower pressure as compared to the embodiment described above. 
     Referring to  FIGS. 5 and 6 , another embodiment of a sealing assembly is shown generally at reference numeral  40 . The sealing assembly  40 , shown in an unexpanded configuration, generally includes an expanding element, a deflecting element, and back-ups at both ends. Specifically, sealing assembly  40  includes a deflecting ring  12  (or “ramping ring”) and a sealing ring  14  arranged between axially opposed back-up systems  16 . The deflecting ring  12  is positioned on the “stroking” or dynamic side of the assembly  40 , and moves with the gauge ring  41  to deflect the sealing ring  14  radially outward in use. An O-ring  18  may be disposed along the interior wall of the deflecting ring  12  that functions to achieve a seal between the deflecting ring  12  and the outer wall of the cylindrical mandrel  32 . 
     The deflecting ring  12  can be made from any suitable material or combination of materials including, but not limited to, PTFE (filled or virgin), PPS, PEEK, elastomer, thermoplastic material or metal/alloy. The ‘upper’ and ‘lower’ back-up systems  16  can be made from any material or combination of materials including, but not limited to, Sintermesh™, Unsintermesh™, steel mesh, wire mesh, graphoil with wire mesh, or the like, with the back-up systems being capable of expanding to close extrusion gaps between the gauge ring and the casing interior. As shown, the ‘upper’ and ‘lower’ back-ups each include Sintermesh™  42  adjacent Unsintermesh™  44 . The ‘upper’ and ‘lower’ Sintermesh™ components  42  may be asymmetrical and have modified shapes. For example, the angle of face  46  of the deflecting ring  12  immediately adjacent to and facing in the direction of ‘upper’ Unsintermesh™ component  44  may be 55 degrees, whereas the angle of face  48  of the sealing ring  14  immediately adjacent to and facing in the direction of ‘lower’ Unsintermesh™ component  44  may be 35 degrees. 
     In comparison to the “single-ramp” arrangement shown in  FIG. 1 , sealing assembly  40  is a “double ramp” arrangement, resulting in a longer axial seal capable of withstanding higher pressures. Specifically, the deflecting ring  12  is an annular ring defining first and second ramps  50 ,  52  (i.e., at an angle to the axial direction) spaced by an intermediate flat  54  (i.e., parallel to the axial direction). The first and second ramps  50 ,  52  face and slide in physical contact against corresponding ramps  56 ,  58  of the sealing ring  14 , also spaced by a flat  60 . During setting, ramps  50  and  58 , as well as ramps  52  and  56 , slide passed one another such that the thin-walled portion of the sealing ring  14  is deflected radially outward of the thick-walled portion of the deflecting ring  12 , and the thin-walled portion of the deflecting ring  12  is forced radially inward of the thick-walled portion of the sealing ring  14 , and wherein the respective portions overlap in the axial direction. When set, the deflecting ring  12  and sealing ring  14  thus effectively interlock based on their predetermined shapes. The larger cross-section of the ‘overlapped’ deflecting ring  12  and sealing ring  14  as compared to the gap between the mandrel and inner wall of the casing forms the seal. 
     The foregoing description provides embodiments of the invention by way of example only. It is envisioned that other embodiments may perform similar functions and/or achieve similar results. Any and all such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the appended claims.