Abstract:
A seal assembly for use between wellbore tubulars employs an inner seal ring partially circumscribed by an outer seal ring. The seal rings are axially slidable with respect to one another and can be made from pliable inelastic materials such as graphite or a fluoropolymer. The seal rings contact one another along profiled surfaces that are angled such that by axially urging the seal rings towards one another produces a bulge in the seal assembly directed radially outwards and inwards. The bulging seal rings come into contact with opposing sides of the wellbore tubulars to define a sealing surface. Axial supports at opposing lateral ends of the seal rings maintain the seal between the tubulars.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to production of oil and gas wells, and in particular to a seal assembly for use between wellbore tubulars. 
     DESCRIPTION OF RELATED ART 
     Wellheads used in the production of hydrocarbons extracted from subterranean formations typically comprise a wellhead assembly attached at the upper end of a wellbore formed into a hydrocarbon producing formation. Wellhead assemblies usually provide support hangers for suspending production tubing and casing into the wellbore. The casing lines the wellbore, thereby isolating the wellbore from the surrounding formation. The tubing typically lies concentric within the casing and provides a conduit therein for producing the hydrocarbons entrained within the formation. 
     Wellhead assemblies also typically include a wellhead housing adjacent where the casing and tubing enter the wellbore, and a production tree atop the wellhead housing. The production tree is commonly used to control and distribute the fluids produced from the wellbore and selectively provide fluid communication or access to the tubing, casing, and/or annuluses between the tubing and casing. Valves assemblies are typically provided within wellhead production trees for controlling fluid flow across a wellhead, such as production flow from the borehole or circulating fluid flow in and out of a wellhead. 
     Seals are used between inner and outer wellhead tubular members to contain internal well pressure. The inner wellhead member may be a tubing hanger that supports a string of tubing extending into the well for the flow of production fluid. The tubing hanger lands in an outer wellhead member, which may be a wellhead housing, a Christmas tree, or a tubing head. A packoff or seal seals between the tubing hanger and the outer wellhead member. Alternately, the inner wellhead member might be an isolation sleeve secured to a Christmas tree. A seal or packoff seals between the isolation sleeve and a casing hanger located within the wellhead housing. 
     A variety of seals of this nature have been employed in the prior art. Prior art seals include elastomeric and partially metal and elastomeric rings. Prior art seal rings made entirely of metal for forming metal-to-metal seals are also employed. The seals may be set by a running tool, or they may be set in response to the weight of the string of casing or tubing. One type of prior art metal-to-metal seal has inner and outer walls separated by a conical slot. An energizing ring is pushed into the slot to deform the inner and outer walls apart into sealing engagement with the inner and outer wellhead members. The deformation of the inner and outer walls exceeds the yield strength of the material of the seal ring, making the deformation permanent. 
     Because elastomers can degrade when subjected to increased operating temperatures, seals that include elastomeric material may necessarily have a truncated life. Also, material properties of elastomers vary more than materials with less elasticity, thereby limiting the temperature ranges in which elastomeric seals may be employed. Elastomeric materials are also prone to fracture when subjected to rapid gas decompression and may swell or degrade when exposed to certain chemicals. Metal to metal seals also have a shortcoming in that the forces required for setting or energizing the seal may be difficult to generate in some wells, such as those subsea. 
     SUMMARY OF THE INVENTION 
     Disclosed herein is an example of a seal assembly for use between wellbore tubulars. In an example embodiment, the seal assembly includes an inner seal ring partially circumscribed by an outer seal ring. The inner and outer seal rings having opposing surfaces that are profiled oblique to an axis of the tubulars. The outer seal ring inner radial surface is in sliding contact with the inner seal ring outer radial surface. When the seal assembly is set between the tubulars and opposing axial forces are applied to lateral ends of the outer seal ring and inner seal ring, the inner and outer seal rings slide against each other and are pushed radially away from one another. The inner radius of the seal assembly contacts an inner tubular and an outer radius of the seal assembly contacts an outer tubular and sealing surfaces form where the seal assembly contacts the tubulars. A spring assembly can be included that applies an axial force on one of the lateral ends of the outer seal ring or inner seal ring. The spring assembly can be a resilient member, such as a Belleville washer, a stack of Belleville washers, wave spring washers, coiled springs or combinations thereof. In an example embodiment, the inner and outer seal rings can be inelastic and include substances such as graphite, a fluoropolymer, or combinations thereof. In an example embodiment, lateral rings can be provided on distal surfaces of the inner ring and outer ring. In an example embodiment, an intermediate ring is disposed between at least a portion of the inner radial surface of the outer ring and the outer radial surface of the inner ring. The intermediate ring can have a hardness greater than a hardness of the inner and outer rings. In an example embodiment, the intermediate ring is a coating on each of the inner radial surface of the outer ring and the outer radial surface of the inner ring. 
     Also disclosed herein is a wellhead assembly. In an example embodiment the wellhead assembly is made up of an outer tubular, an inner tubular inserted within the outer tubular, an annular space defined between the inner and outer tubulars, a seal assembly in the annular space and between axial supports coupled with at least one of the inner or outer tubular. The seal assembly includes an inner seal ring having an inner radial surface in selective contact with a portion of a outer radial surface of the inner tubular. Also included with the seal assembly is an outer radial surface profiled at an angle oblique to an axis of the wellhead assembly and an outer seal ring having an outer radial surface in selective contact with a portion of an inner radial surface of the outer tubular and an inner radial surface profiled at an angle oblique to an axis of the wellhead assembly. The profile of the inner radial surface of the outer seal ring corresponds to the outer radial surface of the inner seal ring, so that when the inner tubular is inserted into the outer tubular and axial forces are applied to the seal assembly by the supports, the inner and outer seal rings slide into respective positions. The sliding action of the inner and outer rings forms sealing interfaces between the inner radius of the inner ring and a portion of an outer radius of the inner tubular and between the outer radius of the outer ring and a portion of an inner radius of the outer tubular. In an example embodiment, at least one of the supports is a resilient member. In an example embodiment, the wellhead assembly further includes a groove formed in the outer radius of the inner tubular, wherein the seal assembly is disposed in the groove and upper and lower edges of the groove comprise supports for the seal assembly. In an example embodiment, the inner and outer seal rings each include a compliant material, so that when the axial forces are applied to distal ends of the inner and outer seal rings, the inner radius of the inner seal ring bulges radially inward to form the sealing interface with the inner tubular and the outer radius of the outer seal ring bulges radially outward to form the sealing interface with the outer tubular. In an example embodiment, the inner and outer tubulars are wellbore casing and production tubing. 
     Also included is a method of sealing an annular space between wellbore tubulars. In an example embodiment the method includes providing a seal assembly that includes an inner seal ring with an outer radial surface profiled oblique to an axis of the wellbore tubulars, and an outer seal ring having an inner radial surface profiled oblique to the axis of the wellbore tubulars and in sliding contact with the inner seal ring outer radial surface. The seal assembly is set between the wellbore tubulars and an axial length of the seal assembly is maintained by applying axial loads to opposing lateral ends of the seal assembly. The applied axial loads bulge out at least one of an inner radial surface on the inner seal ring and an outer radial surface of the outer seal ring to form a sealing surface between the seal assembly and at least one of the tubulars. In an example embodiment, prior to disposing the seal assembly between the tubulars, the seal assembly width exceeds a width of a space between the wellbore tubulars, and as the tubulars are set in place the inner and outer seal rings axially slide a designated distance in opposite directions along the inner and outer radial profiles. In an example embodiment, the designated distance is defined by the position of where the axial loads are applied to the seal assembly. In an example embodiment, the inner and outer seal rings include an inelastic substance that can be graphite, a fluoropolymer, or combinations thereof. In an example embodiment, the wellbore tubulars are inner and outer wellbore tubulars, and a groove is formed on an outer radial surface of the inner wellbore tubular, and wherein the seal assembly is provided in the groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side partial sectional view of an example embodiment of an un-energized seal for use with wellbore tubulars in accordance with the present invention. 
         FIG. 2  is a side sectional view of an example embodiment of the seal of  FIG. 1  in an energized configuration in accordance with the present invention. 
         FIG. 2A  is a side perspective view of an example of a spring assembly. 
         FIG. 3  is a side sectional view of an example embodiment of a wellhead assembly having a seal in an assembled configuration in accordance with the present invention. 
         FIG. 4  is a side sectional view of an alternate embodiment of a wellhead assembly having a seal in an assembled configuration in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatus and method of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. This subject of the present disclosure may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location. 
     It is to be understood that the subject of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the subject disclosure and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the subject disclosure is therefore to be limited only by the scope of the appended claims. 
       FIG. 1  illustrates one example embodiment of a seal assembly  10  between inner and outer tubulars  12 ,  14  and shown in a side sectional view. In the example of  FIG. 1 , tubular  12  can be respectively a hanger for a tubular or an isolation sleeve, whereas tubular  14  can be a hanger for a tubular or a production tree. The tubulars  12 ,  14  may be included within a wellhead assembly and also may be disposed within a wellbore. The configuration of the seal assembly  10  of  FIG. 1  is in an unenergized state and thus not providing a sealing function between the respective tubulars  12 ,  14 .  FIG. 1 , in an example embodiment, illustrates a step of assembling a wellhead assembly where the respective inner and outer tubulars  12 ,  14  are not in their assembled positions. As shown, the seal assembly  10  is disposed at a location along an axis A X  of the tubulars  12 ,  14  adjacent a portion of the outer tubular  14  and with the inner radius  16  of the outer tubular  14  extending radially outward from a shoulder  18  to define an enlarged annular space therebetween. The shoulder  18  of  FIG. 1  is shown formed where the radius of the outer tubular  14  changes abruptly and then slopes radially inward and transitions to an inner radius  19  closer to the axis A X  than inner radius  16 . In an example embodiment and for purposes of reference, the inner radius  19  is below the shoulder  18 . 
     Still referring to  FIG. 1 , the outer radius  20  of the inner tubular  12  is shown having a groove  22  formed along a portion of its length and its entire periphery. It is within the groove  22  where the seal assembly  10  is supported. The seal assembly  10  is shown having an inner seal ring  24  set within the groove  22 , so that an inner radius  26  of the inner seal ring  24  rests along the inner surface of the groove  22 . Optionally, a slight interference fit may exist between the inner seal ring  24  and inner surface of the groove  22 . A lateral surface  28  of the inner ring  24  projects radially outward from the inner radius  26  and terminates at an outer radius of the inner seal ring  24 . The seal ring  24  has an outer radial surface  30  that is profiled to extend along a plane that when viewed in cross-section is generally oblique to the axis A X . More specifically, the radial thickness of the seal ring  24 , which is affected by the profile of the outer radial surface  30 , increases proximate to the lateral surface  28 . In the embodiment of  FIG. 1 , the outer radial surface  30  intersects the inner radius  26  and extends obliquely and radially up to a transition  31 . The remaining portion of the outer radial surface  30 , up to the lateral surface  28 , extends along a plane generally parallel with the axis A X . 
     An outer seal ring  32  is shown circumscribing a substantial portion of the inner seal ring  24 . The outer seal ring  32  includes an inner radial surface  34  that has a profile corresponding to the profile of the outer radial surface  30  of the inner seal ring  24 . As such, the inner and outer seal rings  24 ,  32  may slide in an axial direction along the surfaces  30 ,  34  with respect to one another when disposed in the configuration of  FIG. 1 . An example embodiment exists where the angle at the intersection of the inner ring inner radius  26  and inner ring outer radial surface  30  is at least 22°. Similarly, an example embodiment exists where the angle at the intersection of the outer ring outer radial surface  38  and outer ring inner radial surface  34  is at least 22°. The outer seal ring  32  includes a lateral surface  36  shown largely perpendicular to the axis A X  and distal from the lateral surface  28  of the inner seal ring  24 . The outer seal ring  32  also includes an outer radial surface  38  shown distal from the inner radius  26  of the inner ring  24  and substantially aligned with the axis A X . Also in this configuration, the thickness or width of a cross-section of the seal assembly  10  is greater than the depth of the groove  22  so that the outer radial surface  38  contacts the shoulder  18  above the inner radius  19 . Similar to the transition  31  on the inner seal ring  24 , a transition  40  is shown provided on the inner radial surface  34  of the outer seal  32  and defines a location where the surface  34  changes from an obliquely angled surface to one that is largely parallel with the axis A X . By virtue of the transitions  31 ,  40  each of the inner and outer seal rings  24 ,  32  thereby proximate a rectangular section combined with a triangular section. However, embodiments exist wherein neither of the inner or outer seal rings  24 ,  32  include a transition and thus have a substantially triangular cross-sectional configuration. 
     An optional intermediate ring  42  is illustrated in the embodiment of the seal assembly  10  of  FIG. 1  and shown provided on the contact surface between the inner and outer seal rings  24 ,  32 . In one example embodiment, the intermediate ring  42  is a separate member that coaxially inserts between the inner and outer seal rings  24 ,  32 . Optionally, one or both of the inner or outer seal rings  24 ,  32  may have an applied coating on their respective inner and outer radial surfaces  26 ,  34  that make up the intermediate ring  42 . Example materials for the inner and outer seal rings  24 ,  32  include materials that are pliable. Embodiments also exist wherein the rings  24 ,  32  are formed from an inelastic material, thereby avoiding problems with the prior art of degradation due to prolonged exposure to high temperatures. Specific material examples for the inner and outer seal rings  24 ,  32  include graphite, compression molded graphite, fluoropolymers, including polytetrafluoroethylene and other fluoro carbon solids. 
     Optional lateral rings  44 ,  46  are shown disposed on the lateral surfaces  28 ,  36  respectively of the inner and outer seal rings  24 ,  32 . The lateral rings  44 ,  46 , also referred to as anti-extrusion rings, can support the lateral ends of the seal rings  24 ,  32  and prevent the material of the seal rings  24 ,  32  from extruding out when subjected to axial or radial loads. Example materials of the lateral rings  44 , 46  include polymer thermoplastics such as polyetheretherketone; but may as specific applications vary. A spring assembly  48  is shown in the example embodiment of  FIG. 1  and set on a side of the lateral ring  44  opposite its boundary with the inner ring lateral surface  28 . In the example of  FIG. 1 , the spring assembly  48  which can be any resilient member, is made up of a series of stacked Belleville washers  50  in a relaxed or unflexed state. Further, the lateral ring  46  is sandwiched between the lower end of the groove  22  and outer seal ring lateral surface  36 . Because the inner and outer seal rings  24 ,  32  may slide with respect to one another along their radial surfaces  30 ,  34  the axial length (or height) of the distance between the opposing lateral surfaces  28 ,  36  may vary as the inner and outer seal rings  24 ,  32  slide on one another. In the unenergized configuration of  FIG. 1 , the distance between the lateral surfaces  28 ,  36  is such that the spring assembly  48  may be in a relaxed state thereby occupying more space than in an unrelaxed state. 
     Referring now to  FIG. 2 , inner tubular  12  and seal assembly  10  have been axially moved so that the inner radius  19  is adjacent the outer radial surface  38  of the outer seal ring  32 . Because the inner radius  19  of the outer tubular  14  now occupies space occupied by a portion of the outer seal  32  of  FIG. 1 , by reconfiguring the components as shown in  FIG. 2 , the outer seal ring  32  is forced radially inward that in turn generates a resultant axial force to urge the inner seal ring  24  in a direction away from the lateral surface  36  of the lower seal ring and towards the spring assembly  48 . The dimensions of the groove  22  of  FIG. 2  are such that the axial movement of the inner seal ring  32  compresses the spring assembly  48  thereby in turn generating a spring force F S  that transfers through the lateral ring  44  and into the inner and outer seal rings  24 ,  32 . A counter spring force F′ S  is generated from the lateral ring  46  in a direction opposite spring force F S . As these opposingly directed axial forces exert a compressive force against the seal rings  24 ,  32  thereby creating a radial bulge that produces contact between the inner radius  26  of the inner seal ring  24  and the inner radial wall of the groove  22 . Similarly, there are radial bulges created on the outer radial surface  38  of the outer seal ring  32  thereby urging the outer seal ring  32  into contact with the inner radius  19  of the outer tubular  14 . The spring force F S  (F′ S ) exerted into the seal assembly  10  produces sufficient sealing to prevent leakage across the seal assembly  10  at low differential pressures across the axis of the seal assembly  10 . A sealing surface  52  is defined between the outer seal ring  32  and outer tubular; and a sealing surface S is formed between the inner seal ring  24  and inner radial wall of the gap  22 . 
     Still referring to  FIG. 2 , a gap  53  is shown between the inner radius  19  of the outer tubular  14  and outer radial  20  of the inner tubular  12 . Within the gap  53 , fluid pressure may communicate onto the seal assembly  10  and generate a resultant force F P  shown in a generally axial orientation and directed from the lateral ring  46  against the lateral surface  36  thereby urging the outer seal ring  32  against the inner seal ring  24 . In example embodiments where the inner and outer seal rings  24 ,  32  are generally pliable elements, the inner and outer seal rings  24 ,  32  are able to axially slide with respect to one another. The force F P  produces resultant forces F R  shown directed radially outward from the outer seal ring  34  against the outer tubular  14  and radially inward from the inner radial surface  26  of the inner seal ring  24  against the inner tubular  12 . As such, by an increase in pressure from a wellbore (not shown) as communicated to the gap  53 , the sealing forces increase with increasing wellbore pressure. Similarly, in the event of a pressure in the region adjacent the spring assembly  48  that exceeds that in the gap  53 , a resulting force F P  exerted on the lateral surface  28  of the inner seal ring  24  also may generate resultant forces F R  that increases the magnitude of the pressure seal of the seal assembly  10 . 
     Optionally, the lower end of the groove  22  can be a support ring  54  mounted to the inner tubular  12  along a connection  55 . Where the connection  55  can be a threaded connection, a weld, a press or interference fit, or other attachment means. In an example of installing the seal assembly  10  between the tubulars  12 ,  14 , components of the seal assembly  10  are set onto the inner tubular  12  prior to adding the support ring  54 . More specifically, the components of the seal assembly  10  can be slid onto the inner tubular  12  in the following order (1) the spring assembly  48 , (2) lateral ring  44 , (3) inner seal ring  24 , (4) intermediate ring  42  (in embodiments having the intermediate ring  42  separate from the seal rings  24 ,  32 ), (5) outer seal ring  32 , lateral ring  46 . When the components of the seal assembly  10  are put on the inner tubular  12 , the support ring  54  can then be mounted thereby axially supporting the seal assembly  10 . In optional embodiments when the spring assembly  48  is a coil spring, a stiffener ring (not shown) may be included for distributing the spring load. With the seal assembly  10  and support ring  54  in place, the inner tubular  12  can be inserted within the outer tubular  14 . 
     In one example embodiment of the seal assembly  10  used in a wellhead assembly  56  is shown in a side sectional view in  FIG. 3 . In this example, the wellhead assembly  56  includes a production tree  58  mounted on wellhead housing  60  and where the inner tubular  12 A is a tubing hangar and having a string of tubing  62  depending from its lower end. As such, the seal assembly  10  is provided in an outer radial slot formed on the outer circumference of a portion of the tubing hangar  12 A. In an optional embodiment, the spring assembly  48 A is shown in a side perspective view in  FIG. 2A . In this example embodiment, the spring assembly  48 A is a wave washer that may be a single member as illustrated in  FIG. 2A  or may be made up of a stack of individual wave washers and set in combination with the seal assembly  10 . 
     One of the advantages of using the profiled inner and outer seal rings as disclosed herein is the low friction between these two members thereby providing for an assembly that can be quickly and easily formed. Moreover, the inelastic material of the rings allows for the rings to move easily relative to one another and as such further maximizing the radial load generated with relative axial movement of the inner and outer seal rings  24 ,  32 . Rings formed from the inelastic material will not coalesce like other parts that may be highly compressed over time and at elevated temperatures. Further simplicity is realized with the present example in that it relies on variations in wellbore pressure to generate the sealing force required during these high pressure events. The materials also allows for operation at high temperatures such as in excess of 400° F. and also at cryogenic temperatures well below −20° F. The inelastic materials can mitigate seal failure from explosive decompression and allow rapid bleed down of annulus pressures, and also mitigate risk of material degradation or swelling due to chemical attack. The seal may be included with the tubular on which it is located or it can be set with a running tool. Although shown in the embodiments as being in a groove on an inner tubular, alternate embodiments exist wherein the seal assembly  10  can be between inner and outer respective radiuses of concentric tubulars and between supports coupled with one or two of the tubulars or can be an annular channel provided in an outer tubular. 
     An advantage of embodiments of the seal assembly disclosed herein is that this concept may be pressure energized by the inner and outer seal rings  24 ,  32  interfacing to act as a wedge. The seal assembly can thus have a low interface stress when set as this interface stress is only required to seal at low pressures thereby ensuring a pressure differential always exists across the seal. As pressure is increased, the wedge effect increases the interface stress and continues to maintain a seal. The low interface stress corresponds to a low setting load. On standard bulk seals (one part) the increase in interface stress with applied pressure is much less (relies on Poisson&#39;s effect)—meaning standard bulk seals require much larger interface stresses when set, which corresponds to much higher setting loads. Chevron packing sets which can be made from similar materials are pressure energized to some extent, but are not easily assembled into bi-direction configurations (can seal from either direction) and generally require very good surface finish (the larger interface stresses and contact area offered by the concept should make it more tolerant of minor surface defects). 
     Provided in a side sectional view in  FIG. 4  is an alternate embodiment of a seal assembly  10 A sealing the space between tubulars  12 ,  14 . In this example embodiment, the lateral or anti-extrusion ring  44 A is shown having a wedge or triangular shaped cross section with its inner radial surface largely parallel with the inner radius of the groove  22  and upper lateral surface substantially perpendicular with the inner radius of the groove  22 . The outer radial surface of the anti-extrusion ring  44 A is oblique to the axis AX and extends from the lower end of the inner radial surface of the anti-extrusion ring  44 A to the outer radial end of the upper lateral surface of the anti-extrusion ring  44 A. Combined with the anti-extrusion ring  44 A is a wedge shaped anti-extrusion ring  45 A having an oblique inner radial surface shown set against the oblique outer radial surface of the anti-extrusion ring  44 A. The outer radial surface of the anti-extrusion ring  45 A is substantially aligned with the axis AX, and its lower lateral surface is substantially normal to the axis AX. Also shown in  FIG. 4 , the lateral surface  36 A of the outer seal ring  32 A is adjacent the anti-extrusion ring  44 A proximate the spring assembly  48 A and the inner ring lateral surface  28 A is proximate a lower anti-extrusion ring  46 A distal from the spring assembly  48 A. As such, the portion of the intermediate ring  42 A adjacent the anti-extrusion ring  46 A projects radially outward from the portion of the intermediate ring  42 A adjacent the anti-extrusion ring  44 A. The axial dimension or thickness of anti-extrusion rings  44 A,  45 A is much less than the axial dimension of inner and outer seal rings  24 A,  32 A, when assembled as shown in  FIG. 4 . 
     An inlay  25  is shown on the inner radial surface of the inner seal ring  24 A having a semi-circular cross section. In an example embodiment the inlay  25  extends along the entire circumference of the inner radial surface of the inner seal ring  24 A. In an example embodiment the inlay  25  includes a material have a lower value of hardness than that of the inner seal ring  24 A. The inlay  25  may be continuous or split. An example embodiment includes the groove on the inner seal ring  24 A but without the inlay  25 . The outer seal ring  32 A of  FIG. 4  also includes an inlay  33  set in its outer radial surface. An example embodiment includes the groove on the inner seal ring  32 A but without the inlay  33 . 
     The anti-extrusion ring  46 A of  FIG. 4  also has a triangular or wedge shaped cross section wherein its upper lateral surface disposed adjacent the inner ring lateral surface  28 A is substantially perpendicular with the axis AX and its outer radial surface facing the outer tubular  14  is substantially parallel with the axis AX. The lower lateral surface of the anti-extrusion ring  46 A extends in an oblique direction from an inner end of the upper lateral surface to the outer to a lower end of the outer radial surface. A retainer ring  62  is shown circumscribing the inner tubular  12  on a side of the seal assembly  10 A distal from the spring assembly  48 A. In the example embodiment of  FIG. 4 , the retainer ring  62  has a “C” shaped cross section and is oriented so the end portions of the C face the outer tubular  14  to define an annular space between a mid portion of the retainer ring  62  and the outer tubular  14 . A portion of a lateral side of the support ring  62  facing the seal assembly  10 A is profiled along a line oblique to the axis AX, the slope of the line corresponds to the lower lateral side of the anti-extrusion ring  46 A. The support ring  62  is supported on a metal seal  64  shown mounted over an energizing ring  66 , both of which are also in the annular space between the inner and outer tubulars  12 ,  14 . The metal seal  64  has an elongate inner leg contacting the inner tubular  12  and an elongate outer leg contacting the outer tubular  14 . A mid portion of the metal seal  64  connects the inner and outer legs and has an upper lateral side set against the support ring  62 . The energizing ring  66  has an elongate mid portion that inserts into the space between the inner and outer legs of the metal seal  64 . A wiper ring  68  circumscribes the outer circumference of the energizing ring  66  on its lower end. A retainer ring  70  shown threadingly attached to the inner tubular  12  has a wedge shaped cross section with a generally planar upper surface, wherein the energizing ring  66  and wiper ring  68  are supported on the upper surface of the retainer ring. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.