Abstract:
A full bore support system for a hanger or other equipment in a wellhead features a support groove in the wellhead that can be integrally made or on an insert. A support ring can have a variety of configuration and features an energizing surface and a limit surface that ultimately share the load. The receiving groove is configured to guide the support ring as it expands to minimize bending and distortion. The support ring is recessed and protected until it is actuated outwardly into a supporting position. A high strength low modulus material is preferred to withstand the radial expansion and the applied loads and environmental conditions. Various shapes for the ring are contemplated including a C-ring and a ring made from segments movable with respect to each other.

Description:
FIELD OF THE INVENTION 
   The field of this invention is load rings and corresponding load shoulders in wellheads for support of hangers and other equipment and more particularly where a full bore is needed in the wellhead. 
   BACKGROUND OF THE INVENTION 
   Wellheads are called upon for support of hangers, test plugs and other equipment during drilling and completion phases in a well. Typically the wellhead will have a support shoulder and a reduced bore so that lowering the hanger past a certain point will cause the hanger to become supported. In some designs, multiple shoulders with the same diameter are used to reduce the load applied to each one. A load ring having multiple bearing areas is used in conjunction with these multiple support shoulders to support the hanger off the wellhead. 
   Some of the problems with such designs are the difficulty in machining to close tolerance a combination of multiple shoulders and a load ring having a similar profile so that when the load is applied, it is divided equally between the multiple load shoulders. Another problem with designs that require reduction in bore size is that it is not possible to advance the hanger past the support point without latching into the support shoulder. In situation where the hanger must be advanced beyond the support shoulder and later raised up and only then supported, the reduced bore designs are not effective. The reduced bore designs are also costly because they require over-sizing the wellhead in order to have the requisite minimum bore diameter in it. Even in designs that use a single load surface in the wellhead, problems arise in design of a load ring that could expand to the required dimensions without distortion while still being strong enough to carry the applied load. In some designs the groove into which the expanding load ring was destined to enter did not provide adequate guidance to deal with bending or twisting that could occur as the diameter was increased. In other designs the load ring on the hanger was left unprotected during run in and left exposed to potential physical damage before it was urged into the supporting position. In other designs voids are added to the load ring that is intended to be sprung into a groove in the wellhead in a manner that can weaken the ability of the ring to resist bending and torsional forces that can occur during its release into the wellhead grove and subsequent loading applied from the hanger weight. Some designs only use sloping contact shoulders that maximize radial load components and promote distortion of the load ring as its diameter grows. 
   Some examples of prior designs that include one or more of the above stated shortcomings can be seen in U.S. Pat. Nos. 5,839,512; 4,295,665; 5,209,521; 5,984,008; 6,202,745 B1; 6,598,673 B1 and 3,420,308. 
   The present invention seeks to address these issues with a design that is simple to manufacture and repair and provides full bore access in the wellhead. It features an energizing taper and a limit shoulder that share the load. The receiving groove is shaped to anticipate the potential distortions in the ring as its diameter is increased and bring the ring back to shape. The receiving groove, at its depth is designed to encounter the ring to lend further guidance and support. The load can be shared between the energizing taper and the limit shoulder. The ring can also be made from a high strength low modulus material to enhance load carrying capability while permitting spanning of larger radial distances. Various designs are contemplated including C-rings and segmented rings where the segments are held to each other in a variety of ways. Those skilled in the art will more readily appreciate the various aspects of the invention from a description of the preferred embodiment and the claims, which appear below. 
   SUMMARY OF THE INVENTION 
   A full bore support system for a hanger or other equipment in a wellhead features a support groove in the wellhead that can be integrally made or on an insert. A support ring can have a variety of configuration and features an energizing surface and a limit surface that ultimately share the load. The receiving groove is configured to guide the support ring as it expands to minimize bending and distortion. The support ring is recessed and protected until it is actuated outwardly into a supporting position. A high strength low modulus material is preferred to withstand the radial expansion and the applied loads and environmental conditions. Various shapes for the ring are contemplated including a C-ring and a ring made from segments movable with respect to each other. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a section view of the wellhead with the stop pins extended and the energizing ring about to start pushing the load ring up the energizing taper; 
       FIG. 2  is similar to  FIG. 1  except that the retaining ring is shear pinned to the energizing ring; 
       FIG. 3  is the view of  FIG. 1  showing some movement of the load ring up the energizing taper; 
       FIG. 4  is the view of  FIG. 3  showing the load ring having moved up away from the energizing ring supported by the stop pins to the nearly set position in the recess comprising the load shoulder; 
       FIG. 5  is the view of  FIG. 4  showing the fully set position of the load ring; 
       FIG. 6  is a section through the load ring showing how it can bend or twist as its diameter is increased through movement on the energizing taper; 
       FIG. 7  is a plan view of the load ring shown in section in  FIG. 6  and illustrating how the load ring can bend as its diameter is increased; 
       FIG. 8  shows how an offset in position of the hanger is compensated for in the design of the present invention; 
       FIG. 9  is a detailed view, in section of the load ring set in its receiving groove in the wellhead; 
       FIGS. 10 and 10   a  show an embodiment of a segmented load ring in the contracted and expanded positions, respectively; 
       FIGS. 11 and 12  are two views of an alternative design for a segmented load ring showing an outer band holding the segments together; 
       FIGS. 13 and 14  show an alternative embodiment to  FIGS. 10 and 10   a  in the retracted and expanded positions, respectively. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the wellhead  10  has a bore  12  that remains constant in the region shown. One or more stop pins  14  are in respective bores  16  and sealed with seals  18 . The hanger or other device to be suspended  20  has a retaining ring  22  attached at thread  24 . An energizing ring  26  rests on ring  22  and pins  14  when the hanger  20  is lowered in wellhead  10  to the position shown in  FIG. 1 . Wellhead  10  also has a recess  28  in which a ring  30  is fitted and secured in recess  28  with a split ring retainer  32 . Ring  30  has a groove  34  defined by surfaces  36 ,  38  and  40 . Those skilled in the art will appreciate that groove  34  can be integral to the wellhead  10  as an option. Using the ring  30  to create the groove  34 , whose peak coincides with bore  12 , allows the ring  30  to be replaced if the groove  34  becomes worn or damaged over time. The hanger  20  features an energizing taper  42  and an adjacent limit shoulder  44  which can be flat, as shown in  FIG. 1  or sloping downwardly in a direction toward centerline  46 , as shown in  FIG. 9 . In some situations a slight angle may be desirable to reduce or more uniformly distribute stresses in the load support area. An inherent benefit of this design is to prevent accumulation of debris. 
   As shown in  FIG. 1 , the expanding load shoulder  48  has a top surface  50  that will ultimately engage shoulder  44 . Surfaces  52 ,  54  and  56  correspond to surfaces  36 ,  38  and  40  of groove  34  such that when load shoulder  48  is forced along taper  42  there results a close fit on the respective trio of surfaces as between the groove  34  and the load shoulder  48  as will be described later in more detail. 
     FIG. 2  is similar to  FIG. 1  with the exception that energizing ring  26  is retained to retaining ring  22  by at least one shear pin  58  which eventually breaks as the hanger  20  is advanced with stop pins  14  extended. 
     FIG. 3  shows the continuing sequence of movement. In  FIG. 3  the load shoulder  48  has been advanced part way up the taper  42  but it still bears on the energizing ring  26 . At this point surface  54  has begun to protrude beyond shoulder  44 , which had been previously protecting it from mechanical impacts during earlier operations. At this point, the energizing ring  26  is suspended by the pins  14  and not by ring  22 . 
     FIG. 4  shows a nearly set position that results from further downward movement of the hanger  20  with pins  14  extended. Surface  50  has yet to be engaged circumferentially by shoulder  44 . However, load shoulder  48  has been sufficiently radially expanded so that it has moved up and away from energizing ring  26 . This upward movement is caused by surface  52  moving along inclined surface  36 . The trio of surfaces on the load shoulder  48  has moved closer to their corresponding surfaces that define the groove  34 . Indeed at some points along the circumference there may be guiding contact to help hold the load shoulder ring  48  against bending out of a plane perpendicular to axis  46  or against torsional distortion about its circumferential axis, as will later be described with respect to  FIGS. 6 and 7 . 
     FIG. 5  illustrated the fully set position. Note that surface  60  on ring  48  is still engaged by taper  42 . The top surface  50  is against shoulder  44 . Preferably continuous contact in groove  34  occurs as between the surfaces  52 ,  54  and  54  and the respective groove surfaces  36 ,  38  and  40 . This close fit prevents bending and torsional deformation of the load shoulder ring  48  despite the radially outward deflection resulting from use of a single groove  34  for support of the hanger  20 . Note that the load of the hanger  20  is supported from adjacent surfaces  50  and  60  on the load shoulder ring  48 . 
     FIG. 6  illustrates how groove  34  engages load shoulder ring  48  as ring  48  is expanded along taper  42 . The ring  48  can twist about its own central axis but the configuration of the groove  34  holds and moves it back toward its original plane and resists the torsional forces in part induced by bending during expansion to facilitate the assumption of the final position shown in  FIG. 5 . Prior designs could fail if they allow the bending and/or twisting of the load ring to become great enough which could prevent the preferred situation of uniform circumferential flush contact and thus create areas of high localized stress that can lead to deformation of ring  48  and to failure to support the hanger  20 . 
     FIG. 7  illustrates a C-ring shape to load shoulder ring  48  as viewed from above when its diameter is increasing and gap  62  is opening up. For ease of description gap  62  is referred to as being located at 180°. It can be seen that as the gap  62  increases, the most bending occurs at the 0° position. This location also experiences some twisting in torsion as the ring  48  responds to stresses imposed on it from an increase in its diameter. The fact that inside surface  64  becomes visible from the overhead view of  FIG. 7  during the radial expansion, illustrates the tendency to bend and/or twist graphically. The close fit in groove  34  particularly the intended full bottom contact at surface  38  in the depth of groove  34  resists these tendencies so as to assure the intended load carrying capacity of ring  48  is achieved at the conclusion of the radial expansion. 
   A related phenomenon is shown in  FIG. 8 . Here the hanger  20  has shifted to the left causing the load support ring  48  to bottom in groove  34  on the left side of the drawing while leaving a gap  66  on the right side of the drawing. The gap  66  would normally cause the ring  48  to want to bend or twist out of position but the close fit of groove  34  in conjunction with lateral force exerted on the hanger  20  from the contacting surfaces on the left side of the drawing again contain the ring  48  in the desired plane and resist its tendency to twist responsive to torsional stresses induced from bending during the forced radial expansion as the hanger  20  is set. 
     FIG. 9  shows an inclined shoulder  44 , which is optional. This detailed view also shows the close fit inside groove  34  to ensure a good positioning of ring  48  for adequate support of the hanger  20 . 
     FIGS. 10 and 10   a  show a segmented ring  48  made of segments that are connected for relative movement with respect to each other by bolts  70  which limit the maximum diameter shown in  FIG. 10   a . Between the segments are springs  72  to push the segments  68  apart to assume the position of  FIG. 10   a  if the segments  68  are no longer retained to the run in diameter where shoulder  44  can protect them. The  FIG. 10  position can be retained by a band (not shown), which can be removed as the radius increases during the hang off procedure. 
   An alternative for a segmented ring  48  is shown in  FIGS. 11 and 12 . Here the segments  68  are held together for run in by a circumferential band  74 , which can be in the shape of a C-ring. The segments stay together as they are driven along taper  42  and then become trapped in groove  34  with the weight of the hanger  20  holding them in groove  34 . Yet a slight variation of the design of  FIGS. 10 and 10   a  is the design illustrated in  FIGS. 13 and 14 . Here the springs  72  are mounted around the travel limit bolts  70  but for all intents and purposes, the operation of the load shoulder ring  48  of  FIGS. 10 and 10   a  is similar to the version shown in  FIGS. 13 and 14 . 
   In the segmented designs, the outer surface  54  on each of the segments is made with a radius to conform closely to the depth of groove  34  defined by surface  38 . This results in a wavy appearance of the outer surface of the segmented ring  48  when it is in the run in position. However, after expansion, while the segments may have moved apart their outer surfaces more closely approximate the radius at the depth of the groove  34 . This is done to promote better support by the segmented ring  48  of the tubular  20 . As previously stated the close proximity of these surfaces on expansion of the segmented ring  48  also helps control bending and twisting as the radius of the segmented ring  48  is increased. 
   Those skilled in the art will appreciate the various aspects of the present invention. The design allows run in with the ring  48  protected by shoulder  44 . The hanger or other device  20  can be lowered past groove  34  without a landing engagement to facilitate other operations before the hanger  20  is ready to be tensioned and supported. The bore  12  needs no reduction in size to facilitate support of the hanger  20 . As a result a smaller wellhead  10  can be used with a given bore size to allow further cost savings to the operator. The load ring  48  can take a variety of configurations such as a C-ring or a segmented ring held together in a variety of ways. It should be noted that for the segmented designs shown in  FIGS. 10-14  that the outer diameter of the segments is preferably close in dimension to the inside diameter of the groove  34  into which the segments will expand when the diameter is increased due to movement of the segments along taper  42 . By doing this, the groove  34  will be better able to retain the relative position of the segments with respect to each other after radial expansion and the weight of the string connected to the hanger  20  will be better supported. In the preferred embodiment, if the ring  48  were perfectly centered in groove  34  there would be a clearance of about 0.005 inches all around. In reality the ring  48  may wind up off center such that the gap between surfaces  54  and  38  could vary between about 0.002 and 0.008 inch. Although this clearance may vary a small amount due to tight tolerances on surfaces  54  and  38 , centralization of the ring and subsequent equipment is the desired result. In the present invention the segmented ring design has the segments mounted to the hanger  20  and interacting with each other to support the hanger. This is to be contrasted with prior designs that had individual segments mounted to the wellhead that could be driven in to contact a hanger for support. The ring  48  regardless of its configuration in the present invention is guided by its mating groove  34  to resist bending or twisting under torsional stress that results from driving ring  48  along taper  42 . As noted above, such movement can cause a tendency to bend and/or twist which could result in permanent distortion and inadequate support. In the present invention, the mating groove  34  is designed to counteract such forces by relying on close clearances on a multiplicity of surfaces that gets ring  48  into its original shape and orientation as its diameter is being increased. Specifically, contact is envisioned at surface  38  of groove  34  over a substantial portion of its surface area as the expansion is brought to the final diameter. Specifically, it is envisioned that the ring  48  will slide on hanger surface  42 , possibly unevenly, and when this situation occurs the preferably tightly controlled surface  38  will assist in keeping ring  48  from twisting, bending or being deformed and help position it properly during the setting process. Ring  48  regardless of configuration is preferably constructed of a high strength low modulus metal preferably titanium. Not only does titanium provide the high strength but it also provides corrosion resistance particularly in wells where hydrogen sulfide is anticipated. Another feature is the load sharing of the entire axial load in the set position between the energizing taper  42  and the adjacent shoulder  44 . Shoulder  44  can extend radially or be disposed at an angle, as shown in  FIG. 9  to allow debris in well fluids to run off. 
   The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the invention and the claims below are intended to define the range of the invention.