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CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of, co-pending U.S. Patent Application Ser. No. 61/987,861 filed May 2, 2014 and of co-pending U.S. Patent Application Ser. No. 61/896,401 filed Oct. 28, 2013, the full disclosures of which are hereby incorporated by reference herein for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present disclosure relates in general to a system for coupling annular member to hanger used in a wellhead assembly. 
         [0004]    2. Description of Prior Art 
         [0005]    Wellheads used in the production of hydrocarbons extracted from subterranean formations typically include a wellhead assembly attached at the upper end of a wellbore formed into a hydrocarbon producing formation. Support hangers for suspending production tubing and casing into the wellbore are generally included within the wellhead assemblies. The casing lines the wellbore and isolates the wellbore from the surrounding formation. The tubing, which typically lies concentric within the casing, provides a conduit therein for producing the hydrocarbons entrained within the formation. 
         [0006]    Wellhead assemblies also typically include a wellhead housing and a production tree atop the wellhead housing. Wellhead housings are often adjacent where the casing and tubing enter the wellbore. 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 tees for controlling fluid flow across a wellhead, such as production flow from the borehole or circulating fluid flow in and out of a wellhead. 
         [0007]    Lockdown rings typically restrain each casing hanger within the wellhead housing to prevent relative axial movement between the casing hanger and wellhead housing. Usually proximate the lockdown rings are return passages that allow fluid flow during cementing operations. The passages typically are bored axially through the casing hangers and are in the form of slots along the inner surface of the wellhead housing. 
       SUMMARY OF THE INVENTION 
       [0008]    An example of a wellhead assembly is described herein that is made of a wellhead hanger, a wellhead housing, a lock ring through which an axial lock down force is selectively transmitted between the wellhead hanger and wellhead housing, a slot through the lock ring that registers with a bore radially formed into an outer surface of the wellhead hanger, a pin that inserts into the bore and into the slot, so that the pin is in a path that interferes with axial movement of the lock ring, and a radial stop mounted on the wellhead hanger and in interfering contact with a radial path of the lock ring. Optionally, a portion of the slot projects fully through a radial thickness of the lock ring to define an aperture, and another portion of the slot extends from the aperture along a portion of the circumference of an inner surface of the lock ring and partially through the radial thickness of the lock ring. The radial stop can be made of fastener assemblies, wherein each fastener assembly includes a threaded fastener that anchors into the wellhead hanger, and a washer that projects radially outward from the threaded fastener. In this example, a channel can be formed on an outer radial surface of the lower end of the lock ring, and wherein the washer projects into the channel. Further in this example, the channel extends along a portion of the circumference of the lock ring. In one alternative, the lock ring rests on an upper facing surface of a shoulder, wherein the shoulder projects radially outward from the wellhead hanger, and wherein an outer radial portion of the upper facing surface projects radially upward to define a radial stop. The lock ring can be freely and selectively moveable with respect to the pins along a path radial to an axis of the wellhead hanger. In an alternative, the lock ring selectively projects into a profile formed on an inner surface of the wellhead housing, a wherein the lock ring rests on an upper surface of a shoulder on the wellhead hanger, and wherein the axial lock down force transmitted between the wellhead hanger and wellhead housing passes through the shoulder and the profile. 
         [0009]    Also disclosed herein is a wellhead assembly which includes a wellhead hanger, a wellhead housing circumscribing the wellhead hanger, a lock ring between the wellhead hanger and wellhead housing and for transmitting a lockdown force between the wellhead hanger and wellhead housing, pins anchored in the wellhead hanger that are in interfering contact with axial movement of the lock ring, and radial stops on the wellhead hanger that limit radial movement of the lock ring. Slots can be provided in the lock ring that include apertures, and wherein the pins radially project through the apertures, in this example a portion of each slot extends past each of the apertures and along a portion of the circumference of the lock ring and partially through the thickness of the lock ring. In an example the radial stops incorporate threaded fasteners that project radially into the wellhead hanger, and have a portion projecting into a channel that is formed on a lower end of the lock ring and along an outer circumference of the lock ring. The radial stops can include a shoulder on the wellhead hanger defined where the radius of the wellhead hanger projects outward, and which provides a surface on which the lock ring is disposed, and a wall on an outer end of the shoulder that projects axially upward from the surface. 
         [0010]    Also disclosed herein is a method of forming a wellhead assembly that includes providing an annular lock ring, mounting the lock ring onto a wellhead hanger, landing the wellbore hanger into a wellhead housing, limiting movement of the lock ring radially away from the wellhead hanger while landing the wellbore hanger into the wellhead housing, and resisting axial movement of the lock ring with respect to the wellhead hanger while landing the wellbore hanger into the wellhead housing. The method can further include urging the lock ring radially outward and into engagement with the wellhead housing so that a lockdown force is transmitted from the wellhead housing to the wellhead hanger through the lock ring. Axial movement of the lock ring can be limited by pins that are mounted in the wellhead hanger, and the radial movement of the lock ring can be limited by radial stops on the wellhead hanger that are disposed radially outward from an outer lateral surface of the wellhead hanger. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIGS. 1A and 1B  are side sectional views of an example of a retention system for a wellbore lock ring. 
           [0013]      FIGS. 2A and 2B  are side views respective of portions of the inner and outer surface of the lock ring of  FIGS. 1A and 1B . 
           [0014]      FIGS. 3A and 3B  are side sectional views of an example of a radial retention system for an example of a wellbore lock ring. 
           [0015]      FIG. 4  is an axial sectional view of the lock ring of  FIGS. 1A and 1B . 
           [0016]      FIG. 5  is a side view of an example of the radial retention system of  FIGS. 3A and 3B . 
           [0017]      FIG. 6  is a perspective and partial sectional view of a portion of an example of a wellhead assembly having the retention system of  FIGS. 1A and 1B . 
           [0018]      FIG. 7  is a side sectional view of an example of a wellbore lock ring with an alternative example of a retention system. 
       
    
    
       [0019]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0020]    The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be 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 its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/−5% of the cited magnitude. In an embodiment, usage of the term “substantially” includes +/−5% of the cited magnitude. 
         [0021]    It is to be further understood that the scope 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 and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
         [0022]    Shown in side sectional view in  FIG. 1A  is an example of a portion of a wellhead assembly  10  used in conjunction with producing wellbore fluids from a wellbore (not shown). The wellhead assembly  10  includes a wellhead hanger  12  shown landed within a wellhead housing  14 . In an example, a tubular string, such as a string of casing or tubing (not shown) has an upper end supported by the wellhead hanger  12 , and depends down into the wellbore. An example of a lock ring assembly  16  is shown disposed in an annular space between the wellhead hanger  12  and wellhead housing  14 . The lock ring assembly  16  of  FIG. 1A  includes an annular lock ring  18  and a pin  20  for coupling the lock ring  18  to the wellhead hanger  12 . In the example of  FIG. 1A , the pin  20  anchors to the wellhead hanger  12  by a threaded recess  22  formed radially into an outer surface of the wellhead hanger  12 . The outer radial portion of the pin  20  extends into a slot  24  formed in the lock ring  18  and into interfering contact with axial movement of the lock ring  18  with respect to the wellhead hanger  12 . The wellhead hanger  12  projects radially outward towards the wellhead housing  14  to farm an upward facing surface which defines a shoulder  26 ; the lower end of the lock ring  18  is supported by the shoulder  26 . 
         [0023]      FIG. 1B  illustrates in side sectional view an example of the lock ring  18  moved radially outward and into engagement with a profile  28  formed on an inner radial surface of the wellhead housing  14 . The profile  28  has a shape complementary to the outer radial surface of the lock ring  18 , so that an axial lock down force F LD  can be transferred between the wellhead hanger  12  and wellhead housing  14  for axially coupling the wellhead hanger  12  to the wellhead housing  14 . 
         [0024]      FIGS. 2A and 2B  show perspective views respectively of portions of the inner and outer radial surfaces of the lock ring  18 . As shown in  FIG. 2A , a lateral section  29  of the slot  24  projects radially through only a portion of the thickness of the lock ring  18  and extends along a segment of the circumference of the lock ring  18 . Adjacent the lateral section  29  is an aperture that projects radially through the entire thickness of the lock ring  18 . In some instances, the pin  20  can insert through the aperture  30 , or remain in the lateral section  29  thereby allowing limited rotational movement of the lock ring  18  but mostly limiting axial movement. The pins load against lateral section  29 . 
         [0025]    Referring now to  FIG. 3A , the wellhead hanger  12  and lock ring  18  are shown in a side sectional view, and where the wellhead assembly  10  further includes a radial stop  32  for limiting radial movement of the lock ring  18  with respect to the wellhead hanger  12 . The radial stop  32  of  FIG. 3A  includes a fastener assembly  33  that is made up of a threaded fastener  34  shown anchored into a threaded bore  35  that is formed radially inward from an outer surface of the wellhead hanger  12 . The fastener  34  intersects an opening in a mid-portion of a disk like washer  36  and holds the washer  36  in place on the wellhead hanger  12 . The washer  36  extends upward from fastener  34  and into a channel  38  shown formed into a lower end of the lock ring  18  and along the outer radial surface of the lock ring  18 . Beneath bore  35 , and on a side of bore  35  opposite shoulder  26 , a pocket  40  is shown formed on an outer radial surface of wellhead hanger  12  and which has an upper end that intersects with an outer radial portion of shoulder  26 . A lower end of washer  36  is shown disposed within pocket  40 . As shown in  FIG. 3B , the presence of the radial stop  32  limits outward radial movement of the lock ring  18 , where the radial movement of the lock ring  18  is represented by arrow A. More specifically, the washer  36  and channel  38  are strategically dimensioned so that the radial travel of lock ring  18 , as represented by arrow A R , is held within a range that allows lock ring  18  to move into engagement with the wellhead housing  12 , as shown in  FIGS. 2B ,  3 B, but yet limits excessive outward radial movement of the lock ring  18  that might allow unwanted contact with other hardware and interfere with landing the wellhead hanger  12  within wellhead assembly  10 . 
         [0026]      FIG. 4  is an axial partial sectional view of the lock ring  18  mounted onto wellhead hanger  12 , and which is taken along lines  4 - 4  of  FIG. 3A . In the example of  FIG. 4  multiple pins  20  are shown, wherein some of the pins are intersecting lateral sections  29  of the slots  24 , and wherein one of the pins  20  is shown projecting into an aperture  42  that extends part ways through the thickness of the lock ring  18 , and whose diameter results in a close fit between the pin.  20  and aperture  42 . Moreover, the placement of the radial stops  32  illustrates the limited outward radial movement of the lock ring  18  as represented by arrow A R , and how the placement of the pins  20  limits axial movement of the lock ring  18  along axis A X . In an example, pins  20  restrain the lock ring  18  to the load shoulder  26  when passing through a riser (not shown) during installation. Also illustrated in the example of  FIG. 4  is a split  44  in the lock ring  18 , which can allow for expansion and contraction.  FIG. 5  is a perspective elevational view of a portion of the lock ring  18  mounted onto wellhead hanger  12 . Shown in  FIG. 5  are ports  46  that provide a path for a cement return flow. 
         [0027]      FIG. 6  is a partial sectional perspective view of an example of the wellhead assembly  10 , where a seal assembly  48  is included for sealing between the wellhead hanger  12  and wellhead housing  10  ( FIG. 1B ). Mounted coaxially to a lower end of the seal assembly  48  is a nose ring  50 , which is a ring like member and used for locking the lock ring  18  with the wellhead housing  10 . More specifically, applying an energizing force in a direction as represented by arrow F E , urges the nose ring  50  axially downward between the lock ring  18  and wellhead hanger  12  to bias the lock ring.  18  radially outward and into engaging contact with the wellhead housing  10  as illustrated in  FIG. 1B . 
         [0028]      FIG. 7  is a side sectional view of an alternate example of a wellhead assembly  10 A Where a threaded fastener  52  couples the lock ring  18 A to the wellhead hanger  12 A and provides a counter force for limiting axial movement of the lock ring  18 A with respect to the wellhead hanger  12 A. The fastener  52  has an end that engages a threaded bore  54  shown formed in an outer surface of the wellhead hanger  12 A, and which projects radially into the wellhead hanger  12 A. The fastener  54  also extends into an opening  56  shown extending radially through the thickness of the lock ring  18 A, and which has a diameter slightly greater than a diameter of an enlarged head portion of the fastener  52 . To limit outward radial movement of the lock ring  18 A, a parapet  58  is shown formed on an outer radial end of shoulder  26 A and which corresponds to a ledge  60  on a lower surface of the lock ring  18 A. The combination of the parapet  58  and ledge  60  define an example of a radial stop  32 A. Accordingly, the fastener  32 , parapet  58 , and ledge  60  combine to limit radial and axial movement of the lock ring  18 A with respect to the wellhead hanger  12 A. As indicated above, an advantage of limiting the axial and outward radial movement of the lock ring  18 ,  18 A with respect to the wellhead hanger  12 ,  12 A is that they can be lowered onto the wellhead assembly  10 ,  10 A without the threat of the lock ring  18 ,  18 A becoming inadvertently snagged on another piece of hardware on the way to the wellhead assembly  10 ,  10 A. However, strategic dimensioning of the components that limit the radial and axial movement of the lock ring  18 ,  18 A still allow sufficient radial movement of the lock ring  18 ,  18 A so that it can be locked with the wellhead housing  14 ,  14 A. 
         [0029]    The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.

Summary:
A retention system for limiting axial and radial movement of a wellbore lock ring. The retention system includes pins for resisting axial movement of the lock ring and assemblies for limiting radial outward movement of the lock ring. The lock ring circumscribes and couples to a wellbore hanger. The pins project radially from the hanger into the lock ring and into slots, where the slots extend a distance along the inner surface of the lock ring. The assemblies also project radially into the hanger and each have a portion that registers with a channel on a lower end of the lock ring. Lock ring outer radial movement is limited by contact between the portions of the assemblies and inner surfaces of the channels.