Patent Abstract:
A well production system including a wellhead and a first casing string supported from a first casing hanger landed on a shoulder in the wellhead bore. A loading shoulder assembly is installable in the wellhead and includes an energizing ring, a loading ring threaded into the interior of the energizing ring, a lock ring, and a hold-down ring threaded into the interior of the loading ring. The hold-down ring engages the first casing hanger to prevent rotation of the hold-down ring and restrain rotation of the loading ring. The lock ring is expandable from an unset position into supporting engagement with the wellhead in a set position upon rotation of the energizing ring. The hold-down ring is also moveable axially out of the loading ring to restrain the first casing hanger.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national stage application of PCT/US2009/038520 filed Mar. 27, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/040,328 filed Mar. 28, 2008, both of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     BACKGROUND 
     In subsea or other underwater well drilling procedures an established practice is to run, land, and set casing hangers and annulus packoffs in a submerged wellhead housing by means of a running tool connected to a drill string or other pipe string. The hanger is run into the wellhead using the running tool until the hanger lands on a casing hanger shoulder in the wellhead or on a previously installed hanger. The packoff is then run in and set in the annulus between the hanger and the wellhead housing the hanger running tool to form a seal between the hanger and the wellhead. The hanger and packoff are each releasably connected to the running tool and the running tool is retrievable after the hanger and packoff have been set. However, once the running tool is retrieved, the hanger and/or the packoff may not be sufficiently restrained from above, even with an additional hanger later installed. Thus, there is the possibility that even a set packoff may travel within the wellhead and potentially compromise the integrity of the seal between the hanger and the wellhead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments, reference will now be made to the following accompanying drawings: 
         FIG. 1  is cross section view of a loading shoulder installed in a wellhead housing above a previously installed casing hanger and packoff assembly; 
         FIG. 2  is a cross section view of a close up of the loading shoulder of  FIG. 1 ; 
         FIG. 3  is a cross section of a running tool and a loading shoulder being run into the wellhead housing; 
         FIG. 4  is a cross section view of the loading shoulder landed onto the previously installed casing hanger with the loading ring and the lock ring in the set position; 
         FIG. 5  is cross section view of the loading shoulder locked in position with the running tool removed; 
         FIG. 6  is a cross section of a casing hanger landed on the loading shoulder; and 
         FIG. 7  is a cross section of a packoff assembly installed on the casing hanger of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the drawings and description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. Any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings. 
     Referring to  FIGS. 1 and 2 , a loading shoulder  10  is shown installed in a wellhead housing  12  above a previously installed casing hanger  14  and packoff assembly  16 . The loading shoulder  10  includes an energizing ring  18 , a lock ring  20 , a loading ring  22 , and a hold-down ring  24 . The loading shoulder  10  typically includes only metal components. However, the loading shoulder  10  may also include non-metal components that are capable of providing support for a casing hanger. As shown, the lock ring  20  is positioned externally to and in between the energizing ring  18  and the loading ring  22 . Also, the energizing ring  18 , the lock ring  20 , and the loading ring  22  include angled surfaces for sliding engagements at  26  and  28 , respectively. The lock ring  20  is also expandable and may either be a segmented ring, a “C” ring, or any other suitable expandable configuration. Further, the lock ring  20  is shown in a configuration for engaging a corresponding lock ring groove  42  in the wellhead. It should be appreciated, however, that the lock ring  20  and the lock ring groove  42  may be any suitable configuration for proper locking engagement of the loading shoulder  10 . Additionally, the energizing ring  18  and the loading ring  22  overlap in a loading ring threaded connection  30  with the loading ring  22  threaded into the energizing ring  18 . 
     Opposite the portion threaded into the energizing ring  18 , a catch ring  32  extends from an interior surface of the loading ring  22  into an annular groove  34  on the outside surface of the hold-down ring  24 . Although the catch ring  32  is secured to the loading ring  22 , the size of the groove  34  allows both vertical and rotational movement of the hold-down ring  24  relative to the loading ring  22 . However, the catch ring  32  only allows a certain amount of vertical travel of the hold-down ring  24  relative to the loading ring  22  before the catch ring  32  engages an edge of the groove  34 . 
     In addition to the catch ring  32 , the loading ring  22  interacts with the hold-down ring  24  through a hold-down ring threaded connection  36 . The direction of the threads of the hold-down ring threaded connection  36  may either be right-handed or left-handed. However, the threads of the hold-down ring threaded connection  36  are an opposite turn than the threads of the loading ring threaded connection  30 . Thus, if the loading ring threaded connection  30  threads are right-hand threads, the hold-down ring threaded connection  36  will include left-hand threads and vice versa. 
       FIG. 3  illustrates the loading shoulder  10  being run into a wellhead housing  12  for landing on a previously installed casing hanger  14  and packoff assembly  16 . The loading shoulder  10  is run into the wellhead housing  12  using a loading shoulder running tool  38  connected to a drill string or other pipe string. As shown, the landing shoulder  10  is in the unset position and as such may be configured to be run though a blowout preventer stack  40  attached above the wellhead housing  12 . The running tool  38  is used to land the loading shoulder  10  onto a previously installed casing hanger  14  with both the loading ring  22  and the lock ring  20  in the unset position. When landed, the lock ring  20  is aligned with a corresponding lock ring groove  42  in the wellhead housing  12 . Additionally, the lower portion of the hold-down-down ring  24  engages the upper portion of the previously installed casing hanger  14  in a tongue-and-groove arrangement  44  that restrains relative rotation between the hold-down ring  24  and the casing hanger  14 . It should be appreciated, however, that any arrangement suitable for restraining relative rotation may be used. 
     To set the loading shoulder  10 , the running tool  38  rotates the energizing ring  18 . Because of the tongue-and-groove engagement  44 , both the hold-down ring  24  and the loading ring  22  resist being rotated with the energizing ring  18 . Consequently, the energizing ring  18  rotates relative to the loading ring  22  and the hold-down ring  24 . Because of the loading ring threaded connection  30 , the rotation of the energizing ring  18  relative to the loading ring  22  draws the loading ring  22  further into the energizing ring  18 . Doing so actuates the lock ring angled engagements  26 ,  28  to expand the lock ring  20  into engagement with the lock ring groove  42  in the wellhead  12  as shown in  FIG. 4 . 
     Rotation of the energizing ring  18  relative to the loading ring  22  proceeds until either the loading ring threaded connection  30  bottoms out or the lock ring  20  becomes fully expanded into the wellhead lock ring groove  42 . At such time, the loading ring  22  no longer rotates relative to the energizing ring  18  and begins to rotate with the energizing ring  18 . However, the tongue-and groove arrangement  44  still restrains the hold-down ring  24  from rotating, thus producing relative rotation between the loading ring  22  and the hold-down ring  24  with the catch ring  32  rotating within the annular groove  34 . 
     As previously mentioned, the threads of the hold-down ring threaded connection  36  turn in a different direction than the threads of the loading ring threaded connection  30 . Thus, although the energizing ring  18  rotation direction draws the loading ring  22  further into the energizing ring  18 , the same rotation direction expands the hold-down ring  24  out from the loading ring  22 . Thus, rotation of the loading ring  22  as described expands the hold-down ring  24  out from the loading ring  22  to restrain movement of the casing hanger  14  as well as the packoff assembly  16  below. 
     As shown in  FIG. 5 , once the loading shoulder  10  is set, the running tool  38  may then be disengaged from the loading shoulder  10  and retrieved from the wellhead housing  12 . Further drilling, completion, or other well operations may then proceed. 
     As shown in  FIGS. 6 and 7 , the loading shoulder  10  provides a bi-directional loaded shoulder for the installation of an additional casing hanger  46  that is run into the wellhead  12  and landing on the loading shoulder  10 . When landed, the weight of the casing hanger  46  and the casing string  48  may thus be transferred at least in part to the wellhead housing  12  through the loading shoulder  10 . As shown in  FIG. 7 , an additional packoff assembly may also be installed to form a seal between the additional casing hanger  46  and the wellhead  12 . 
     The loading shoulder  10  may thus provide a positive lock in both the direction extending into the wellbore and the direction extending out of the wellbore to support an additional casing hanger  46  above as well as restrain the casing hanger  14  and packoff assembly  16  below. 
     While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.

Technology Classification (CPC): 4