Abstract:
The invention provides a wellhead assembly including a wellhead housing supporting a tubing hanger within its central bore and forming a housing stem port through its outer wall to the central bore. The tubing hanger has a side stem port formed through its body intermediate its upper and lower ends providing access to the central bore of the hanger and being aligned with the housing stem port. The tubing hanger includes a ball valve member having a spherical exterior surface sealed and seated from above and below within the central bore of the hanger. The ball valve member forms a through port extending therethrough aligned with the production bore, and is rotatable in its seated position between open and closed positions with the through port being aligned with the production bore when in the open position. A slot in the exterior surface of the ball valve member if formed proximate the stem port. A ball stem assembly is sealed for axial rotation in both the stem port of the body and the housing stem port of the wellhead housing, one end of the stem providing a coupling for rotatably coupling to the slot in the ball valve member, the other end of the stem assembly extending exterior of the wellhead housing. The ball valve member is externally operated between open and closed positions by an operator coupled to the ball stem assembly exterior the wellhead housing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims benefit of U.S. Provisional Patent Application No. 60/609,931, filed Sep. 14, 2004, which is incorporated in its entirety herein by reference to the extent not inconsistent herewith. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to a wellhead assembly with a tubing hanger having a production bore extending generally vertically there through and a ball valve assembly which is externally operable for controlling fluid flow through the production bore.  
       BACKGROUND OF THE INVENTION  
       [0003]     In a conventional flow completion system, a tubing hanger is landed in a wellhead housing, typically a tubing head, at the upper end of a well bore, and a Christmas tree is connected to the top of the wellhead housing over the tubing hanger. The tubing hanger supports at least one tubing string which extends into the well bore and defines a production bore within the tubing string. The tubing hanger itself forms at least one vertical production bore for communicating fluid between the tubing string and a corresponding production bore in the Christmas tree located above the tubing hanger. While it is common to provide for one or more valve closures in the production bore, this is usually provided in the Christmas tree above the tubing hanger, or is run into the production bore of the tubing hanger. For some applications, it is desirable to have an in-dwelling valve closure member in the tubing hanger. For instance, should one or more of the valves in the Christmas tree need replacing, it is desirable to make provision for running in of a valve or plug in the production bore or tubing hanger. As well, it may be desirable to have a removable valve or plug in place in the tubing hanger when running or retrieving the tubing hanger. However, running of a back pressure valve or plug in the tubing hanger is a complex and expensive task, particularly if the well is remotely located.  
         [0004]     Thus, for some applications, it is desirable to have an in-dwelling valve member in the tubing hanger. To date, ball valves have not traditionally been used for this purpose. While ball valve closure members are described in the smaller annulus bore of a tubing hanger (see for example U.S. Pat. No. 6,679,330 to Compton et al.), they are not traditionally used in the production bore. A few patents describe ball valves in the production bore of a tubing hanger, but these devices are generally complex, involving complicated actuation sleeves which are hydraulically or electrically activated for operation (see for example U.S. Pat. No. 6,698,712 to Milberger et al.). There remains a need for a simple wellhead device to provide for flow control in the production bore of a tubing hanger.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention provides an externally operable ball valve closure member in the production bore of a tubing hanger.  
         [0006]     Broadly stated, the invention provides a wellhead assembly which houses the tubing hanger of the present invention. In combination, the invention includes a wellhead housing such as a tubing head, having an outer wall and a central bore, the housing forming an inwardly extending landing shoulder for supporting a tubing hanger within its central bore, and a housing stem port in the outer wall providing access to the central bore. The tubing hanger itself includes:  
         [0007]     a) a generally tubular body forming a vertical central bore which provides a production bore extending generally axially through the body, and a landing shoulder formed on the outer surface of the body to cooperate with the housing landing shoulder in supporting the tubing hanger therein;  
         [0008]     b) the lower end of the body being adapted for suspending a tubing string;  
         [0009]     c) the upper end of the body being adapted for receiving a landing joint;  
         [0010]     d) a side stem port formed through the body intermediate its upper and lower ends providing access to the vertical central bore of the body and being aligned with the housing stem port;  
         [0011]     e) seals on the exterior of the body above and below the side stem port for sealing the body in the central bore of the wellhead housing; and  
         [0012]     f) a ball valve member having a spherical exterior surface sealed and seated from above and below within the central bore of the body, the ball valve member forming a through port extending therethrough aligned with the production bore, the ball being rotatable in its seated position between open and closed positions with the through port being axially aligned with the production bore when in the open position, the ball valve member forming a slot in the exterior surface proximate the stem port.  
         [0013]     The invention also provides a ball stem assembly sealed for axial rotation in both the side stem port of the tubing hanger body and the housing stem port of the wellhead housing. A first end of the ball stem assembly provides a coupling for rotatably coupling to the slot in the ball valve member, while the second end of the ball stem assembly extends exterior of the wellhead housing. An external operator is coupled to the second end of the ball stem assembly exterior the wellhead housing for rotating the ball stem assembly, and thus the ball valve member, between open and closed positions.  
         [0014]     As used herein and in the claims, the word “comprising” is used in its non-limiting sense to mean that items following the word in the sentence are included and that items not specifically mentioned are not excluded. The use of the indefinite article “a” in the claims before an element means that one of the elements is specified, but does not specifically exclude others of the elements being present, unless the context clearly requires that there be one and only one of the elements.  
         [0015]     It should be understood that reference herein and in the claims to the tubing string which is suspended from the lower end of the tubing hanger is meant to include coil tubing. Further, it should be understood that reference to a ball valve member herein and in the claims is meant to include generally spherical ball members which are not strictly spherical on all sides, such as a ball member which is generally cylindrical between its spherical ends. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a side view, partially in section, showing a prior art tubing head and tubing hanger with a run in back pressure valve, the tubing head being located below typical Christmas tree components.  
         [0017]      FIG. 2  is a side sectional view of the tubing hanger of the present invention, landed in a wellhead housing comprising a tubing head.  
         [0018]      FIG. 3  is a side view of the tubing hanger of  FIG. 2 , showing the aligning slot to align the stem ports and stems in the tubing hanger and tubing head.  
         [0019]      FIG. 4  is a perspective view of the tubing hanger of  FIG. 2 .  
         [0020]      FIG. 5  is a side sectional view of the tubing hanger of the present invention, with the lower portion of the tubing head cut away in order to show greater detail of the ball valve member, the ball stem assembly, and the external operator for the ball valve.  
         [0021]      FIG. 6  is a perspective view of the tubing head stem (or housing stem) for connection to the external operator, and showing the aligning slots on the tubing head stem for the locator pin.  
         [0022]      FIG. 7  is a cut away side view of the stopper plate in the connected end of the hanger stem, which allows the hanger stem to be rotated only through 90° in order to rotate the ball valve member between open and closed positions.  
         [0023]      FIG. 8  is a side sectional view of the of the ball stem assembly for the ball valve member showing the tubing head stem in the extended or engaged position, such that rotation of the tubing head stem (not in section) rotates the hanger stem and the ball valve member.  
         [0024]      FIG. 9  is a side sectional view of the ball stem assembly for the ball valve member as described for  FIG. 8 , but showing the tubing head stem in the retracted position for initial landing or removal of the tubing hanger within the tubing head.  
         [0025]      FIGS. 10A-10E  are schematic side sectional views of the tubing hanger of this invention showing alternate retainers (retainer means) for retaining the ball valve member within the production bore of the tubing hanger. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIG. 1  is included to show a tubing head/tubing hanger arrangement of the prior art, in which a tubing hanger  10  is sealed and supported within a wellhead housing, here shown as a tubing head  12 . The tubing head  12  is adapted at its lower end for connection to the next wellhead member, typically a casing head (not shown) to suspend casing  13 . The tubing head  12  is shown connected at its upper end to a tubing head flange adaptor  14 , and Christmas tree components  15  (shown in order in  FIG. 1  is a master valve, a flow tee with a wing valve and a top connector). The Christmas tree components  15  are known in the art and will typically include one or more valves and blow out preventer (BOP) stack). The tubing hanger  10  is adapted at its lower end to suspend production tubing  16 . Shown in  FIG. 1  is a back pressure valve  17 , which must be run in as described above when one wishes to close off the production bore  18  at the tubing hanger  10 . As indicated above, running and retrieving a back pressure valve  17  or plug in the tubing hanger is a complex operation, a problem which is addressed by the present invention.  
         [0027]     Having reference to  FIG. 2 , the tubing hanger of this invention is shown generally at  20 , to include a generally tubular body  22 , formed with a vertical central production bore  24 . The tubing hanger  20  is sealed and suspended within a pressure-containing wellhead housing, here shown as a tubing head  26 . The tubing hanger  20  includes a tapered landing shoulder  28  on its outer wall to land against the reduced diameter landing seat  30  formed in the central bore  32  of the tubing head  26 . The tubing head  26  is adapted at its upper and lower ends to form pressure sealed top and bottom connectors  34 ,  36 , here shown as flanged up and down connectors, however alternate connectors as known in the art may be used. Typically, the tubing head  26  is connected above to Christmas tree components (not shown), and below to the casing head (not shown), as mentioned with reference to  FIG. 1 . The wellhead housing which lands the tubing hanger  20  may be other than the separate tubing head  26  shown in the Figures. For instance, the tubing head could comprise multiple connected tubulars, such as a tubing head and a tubing head adapter. Still alternatively, the tubing head might be replaced by an integral wellhead member which combines the tubing head with a casing head and/or one or more of the Christmas tree components, as is known in the art.  
         [0028]     Having reference to  FIGS. 2-5 , the hanger body  22  includes outer annular grooves  38 ,  40  adapted to receive seals  42 ,  43 , such as O-ring seals, for sealing into the central bore  32  of the tubing head  26 . The tubing head  26  and hanger  20  include a lock down mechanism, as known in the art to prevent the tubing hanger from being upwardly dislodged once it is landed. In the Figures, the tubing head  26  is shown to be formed with a plurality of pin side ports  44  at its upper end for tubing hanger locking pins  46 . The tubing hanger body  22  is formed with a plurality of dimples  48  spaced circumferentially around its outer surface to align with the ports  44  and locking pins  46  in order to receive the tapered heads  50  of the locking pins  46 . The locking pins  46  are threaded at their tapered ends for threading into the side ports  44 . The locking pins  46  are sealed within the ports  44  with a plurality of packing rings  52  and gland nuts  53 . The gland nuts  53  are threaded into the ports  44  in order to retain and seal the packing rings  52 . It will be evident to one skilled in the art that the dimples  48  may alternatively be provided as a circumferential groove in the outside diameter of the tubing hanger body  22 . Other lock down mechanisms may also be used, as is known in the art.  
         [0029]     Having reference to  FIG. 5 , each of the tubing head  26  and tubing hanger body  22  is formed with a stem port formed in its side wall. These stem ports are herein termed tubing head stem port  54  (or housing stem port) and tubing hanger side stem port  56  (or hanger stem port). The seals  42 ,  43  on the outer surface of the tubing hanger  20  are located above and below these stem ports  54 ,  56  to seal the hanger  20  against the central bore  32  of the tubing head  26 . These stem ports  54 ,  56  must be strictly axially aligned in order that a tubing head stem  58  (or housing stem) and a hanger stem  60  located therein may co-operate to engage and rotate a ball valve closure member  82  in the manner to be described below. Thus, an alignment mechanism is provided between the tubing head  26  and the tubing hanger  20  such that, on landing of the tubing hanger  20 , the tubing hanger stem  60  and hanger stem port  56  are strictly aligned with the tubing head stem  58  and tubing head stem port  54  respectively. One embodiment of this alignment mechanism is shown in  FIGS. 2-5  to include an aligning pin  62  extending horizontally through a pin bore  64  in the wall of the tubing head  26 , and sealed with a seal  66 , such as an O-ring seal. A generally key shaped aligning slot  68  is formed at the lower end of the hanger body  22 . Thus, on landing in the tubing head  26 , the hanger body  22  is rotated to align with the extended aligning pin  62 . Alternate alignment mechanisms may be used. For instance, although not shown, a tapered alignment block (ex. triangular, with apex pointing upward) could be provided in the central bore  32  of the tubing head  26  (ex. attached by welding) for alignment with a matching recess milled on the outside diameter of the tubing hanger  20 . Other alignment mechanisms will be evident to persons skilled in the art.  
         [0030]     The lower end of the production bore  24  of the tubing hanger  20  is adapted to suspend a tubing string (not shown), as is known in the art. In  FIG. 5 , one embodiment is shown to include an upper threaded portion  70  for suspending threaded tubing string sections (not shown) as is known in the art. The tubing string (which could be coiled tubing instead of production tubing) might be suspended by other connectors such as by welding or slip lock connectors, as is known in the art. The upper end of the production bore  24  of the tubing hanger  20  is adapted to accept a landing joint (not shown), as is known in the art. In  FIG. 5 , one embodiment is shown to include an upper threaded portion  72  for this purpose. The hanger body  22  is formed to provide a ball chamber  74  within its production bore  24  between its upper and lower ends. This ball chamber  74  is shown to have a widened diameter relative to that of the production bore  24 .  
         [0031]     As shown in the  FIGS. 2-5 , the hanger body  22  is formed with a counterbore  76  at the lower end of the ball chamber  74 . A lower annular seat  78  is located in the counterbore  76 . A lower annular seat seal  80  is held within the seat  78  for sealing against the spherical surface of the ball valve member  82 . Similarly, at the upper end of the ball chamber  74 , an upper annular seat  84  is provided, with an upper annular seat seal  86  for sealing against the spherical surface of the ball valve member  82 . Seals  87 , such as O-ring seals, are located between the seats  78  and  84  for sealing against the central bore  24  of the tubing hanger  20 . The upper annular seat  84  is retained in the ball chamber against upward movement by an externally threaded tubular retainer ring  88 , which is threaded into the central bore  24  of the hanger body  22 . Preferably, an upper annular retainer ring  90 , also externally threaded, is threaded into the central bore  24  above the retainer ring  88  to prevent backing off of the retainer ring  88 . Each of the retainer rings  88 ,  90  are formed with a central bore  92 ,  94  respectively. The hanger body  22  is preferably formed with an enlarged diameter counterbore section  96  in its central bore  24  at its upper end to accept the retainer rings  88 ,  90 , such that an enlarged diameter section  98  of the retainer ring  88  seats against the base of the counterbore  96 . A seal  100 , such as an O-ring seal, is carried at the lower end of the retainer ring  88  for sealing into the central bore  24  of the hanger body  22 . Alternate means for retaining the ball valve member  82 , seats  78 ,  84 , and seat seals  80 ,  86  in the ball chamber may be used, as will be evident to persons skilled in the art. Exemplary alternatives are shown in  FIGS. 10A-10E , described below.  
         [0032]     Having reference to  FIG. 5 , the ball valve member  82  has a spherical exterior and is formed with a through port  102 . When the ball valve member  82  is in the open position, the through port  102  is aligned with the production bore  24 . The central bores  92 ,  94  and through port  102  are preferably axially aligned with and form part of the production bore  24  through the hanger body  22 . When the ball member  82  is in the closed position, it is turned 90° relative to the open position shown in the Figures, such that the spherical exterior of the ball is seated and closes off the production bore  24  of the tubing hanger  20 . A ball slot  104  is formed along one side of the ball valve member  82 .  
         [0033]     Having reference to  FIGS. 8-9 , a protruding tongue  106  formed at the ball-facing inner end of the hanger stem  60  is received in the ball slot, such that 90° rotation of the hanger stem  60  results in the open and closing action of the ball valve member  82 . The hanger stem  60  is formed with a widened diameter stop shoulder  108  which is held in a stop counterbore  110  formed in the central bore  24  of the hanger body  22  adjacent the ball valve member  82 . This stop shoulder  108  prevents the hanger stem  60  from being dislodged from the hanger stem port  56  from pressure in the production bore  24 . A hanger stem seal  112 , such as an O-ring seal, seals the hanger stem  60  against the hanger stem port  56 . The outer end of the hanger stem  60  is formed with a hanger stem slot  114 , adapted to receive a protruding tongue  116  formed at the hanger-facing end of the tubing head stem  58 . As best shown in  FIGS. 7-9 , a stop plate  118  is fastened by screw  120  into the hanger stem slot  114 . The stop plate  118  is restricted to 90° rotational movement within a 90° arc slot  122  which is formed by the hanger body  22  at the outer end of the hanger stem port  56 . This restricts the movement of the hanger stem  60  to the strict 90° to open and close the ball valve member  82  as the tongue  116  of the tubing head stem  58  is likewise moved through 90°.  
         [0034]     Turning to the tubing head stem  58 , it is shown in detail in  FIGS. 6, 8  and  9 . The protruding tongue  116  is formed on an enlarged diameter inner end portion  124  so as to form a tapered stop shoulder  126  which back seats and seals with a metal to metal seal against a tapered back seating counterbore  128  formed at the inner end of the tubing stem port  54 . This back seating prevents the tubing head stem  58  from being dislodged from the tubing head stem port  54  with pressure from the production bore  24  and/or the central bore  32 .  
         [0035]     The outer end of the tubing head stem  58  extends externally of the tubing head  26  for coupling to an external operator. As shown in  FIGS. 6, 8  and  9 , the outer end of stem  58  is formed with flattened portions  130  for rotation by a wrench or other external operator, for instance a hand crank. Other external operators may also be coupled to the tubing head stem  58 , for example an electrical or hydraulic actuator (not shown), as is understood in the art.  
         [0036]     A circumferential seal groove  132  ( FIG. 6 ) is preferably formed in the tubing head stem  58  for a seal  134 , such as an O-ring seal, to seal the tubing head stem  58  within the tubing head stem port  54 .  
         [0037]     The tubing head stem  58  is preferably formed with a locator mechanism to initially locate the stem tongue  116  in either the open or closed position, depending on whether the ball valve member  82 , and thus the tubing hanger stem slot  114 , is being landed in the open or closed position. One embodiment of such locator mechanism is shown in  FIGS. 6, 8  and  9  to include first and second axial stem slots  136 ,  138 , which are circumferentially spaced by 90° on the tubing head stem  58 . A locator pin  140  extends through a vertical pin aperture  142  formed in the tubing head  26  through to the tubing head stem slots  136 ,  138 . A second circumferential groove  144  is formed in the tubing head stem  58  to receive the locator pin  140 . In  FIG. 9 , the locator pin  140  is shown to be located in the second axial stem slot  136  for initial landing of the tubing hanger  20  in the ball open position, with the tubing head stem  58  in the retracted position. The stem  58  will also be in this position for removal of the tubing hanger  20 . In  FIG. 8 , the locator pin  140  is shown to be still within axial stem slot  136 , but now aligned with the circumferential groove  144  such that the tubing head stem  58  can be rotated.  
         [0038]     In order to extend and retract the tubing head stem  58 , the tubing head stem port  54  is threaded at its outer end. A stem nut  146  which is externally threaded is received in the stem port  54 . The stem nut  146  is shown in the extended (forward threaded) position in  FIG. 8 . In  FIG. 9 , the stem nut  146  is shown in the retracted (reverse threaded) position to retract the stem  58 . During this reverse threading action, the stem nut  146  acts against a snap ring  148 , held within groove  150  (see  FIG. 6 ) on the tubing head stem  58 , to retract the stem  58 .  
         [0039]      FIGS. 10A-10E  show schematically, alternate retainer embodiments for retaining the ball valve member  82 , the annular seats  78 ,  84 , and the annular seat seals  80 ,  86  (collectively the ball valve elements) within the ball chamber  74 , and thus within the production bore  24  of the tubing hanger  20 . In  FIG. 10A , the tubular body of the tubing hanger  20  is shown to be formed as a two piece bolted design  152 ,  154 , with the top piece  154  forming an inwardly extending lip  156  to retain the ball valve elements. In  FIG. 10B , the tubular body of the tubing hanger  20  is formed as a three piece bolted design  158 ,  160 ,  162  with a top ring  160  providing an inwardly extending lip  164  to retain the ball valve elements. In  FIG. 10C , the tubular body of the tubing hanger  20  is formed as a three piece threaded design  166 ,  168 ,  170  with an upper, outer ring  168  which locks a middle ring  170  in place. Here, the middle ring  170  forms an inwardly extending lip  172  to retain the ball valve elements. In  FIG. 10D , the tubular body of the tubing hanger  20  is formed as a two piece threaded design  174 ,  176 , with an inner ring  176  providing the lip  178  which retains the ball valve elements. In this design, thread locking is provided between the threaded body parts  174 ,  176 . In  FIG. 10E  another embodiment of a two piece  180 ,  182  threaded tubular body is shown with the inner ring  182  providing the upper lip  184  to retain the ball valve elements. Here again, thread locking is provided between the body parts  180 ,  182 . Other embodiments of the invention for retaining the ball valve member in a seated and sealed relation within the production bore of the tubing hanger will be evident to persons skilled in the art.  
         [0040]     The tubing hanger  20  and tubing head  26  will typically be formed of pressure containing metal materials such as carbon steel. The stems  58 ,  60  will likewise typically be formed from a metal material such as carbon steel. The ball valve member  82  may be made of any suitable material, but will usually be made of carbon steel. The annular seats  78  and  84  will typically be formed as metal rings. The annular seat seals  80  and  86  are preferably formed from a thermoplastic material, while the remaining seals  42 ,  43 ,  52 ,  66 ,  87 ,  100 ,  112  will typically be formed from elastomeric sealing materials.  
         [0041]     All publications mentioned in this specification are indicative of the level of skill in the art of this invention. All publications are herein incorporated by reference to the same extent as if each publication was specifically and individually indicated to be incorporated by reference. The terms and expressions used are, unless otherwise defined herein, used as terms of description and not limitation. There is no intention, in using such terms and expressions, of excluding equivalents of the features illustrated and described, it being recognized that the scope of the invention is defined and limited only by the claims which follow. Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to the subject matter of the invention.