Patent Publication Number: US-2022228462-A1

Title: Wellhead assembly valve systems and methods

Description:
CROSS REFERENCE PARAGRAPH 
     This application claims the benefit of U.S. Provisional Application No. 62/856,553, entitled “INTEGRATED ANNULUS VALVE SYSTEM AND METHOD,” filed Jun. 3, 2019, and U.S. Provisional Application No. 62/960,673, entitled “WELLHEAD ASSEMBLY VALVE SYSTEMS AND METHODS,” filed Jan. 13, 2020, the disclosure of each of which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components, such as various casings, wellhead components, trees, valves, fluid conduits, and the like. 
     Various wellhead assembly components and other oilfield components can include ports for accessing internal volumes. A wellhead can include access ports in fluid communication with various annuli in the well, for example. External valves, such as gate valves, can be attached to the side of the wellhead to control flow through the outlet ports. In some instances, a plug may be installed through an external valve and threaded into an outlet port to seal the outlet port and allow the external valve to be removed from the wellhead. 
     SUMMARY 
     Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
     Certain embodiments of the present disclosure generally relate to valve assemblies for controlling flow into or out of a wellhead, tree, or other oilfield component. In some embodiments, a pressure-containing component of a wellhead assembly includes an internal valve integrated into a body of the pressure-containing component. The body can include a bore and an access passage in fluid communication with the bore, and the internal valve can include a sealing element positioned along the access passage in the body to control flow through the access passage. Examples of the sealing element include plugs, gates, and balls that can be moved between an open position to allow flow through the access passage and a closed position to block flow. In some instances, the sealing element can be moved between these positions without actuating the sealing element through an outer end of the access passage and without the valve protruding outside the pressure-containing component from the access passage. 
     Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  depicts a well apparatus including pressure-containing components having integrated valves for controlling flow into or out of the components in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a cross-section of a portion of a pressure-containing component having an integrated valve with a moveable plug for controlling flow through an access passage of the component in accordance with one embodiment; 
         FIG. 3  is a detail view of the valve of  FIG. 2  and shows the plug in a closed position blocking flow through the access passage; 
         FIG. 4  is a detail view of the valve of  FIGS. 2 and 3  and shows the plug in an open position allowing flow through the access passage; 
         FIG. 5  is a cross-section of a portion of a pressure-containing component having an integrated valve with a moveable gate for controlling flow through an access passage of the component, and shows the gate in an open position allowing flow through the access passage, in accordance with one embodiment; 
         FIG. 6  is similar to  FIG. 5  but shows the gate in a closed position blocking flow through the access passage; 
         FIG. 7  depicts an integrated valve with a moveable gate in accordance with one embodiment, with a sealing groove and mounting holes positioned differently than in  FIG. 6  for mounting an external component; 
         FIG. 8  shows a sealing plug installed in the access passage of  FIG. 5  through an aperture of the gate in accordance with one embodiment; 
         FIG. 9  generally depicts mechanical actuation of the gate and alignment pins for guiding movement of the gate during operation in accordance with one embodiment; 
         FIG. 10  generally depicts a tongue-and-groove arrangement for guiding movement of the gate during operation in accordance with one embodiment; 
         FIG. 11  is similar to  FIG. 5  but includes ports and seals to facilitate hydraulic actuation of the gate to control flow through the access passage in accordance with one embodiment; 
         FIG. 12  is a cross-section of a portion of a pressure-containing component having an integrated ball valve for controlling flow through an access passage of the component in accordance with one embodiment; 
         FIG. 13  is a detail view of the valve of  FIG. 12  and shows the ball of the ball valve in an open position allowing flow through the access passage; 
         FIG. 14  is a detail view of the valve of  FIGS. 12 and 13  and shows the ball in a closed position blocking flow through the access passage; 
         FIG. 15  is a detail view of a ball valve like that of  FIG. 12  but having a flexible actuator for rotating the ball in accordance with one embodiment; 
         FIG. 16  is a cross-section of a portion of a pressure-containing component having an integrated ball valve and a sealing plug installed in an access passage of the component in accordance with one embodiment; 
         FIG. 17  is an axial cross-section of a pressure-containing component having integrated valves with hinged gates for controlling flow through access passages of the component in accordance with one embodiment; 
         FIG. 18  is a detail view of an integrated hinged-gate valve of  FIG. 17  and shows a hinged gate, an actuation assembly, and an automatic valve shut-off assembly in accordance with one embodiment; 
         FIG. 19  shows an external valve coupled in-line with the access passage having the integrated hinged-gate valve of  FIG. 18  and shows the hinged gate in a closed position to block flow in accordance with one embodiment; 
         FIGS. 20 and 21  show the hinged gate of  FIG. 19  in open positions allowing flow through the access passage; 
         FIG. 22  is an axial cross-section of a pressure-containing component having integrated valves with hinged gates for controlling flow through access passages of the component in which the access passages are aligned along an axis and extend radially through the pressure-containing component in accordance with one embodiment; 
         FIGS. 23 and 24  depict a hydraulically actuated valve with a hinged gate in a valve housing in accordance with one embodiment; 
         FIGS. 25 and 26  depict a manually actuated valve with a hinged gate in a valve housing in accordance with one embodiment; 
         FIGS. 27-29  depict valves integrated into a pressure-containing component and having swinging gates that close against seats in accordance with certain embodiments; and 
         FIG. 30  shows a cartridge valve with a swinging gate installed in an access passage of a pressure-containing component in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Specific embodiments of the present disclosure are described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     Turning now to the present figures, an apparatus  10  is illustrated in  FIG. 1  by way of example. The apparatus  10  is a well installation that facilitates production of a resource, such as oil or gas, from a reservoir through a well  12 . A wellhead assembly  14  of the apparatus  10  in  FIG. 1  includes a wellhead  16  and a tree  18 . The wellhead  16  is depicted as having heads  20  (e.g., casing and tubing heads), but the components of the wellhead  16  can differ between applications and could include a variety of casing heads, tubing heads, spools, hangers, sealing assemblies, valves, and pressure gauges, to name only a few possibilities. The tree  18  may be a production tree, a fracturing tree, or some other tree coupled to the wellhead  16 . 
     Various tubular strings  22 , such as casing and tubing strings, extend into the ground below the wellhead assembly  14 . As will be appreciated, casing strings generally serve to stabilize wells and to isolate fluids within wellbores from certain formations penetrated by the wells (e.g., to prevent contamination of freshwater reservoirs), and tubing strings facilitate flow of fluids through the wells. Hangers can be attached to casing and tubing strings and received within wellheads to enable these tubular strings to be suspended in the wells from the hangers. The wellhead assembly  14  can be mounted on the outermost tubular string  22  (e.g., a conductor pipe) and each of the remaining tubular strings  22  may extend downwardly into the ground from a casing or tubing head  20 . In one embodiment, the innermost tubular string  22  is a tubing string and the remaining tubular strings  22  are casing strings. 
     The tubular strings  22  define annular spaces  24 , which may also be referred to as annuli  24 . Valve assemblies  30  may be used to selectively permit flow between the wellhead assembly  14  and external equipment. In  FIG. 1 , the valve assemblies  30  include external gate valves  32  mounted outside the casing and tubing heads  20  and in-line with annulus access passages in the heads  20  to control flow between the annuli  24  and external equipment through the access passages. The gate valves  32  could be mounted directly to the heads  20 , but in some embodiments one or more other components are interposed between the gate valves  32  and the heads  20 . In  FIG. 1 , for instance, separate flanges  34  (e.g., instrument flanges) are installed between the gate valves  32  and the heads  20 . 
     In addition to or instead of the external valves  32 , valves  36  may be integrated into pressure-containing components of the wellhead  16  (e.g., in heads  20 ), the tree  18 , or other equipment to control flow through access passages. In some embodiments, for instance, valves  36  may be integrated into hollow bodies of such pressure-containing components to control flow through access passages in fluid communication with bores in the components. More specifically, the valves  36  may be used as annulus safety valves installed in ports of the wellhead  16  to control access to the annuli  24  in some cases, but the valves  36  may be used in different applications in other cases. These internal valves  36  can include sealing elements that can be moved between an open position to allow flow through an access passage and a closed position to block flow through the access passage. Consequently, the valves  36  can be opened to enable fluid flow into or out of the components. In certain embodiments, the valves  36  are positioned fully within a hollow body of a pressure-containing component (e.g., along an access passage) and do not protrude outwardly from the pressure-containing component. Further, in at least some instances an internal valve  36  in an access passage of a pressure-containing body (e.g., an annulus outlet port of a wellhead) can be used, in lieu of a separate valve-removal (VR) plug in the access passage, to block flow through the access passage and facilitate removal of an external valve  32  attached in fluid communication with the access passage. Such an internal valve  36 , which may be referred to as a valve-removal (VR) valve, can remain in the access passage to control flow even after removal of the external valve  32 . 
     One example of an internal valve  36  is shown in  FIG. 2  as being integrated into a pressure-containing component  40  of the wellhead assembly  14  (e.g., in the tree  18  or a head  20 ). The pressure-containing component  40  includes a hollow body  42  with a bore  44  and an access passage  46  in fluid communication with the bore  44 . Although a single access passage  46  is depicted in  FIG. 2 , the body  42  may include additional access passages  46 , any or each of which could also include an internal valve  36 . In the presently illustrated embodiment, the access passage  46  in the body  42  includes an inner end  48  and an outer end  50 . In certain embodiments, the access passage  46  could be an annulus access passage, which may also be referred to as an annulus outlet port, in fluid communication with one of the annuli  24  in the well  12  (e.g., an “A” annulus, a “B” annulus, or a “C” annulus). A flange  34  is shown attached to the body  42  such that a bore  52  of the flange  34  is in-line with the access passage  46 . The flange  34  could be a spool flange, a valve flange, or an instrument flange, to name several examples. 
     In at least some embodiments, the valve  36  includes a sealing element that is moved between a closed position and an open position without actuating the sealing element through the outer end  50  of the access passage  46  (e.g., without using an actuator installed so as to extend into the access passage  46  through the outer end  50 ). By way of example, the valve  36  is shown in  FIG. 2  as having a sealing element in the form of a moveable plug  54  installed along the access passage  46 . The plug  54  may be retained in the access passage  46  with a retaining ring  56  and biased toward a closed, sealing position by a spring  58 . During assembly, the plug  54  can be inserted into the access passage  46  from the bore  44  through the inner end  48 . While the retaining ring  56  is threaded into the access passage  46  behind the plug  54  via a threaded interface  64  in some embodiments, such as shown in  FIG. 2 , the retaining ring  56  could be secured to the body  42  behind the plug  54  in some other fashion. In still other embodiments, the ring  56  could be omitted and the plug  54  could be retained in the passage  46  in some other suitable manner. 
     Generally, the plug  54  may be moved between a closed position that blocks flow through the access passage  46  and an open position that allows flow through the passage  46 . In some embodiments, the plug  54  acts as both a movable sealing element of the internal valve  36  (e.g., an annulus safety valve) and a VR plug facilitating removal or omission of an external valve  32  from the body  42 ; in such cases the plug  54  may also be referred to as an actuatable VR plug. Although the plug  54  could be actuated in other ways, in some instances the plug  54  is a hydraulically actuated plug controlled by routing control fluid to the valve through an actuation passage. As shown in  FIG. 2 , for example, control fluid may be routed to the valve  36  through a hydraulic control passage  60  or  62  in the body  42 . Rather than passing through a device (e.g., a valve housing) installed in the access passage  46 , the passages  60  and  62  are in the body  42  independent of the access passage  46 . 
     The passage  60  is accessible at the exterior surface of the body  42  with the flange  34  mounted to the body  42 . In contrast, the passage  62  extends to a face of the body  42  covered by the flange  34 . While the flange  34  could be removed to access the passage  62  in some instances, hydraulic control fluid may be routed into the passage  62  through another actuation passage, such as hydraulic control passage  68  of flange  34 . The apparatus can include a sealing sub  70  or any other suitable sealing arrangement to inhibit leakage where the passages  62  and  68  meet. Although the body  42  may have both passages  60  and  62 , such as shown in  FIG. 2 , in some embodiments either of these passages may be omitted while allowing hydraulic control of the valve  36  through the other. 
     The flange  34  may include one or more conduits  72 . Two such conduits  72  are shown in  FIG. 2  as extending through the flange  34  to its bore  52  and may be used to measure pressure, temperature, or some other characteristic of fluid in the flange  34 . As will be appreciated, various sensors, gauges, meters, or other devices may be used in such measurements. Pressure, temperature, or other characteristics of fluid within the pressure-containing component  40  may also or instead be measured through the body  42 . 
     As shown in the detailed views of  FIGS. 3 and 4 , the plug  54  and the body  42  include mating seating surfaces  80  and  82 . In at least some embodiments, these surfaces  80  and  82  are metal sealing surfaces forming a metal-to-metal seal when the plug  54  is in the closed position seated against the body  42 , as depicted in  FIG. 3 . In other instances, either or both surfaces  80  and  82  may carry a seal (e.g., a thermoplastic, elastomer, or metal seal) that presses and seals against the opposing surface or seal when the plug  54  is in the closed position. In some cases, the surfaces  80  and  82  may seal with both a metal-to-metal seal and a carried elastomer or thermoplastic seal. 
     The valve  36  may be opened by routing control fluid into a control chamber  84  to push the plug  54  off the seat  82  to an open position. Seals  86  isolate the control chamber  84  from other fluid regions, and the control chamber  84  is bounded in part by a shoulder  88  of the plug  54 . In operation, control fluid (e.g., a hydraulic control fluid) may be routed into the control chamber  84 , such as through passage  60  or  62 , to pressurize the chamber  84  and push the plug  54  (via the shoulder  88 ) to an open position, as generally shown in  FIG. 4 . The body of plug  54  includes one or more fluid ports  90  to allow flow through the plug  54  when in the open position. The characteristics of the ports  90  (e.g., size, number, and arrangement) may vary between embodiments, such as to optimize flow through the open plug  54 . To close the plug  54 , the pressure in the chamber  84  can then be reduced (e.g., by allowing control fluid to exit the chamber  84 ) such that the spring  58  pushes the plug  54  back to its seated position of  FIG. 3 . 
     Another example of an internal valve  36  integrated into the pressure-containing component  40  is shown in  FIGS. 5 and 6  as having a sealing element in the form of a moveable gate  102  installed along the access passage  46 . The gate  102  can be integrated into the body  42  of the pressure-containing component  40  in any suitable manner. In  FIGS. 5 and 6 , for instance, the body  42  includes a first body portion  104  and a second body portion  106 , and the gate  102  is installed in a cavity  108  between the first and second body portions  104  and  106 . The depicted body portions  104  and  106  are constructed such that the second body portion  106  is a cover inserted in a recessed portion of the first body portion  104 . But the body portions  104  and  106  could be constructed in other ways, such as the second body portion  106  serving as a cover that attaches to a non-recessed surface of the first body portion  104 . 
     The second body portion  106  may be connected to the first body portion  104  with fasteners (e.g., bolts  110 ) or in some other manner to enclose the gate  102  in the cavity  108 . A gasket or other seal  112  isolates the cavity  108  from the surrounding environment. The second body portion  106  can include a port  114  that, in at least some embodiments, facilitates measurement of a characteristic of fluid (e.g., temperature and pressure) within the cavity  108 . As shown in  FIGS. 5 and 6 , the outer end of the second body portion  106  also includes a sealing groove and mounting holes (e.g., a bolt circle) to facilitate connection of another component (e.g., a gate valve  32  or an instrument flange  34 ) to the body  42 . But in some other embodiments, an example of which is depicted in  FIG. 7 , the first body portion  104  also or instead includes such a sealing groove and mounting holes (e.g., a bolt circle) to facilitate connection of a gate valve  32 , instrument flange  34 , or other component to the first body portion  104  of the body  42 . As shown in  FIG. 7 , the sealing groove in the first body portion  104  surrounds the second body portion  106  such that a gasket or other seal received within the sealing groove (e.g., when an external valve  32  or flange  34  is fastened to the first body portion  104  via the mounting holes) encloses the second body portion  106 . 
     The gate  102  includes an aperture  118  and can be moved across the access passage  46  between an open position ( FIG. 5 ) to allow flow through the access passage  46  and a closed position ( FIG. 6 ) to block such flow. Like discussed above with the plug  54 , the gate  102  can be moved to the closed position to facilitate removal of an external valve  32  (or other equipment) from the body  42 . A seat  120  with an aperture  122  seals against the gate  102 . When the gate  102  is in the open position, the seat  120  seals around the aperture  118 , and the aperture  122  of the seat  120  is aligned with the aperture  118  to allow flow through the access passage  46 . A seal  126  inhibits leakage between the seat  120  and the body  42  (e.g., second body portion  106  in  FIG. 5 ) and can also push the seat  120  toward the gate  102 . 
     In  FIGS. 5 and 6 , the gate  102  is a curved gate that travels an arcuate path across the access passage  46  between the open and closed positions. But the gate  102  may have a different shape, such as a flat or wedge-shaped gate, in other instances. Additionally, while the seat  120  is shown abutting the front face of the gate  102  in  FIGS. 5 and 6 , in other embodiments the seat  120  could abut the rear face of the gate  102  or multiple seats  120  could be used to abut both the front and rear faces of the gate  102 . 
     In addition to or instead of the gate  102 , a plug can be installed to block flow into or out of the pressure-containing component  40  through the access passage  46 . One example of this is shown in  FIG. 8 , in which a sealing plug  134  (e.g., a VR plug) is threaded to a threaded surface  132  (e.g., a VR preparation) of the body  42 . In some embodiments, the plug  134  can be installed by opening the gate  102 , running the plug  134  through the outer end  50  of the access passage  46  and the aperture  118  of the open gate  102 , and then rotating the plug  134  to engage the threaded surface  132  of the access passage  46  with a mating thread of the plug  134 . As will be appreciated, the plug  134  may be installed in the access passage  46  using a suitable installation tool, such as a tool having a lubricator coupled directly or indirectly to the exterior of the second body portion  106  and a telescoping arm to position the plug  134  in the access passage  46 . The plug  134  and the gate  102  can serve as two pressure barriers along the access passage  46 , even with the removal or omission of an additional, external valve (e.g., gate valve  32 ) connected in-line with the access passage  46 . In other instances, the plug  134  may be installed behind the gate  102 , such as shown in  FIG. 8 , to facilitate removal of the second body portion  106  for servicing or removal of the valve  36 . 
     The gate  102  can be actuated in any suitable manner. In some embodiments the gate  102  is moved with a mechanical actuator. One example of this is generally depicted in  FIG. 9 , in which a gear  136  drives movement of the gate  102  between the open and closed positions. Teeth of the gear  136  engage a mating surface  138  such that rotation of the gear  136  moves the gate  102  along its path across the access passage  46 . A motor  140 , such as an electric motor, a hydraulic motor, or an electrohydraulic motor, may be connected to drive rotation of the gear  136 . In other embodiments, a motor  140  could be used with a linear actuator to push or pull the gate  102  along its path. 
     The gate  102  can include various alignment features that help guide and facilitate travel between the open and closed positions. By way of example, the gate  102  is shown in  FIG. 9  as having an alignment slot  142  for receiving one or more alignment pins  144 . The depicted alignment pins  144  are arranged horizontally and can help maintain the vertical position of the gate  102  (and engagement with the gear  136 ) as the gate  102  moves between the open and closed positions. Alignment pins  144  could also or instead be provided in other orientations, such as one or more vertical pins  144  received by the gate  102  to help maintain horizontal position of the gate  102  in operation. 
     In some embodiments, the gate  102  may also or instead include a tongue-and-groove arrangement to limit movement of the gate  102  in one or more directions. In  FIG. 10 , for example, the gate  102  includes a tongue  146  received in a mating groove  148  of the second body portion  106 . Although generally depicted on a lower end of the gate  102 , it will be appreciated that a tongue  146  may also or instead be provided on other portions of the gate  102 . 
     The gate  102  can be driven hydraulically in some other embodiments. As generally depicted in  FIG. 11 , for example, the gate  102  can be moved to the closed position by routing control fluid into a control chamber  152  of the cavity  108  and to the open position by routing control fluid into a control chamber  154  of the cavity  108 . More specifically, in the presently depicted embodiment, control fluid may be routed into the control chamber  152  through a port  114  to pressurize the chamber  152  and act on the end of the gate  102  to cause the gate  102  to move to the closed position. Similarly, control fluid may be routed into the control chamber  154  through another port  114  to pressurize the chamber  154  and act on the opposite end of the gate  102  to cause the gate  102  to return to the open position. The control chambers  152  and  154  may be isolated from other portions of the cavity  108  and from the access passage  46  with any suitable seals  156 . In yet another embodiment, the hydraulically actuated gate  102  could be spring-biased (e.g., fail-safe closed), such that hydraulic pressure in a control chamber (e.g., chamber  154 ) is used to drive the gate  102  to one position (e.g., the open position), while a biasing spring pushes the gate  102  to the other position upon a sufficient drop in pressure in that control chamber. 
     A further example of an internal valve  36  integrated into the pressure-containing component  40  is shown in  FIG. 12 . In this embodiment, the valve  36  includes a ball  162  as a moveable sealing element. Seats  164  and  166  seal against opposing sides of the ball  162 . In some embodiments, the seats  164  and  166  directly contact the ball  162  to provide metal-to-metal sealing, though other seals could also or instead be used, such as thermoplastic or elastomer seals carried by the seats  164  and  166 . 
     The seats  164  and  166  may be installed in the access passage  46  in any suitable manner. As shown in  FIG. 12 , for instance, the seats  164  and  166  are threaded into the access passage  46  along threaded surfaces  168  and  170 . The seat  164  can be installed through the inner end  48  of the passage  46  and the seat  166  can be installed through the outer end  50 . But in other embodiments, both seats  164  and  166  could be installed through the same end of the passage  46 . 
     The ball  162  includes a bore  172  and can be rotated between open and closed positions to control flow through the valve  36  and the access passage  46 . The ball  162  is shown in the open position in  FIG. 13 , in which the bore  172  is aligned with the access passage  46  to allow flow. The valve  36  can be closed by rotating the ball  162  to the closed position in  FIG. 14 . In this position, the bore  172  is no longer aligned with the access passage  46  and sealing between the ball  162  and the seats  164  and  166  blocks flow through the valve  36 , which may facilitate removal of an external valve  32  as discussed above. 
     The ball  162  can be actuated with a mechanical actuator or in any other suitable manner. In the embodiment depicted in  FIG. 12 , the ball  162  is rotated via a stem  174  that extends through a control passage in the body  42  and is driven by a motor  176  (e.g., an electric motor or a hydraulic motor). Although other arrangements are envisaged, the motor  176  is shown in  FIG. 12  to be installed above the ball  162  in a recessed portion  182  of the body  42  to facilitate use of a straight stem  174  along the axis of rotation of the ball  162 . 
     In other embodiments, the stem or other mechanical actuator for rotating the ball  162  could extend to some other surface of the body  42 . In  FIG. 15 , for example, a flexible mechanical actuator  186  (e.g., a flex coil or flexible shaft) extends to a radially outward facing surface (e.g., a front face) of the body  42  and is coupled to a motor  188  for controlling rotation of the ball  162  between the open and closed positions. The actuator could also or instead include a U-joint to transmit torque from the motor  188  to the ball  162 , such as a U-joint connecting an actuator shaft to a stem extending from the ball  162 . In still other embodiments, the ball  162  could be manually rotated (e.g., with a handle connected to the stem  174 , the actuator  186 , or another actuator). 
     Although the ball  162  may be used to block flow through the access passage  46  and facilitate removal of an external valve  32 , in some embodiments a sealing plug could also be installed in the access passage  46 . One such example is shown in  FIG. 16 , in which the access passage  46  and the internal valve  36  permit installation of a sealing plug  196  (e.g., a VR plug). In this depicted embodiment, the seats  164  and  166  may both be installed through the outer end  50  of the access passage  46 . During assembly, the seat  164  can be threaded into the access passage  46 , and the ball  162  can be positioned in the access passage  46  after the seat  164 . The seat  166  can then be threaded into the access passage  46 . Shoulders  192  and  194  provide positive stop surfaces for the seats  164  and  166 . As shown in  FIG. 16 , the outer diameter of the seat  164  is less than that of the seat  166  to facilitate passage of the seat  164  beyond the shoulder  194 . The sealing plug  196  can be run through the outer end  50  and the open ball  162  (e.g., with an installation tool), and then threaded into a threaded surface  198  (e.g., a VR preparation) of the access passage  46 . 
     While the access passage  46  is shown with a smaller diameter at the sealing plug  196  than at the seat  164 , and with an integral shoulder  192  of the body  42  defining a step-change in the diameter of the passage  46 , other arrangements could be used. By way of example, a sleeve could be installed in the access passage  46  of  FIG. 12  between the seat  164  and the bore  44  to facilitate installation of the sealing plug  196 . Rather than the body  42  having an integral shoulder  192 , this sleeve could include the shoulder  192 , as well as an internal threaded surface  198  for receiving the plug  196  and an external threaded surface for engaging threaded surface  168  of the access passage  46  in  FIG. 12 . The plug  196  could then be run into the sleeve through the ball  162  as generally described above. With the plug  196  blocking flow through the access passage  46 , the internal valve  36  may be serviced, removed, or used as a second fluid barrier. 
     Another example of an internal valve  36  integrated into a pressure-containing component  40  of the wellhead assembly  14  is shown in  FIG. 17 . More particularly,  FIG. 17  depicts a pair of internal valves  36  with hinged gates  210  (i.e., hinged-gate valves) integrated into the hollow body  42  of the pressure-containing component  40  (e.g., a head  20  or other wellhead housing, or a tree  18 ). The gates  210  are positioned along the access passages  46  and swing between open and closed positions to control flow through the valves  36  and the access passages  46 . In  FIG. 17 , the valve  36  on the left is shown with its gate  210  in a closed position to block fluid flow, and the valve  36  on the right is shown with its gate  210  in an open position to allow fluid flow. 
     External valves  32  may be mounted to the hollow body  42  in-line with access passages  46 . One such external valve  32  is partially depicted on the right side of the body  42  aligned with one of the access passages  46  in  FIG. 17 , and another external valve  32  may be similarly connected to the left side of the body  42  and aligned with the other depicted access passage  46 . While the axial cross-section of  FIG. 17  depicts two access passages  46  with internal valves  36 , it will be appreciated that the body  42  can include additional access passages  46 , any or all of which may similarly include internal valves  36 . 
     Certain aspects of the hinged-gate internal valve  36  of  FIG. 17  and its operation may be better understood with reference to the detailed view of  FIG. 18 . As shown, the internal valve  36  includes a gate  210  with a hinge  212  that allows the gate  210  to swing between closed and open positions within the body  42 . Further, in at least some embodiments, an actuator is coupled to move the gate  210  between the closed and open positions. As depicted in  FIG. 18 , for instance, the valve  36  includes an actuation assembly  214  including a linearly moveable stem  216  connected to control swinging of the gate  210 . The stem  216  may be connected to the gate  210  in any suitable manner. In at least some embodiments, the stem  216  is connected to the gate  210  with a pivot joint  218 . In the specific example shown in  FIG. 18 , the pivot joint  218  includes a pin  220  through a slot  222  to fasten the gate  210  to the stem  216  (e.g., a clevis fastener). 
     The closed gate  210  is shown in  FIG. 18  with a sealing surface  228  for closing against a mating sealing surface  230  of the body  42 . In some instances, the gate  210  includes a seal  232  (e.g., an elastomer seal) carried in a groove of the sealing surface  228  for sealing against the surface  230  of the body  42  when the gate  210  is in the closed position. In other instances, the seal  232  could be provided in a groove of the sealing surface  230  or in some other seat against which the gate  210  closes. Further, the sealing surface  228  of the gate  210  may also or instead create a seal directly against the mating sealing surface  230  of the body  42  (e.g., a metal-to-metal seal of the gate  210  against the body  42 ), with or without a carried seal  232 . When closed, pressure in the inner end  48  of the access passage  46  can push the back of the gate  210  and reinforce sealing of the gate  210  against the sealing surface  230 . 
     The valve  36  of  FIG. 18  may be installed transverse to the access passage  46 . That is, rather than being inserted into the access passage  46  through either the inner end  48  or outer end  50 , the gate  210  and the actuation assembly  214  may be inserted via a side passage (e.g., the perpendicular passage in the body  42  through which the actuation assembly  214  extends in  FIG. 18 ). A bonnet  236  fastened to the body  42  encloses the gate  210  and the actuation assembly  214  within the body  42 . As shown in  FIGS. 17 and 18 , the exterior of the body  42  may be recessed to facilitate receipt and connection of the bonnet  236 . 
     Some embodiments include a spring  240  that biases the gate  210  toward its closed position. Although the biasing spring  240  is shown as a compression spring in  FIG. 18 , different forms of springs (e.g., torsion springs) may be used in other instances. The spring  240  in  FIG. 18  pushes the stem  216  and biases the gate  210  toward the closed position. The stem  216  includes a piston  242 , and the biasing force of the spring  240  may be overcome through actuation of the piston  242 . Any suitable control fluid, such as a hydraulic control fluid in the case of a hydraulic actuation system  214 , may be injected through an inlet port  246  and a conduit  244  into an interior working chamber  250  ( FIG. 20 ) of the valve  36  to move the stem  216  against the biasing force of the spring  240  and open the hinged gate  210 . A plug  248  may be inserted into the inlet port  246 , such as when the valve  36  is kept in the closed position and is not in active use. 
     The apparatus of  FIG. 18  also includes an automatic valve shut-off assembly  254 . This depicted shut-off assembly  254  includes a vent shuttle  256  installed in a chamber  258  of the body  42  and various conduits arranged to vent actuation pressure from the valve  36  upon movement of the shuttle  256  to a pressure-venting position. In  FIG. 18 , the vent shuttle  256  is shown at a pressure-venting position that allows fluid communication between conduits  262  and  264  of the body  42  through the chamber  258 . A conduit  266  of the bonnet  236  is in fluid communication with the conduit  244  and the conduit  264  (via a seal sub  268 ). The vent shuttle  256  can be moved between a pressure-retaining position (e.g., as shown in  FIG. 19 ) and a pressure-venting position (e.g., as shown in  FIG. 18 ) that allows pressure to vent from the chamber  250  and cause the gate  210  to move to the closed position. That is, with the shuttle  256  in the position depicted in  FIG. 18 , conduits  262  and  264  are in fluid communication and provide a vent path for actuation pressure to escape the valve  36  (i.e., from the chamber  250  and through the conduit  244 , the conduit  266 , the seal sub  268 , the conduit  264 , the chamber  258 , and the conduit  262 ), allowing the spring  240  to drive the gate  210  closed. In contrast, when the shuttle  256  is moved to the pressure-retaining position of  FIG. 19 , the shuttle  256  (e.g., via a carried seal  272 ) isolates conduit  262  from conduit  264  and prevents venting of the actuation pressure from the valve  36  through the conduit  262 . 
     In some instances, the shuttle  256  includes a stem  274  that protrudes outwardly from the body  42  when the shuttle  256  is in the pressure-venting position, such as shown in  FIG. 18 . In use, however, an external valve  32  (or other component, such as a flanged pipe or an instrument flange) can be connected to the body  42  in-line with the access passage  46  and hold the shuttle  256  in the pressure-retaining position shown in  FIG. 19 . The external valve  32  or other component can be connected to the body  42  in any suitable manner, such as with studs, nuts, bolts, or other fasteners. With the shuttle  256  held in the position shown in  FIG. 19 , hydraulic control fluid may be pumped into the chamber  250  through the inlet port  246  and the conduit  244  to retract the stem  216  and swing the gate  210  from the closed position to open positions depicted in  FIG. 20  (half-open) and  FIG. 21  (fully open). It will be appreciated that the amount by which the gate  210  opens may be controlled by the amount of hydraulic fluid pumped into the valve  36 . In the pivot joint  218 , the slot  222  may be angled with respect to both the flow direction through the valve  36  and the direction of stem movement to allow translation of the pin  220  in the slot  222  during retraction of the stem  216  and opening of the gate  210 . 
     With hydraulic pressure in the chamber  250  holding the gate  210  in an open position that allows flow through the valve  36 , various fluids may be injected into or vented from the bore  44  through the access passage  46 . When finished, the valve  36  may be closed by reducing pressure within the chamber  250  and allowing the hydraulic control fluid to flow out of the valve (e.g., via port  246  or another port). But if the external valve  32  or other component holding the shuttle  256  in the pressure-retaining position ( FIGS. 19-21 ) is removed while the gate  210  is open, such as if the external valve  32  is accidentally separated from the body  42  during injection or venting of fluid through the internal valve  36 , the hydraulic control pressure (from the valve  36  via the conduit  264 ) acts on the right face of the shuttle  256  in  FIGS. 19-21  and pushes the shuttle  256  to the pressure-venting position of  FIG. 18 . This puts the conduits  264  and  262  in fluid communication, causes the hydraulic control fluid to vent to atmosphere from the chamber  250  in the bonnet  236 , as described above, and allows the spring  240  to push the stem  216  and return the gate  210  to its closed position. In this manner, the automatic valve shut-off assembly  254  can generally operate to automatically close the gate  210  if the shuttle  256  is not held in its pressure-retaining position while the gate  210  is opened, as well as to prevent hydraulic actuation of the valve  36  unless the shuttle  256  is in its pressure-retaining position. Still further, in at least some embodiments, the stem  274  of the shuttle  256  is a visual indicator that signals the gate  210  is closed when the stem  274  is protruding outwardly from the body  42 , such as shown in  FIG. 18 . 
     As described with other embodiments above, a plug  134  (e.g., a VR plug) can be inserted through the valve  36  and threaded to a threaded surface  132  (e.g., a VR preparation) of the body  42  to provide an additional barrier and facilitate removal of the external valve  32  or the internal valve  36 . In some instances, such as shown in  FIG. 22 , the body  42  includes a pair of access passages  46  that are aligned with one another (e.g., along centerline  278 ) and extend radially through the body  42 . This is in contrast to the arrangement shown in  FIG. 17 , in which the access passages  46  are not aligned with one another (they are offset from a centerline) and do not extend radially through the body  42 . Again, the body  42  can include additional access passages  46 , each of which may or may not be aligned with another access passage  46 . 
     While the hinged-gate valves described above with respect to  FIGS. 17-22  can be used as internal valves integrated into a pressure-containing component of a wellhead assembly, in other embodiments the hinged-gate valves may be provided as standalone valves that are not integrated into a pressure-containing component of a wellhead assembly. In some instances, for example, such valves may be used as an external valve  32  described above, a production valve, or a pipeline valve. 
     By way of example, a valve  282  with a hinged gate  210  is depicted in  FIGS. 23 and 24 . The gate  210 , the hinge  212 , and the actuation assembly  214  are enclosed in a valve housing  284  with a bonnet  236 . A stem  216  of the actuation assembly  214  can be connected to the gate  210 , such as described above. In the embodiment shown in  FIGS. 23 and 24 , the gate  210  can be opened and closed through hydraulic actuation (via the piston  242  and the stem  216 ) to selectively control flow through a bore  286  of the valve  282 . In the closed position, the gate  210  can seal against a mating surface of the valve housing  284  (or of a seat installed in the housing  284 ), such as with either or both an elastomer seal and a metal-to-metal seal. Hydraulic fluid can be routed into a chamber  288  of the valve  282  through a conduit  290  to drive the gate  210  to a closed position ( FIG. 24 ) or through a conduit  292  to drive the gate  210  to an open position ( FIG. 23 ). In some other embodiments, the valve  282  may be manually actuated. One example of this is shown in  FIGS. 25 and 26 , in which a handwheel or other handle  298  may be rotated to drive the stem  216  via a threaded rod  296  to move the gate  210  between an open position ( FIG. 25 ) and a closed position ( FIG. 26 ). In still other embodiments, a mechanical actuator may be used to drive the gate  210  of the valve  282  between open and closed positions. 
     The valve  282  is a standalone valve capable of use independent of a wellhead assembly and is not integrated into a wellhead housing, tree, or other pressure-containing component of a wellhead assembly. In some instances, the valve  282  could be used as an external valve  32  mounted on an exterior of a pressure-containing component of a wellhead assembly. But the valve  282  could also be used to control flow in other applications apart from wellhead assemblies. 
     In another embodiment depicted in  FIG. 27 , the body  42  includes an internal valve  36  with a hinged gate  210  that swings between an open position (as shown in  FIG. 27 ) to allow flow through the valve  36  and a closed position against a seat  304  to block flow through the valve  36 . The depicted seat  304  includes a seal  306  (e.g., a metal or elastomer seal) that seals against the gate  210  when closed. This valve  36  also includes a biasing spring  240 , which is shown in  FIG. 27  as a torsion spring. In some embodiments, the torsion spring  240  biases the gate  210  toward its closed position against the seat  304 . A plug  134  (e.g., a VR plug) can be threaded to the threaded surface  132 , as described above. 
     While various actuators are described above with respect to the hinged-gate valves of  FIGS. 17-26 , it will be appreciated that any other suitable actuators may be used to move the hinged gate  210  between closed and open positions in accordance with the present techniques. Accordingly, an actuator  310  is generally depicted in  FIGS. 27 and 28  as being connected to move the gate  210 . The actuator  310  may take the form of an actuator described above or of any other suitable actuator. The actuator  310  may be enclosed within a bonnet  236  in some embodiments or coupled to the body  42  in some other manner. Additionally, while certain embodiments described above in connection with  FIGS. 17-22  include a hinged gate  210  and an automatic shut-off assembly  254  for venting hydraulic control fluid in some instances, other embodiments having hinged gates  210  may omit such a shut-off assembly  254 . 
     In  FIG. 28 , the actuator  310  is connected to push against a cam surface  314  of the gate  210  to facilitate swinging the gate  210  from a closed position (against the seat  304 ) to an open position (off of the seat  304 ) to allow flow through the valve  36 . The seat  304  may have an angled sealing face, such as shown in  FIG. 28 . This arrangement keeps the gate  210  from being perpendicular to the flow direction through the access passage  46  when the gate  210  is closed against the angled sealing face and may facilitate opening of the gate  210  off the seat  304  during operation. A seal  306  (e.g., carried in a groove of the seat  304 ) can be used to seal between the seat  304  and the closed gate  210 . The seats  304  of  FIGS. 27 and 28  could be used in other embodiments, including those described above with respect to  FIGS. 17-26 . Further, while not shown in  FIG. 28 , it will be appreciated that a biasing spring  240 , such as a compression spring or a torsion spring, can be used to bias the gate  210  closed in some instances. 
     In some other embodiments, the valve  36  includes a hinged gate  210  without an actuator. One example of this is shown in  FIG. 29 , in which the gate  210  is enclosed within the access passage  46 . The gate  210  is shown here in an open position but may be biased by spring  240  toward a closed position against the seat  304 . In operation, movement of the hinged gate  210  is controlled by a pressure differential across the gate  210  without an actuator. When the gate  210  is closed and the pressure is greater at the inner end  48  of the access passage  46  than the outer end  50 , the pressure differential pushes the gate  210  against the seat  304  and reinforces sealing of the closed gate  210 . But when pressure at the outer end  50  sufficiently exceeds the pressure at the inner end  48  (i.e., by enough to overcome the biasing force from the spring  240 ), such as when injecting a fracturing fluid or some other fluid into the bore  44  through the access passage  46 , the pressure differential pushes the gate  210  open and allows fluid flow. With the gate  210  open, a plug  134  can be installed in the access passage  46  via threaded portion  132 , as described above. 
     In still another embodiment, an internal hinged-gate valve  36  can be provided as a cartridge valve. In  FIG. 30 , for example, an internal valve  36  includes a cartridge valve  322  having a gate  210 , a hinge  212 , a biasing spring  240 , and a seat  304  housed within a hollow cartridge body  324 . The cartridge valve  322  may be installed as a single unit, such as by inserting the cartridge body  324  with the internal valve components into the access passage  46  through the outer end  50 . Like  FIG. 29 , the spring  240  can bias the hinged gate  210  to a closed position against the seat  304  and a pressure differential can be used to control movement of the hinged gate  210  without an actuator. In other cartridge valves  322 , however, an actuator could also or instead be used to move the hinged gate  210 . One or more seals  328  can be provided to seal within the access passage  46  between the body  42  and the outer surface of the cartridge body  324 . Additionally, the cartridge body  324  may be retained within the access passage  46  with a retaining ring  332  or in any other suitable manner. 
     While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.