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CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims priority to and the benefit of, U.S. Patent Application Ser. No. 62/024,260, filed Jul. 14, 2014, the full disclosure of which is hereby incorporated by reference herein for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present disclosure relates in general to a system for selectively providing access to a wellbore annulus through a sidewall of a wellhead hanger. More specifically, the present disclosure relates to an annulus access valve in the side wall of a tubing hanger for controlling a flow of annular fluid. 
     2. Description of Prior Art 
     High pressure wellheads used in the production of hydrocarbons extracted from subterranean formations typically include a wellhead assembly attached at the upper end of a wellbore formed into a hydrocarbon producing formation. Wellhead assemblies usually provide support hangers for suspending production tubing and casing into the wellbore. The casing lines the wellbore, thereby isolating the wellbore from the surrounding formation, whereas the tubing usually inserts within the casing and provides a conduit therein for producing the hydrocarbons entrained within the formation. Wellhead assemblies also typically include a wellhead housing and a production tree atop the wellhead housing, where the wellhead housing circumscribes the hangers that support the casing and tubing. The production tree is commonly used to control and distribute the fluids produced from the wellbore, and to selectively provide fluid communication or access to the tubing, casing, and/or annuluses between the tubing and casing. Valves assemblies are typically provided within production trees for controlling fluid flow from a wellhead, such as production flow from the borehole or circulating fluid flow in and out of a wellhead. 
     Wellhead assemblies are usually mounted over a wellbore that intersects a subterranean formation and typically include a main bore that registers with the wellbore. Swab valves are generally set within the main bore for isolating the main bore and wellbore from ambient conditions above the wellhead assembly. Production from the wellbore is generally accomplished via a production line that intersects the main bore and extends laterally through a production tree. A production wing valve is generally provided within the production line for selectively regulating flow through the production flow line. Annulus line within a production tree usually includes an annulus wing valve for controlling flow therein. An annulus is defined between the tubing and casing which typically is in communication with the annulus line. Often, an annulus bleed line is included for annulus access or for venting of the annulus, and usually has one end connected to the annulus. 
     SUMMARY OF THE INVENTION 
     Described herein is an example of a wellhead assembly which includes a wellhead housing, a wellhead hanger disposed in the housing, a valve bore in a sidewall of the wellhead hanger, a valve body axially selectively reciprocal in the valve bore between open and closed positions, and upper and lower annulus access circuits in the sidewall of the wellhead hanger and that each intersect the valve bore at axially spaced apart locations and that are in communication with one another when the valve body is in the open position and that are out of communication when the valve body is in the closed position. A pressure source may be included that is selectively in communication with opposing ends of the valve body and for selectively reciprocating the valve body between the open and closed positions. In an example the valve body has an inner cavity, and upper and lower apertures formed through an outer surface of the body and that intersect the inner cavity at axially spaced apart locations, and wherein when the valve body is in the open position, the upper apertures register with the upper access circuit and the lower apertures register with the lower access circuit, so that the upper and lower access circuits are in communication with one another via the inner cavity. In an alternative, the valve body includes an inner cavity, and upper and lower apertures formed through an outer surface of the body and that intersect the inner cavity at axially spaced apart locations, and wherein when the valve body is in the closed position, a solid portion of the valve body is in a path of communication between the cavity and a one of the upper or lower apertures, so that communication between the upper and lower access circuits via the inner cavity is blocked by the solid portion of the valve body. Optionally included is an override assembly which is made up of a housing, a piston in the housing, and a latching assembly coupling the valve body to the piston, wherein the piston is selectively moveable to a first position and a second position, and wherein when the valve body is in the open position when the piston is in the first position, and the valve body is in the closed position when the piston is in the second position. In this example, further provided are pressure ports on the housing on opposing sides of the piston, so that when pressure is communicated to a one of the pressure ports, the piston is urged away from the one of the pressure ports. The latching assembly may be made from a sleeve with a profiled end that selectively couples with a profiled end on an override head, where the override head is attached to the valve body. The override assembly can be optionally mounted in a running tool that is used for landing the wellhead hanger in the wellhead housing. In one embodiment the wellhead hanger is a tubing hanger. An annulus can be formed which is defined between tubulars. 
     Also described herein is an example of a wellhead assembly which includes a wellhead housing, a wellhead hanger landed in the housing, an annulus defined between tubulars in the wellhead housing, an annulus access circuit having an end in communication with the annulus and that intersects the wellhead hanger, a valve member in the wellhead hanger that is selectively moved into a blocking position in the annulus access circuit to isolate portions of the annulus access circuit that are on opposing ends of the valve member, and a hydraulic circuit in selective communication with opposing sides of the valve member and that selectively urges the valve member into the blocking position. An override assembly may be further included which is moveable into a first position and a second position, and that is coupled to the valve member, so that when the override assembly is in the first position the valve member is in the blocking position, and so that when the override assembly is in the second position, the valve member is spaced away from the blocking position. This embodiment may further have a latching assembly on the override assembly that selectively engages an override head that couples to the valve member, and wherein the latching assembly comprises a sleeve with a profiled end that inserts into an upper end of the override head that is shaped complimentary to the profiled end. The override assembly may include a piston housed in a cylinder, and wherein a hydraulic fluid source selectively delivers pressurized hydraulic fluid to opposing ends of the piston for moving the override assembly between the first and second positions. The annulus access circuit may be made up of an upper portion that extends from a bore in the wellhead hanger having the valve member to an upper portion of the wellhead hanger and that is distal from the annulus. The annulus access circuit may optionally include a lower portion that extends from a bore in the wellhead hanger having the valve member to a lower portion of the wellhead hanger and that is proximate the annulus. In one embodiment, the hydraulic circuit has a pressurized fluid passage formed through the wellhead hanger having an end in communication with a pressure source. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side sectional view of an example of an annulus access valve disposed within a wellhead hanger, which in turn is landed within a wellhead assembly. 
         FIGS. 2A and 2B  are side sectional views of an example of the annulus access valve of  FIG. 1  respectively n open and closed positions. 
         FIG. 3  is a side sectional detail view of an example of the annulus access valve of  FIG. 1 . 
         FIG. 4  is a side sectional view of an example of an override assembly for use with the annulus access valve of  FIG. 1 . 
         FIGS. 5A-5D  illustrate in side sectional views examples of operation of the override assembly of  FIG. 4 . 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF INVENTION 
     The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/−5% of the cited magnitude. In an embodiment, usage of the term “substantially” includes +/−5% of the cited magnitude. 
     It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
       FIG. 1  shows in cross sectional view one example of a wellhead assembly  10  made up of an annular wellhead housing  12  and which has a tubing hanger  14  landed therein. Tubing hanger  14  is an annular member and is shown landed on top of a casing hanger  16 , which in turn lands on an outer casing hanger  18  within wellhead housing  12 . Seal assemblies  20 ,  22  seal the interface between the casing hangers  16 ,  18  and wellhead housing  12 . Circumscribing an upper portion of tubing hanger  14  is an actuation sleeve  24  shown behind locking dogs  26  that are mounted to an inner surface of wellhead housing  12 . Driving actuation sleeve  24  downward pushes dogs  26  radially outward to lock tubing hanger  14  in wellhead assembly  10 . A string of tubing  28  connects to a lower end of tubing hanger  14  and depends downward into a well (not shown) that is disposed beneath wellhead assembly  10 . An annulus  30  is formed between the tubing  28  and inner surface of casing hanger  16 ; casing  31  shown mounted on a lower end of casing hanger  16 . An example of an annulus access valve  32  is illustrated disposed in a valve bore  34 ; where valve bore  34  is axially formed within a sidewall of tubing hanger  14 . As will be described in more detail below, annulus access valve  32  provides selective communication between the annulus  30  and locations above wellhead assembly  10 . 
       FIGS. 2A and 2B  show in a side sectional view detailed examples of the annulus access valve  32  set in the tubing hanger  14 . In  FIG. 2A  annulus access valve  32  is in an open position, which allows the annulus  30  ( FIG. 1 ) may be accessed from locations above tubing hanger  14 . The path for providing communication to annulus  30  is through an annulus access circuit  36  shown made up of an upper annulus access bore  38 . Upper annulus access bore  38  is shown axially projecting through tubing hanger  14  and offset from valve bore  34 . An upper annulus access port  40  extends laterally through tubing hanger  14  from a lower end of upper annulus access bore  34  and intersects with valve bore  34 . Upper annulus access bore  38  thus communicates with valve bore  34  via upper annulus access port  40 . Circuit  36  further includes a lower annulus access bore  42  shown axially formed through the tubing hanger  14  below upper annulus access port  40 . Lower annulus access bore  42  has an upper end intersecting a lower annulus access port  44 , where lower annulus access port  44  intersects with valve bore  34  at a location that is axially spaced away from where upper annulus access port  40  intersects with valve bore  34 . Lower annulus access bore  42  is in communication with annulus  30  ( FIG. 1 ); thus valve bore  34  is in selective communication with annulus  30  via lower annulus access port  44  and lower annulus access bore  42 . Upper and lower apertures  46 ,  48  are provided in a sidewall of the body  49  of the annulus access valve  32 . In the example, upper apertures  46  are adjacent the intersection between valve bore  34  and upper annulus access port  40 , and lower apertures  48  are adjacent where lower annulus access port  44  intersects with valve bore  34 . 
     A fluid supply line  50  is shown formed through the tubing hanger  14  and has one end intersecting with an upper portion of valve bore  34  proximate an upper terminal end of tubing hanger  14 . An opposite end of fluid supply line  50  connects to a fluid source  52  distal from its intersection of valve bore  34 . Fluid source  52  can be any source of pressurized fluid, such as a pump, a pressurized vessel or a combination thereof. Moreover, fluid source  52  may be proximate wellhead assembly  10 , or remotely located, such as above sea surface. Another fluid supply line  54  is shown formed through tubing hanger  14  and which intersects a lower portion of valve bore  34 ; and at a location distal from intersection between fluid supply line  50  and valve bore  34 . Fluid source  56  connects to an end of fluid supply line  54  and opposite from its connection to valve bore  34 . Examples exist where fluid source  52  and fluid source  56  are combined within a single unit and/or are at the same general location. 
     Still referring to  FIG. 2A , further illustrated is a chamber  60  formed within valve body  49  which projects axially within valve body  49  above the upper apertures  46  and below the lower apertures  48 . Upper and lower apertures  46 ,  48  project through a sidewall of valve body  49  and thereby allowing communication from the outer surface of valve body  49  and into chamber  60 . As such, in the example of  FIG. 2A  and with annulus access valve  32  in the open position, fluid communication (as illustrated by the arrows) is provided through valve body  49  into upper apertures  46 , through chamber  60 , and out lower apertures  48 . Thus, upper and lower access ports  40 ,  44  may be in communication with one another via the path shown that extends through apertures  46 , through chamber  60 , and through aperture  48 . Moreover, in the example of  FIG. 2A  pressurized fluid from fluid source  52  is provided to fluid supply line  50  and applied to a side of valve body  49  which urges valve body  49  into the position shown and allowing the above described communication through circuit  36 , and thereby allowing access to annulus  30  through annulus access valve  32 . 
     Referring now to  FIG. 2B , shown is an example of the annulus access valve  32  in a closed configuration. In this example, pressurized fluid is provided to fluid supply line  54  via fluid source  56 , and delivered to a lower end of valve body  49  thereby urging valve body upward and away from the intersection with valve bore  34  and fluid supply line  54 . As shown, the valve body  49  includes solid portions  61  above and below the chamber  60 . In this example, the solid portion  61  of valve body  49  below chamber  60  is adjacent lower annulus access port  44 , thereby blocking communication between chamber  60  and lower annulus access port  44 . The illustrated closed configuration thus blocks communication to annulus  30  ( FIG. 1 ) through annulus access valve  32 . In one embodiment, fluid within valve bore  34  above valve body  49  may be bled from valve bore  32  and into fluid supply line  50  to allow the upward movement of valve body  49 . Thus, by selectively activating fluid sources  52 ,  56  and flowing fluid through one of fluid supply lines  50 ,  54  to the valve bore  34 , the valve body  49  may be cycled upward and downward into open and closed positions to selectively allow and/or block annulus access through the annulus access valve  32 . 
       FIG. 3  illustrates a detailed example of a portion of the annulus access valve  32  and further shows seals  62 ,  64  circumscribing the valve body  49 . Seals  62 ,  64  provide sealing capability to isolate fluid delivered to valve bore  34  on one side of the valve body  49  from the opposing side of the valve body  49 . Further in the example of  FIG. 3 , apertures  46 ,  48  are respectively registered with ports  40 ,  44  thereby putting the annulus access valve  32  into an open position and allowing access to annulus  30  ( FIG. 1 ). 
       FIG. 4  shows in a side sectional view one example of an override assembly  66  that provides a redundant means for operating the annulus access valve  32  ( FIG. 2A, 2B ) in the event of hydraulic failure to the tubing hanger  14 . In this example, override assembly  66  can be provided within a running tool  68  that may be used for landing the tubing hanger  14  ( FIG. 1 ) into the wellhead assembly  10 . Alternatively, override assembly  66  is provided within a production tree  100  shown mounted onto housing  12  ( FIG. 1 ). Included within the override assembly  66  is a piston head  70 , piston rod  72  attaches to a lower end of piston head  70 . Both piston head  70  and piston rod  72  are disposed within a cylinder  74  defined within a housing  76 . Hydraulic lines  78 ,  80  are shown formed through the body of the running tool  68  and intersect housing  76  on opposite ends of piston head  70 . Thus, selectively delivering pressurized fluid to hydraulic lines  78 ,  80  may reciprocate piston head  70  and piston rod  72  within housing  76 . Coupled to a lower end of piston rod  72  distal from piston head  70  is a latching assembly  82  that is shown made up of a latching sleeve  84 ; which is an annular member and has a groove circumscribing its outer surface and proximate its lower end. Latching sleeve  84  is circumscribed by an outer sleeve  88  that is in close contact with an inner surface of housing  76 . In the example, the sleeves  84 ,  88  are generally coaxial with one another and circumscribe an axis AX of the housing  76 . 
     In one example of use, the latching assembly  82  couples with the annulus access valve  32  via an override head  90 , shown attached to annulus access valve  32  via rod  92  ( FIG. 2A, 2B ). Override head  90  has a generally cylindrical base with a sleeve-like portion that projects upward from the base. Proximate the upper terminal end of the sleeve on the override head  90  is a profile  93  designed for attaching to groove  86  on the lower end of sleeve  84 . An example of this coupling is illustrated in  FIGS. 5A, 5B  where the override assembly  66  has been coupled to override head  90 . In  FIGS. 5A, 5B  up and down movement of the override head  90  is achieved by axially upward and downward movement of the piston head  70  and piston rod  72  as described above. More specifically, in  FIG. 5A , pressurized fluid has been delivered into cylinder  74  from hydraulic line  78  thereby upwardly moving piston head  70  within cylinder  74 , and in turn drawing override head  90  upward as well. In this configuration, and as can be seen in  FIG. 2B , the annulus access valve  32  is positioned into a closed position. Similarly, by venting fluid from cylinder  74  and into hydraulic line  78 , while introducing fluid into cylinder  74  above piston head  70  and from hydraulic  80 , latching assembly  82  and override head  90  are urged downward thereby putting the annulus access valve  32  into a closed position, as illustrated in  FIG. 2A . 
     Referring back to  FIG. 4 , the override assembly  66  is shown further equipped with a cylindrically-shaped bulkhead  94  that mounts into the housing  76  and below where hydraulic line  78  intersects with cylinder  74 . Piston rod  72  reciprocatingly inserts through bulkhead  94 , and seals are provided on the outer and inner circumferences of bulkhead  94  so that any fluid within cylinder does not make it way downward past bulkhead  94  and to the latching assembly  82 . A cavity  96  is defined within the housing lower portion  98  which is the portion of the housing  76  below bulkhead  94 . Housing lower portion  98  provides a means for covering the latching assembly  82  and structural support for coupling the override assembly  66  to the tubing hanger  14  and for coupling with the override head  90 . 
     The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.

Summary:
A wellhead assembly includes an annulus access valve (AAV) disposed in a wellhead hanger. Upper and lower annulus access bores intersect the bore at upper and lower ports. The AAV includes a body that reciprocates within the bore between open and closed positions. Hydraulic fluid moves the body between the open and closed positions. Axially spaced apart upper and lower apertures are formed through the body outer surface allow communication to a chamber within the body. When in the open position, the upper and lower apertures respectively register with the inlet and outlet ports so that the upper and lower annulus access bores are in communication through the AAV. When in the closed position, a solid portion of the body registers with one of the inlet or outlet ports, thereby blocking communication through the AAV between the upper and lower annulus access bores.