Abstract:
A valve assembly for use in a wellhead assembly that includes a valve body, a cavity formed in the valve body, and a flow passage through the valve body that intersects the cavity. Also included is a gate slidable in the cavity between an open position and a closed position. A bore is formed through the gate. A fluidic passage is also formed through the gates that provides fluid communication between the bore and an upstream side of the valve member. The fluidic passage is formed so that when the gate is being moved into the closed position, fluid upstream of the gate enters the fluidic passage and exits into the bore to assist closing the valve.

Description:
1. FIELD OF THE INVENTION 
       [0001]    This invention relates in general to production of oil and gas wells, and in particular to a valve, that when closing, diverts a portion of fluid flowing through the valve to reduce resistance to closing the valve. 
       2. DESCRIPTION OF RELATED ART 
       [0002]    Wellheads used in the production of hydrocarbons extracted from subterranean formations typically comprise 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. The tubing typically lies concentric within the casing and provides a conduit for producing the hydrocarbons entrained within the formation. 
         [0003]    Wellhead assemblies also typically include a wellhead housing adjacent where the casing and tubing enter the wellbore, and a production tree atop the wellhead housing. The production tree is commonly used to control and distribute the fluids produced from the wellbore and selectively provide fluid communication or access to the tubing, casing, and/or annuluses between the tubing and casing. Valves assemblies are typically provided within wellhead production trees for controlling fluid flow across a wellhead, such as production flow from the borehole or circulating fluid flow in and out of a wellhead. Gate valves and other sliding stem-type valves have a valve member or disk that is actuated by selectively moving the stem to insert/remove the valve member into/from the flow of fluid to stop/allow the flow when desired. 
       SUMMARY OF THE INVENTION 
       [0004]    Disclosed herein is a valve assembly, that in an example embodiment is made up of a housing with a cavity inside and a flow passage through the housing that intersects the cavity. The valve assembly also includes a gate that slides within the cavity into a selectively open and/or closed position. The gate has a bore formed therethrough that registers with the flow passage when the gate is in the open position. The gate also has a fluidic passage formed therein extending between the upstream side of the gate and the bore. Thus, when the gate is being moved from an open to a closed position and fluid is flowing through the valve assembly, a portion of the fluid passes into the fluidic passage at the upstream side and exits the fluidic passage into the bore. In an example embodiment, the bore is offset from the mid portion of the gate and the fluidic passage intersects the bore along a side proximate the mid portion. An interface may be included that is between the fluidic passage and the bore, where the interface is configured so that fluid entering the bore from the interface is directed oblique to an axis of the flow passage. Alternatively, included can be an interface between the fluidic passage and the bore that is configured so that fluid entering the bore from the interface is directed proximate a gap between the flow passage and the bore when the gate is almost closed where the flow passage registers with the bore on a downstream side of the valve body. In yet another alternative, an interface may be provided between the fluidic passage and the bore and formed so fluid entering the bore from the interface is directed towards an opposite side of the bore from the interface. Yet further optionally, an interface may be included that is between the fluidic passage and the bore and that is closer to a downstream side of the gate than an upstream side. In an example embodiment, the fluidic passage has a diameter less than the diameter of the bore. 
         [0005]    Also provided herein is a method of controlling flow through a wellhead assembly. In an example embodiment the method includes directing the flow from an upstream flow line to a valve assembly. The valve assembly may include a valve body with a cavity formed therein, a flow passage through the body that intersects the cavity, a gate selectively moveable in the cavity, and a bore in the gate. While closing the gate a portion of the flow from the upstream flow line is diverted through a fluidics channel extending from an upstream side of the gate into the bore. In an example, a pressure drop of the flow through the valve assembly is increased while closing the valve. The pressure drop can be reduced by mixing the diverted flow with the flow in the valve passage. In an example embodiment, the step of mixing involves directing the diverted flow from the fluidics passage toward a gap between the bore and the flow passage. Yet further optionally, the step of mixing may involve directing the diverted flow from the fluidics passage to an opposite side of the bore. The valve may be moved completely to the closed position thereby stopping flow through the fluidic passage. 
         [0006]    Yet further described herein is a wellhead. In an example embodiment, the wellhead has an upstream flow line, a downstream flow line, and a valve assembly connected on one end to the upstream flow line and on another end to the downstream flow line. The valve assembly can include a valve body equipped with a cavity and a flow passage formed through the cavity. The valve assembly also includes an upstream side in fluid communication with the upstream flow line and a downstream side in fluid communication with the downstream flow line. A gate can be included that has a substantially solid portion and a portion with a bore formed therethrough. Thus moving the gate can partially registers the bore and flow passage to define a flow path through the valve body. The flow path varies in cross sectional area with selective movement of the gate. A fluidic passage is formed through the valve member between a side of the gate facing the upstream flow line and a side of the bore proximate the downstream flow line. The fluidic passage can have an outlet formed along a path directed towards a space where the flow path transitions into the downstream flow line when the gate is almost closed. Optionally, the fluidic passage has an outlet formed along a path directed towards a side of the bore distal from where the fluidic channel intersects the bore. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side partial sectional schematic view of an example embodiment of a wellhead assembly having a valve assembly in accordance with the invention. 
           [0008]      FIG. 2  is a side sectional view of an example embodiment of the valve assembly of  FIG. 1  in an open position. 
           [0009]      FIG. 3  is a side sectional view of the valve assembly of  FIG. 2  in a closed position. 
           [0010]      FIG. 4  is a perspective view of an example embodiment of a gate for use in the valve assembly of  FIG. 2 . 
           [0011]      FIG. 5  is a side sectional view of an alternative embodiment of the valve assembly of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    The apparatus and method of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. This subject of the present disclosure may, however, be embodied 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 the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location. 
         [0013]    It is to be understood that the subject 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 of the subject disclosure and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the subject disclosure is therefore to be limited only by the scope of the appended claims. 
         [0014]      FIG. 1  is a partial sectional side schematic view of a wellhead assembly  10  shown set above a wellbore  12  that intersects a formation  14 . Also included is a wellhead housing  16  depicted anchored on a surface  18  above the formation  14 . Example embodiments exist where the surface  18  is subsea as well as on land. A production tree  19  is coupled atop the wellhead housing  16  wherein production tubing  20  is shown extending through the wellhead housing  16  and production tree  19 . A swab valve  22  and a master valve  23  are shown provided in the production line  20  and may be used, individually, or in combination, for selectively regulating flow through the production line  20 . Shown laterally extending from a side of the production tree  19  is a line  24  having a wing valve  26  within the line  24 . In this example, the line  24  can be used for accessing various annuluses within the wellbore  12  defined by concentrically disposed strings of casing and tubing (not shown). Also laterally extending from the production tree  19  is a line  28  having a wing valve  30  set in line. In the example of  FIG. 1 , the line  28  is a production flow line for receiving produced fluids from the production tubing  20  and directing the fluids for processing and/or delivery. 
         [0015]      FIG. 2  illustrates an example embodiment of a valve assembly  32  that in an example embodiment can be one of the swab valve  22 , or the wing valves  26 ,  30 . In the example of  FIG. 2 , the valve assembly  32  is shown connected with an upstream line  33  that connects to a flow passage  34  within the valve assembly  32 . The interface between the upstream line  33  and flow passage  34  defines an upstream side of the flow passage  34 . Similarly, a downstream line  35  is shown attached on a side of the flow passage  34  opposite the upstream line  33 . The interface between the flow passage  34  and downstream line  35  defines a downstream side of the valve assembly  32 . A valve housing (or body)  36  is included with the valve assembly  32  of  FIG. 2 , where the valve housing  36  is an elongate member disposed generally perpendicular to the upstream and downstream flow lines  33 ,  35 . A cavity  38  is formed within the housing  36  wherein the flow passage  34  extends through the valve body  36  and intersects the cavity  38 . 
         [0016]    Illustrated provided within the cavity  38  is a valve gate  40  adapted to slidingly move within the cavity  38  along a path substantially perpendicular with an axis A X  of the flow lines  33 ,  35 . The valve gate  40  includes a bore  42  that is formed through the valve gate  40  and in a direction along the axis A X . In the embodiment of  FIG. 2 , the portions of the valve gate  40  on opposite sides of the bore  42  are substantially solid. In the example embodiment of  FIG. 2 , the valve gate  40  is illustrated as a gate. Also shown in  FIG. 2  is a fluidic passage  44  that intersects the bore  42  and extends through the side of the valve gate  40  proximate the upstream side of the flow passage  34 . The fluidic passage  44  of  FIG. 2  is formed along a path substantially oblique to the axis A X . The fluidic passage  44  has a downstream end, or outlet, that intersects bore  42  closer to the downstream side  52  of the valve gate  40  than the upstream side  50 . Passage  44  has a diameter smaller, and alternatively significantly smaller, than the diameter of the bore  42 . A straight line extending from the outlet of the fluidic passage  44  pass through the outlet of the bore  40 . 
         [0017]    An actuation rod or stem  46  is shown connecting to an end of the valve gate  40  and projecting laterally away from flow passage  34  and through the housing  36 . An actuating mechanism  48  is provided on the opposite end of the actuation rod  46  that reciprocates the actuation rod  46  to slide the valve gate  40  within the cavity  38 . Reciprocating the valve gate  40  in this manner can selectively move the bore  42  in and out of registration with the flow passage  34 . 
         [0018]    An annular valve seat  50  is shown provided in the valve body  36  and adjacent where the upstream line  33  interfaces with the flow passage  34 . Another annular valve seat  52  is shown in the valve body  36 , but adjacent where the downstream line  35  interfaces with the flow passage  34 . The valve seats  50 ,  52  provide a sealing surface between flow through the valve assembly  32  and the respective upstream and downstream sides  54 ,  56  of the valve gate  40 . 
         [0019]    In the embodiment of  FIG. 2 , the bore  42  is registered with the flow passage  34  to define a flowpath  58  through the valve assembly  32 . As such, when fluid flow is introduced into the upstream side  33 , the flow can pass through the valve assembly  32  and to the downstream line  35  largely unaffected by the presence of the valve assembly  32 . This is because the flowpath  58  through the valve assembly  32  of  FIG. 2  has a cross sectional area that remains substantially the same through the flow lines  33 ,  35  and the flow passage  34 . 
         [0020]    Referring now to  FIG. 3 , an example embodiment is illustrated wherein the actuator  48  selectively moves the valve gate  40  laterally within the cavity  38 , thereby moving the bore  42  out of full registration with the flow passage  34 , but not completely closed. A gap  58 A remains between bore  42  and the passages  33 ,  34  for fluid to flow from upstream of the passage  33  to downstream of the passage  34 . This example configuration illustrated in  FIG. 3 , reduces the cross sectional area of the flowpath  58 A through the valve assembly  32  over that of  FIG. 2 . As a result, pressure drop and flow velocity through the valve assembly  32  increase. In prior art valve assemblies, an increase in pressure drop and flow velocity may rise to levels where it hinders closing of the valve. For example, the low pressure in the gap  58 A may cause a backflow of fluid from higher pressure areas in opposition to the flowpath  58 . Moreover, high pressure drop can cause associated drops in temperature during closing, either through gas expansion or liquid vaporization, that may ultimately prevent closing of the valve. 
         [0021]    When gate  40  is in the almost closed position of  FIG. 3 , the inlet passage  44  is in communication upstream of the flow passage  33 . The outlet passage  44  communicates with the gap  58 A. A portion of the upstream flow contacting the valve upstream side  54  is then diverted into the fluidics passage  44 , where it is then directed into a portion of the bore  42  proximate the valve downstream side  56 . This provides an additional path for higher pressure fluid on the valve upstream side to flow to the gap  58 A, thereby, increasing the pressure in the gap  58 A. Increasing the pressure in the gap  58 A proximate where the flowpath  58  through the valve assembly  32  intersects the downstream line  34  reduces flow from the upstream line  33  into the gap  58 A, that in turn lowers flow velocity in the flow passage  34  to mitigate pressure drop and cooling therein. As such, the resistive force experienced by closing a valve is alleviated. When the valve gate  40  is fully closed the bore  42  is no longer in registration with the flow passage  34  thereby blocking all communication between the upstream flow line  33  and exit of the fluidic passage  44  with the downstream flow line  35 . As such, when the valve gate  40  is closed, fluid will not flow through the fluidic passage  44 . 
         [0022]    Referring now to  FIG. 4 , shown in a perspective view is an example embodiment of the valve gate  40 . Here, the bore  42  is illustrated passing from one side of the valve gate  40  to the other and being intersected by an end of the fluidic passage  44 . Also shown in this embodiment is the largely planar shape of the valve gate  40 . A portion of the stem  46  is shown attached on an upper connection end of the valve gate  40 . Also evident in this embodiment is how the bore  42  is offset from the mid portion of the valve gate  40  leaving a substantially solid configuration on the portion of the valve gate  40  distal from the attachment to the stem  46 . It is through the solid portion of the valve gate  40  of  FIG. 4  where the fluidic passage  44  is formed. 
         [0023]    In an alternative embodiment of the valve assembly  32 A, as shown in  FIG. 5 , a fluidic channel  44 A is illustrated that intersects the bore  42  at an angle so that fluid exiting the fluidic channel  44 A is directed within the bore  42  and towards a side of the bore  42  opposite from the interface of the fluidic channel  44  in the bore  42 . In this example, directing the bypass fluid in this manner towards the opposite side of the bore  42 , rather than the outlet of bore  42  as in  FIG. 3 , creates a pressure differential across the valve gate  40 A to urge it in a closing direction, thereby assisting closing of the valve assembly  32 A. The angle of the passage  44 A relative to the upstream side of the gate  40 A is less than the passage  44  of  FIG. 3 . In the embodiment of  FIG. 3 , the outlet of the passage  44  is approximately equidistant between the upstream and downstream sides of the gate  40 A. A straight line extending from channel  44 A would contact the opposite side of the bore  44 A near the intersection with the downstream side of the gate  40 A. 
         [0024]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, passages  44 ,  44 A can be curvilinear as well as substantially linear. Additionally, embodiments of the valve assembly  32  may exist that do not include a body  36  so that the upstream and downstream sides  54 ,  56  of the valve gate  40  are in contact with a fluid different from the fluid flowing through the valve assembly  32 . In this example, a planar shaped ramp (not shown) may be provided that seals against the upstream side  54  of the gate  40  to prevent the different fluid from entering the passage  44 .