Abstract:
Disclosed herein is a device that relates to a non-return valve. The valve comprising, a valve seat, a valve piston in operable communication with the valve seat. The valve further comprising, a first seal disposed at the piston to interact with the valve seat, and a second seal positioned at the piston to interact with the valve seat temporally after the first seal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to G.B. provisional application, 0515071.9, filed Jul. 22, 2005, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a non-return valve and particularly to a non-return injection valve for use downhole. 
     BACKGROUND OF THE INVENTION 
     Injection valves are used where an operator wishes to inject a fluid into a pressurized downhole environment. The fluid may, for example, be water or gas which is to be injected into the formation to maintain reservoir pressure. 
     Some conventional injection valves comprise a plug biased by a spring to a position in which the valve outlet is sealed closed. To inject fluid through the valve, the fluid is pressurized against the plug until there is sufficient fluid pressure to overcome the closing force of the spring, permitting the valve to open. 
     There are disadvantages associated with this type of arrangement. For example, when the fluid pressure has built up sufficiently to overcome the spring closing force, and the plug moves to open the outlet, there is an immediate release of pressure as fluid flows through the valve. In this situation the fluid pressure can drop sufficiently to permit the valve to close under the action of the spring. The pressure then builds up behind the plug and an oscillation cycle of valve opening and closing can be established. This oscillation cycle causes vibration in the string and can lead to damage of the sealing interface between the plug and the valve housing. Additionally, as the plug is opened, and the pressurized fluid passes between the plug and the housing, the movement of the fluid can erode the valve and the surrounding components such as the bore casing or tubing. 
     It is an object of the present invention to obviate or mitigate at least one of the aforementioned disadvantages. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed herein is a device that relates to a non-return valve. The valve comprising, a valve seat, a valve piston in operable communication with the valve seat. The valve further comprising, a first seal disposed at the piston to interact with the valve seat, and a second seal positioned at the piston to interact with the valve seat temporally after the first seal. 
     Further disclosed herein is a downhole non-return valve. The non-return valve comprising, a housing defining a valve inlet and a valve outlet, a plug moveable between an open position and a fully sealed position. Additionally comprising a biasing member urging the plug towards the fully sealed position wherein the urging force of the biasing member is sufficient to move the plug to a partially sealed position but is selected to be insufficient to move the plug to a fully sealed position. 
     Further disclosed herein relates to a downhole non-return valve. The valve comprising, a housing defining a valve inlet and valve outlet, and a plug moveable between an open position and a fully closed position. The valve further comprising a sacrificial member adapted to divert fluid injected through the valve axially along an external surface of the valve housing. 
     Further disclosed herein is a method that relates to injection fluid into a well bore through a non-return valve. The method comprising, injecting fluid into a non-return valve the valve being in a fully sealed configuration, pressurizing the fluid sufficiently to overcome a closing force comprising a combination of a biasing force and well pressure to open a valve outlet. The method further comprising, injecting fluid through the valve outlet into a well and ceasing injection of the fluid thereby permitting the closing force to fully seal the valve outlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  is a perspective view of a non-return injection valve in the run-in configuration according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional side view of the valve of  FIG. 1  in the run-in configuration; 
         FIG. 3  is a partially cut-away perspective view of the valve of  FIG. 1  shown in the run-in configuration; 
         FIG. 4  is a partially cut-away perspective view of the valve of  FIG. 1  in a partially open configuration; 
         FIG. 5  is a partially cut-away perspective view of the valve of  FIG. 1  in an open configuration; 
         FIG. 6  is a partially cut-away perspective view of the valve of  FIG. 1  in a partially sealed configuration; 
         FIG. 7  is a partially cut-away side view of the valve of  FIG. 1  in a partially sealed configuration; 
         FIG. 8  is an enlarged closed-up view of the seals and part of the housing of  FIG. 7 ; 
         FIG. 9  is a partially cut-away perspective view of the valve of  FIG. 1  in a fully sealed configuration; and 
         FIG. 10  shows a partially cut-away side view of the valve of  FIG. 1  in a fully sealed configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of several embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring firstly to  FIG. 1 , there is shown a perspective view of a non-return injection valve generally indicated by reference numeral  10  in a run-in-configuration according to an embodiment of the present invention. The internal arrangement of the injection valve  10  can be seen more clearly with reference to  FIG. 2 , a cross-sectional side view of the non-return injection valve  10  of  FIG. 1  in the run-in-configuration. 
     The valve  10  comprises a housing  12  having an upper housing portion  14  and a lower housing portion  16 . The housing  12  defines a housing inlet  18  and a housing outlet  20 . The housing outlet  20  is partially covered by a sacrificial shield  21 . 
     Contained within the housing  12  is an injection valve plug  22  and a spring  24 . The plug  22  comprises a shaft  25 , a packing mandrel  26  and an end cap  27 . The packing mandrel  26  and the end cap  27  are fixed to the shaft  25  by means of rivet pins  28 . 
     The plug  22  further comprises a shear screw ring  30  defining a groove  32 , which is adapted to receive a number of shear pins  34  of which only one is shown for clarity. The shear pins  34  secure the valve  10  in the run-in-configuration during transit and location downhole and permit a pressure application to a pre-determined rate to test the correct placement and setting of the hanging device. 
     The sacrificial shield  21  diverts the flow of fluid from the outlets  20  axially along the external surface  23  of the lower housing portion  16 . This prevents erosion of the surrounding bore casing (not-shown) and ensures that any erosion which occurs will take place on the sacrificial shield  21 . 
     Finally, the lower housing portion  16  defines well fluid inlet ports  40 , the purpose of which will be discussed in due course. 
     Referring now to  FIG. 3 , there is shown a partially cut away perspective view of the non-return injection valve  10  of  FIG. 1  shown in the run-in configuration. As can be seen from this Figure, the plug  22  is located in the fully sealed position in that the plug  22  is preventing fluid from flowing between the housing inlet  18  and the housing outlet  20 . In this configuration, both the wiper seal  38  and the V-packing seal  36  engage an internal surface  42  of the upper housing portion  14  and the seal surface  46  engages the seal seat  48 . Additionally, the shear screws  34  are shown engaged with the shear screw ring  30 . 
     As fluid is pumped into the valve  10 , the pressure being applied to the plug face  50  increases to a point when the pressure is sufficient to shear the screws  34  and move the plug  22 . 
     Referring now to  FIG. 4 , there is shown a partially cut-away view of the valve of  FIG. 1  in a partially open configuration. In this Figure, fluid pressure acting on the plug face  50  has increased sufficiently to overcome the combination of the pressure applied by the spring  24 , the external well pressure and the force retaining the plug  22  in the run-in position by the shear screws  34 . To get to this point, the shear screws  34  shear freeing the plug  22  to move in the direction of the arrow. 
       FIG. 5  shows a partially cut-away perspective view of the valve  10  of  FIG. 1  in an open configuration. In this configuration, the outlet ports  20  are fully open and fluid can flow through the outlet  20  in the direction indicated by the small arrows. The plug  22  is held in the open configuration by the fluid pressure, indicated by the large arrow. 
     The sacrificial shield  44  diverts the flow of fluid from the outlets  20  axially along the external surface of the lower housing portion  16 . This prevents erosion of the surrounding bore casing (non-shown) and ensures that any erosion which occurs will take place on the sacrificial shields  44 . 
     In this fully open configuration, it will be seen that the shear screw ring  30  has moved under gravity from the position shown in  FIG. 3  to a position on which it is abutting the end cap  27 . The purpose of this movement will be discussed in due course. 
     It will also be noted that the well fluid inlet ports  40  are covered by a lower end portion of the packing mandrel  26 , preventing well fluids entering the lower housing portion  16  and acting on the plug  22 . 
     When the plug  22  is in this open configuration, the wiper seal  38  and the V-packing seal  36  are contained within the lower housing portion  16 . The lower housing portion  16  has a slightly larger internal bore than the upper housing portion  14  such that the V-packing seal  36  does not rub and wear on the internal surface of the lower housing portion  16 . The wiper seal  38  does engage the lower housing portion  16  protecting the V-packing seal  36  from the injected fluid and any circulating debris. 
     Referring to  FIG. 6 , a partially cut-away perspective view of the valve of  FIG. 1  in a partially sealed configuration. In this Figure, the pressure applied by the well fluid has been removed, and the plug  22  has moved in the direction of the arrow towards a partially sealed configuration under the action of the spring  24 . The partially sealed configuration is better seen in  FIG. 7 , a partially cut-away side view of the valve  10  of  FIG. 1  in the partially sealed configuration and  FIG. 8  an enlarged close-up view of the seals and part of the housing  12  of  FIG. 7 . 
     Referring to  FIGS. 7 and 8 , it can be seen that in the partially sealed configuration, the plug  22  has been moved sufficiently by the spring  24  for the wiper seal  38  to engage the internal surface of the upper housing portion  14 . In this configuration, the valve outlet  20  is sealed sufficiently by the wiper seal  38  to prevent ingress of well fluid and the well fluid inlet ports  40  (visible on  FIG. 7 ) are no longer covered by the packing mandrel  26 , permitting well fluid to enter the lower housing portion  16  and act on the packing mandrel  26 . 
       FIG. 9  shows the plug  22  of  FIG. 1  in the fully sealed configuration. The plug  22  has moved from the partially sealed configuration shown in  FIGS. 7 and 8  to the fully sealed configuration shown in  FIG. 9  by the action of well pressure. As indicated by the arrows, well fluid has entered the well fluid inlet ports  40  and the valve outlet  20  and is acting on the packing mandrel  26 . In the absence of a counter pressure on the plug face  50 , the well pressure is sufficient to move the plug  22  to the fully sealed configuration in which both the wiper seal  38  and the V-packing seal  36  are engaged with the upper housing portion internal surface  42 , and the seal surface  46  is engaged with the seal seat  48 . 
     As the plug  22  moves from the partially sealed configuration to the fully sealed configuration, the wiper seal  38  cleans the upper housing portion internal surface  42  ensuring a good seal is created between the internal surface  48  and the V-packing seal  36 . 
     It can be also seen from  FIG. 9  that the shear screw ring  30  has not re-entered the housing  12 . This can be more clearly seen in  FIG. 10 . 
       FIG. 10  shows a partially cut-away side view of the valve  10  of  FIG. 1  in the fully sealed configuration. In this Figure the position of the shear screw ring  30  on the plug  22  outside of the housing  12  can most clearly be seen. This arrangement is adopted to prevent the stubs of the shear screws  34  fouling on the plug  22  as it moves to the fully sealed configuration. If the shear screws  34  did foul on the plug  22 , which may occur if a moveable shear screw ring  30  was not used, the fouling may be sufficient to prevent the metal seal  44 , the wiper seal  38  and the V-packing seals  36  from obtaining their optimum sealing position to fully seal the valve  10 . 
     Various modifications may be made to the described embodiment without departing from the scope of the invention. For example, it will be understood that although the seal surface and the seal seat are shown machined respectively into the surface of the plug and the housing, they could equally be formed on separate elements which are inserted into the surface of the plug and/or the housing. Similarly, although the valve is shown with the sacrificial shields, these are not essential to the smooth running of the valve and could be omitted. Furthermore, the V-packing seals may be replaced with a Zertech™ Deformable Z-seal which could be energized due to the effect of piston and pressure differential. 
     Those of skill in the art will recognize that the above described embodiment of the invention provides a non-return valve which permits fluid to be injected into a downhole environment at a reduced pressure and with a reduced possibility of oscillation cycles being established within the valve. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.