Abstract:
A system for completing a well bore, comprises, a string having a housing, a valve having a valve seat positioned within the housing, the valve seat having an inner channel, a flapper pivotally coupled to the valve seat in which the flapper is configured to move from a first open position to a second closed position such that the inner channel is at least partially obstructed. An energy dampening device is coupled to the valve seat, such that the energy dampening device is configured to at least partially absorb an impact of the flapper on the valve seat.

Description:
BACKGROUND 
       [0001]    The present application relates generally to the field of tools for completing subterranean wells. In particular, the application relates to subsurface valves. 
         [0002]    Hydrocarbon fluids such as oil and gas are found in subterranean portions of geological formations or reservoirs. Wells are drilled into these formations for extracting the hydrocarbon fluids. Completed wells are often equipped with one or more safety valves. The safety valve provides a failsafe in the event of a catastrophic event at the surface or along the well bore above the safety valve. 
         [0003]    Safety valves are commonly flapper valves which open downwards. Pressure of the wellbore fluids bias the flapper towards the closed position. A sleeve inside the flapper valve keeps the valve open when the well is in operation. The sleeve may be maintaned in position by hydraulic pressure from the surface. Should the wellhead be lost or, in the case of a deep sea well, the fluid lines from the sea bed to the platform be compromised, the loss of hydraulic pressure against the sleeve would result in the sleeve sliding upwardly and the safety valve will close to prevent further flow of wellbore fluids out of the well. 
         [0004]    Prior to producing hydrocarbon fluids, wells must often be completed by one or more of a variety of processes. The completion processes may include perforating the well casing and/or reservoir (i.e., by use of shape charges), fracturing the formation, applying chemical treatments to the formation, gravel packing the well, or other processes. 
         [0005]    In many applications, a single well bore may pass through more than one reservoir. In these cases, it may be desirable to complete more than one well bore zone. Accordingly, a first production zone may be completed at a down hole location. Then a second production zone may be completed in a position above (i.e., closer to the surface) the first production zone. When carrying out the completion processes above the first production zone, completion fluids (i.e., gravel slurries, propants, acidifiers, and other completion fluids) from the second production zone may migrate down hole. Additionally, the addition of completion fluids in the well bore region proximate to the second production zone may pressurize the well bore and cause completion fluids from well bore region proximate to the second production zone to migrate to the well bore region proximate to the first production zone and ultimately into the first production zone of the formation. Also, the pressurization of the well bore may cause completion fluids remaining in the well bore region proximate to the first production zone to migrate into the first production zone of the formation. 
         [0006]    The migration of undesired completion fluids into a production zone may damage the formation and reduce the productivity of the well. Accordingly, it may be desirable to isolate the first production zone from the second production zone during the time when the first production zone has been completed and the second production zone is undergoing completion processes. This isolation may be carried out by the use of a flapper valve. 
         [0007]    In both the case of isolation and safety valves, the flapper valve may be damaged if it is closed too harshly. This is especially true for safety valves where a sudden loss of hydraulic pressure on the sleeve could result in the slamming or forceful impact of the flapper against a flapper seat. This may damage one or more of the valve components and result in a fluid losses. Accordingly, there is a need for a device to absorb the energy of a sudden valve closure to prevent or mitigate damage to the valve. 
       SUMMARY 
       [0008]    One embodiment of the invention relates to a system for use in a wellbore. The system comprises a string having a housing, a valve having a valve seat positioned within the housing, the valve seat having an inner channel, a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position in which the inner channel is obstructed, and an optional sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. An energy dampening device is coupled to the valve seat, such that the energy dampening device is configured to at least partially absorb an impact of the flapper on the valve seat. 
         [0009]    Another embodiment relates to a system for conveying wellbore fluids. The system comprises a string having a housing, a safety valve having a valve seat positioned within the housing, the valve seat having an inner channel, a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position in which the inner channel is obstructed, and an optional sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. An energy dampening device is coupled to the valve seat, and the energy dampening device is configured to at least partially absorb an impact of the flapper on the valve seat. 
         [0010]    Yet another embodiment relates to a valve for use in a wellbore comprising a valve seat, the valve seat having an inner channel, a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position in which the inner channel is obstructed, and an optional sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. An energy dampening device is coupled to the valve seat and the energy dampening device is configured to at least partially absorb an impact of the flapper on the valve seat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a cross-sectional view of wellbore system. 
           [0012]      FIG. 2  is a cross-sectional view of a flapper valve. 
           [0013]      FIG. 3  is a perspective view of a flapper valve. 
           [0014]      FIG. 4  is another cross-sectional view of a flapper valve. 
           [0015]      FIG. 5  is a cross-sectional view of the flapper valve. 
           [0016]      FIG. 6  is another cross-sectional view of a flapper valve. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring to  FIGS. 1 ,  2 , and  3 , a system  10  for use in a down hole wellbore application includes a housing  12 , a valve  14  and a sleeve  16 . Housing  12  at least partially encloses channel  13 . Valve  14  includes a seat  18  and a flapper  22 . Valve  14  may be positioned in region  20  of housing  12 . In some embodiments, the valve seat may be formed as a single unitary body with the housing. Region  20  comprises a region having a greater interior diameter than adjacent regions. Flapper  22  may be generally curved so that when the valve is in the open position the cross-section of flapper  22  is curved and generally concentric with housing  12 . Valve seat  18  may be generally cylindrical. Flapper  22  may be pivotally coupled to valve seat  18 . By coupled, it is understood that flapper may be directly coupled to valve seat, or indirectly coupled by an intermediate member that is coupled to both the flapper and the valve seat (i.e., a flapper seat). 
         [0018]    Sleeve  16  is positioned within valve  14  and prevents flapper  22  from closing against valve seat  18 . Sleeve  16  may be specifically included as a component of system  10 . An energy absorption device  24  is disposed between valve  14  and housing  12 . In the case of a subsurface safety valve, upward pressure from wellbore fluids will cause valve  14  to close in the absence of sleeve  16 . When valve  14  is closed, flapper  22  pivots about hinge  26  to mate with seat  18 . The impact of flapper  22  on seat  18  may result in damage to the flapper, the seat, or other wellbore devices. Damage to valve  14 &#39;s components may result in failure of valve  14  to retain wellbore fluids. 
         [0019]    Housing  12  includes a projection  28  defining a shelf  30 . Seat  18  includes an extension  32  that, with projection  28  partially defines region  34 . In some embodiments, extension  32  may be sealingly and translatably coupled to projection  28 . Energy absorption device  24  may be disposed within region  34 . In the embodiment shown, energy absorption device  24  may comprise a first Belleville spring  36  and a second Belleville spring  38 . Springs  36  and  38  are positioned such that springs  36  and  38  may be deflected when region  34  is compressed by lateral movement of the valve seat  18  with respect to housing  12 . The deflection and subsequent return of springs  36  and  38  allows for the dissipation of impact energy from flapper  22  closing on seat  18 . In alternative embodiments, a single Belleville spring may be used. In yet other embodiments, more than two Belleville springs may be used depending on the design needs for the wellbore. 
         [0020]    Referring to  FIG. 4 , a system for use in a down hole wellbore application includes a housing  112 , a valve  114  and a sleeve  116 . Valve  114  includes a seat  118  and a flapper  122 . Valve  114  may be positioned in region  120  of housing  112 . Region  120  comprises a region having a greater interior diameter than adjacent regions. Flapper  122  may be generally curved so that when the valve is in the open position the cross section of flapper  122  is curved and generally concentric with housing  112 . Flapper  122  may be hingedly coupled to the valve seat  118  through a hinge  126 . 
         [0021]    Housing  112  includes a projection  128  defining a shelf  130 . Seat  118  includes an extension  132  that, with projection  128  partially defines region  134 . In some embodiments, extension  132  may be sealingly and translatably coupled to projection  128 . Energy absorption device  124  may be disposed within region  134 . In the embodiment shown, energy absorption device  124  comprises a coil spring  140 . Spring  140  is positioned such that springs  140  may be deflected when region  134  is compressed by lateral movement of the valve seat  118  with respect to housing  112 . The deflection and subsequent return of spring  140  allows for the dissipation of impact energy from flapper  122  closing on seat  118 . In alternative embodiments, other resilient devices including, but not limited to, multiple springs or types of springs may be used in combination. 
         [0022]    Referring to  FIG. 5 , a system for use in a down hole wellbore application includes a housing  212 , a valve  214  and a sleeve  216 . Valve  214  includes a seat  218  and a flapper  222 . Flapper  222  may be rotatively coupled to seat  218  via hinge  226 . Valve  214  may be positioned in region  220  of housing  212 . Region  220  comprises a region having a greater interior diameter than adjacent regions. Flapper  222  may be generally curved so that when the valve is in the open position the cross section of flapper  222  is curved and generally concentric with housing  212 . 
         [0023]    Housing  212  includes a projection  228  defining a shelf  230 . Seat  218  includes an extension  232  that, with projection  228  partially defines region  234 . In some embodiments, extension  232  may be sealingly and translatably coupled with projection  228 . Energy absorption device  224  may be disposed within region  234 . In the embodiment shown, energy absorption device  224  comprises a resilient ring  242  which may be composed of a polymer, such as an elastomeric or plastic material, among others. In other embodiments, a metal ring or other rigid material may be used such that the ring comprises a material having a low bulk modulus relative to the housing or the seat. Ring  242  is positioned such that ring  242  may be deflected and/or compressed when region  234  is compressed by lateral movement of the valve seat  218  with respect to housing  212 . The deflection and subsequent return of spring  242  allows for the dissipation of impact energy from flapper  222  closing on seat  218 . In alternative embodiments, multiple springs or types of springs may be used in combination. 
         [0024]    Referring to  FIG. 6 , a valve  314  comprises a valve seat  318 , a flapper seat  319 , and a flapper  322 . Flapper  322  is pivotally coupled to flapper seat  319  by a hinge  326 . Flapper seat  319  is in turn coupled to valve seat  318 . Valve  314  includes an energy absorption device  324 . Energy absorption device  324  comprises a plunger  346  coupled to a spring  348  and is recessed into flapper seat  319 , or, in other embodiments, valve seat  318 . Plunger  346  extends beyond valve seat  318  and is configured to contact surface  350  of flapper  322  at a point prior to complete closure of valve  314 . Spring  438  may be compressed and/or deflected to absorb the impact energy of flapper  322  as it closes on valve seat  318 . 
         [0025]    Although the foregoing has been described with reference to exemplary embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope thereof. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. 
         [0026]    The present subject matter described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. In addition, for example, unless specifically otherwise noted, the claims reciting components coupled, mounted, or otherwise interacting together, may do so either directly or indirectly through one or more intermediate components. 
         [0027]    Many other changes and modifications may be made to the present invention without departing from the spirit thereof. The scope of these and other changes will become apparent from the appended claims. The steps of the methods described herein may be varied, and carried out in different sequences.