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BACKGROUND 
       [0001]    The present invention relates to subterranean operations and, more particularly, to a method and system for opening and closing a subsurface valve used in conjunction with such operations. 
         [0002]    Hydrocarbons, such as oil and gas, are commonly obtained from subterranean formations that may be located onshore or offshore. The development of subterranean operations and the processes involved in removing hydrocarbons from a subterranean formation are complex. Typically, subterranean operations involve a number of different steps such as, for example, drilling a wellbore at a desired well site, treating the wellbore to optimize production of hydrocarbons, and performing the necessary steps to produce and process the hydrocarbons from the subterranean formation. 
         [0003]    When performing subterranean operations, it may be desirable to close off a well in the event of an uncontrolled condition that may damage property, injure personnel or cause pollution. One of the mechanisms used to close off a well is a Surface Controlled Subsurface Safety Valve (“SCSSV”). An SCSSV typically includes a flapper. The flapper is a closure member that may be pivotally mounted such that it is rotatable between a first “open” position and a second “closed” position. When in the closed position, the flapper may close off the well. However, SCSSVs are often made with many small, specialized parts that are costly to implement and/or replace. 
         [0004]    It would be advantageous to have a fail-safe SCSSV that may be installed without the use of small, specialized parts. This would reduce costs and increase efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  depicts a general view of an SCSSV installed in a wellbore in accordance with an illustrative embodiment of the present disclosure; 
           [0006]      FIGS. 2A and 2B  show an SCSSV in accordance with an illustrative embodiment of the present disclosure; 
           [0007]      FIGS. 3A and 3B  show a flapper valve assembly in accordance with an illustrative embodiment of the present disclosure where the flapper is in an open position; 
           [0008]      FIGS. 4A and 4B  show a flapper valve assembly in accordance with an illustrative embodiment of the present disclosure where the flapper is in a closed position; and 
           [0009]      FIG. 5  shows an exemplary wave spring that may be employed in any of the embodiments of the present disclosure. 
       
    
    
       [0010]    While embodiments of this disclosure have been depicted and described and are defined by reference to examples set forth in the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure. 
       DETAILED DESCRIPTION 
       [0011]    The terms “couple” or “couples,” as used herein are intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect mechanical connection via other devices and connections. The terms “up” or “uphole” as used herein means along the drillstring or the hole from the distal end toward the surface, and “down” or “downhole” as used herein means along the drillstring or the hole from the surface toward the distal end. Further, the terms “up”, “uphole”, “down” and “downhole” are merely used to denote the relative location of different components and are not meant to limit the present disclosure to only a vertical well. Specifically, the present disclosure is applicable to horizontal, vertical, deviated or any other type of well. 
         [0012]    It will be understood that the term “well” is not intended to limit the use of the equipment and processes described herein to developing an oil well. The term also encompasses developing natural gas wells or hydrocarbon wells in general. Further, such wells can be used for production, monitoring, or injection in relation to the recovery of hydrocarbons or other materials from the subsurface. 
         [0013]    Referring now to  FIG. 1 , oil well drilling equipment used in an illustrative drilling and completion environment is shown. A cross-sectional view of a wellbore  116  that has been drilled with casing  128  and tubing  126  in accordance with certain embodiments of the present disclosure is denoted generally with reference numeral  100 . A drilling platform  102  supports a derrick  104  having a traveling block  106  for raising and lowering a drill string (not shown), wireline, slickline, or coiled tubing. An annulus  132  is formed between the casing  128  and the formation  130 . Cement  118  is pumped down the wellbore  116 , e.g., through the interior of the casing  128  and up through the annulus  132  where it sets and holds the casing  128  in place. The cement  118  may be directed downhole using a cement pumping unit (not shown) or other types of rig pumping equipment (not shown), as appropriate. The casing  128  and tubing  126  may be concentric tubes inside the wellbore  116 . An SCSSV  120  may be installed in the wellbore  116  with tubing  126  coupled to each side as shown in  FIG. 1 . In such embodiments, the SCSSV  120  would be semi-permanently installed in the wellbore  116 . In order to remove the SCSSV  120 , the entire string of tubing  126  may be removed from the wellbore  116 . In other embodiments, not shown in  FIG. 1 , the SCSSV  120  may be installed in the wellbore  116  on wireline, coiled tubing, or some other semi-flexible work string. In such embodiments, the SCSSV  120  may be installed in a profile that is communicatively coupled to a control line (not shown) that runs to the surface of the wellbore  116 . 
         [0014]    Turning now to  FIG. 2A , an SCSSV in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference numeral  200 . In the embodiment shown in  FIG. 2A , the flapper  206  is shown in a first open position. The SCSSV  200  includes a rod piston  202  disposed within a housing  204 . For illustrative purposes, SCSSV  200  of  FIG. 2A  may have a first distal end  202 A, a middle portion  202 B and a second distal end  202 C. The rod piston  202  may be coupled to a tubing member  216 . A seat  214  in a valve housing (not shown) may surround the tubing member  216 . A flapper  206  may be pivotally mounted to a first connector beam  210  such that the flapper  206  is rotatable between an open position and a closed position. In the embodiment shown in  FIG. 2A , the flapper  206  is shown in an open position. 
         [0015]    In operation of the SCSSV  200 , a control line  220  may be coupled to the rod piston  202 . The control line may deliver pressure to the rod piston  202  from the surface or from a desirable subsurface location. Pressure from the rod piston  202  may hold the tubing member  216  in place and in engagement with the flapper  206 . Thus, when the flapper  206  is in the open position, it may be held in contact with the tubing member  216 . The flapper  206  is shown in further detail in  FIGS. 2A-2B  and  FIGS. 3A-3B . If it is desirable to close the flapper  206 , the pressure applied to the rod piston  202  may be reduced or eliminated. In some embodiments, pressure may be applied to the control line  220  which communicates with the rod piston  202  at surface or from a desirable subsurface location prior to deployment of the SCSSV  200 . Pressure may be maintained throughout deployment to verify integrity of the control system and SCSSV  200 . Thus, in order to close the flapper  206 , the operator may alter the pressure applied to the control line at the surface. In other embodiments, the flapper  206  may be mechanically propped open during installation. Thus, in order to close the flapper  206  in those embodiments, the operator may retract the mechanical prop to the surface. Either of these scenarios may allow the spring  202 B to partially decompress, allowing the tubing member  216  to move uphole. The tubing member  216  thus may be disengaged from the flapper  206 . This in turn may allow a wave spring  318  to partially decompress, causing the flapper  206  to close. Thus, the wave spring  318  may rotate the flapper between its open and closed positions. This is shown in further detail in  FIGS. 2B, 3A, and 3B . An exemplary wave spring  500  is shown in further detail in  FIG. 5 . 
         [0016]    The wave spring  318  may be made from flat wire, and may include waves that are in contact with each other, as shown in further detail by the exemplary wave spring  500  in  FIG. 5 . The waves may deflect during compression. A coiled spring, by contrast, may be manufactured from round or square wire that is coiled into a desired shape. As a coiled spring is compressed, the coils get closer together. There are several advantages associated with using the wave spring  318  rather than a coiled spring in an SCSSV application. First, the shorter size of the wave spring  318  compared to a coiled spring that is able to deliver the same operating load makes the wave spring  318  more desirable because of the limited space available in the SCSSV and in the wellbore  116 . In other words, the wave spring  318  may be able to provide the same operating loads as a coiled spring but using a shorter design. Thus, the wave spring  318  may provide a greater operating load than a coiled spring of the same length and diameter. Second, use of a wave spring  318  allows the motion of the flapper  206  to be more controlled and adjustable as compared to using a coiled spring. The wave spring  318  may be of any length, so that the speed and motion of the flapper  206  closure may be controlled as desired. Third, an SCSSV that includes a wave spring  318  as provided in the present disclosure requires fewer components than previous SCSSVs that included a coiled spring. Therefore, the SCSSV is less expensive to replace and manufacture. 
         [0017]    Turning now to  FIG. 2B , the flapper  206  of  FIG. 2A  is shown in the closed position. When the flapper  206  is in the closed position, it may engage with the seat (not shown in  FIG. 2B ), creating a seal in the wellbore. 
         [0018]    Turning now to  FIGS. 3A and 3B , a flapper valve assembly in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference numeral  300 .  FIG. 3B  depicts a cross-sectional view. In the embodiment shown in  FIGS. 3A and 3B , the flapper  206  is shown in the open position. In certain illustrative embodiments, a collapsible member  308  may be coupled to the flapper  206 . The connector beam  210  may be coupled to the collapsible member  308 . The collapsible member  308  is shown in a collapsed position. A wave spring housing  312  may be coupled to the connector beam  210 . The wave spring housing  312  includes a wave spring  318 , which may be in an at least partially compressed position when the flapper  206  is in the open position. In other words, the wave spring housing  312  may surround or contain the wave spring  318 . The wave spring  318  may be in a compressed position, and therefore may exert force on the connector beam  210  and the collapsible member  308 . However, the tubing member  216  may be engaged with the flapper  206  and may prevent it from closing. Thus, the tubing member  216  is engaged with the flapper  206  when the flapper  206  is in the open position, as shown in  FIGS. 3A and 3B . 
         [0019]    In operation of the system  300 , when a well operator desires to shut off the well, pressure may be removed from the rod piston  202  at the surface. Thus, the tubing member  216  may move uphole, allowing the tubing member  216  to disengage from the flapper  206  and thus removing support from the flapper  206 . This may allow the wave spring  318  to partially decompress and the flapper  206  to close, engaging with the seat  214 . 
         [0020]    Turning now to  FIGS. 4A and 4B , a flapper valve assembly in accordance with another illustrative embodiment of the present disclosure is denoted generally with reference numeral  400 .  FIG. 4B  depicts a cross-sectional view. In the embodiment shown in  FIGS. 4A and 4B , pressure has been removed from the rod piston  202 , allowing the tubing member  216  to disengage from the flapper  206 . Thus, the force exerted from the wave spring  318  on the connector beam  210  and the collapsible member  308  may allow the collapsible member  308  to extend, pushing the flapper  206  into a closed position. Thus, in  FIGS. 4A and 4B , the wave spring  318  is shown in a partially decompressed position, the collapsible member  308  is shown in an extended position, and the flapper  206  is shown in a closed position such that it is engaged with the seat  214 . 
         [0021]    In existing SCSSVs, debris may prevent the flapper closure mechanism from functioning properly and may have prevented flapper  206  from engaging with the seat  214  and closing completely. In contrast, in the improved design disclosed herein, the wave spring housing  312  and wave spring  318  may be located uphole of the flapper  206 . As a result, unlike typical prior art SCSSV designs, the flapper closure mechanism disclosed herein is located outside of the direct debris path of the wellbore  116  because the wave spring housing  312  and wave spring  318  may be located uphole of the flapper  206 . 
         [0022]    As would be appreciated by those of ordinary skill in the art, the methods and systems disclosed herein may be applicable to more than just SCSSVs. Accordingly, any reference to a “tubing member” is made for illustrative purposes only and is intended to generically refer to a part of a tool that is actuated by a rod piston of a control system. 
         [0023]    The present invention is therefore well-adapted to carry out the objects and attain the ends mentioned, as well as those that are inherent therein. While the disclosure has been depicted, described and is defined by references to examples of the disclosure, such a reference does not imply a limitation on the disclosure, and no such limitation is to be inferred. The disclosure is capable of considerable modification, alteration and equivalents in form and function, as will occur to those ordinarily skilled in the art having the benefit of this disclosure. The depicted and described examples are not exhaustive of the disclosure. Consequently, the disclosure is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.

Summary:
An apparatus is disclosed herein, including a connector beam, a flapper, a collapsible member coupled to the connector beam and to the flapper, and a wave spring coupled to the connector beam. The flapper may be pivotally mounted to the connector beam such that it is rotatable between an open position and a closed position. The wave spring rotates the flapper between the open and closed positions. A method of sealing a wellbore is disclosed herein, including the steps of: retracting a tubing member, partially decompressing a wave spring coupled to a connector beam after retracting a tubing member, collapsing a collapsible member coupled to the connector beam and to the flapper, and engaging a flapper with a seat positioned in a wellbore.