Abstract:
A subsurface safety valve has a closure sleeve or rod mounted below the closure mechanism. Control signal pushes the sleeve up (uphole) or down (downhole), whichever is applicable, which causes the closure element to rotate (or slide, or otherwise translate) to its open position. A loss of control signal allows the closure spring to push the sleeve or rod downhole (or uphole, whichever is appropriate). This movement causes the closure element to be driven to its closed position against the seat.

Description:
PRIORITY INFORMATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/334,321 filed on Nov. 30, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The field of this invention is surface controlled subsurface safety valves and more particularly actuating mechanisms for the closure element.  
         BACKGROUND OF THE INVENTION  
         [0003]    Traditionally, sub-surface safety valves (SSSV) have had a flat or curved closure element known as a flapper, or a ball-shaped closure element, which rotates approximately 90 degrees, from opened to closed positions, under the bias of a closure spring generally mounted to the hinge holding the closure element to the valve body. The closure spring acts on the closure element after a flow tube or other actuating element is retracted. The flow tube and actuator mechanism are typically mounted above the closure element and inside the seat against which the closure element contacts for closure. The flow tube and actuator are biased in the uphole (closed) direction by a separate spring, commonly known as the power spring, and are driven down against the spring bias and into the closure element by pressure (or other appropriate signal) delivered through a control line extending to the SSSV from the surface. As long as control line pressure (or other appropriate signal) is applied to the actuator the power spring bias on the flow tube is overcome and the flow tube stays in a down (open) position. In the down position of the flow tube, the closure element is rotated against the bias of the closure spring, and away from contact with the mating seat. The closure element winds up behind or adjacent to the flow tube when the SSSV is open. If control line pressure (or signal) is lost, the power spring bias on the flow tube pushes it and the actuator mechanism uphole. This movement, in turn, allows the closure spring, acting on the closure element, to rotate the closure element on its hinge in an uphole direction until it makes contact with the mating seat.  
           [0004]    Traditionally, the flow tube and the actuator mechanism have always been above the closure element. This required the bias (power) spring on the flow tube to support the weight and overcome friction of the flow tube as well as to bias it uphole to allow the closure element to shut. Since the flapper had to rotate 90 degrees in the uphole direction to close the SSSV, a hinge closure spring was always necessary to create that motion to overcome the weight of the flapper and apply a contact force to it to hold it against its mating seat. As a result of this configuration, the overall length of SSSVs was longer than it needed to be. In low pressure applications, there was concern about the ability of the closure spring on the flapper to apply a sufficient closing force against the mating seat to keep the SSSV closed. This concern also arose when there was sand, paraffin, asphaltine or other friction increasing compounds in the well fluids, creating doubt as to the available closure force on the flow tube from its power spring. If the flow tube gets stuck, the SSSV cannot close.  
           [0005]    The present invention presents a unique design where the actuator mechanism is below the flapper. The power spring acts on a sleeve or rod operably connected to the flapper on an opposed side of the pivot mounting. The spring pushes the sleeve or rod downhole to rotate the flapper closed, upon loss of control line signal. The details and other features of the invention will become more readily apparent from a detailed review of the description of the preferred embodiment, which appears below.  
         SUMMARY OF THE INVENTION  
         [0006]    A subsurface safety valve has a closure sleeve or rod mounted below the closure mechanism. Control signal pushes the sleeve up (uphole) or down (downhole), whichever is applicable, which causes the closure element to rotate (or slide, or otherwise translate) to its open position. A loss of control signal allows the closure spring to push the sleeve or rod downhole (or uphole, whichever is appropriate). This movement causes the closure element to be driven to its closed position against the seat. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a sectional elevation view of the safety valve of the present invention in the closed position using an annular sleeve to actuate the flapper  
         [0008]    [0008]FIG. 2 is an alternative to FIG. 1 using a rod piston to actuate the flapper;  
         [0009]    [0009]FIG. 3 is a section view of a rack and pinion assembly for operating the flapper  
         [0010]    [0010]FIG. 4 is an alternative to FIG. 1 illustrating an actuator which moves in the opposite direction as that of FIG. 1, yet accomplishes the same task—moving the closure element to the closed position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    Referring to FIG. 1, the flapper  10  is shown in the closed position against a seat  12  located in body  14  of the SSV. The flapper  10  is connected to body  14  at pin  16  and hinge  17 . Extending away from the sealing portion of the flapper  10  in contact with the seat  12  is an arm  18 . Arm  18  extends into a groove  20  in annular piston  22 . Spring  24  acting against stop  26  biases annular piston  22  downwardly. Seals  28  and  29  define a variable volume annular cavity  30 . Arrow  32  shows schematically how the control line communicates hydraulic pressure (signal) from the well surface to overcome the downward bias of spring  24 . Those skilled in the art will appreciate that the signal can be surface or downhole generated and can take various forms. The control system can involve electro-hydraulic (U.S. Pat. No. 6,269,874), electromechanical (U.S. Pat. No. 6,253,843), and photo-hydraulic techniques. When enough pressure is applied or some other signal is transmitted such as electromechanical, acoustic, or electromagnetic, for example, the annular piston moves up and rotates arm  18  about pin  16  to rotate the flapper  10  away from seat  12 . If pressure or other signal is removed or lost in the control line represented by arrow  32  or due to leakage of seal  28  or for other reasons, the spring  24  will push the annular piston downhole. Groove  20  will rotate arm  18  clockwise to forcibly bring the flapper  10  into contact with the seat  12 .  
         [0012]    The arm  18  extending into the groove  20  can be replaced with a rack and pinion design, as shown in FIG. 3. Annular piston  22 ′ has teeth  34  which extend into contact with pinion  36 . Pinion  36  is attached or made integral with the flapper  10 . In each instance movement of the annular piston  22  or  22 ′ in opposed directions results in a desired 90 degree rotational movement of the flapper  10 . The torsion spring for flapper closure in prior designs has been eliminated. In this design there is only one spring  24 . Due to the orientation of the annular piston  22  below the flapper  10 , the weight of the annular piston  22  adds to the closure force of spring  24  on flapper  10 . Additionally using arm  18  extending into groove  20  or the rack and pinion connection shown in FIG. 3, the stroke length of the annular piston  22  is significantly reduced as compared to prior designs having a flow tube and actuator above the flapper. In the prior designs, the stroke length had to be longer to get the flow tube down far enough so that the entire flapper would be disposed behind it. For a similar size SSV the overall length of the present design could be significantly shorter since the stroke length has been reduced from several inches for a traditional flow tube to less than an inch for the versions of the present invention shown in FIGS. 1 and 3.  
         [0013]    [0013]FIG. 2 is a schematic illustration showing the use of a rod piston  38  instead of the annular piston  22  shown in FIG. 1. The part positions and operation are otherwise the same as described for the FIG. 1 embodiment. The rod piston  38  can have a slot  40  into which arm  18 ′ is engaged for forced movement of the flapper  10 ′ in opposed directions. A rack and pinion design, as described above, can also be employed.  
         [0014]    Those skilled in the art will appreciate that the present invention allows SSVs to be made shorter and more economically. Fewer moving parts also imply increased reliability. The torsion spring, the flow tube, and the components linking the piston to the flow tube are eliminated. A single spring forcibly moves the flapper and the piston to the closed position. The closure spring  24  does not have to support the weight of the piston  22  or  38  when moving the flapper  10  to its closed position. Control line pressure or other signal moves the piston  22  or  38 , either of which is linked directly to the flapper for application of a moment to rotate it to the open position. Those skilled in the art will appreciate that a variety of connections can be used between a piston mounted below the flapper and the flapper, as being contemplated by the invention. While direct contact, such as arm  32  extending into groove  20  is preferred, indirect contact is also envisioned. For example, an arrangement of components can be envisioned such that the piston is urged in the opposite direction as that described above. In this case, indirect contact between the arm (or sleeve) and the closure element may be appropriate.  
         [0015]    Those skilled in the art will appreciate that the closure element can be a flapper, a ball, a sliding gate or any other device that effects closure. Reference to one type of closure element is intended to encompass any of the known alternative designs. The actuator can be linked to the closure member directly such as when the rack and pinion mechanism illustrated in FIG. 3 is employed. The actuator can be linked to the closure member indirectly such as when the actuator is configured to move uphole to close the closure element, as shown in FIG. 4. The disclosed embodiments allow the safety valve to be shorter in overall length and have fewer moving parts than prior designs, thus offering greater reliability. Another advantage is that a single biasing source, such as a closure spring operates both the actuator and the closure element.  
         [0016]    The full extent of the invention is delineated in the claims below.