Abstract:
A subsurface safety valve is operable to close a fluid flow path by virtue of an axially movable flow sleeve. The valve includes a recockable linear actuator and a latch mechanism so that the valve can be moved from an open to a closed position as a result of axial movement of the flow sleeve without overcoming the pressure head and frictional forces currently encountered in conventional safety valves.

Description:
[0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/593,927 with a filing date of Feb. 2, 2012. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This application is directed to a subsurface safety valve system for use in drilling oil or gas wells. Such valves are commonly used to prevent flow of oil or gas from the well to the surface when certain conditions occur. 
         [0004]    2. Description of Related Art 
         [0005]    Currently such safety valves are held in an open position by virtue of pressure in a control line from the surface acting on a piston in the valve which is operatively connected to a flow sleeve which moves axially to open a valve member. Movement of the sleeve also compresses a spring surrounding the flow sleeve. 
         [0006]    Upon the occurrence of an unfavorable event, the pressure is relieved via the control line so that the spring will move the flow sleeve upwardly so as to allow the valve, which may be a flapper valve as shown in  FIG. 2  of this application to close. In so doing, the spring must overcome the pressure head caused by the hydraulic fluid and the flow resistance due to the small diameter of the control line. 
         [0007]    Some control lines in deep water subsea wells may be up to two miles or more in length and may extend a vertical distance of more than a mile. 
         [0008]    Consequently the pressure head and resistance to flow is quite high which can delay the response time for the valve and may in some cases result in failure. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The above mentioned design defects are overcome by the current invention. A recockable actuator is located within the valve body that is not subject to the pressure head or flow line resistance to move the flow sleeve to open the valve. When the flow sleeve is moved to a position which opens the valve, a latching mechanism engages the flow sleeve to hold it in place and the actuator is disengaged from the flow sleeve. To close the valve, the latch mechanism is disengaged and the flow sleeve will move upwardly by virtue of the compressed spring without having to overcome the pressure head or fictional forces. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0010]      FIG. 1  is a schematic diagram of a typical off shore producing oil well. 
           [0011]      FIGS. 2A and 2B  are cross-sectional views of a conventional safety valve in the close and open position, respectively. 
           [0012]      FIGS. 3A and 3B  are cross-sectional views of an embodiment of a recockable actuator and latch mechanism according to the invention in an open and closed position, respectively. 
           [0013]      FIGS. 4A and 4B  are further embodiments of a recockable actuator and latch mechanism according to the invention in an open and closed position, respectively. 
           [0014]      FIGS. 5A and 5B  are another embodiment of a recockable actuator and latch mechanism according to the invention in the open and closed position. 
           [0015]      FIG. 6  is a view of an embodiment of a latch mechanism according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]      FIG. 1  illustrates a typical deep water, producing well system. A floating production, storage, and offload ship  2  is tethered to a buoy  4 . Production tubing  6  extends from the buoy to the sea floor  14  and runs to the well head  8 . The well includes casing  18  and production tubing  16  which may extend vertically and then is directed horizontally through the production zone  20  of formation  22 . Perforations  24  may be formed in the formation. 
         [0017]    A safety valve  12  is typically located in the production  12  tubing  16  between the well head  8  and the producing zone  20 . A control line  10  extends from the surface vessel to valve  12 . 
         [0018]      FIG. 2A  illustrates a typical known valve  12  which includes a valve body  26  having threaded connection points at each end. An axially movable flow sleeve  28  having an annular shoulder  29  is located within the valve body. A piston  30  has its upper portion located in a pressure chamber  35  which is coupled to a hydraulic pressurized control line  10  as is known in the art. A spring  32  is captured between shoulder  29  and a shoulder  31  formed within the valve body. A flapper valve  34  is pivotably mounted at a lower portion of the valve body and is biased to the closed position shown in  FIG. 2A  by a coil spring. 
         [0019]    In order to open the valve, fluid under pressure is conveyed by control line  10  to the pressure chamber  35  above piston  30  which moves downwardly and engages shoulder  29  of flow sleeve  28 . Flow sleeve in turn moves downwardly while compressing spring  32  and the lower end  33  of the flow sleeve will open valve  34  as shown in  FIG. 2B . 
         [0020]    To close the valve, pressure within control line  10  is relieved and spring  32  will force flow sleeve  28  in an upward direction thus allowing the valve member to close. While moving upward, the flow sleeve  28  must overcome the pressure head and flow resistance associated with control line  10 . 
         [0021]    An embodiment according to the invention is shown in  FIG. 3A . The valve  40  is similar to that shown in  FIG. 2A  and includes a valve body  42 , flow sleeve  44 , spring  48 , shoulder  49 , and biased valve  50 . However, in lieu of a pressure operated piston, a recockable actuator  46  is provided for axially moving flow sleeve  44 . Actuator  46  may be a motorized electric linear actuator, as is well known in the art. The valve body  42  is provided with a latching mechanism shown at  47  in  FIG. 3B . Latching mechanism  47  locks flow sleeve  44  in place against axial movement in the open position shown in  FIG. 3A . 
         [0022]    The latching mechanism may be a semi-circular split ring  47  as shown in  FIG. 7  formed of a shape memory alloy (SMA) positioned within an annular groove  60  provided in the interior surface of valve body  42 . An annular groove  61  may be provided on the outer periphery of the upper portion of flow sleeve  44 . As the flow sleeve is moved downwardly by the recockable mechanism  46 , the groove  61  on the outer surface of sleeve  44  is brought into registry with the shape memory alloy ring. Energizing the ring by completion of an electrical circuit connected to the ring will cause the ring to partially contract into the annular groove on the outer surface of the flow sleeve, thus latching or locking the flow sleeve in place with valve  50  in the open position as shown in  FIG. 3A . At this point linear activator  46  can be backed off from shoulder  49  by reversing the motor actuator. 
         [0023]    In order to close the valve, the SMA split ring is de-energized so that it no longer partially occupies the groove  61  in the outer surface of the flow sleeve. At this point compressed spring  48  will move flow sleeve  44  in an upward direction past valve  50  so that the spring biased valve  50  will now move to the closed position as shown in  FIG. 3B . However since the recockable actuator  46  is not mechanically linked to the flow sleeve, movement of the flow sleeve will not be retarded. 
         [0024]      FIGS. 4A and 4B  illustrate yet another embodiment of the invention. In this embodiment, a hydraulically activated piston  56  moves flow sleeve  44  so as to open valve  50  and disengages by virtue of a tilting mechanism as the flow sleeve reaches its lowermost position. Tilting mechanism includes a notch  71  formed in the piston  56  and a tab  72  that loosely is received within notch  71 . A beveled surface  73  is formed at the end of piston  56  which cooperates with a beveled surface  74  on shoulder  49  of the flow sleeve. As surfaces  73  and  74  engage at the lower portion of flow sleeve  44  shown in  FIG. 4A , piston  56  tilts sideways such that tab  72  is no longer located within notch  71 . As in previous embodiments SMA ring  47  may be used to latch and unlatch the flow tube. 
         [0025]      FIGS. 5A and 5B  illustrate a further embodiment of the invention. According to this embodiment the actuator comprises a shape memory alloy linear actuator  58  commonly referred to as a SMA muscle. When energized, SMA actuator  58  will expand thus moving flow sleeve  44  downwardly to open valve  50 . As the flow sleeve reaches its lowermost position, SMA ring is activated to move partially into annulus recess  61  on the outer surface of flow sleeve  44  as shown in  FIG. 5A  in the valve open position. Linear SMA actuator is de-energized to decouple the actuator  58  from the flow sleeve. In order to close the valve, SMA ring  47  is de-energized so that it withdraws from groove  61  and compressed spring  48  will move flow sleeve  44  upwardly as shown in  FIG. 5B  in the closed position. 
         [0026]    Latch mechanisms may take various forms, for example it could be a piston member that is radially actuated to engage a slot on the outer surface of the flow sleeve. Other well-known latching mechanism may also be utilized. 
         [0027]    Other embodiments include:
       1) All hydraulic solution: a fit for purpose all-hydraulic Surface Controlled Subsurface Safety Valve, designed with no gas charge, adapted to close more rapidly than currently available products.   2) Hydraulic-Electric solution: A fit for purpose Hydraulic Electric solution for a Surface Controlled Subsurface Safety Valve, having a (low voltage/amperage) electrically activated and deactivated latching and unlatching device, and adapted to close virtually instantaneously upon loss of current. Further, the valve would contain a separate hydraulic recocking mechanism, to open and rearm the valve. The valve would have a much longer design life, higher cyclic integrity and therefore higher reliability than known products.   3) All Electric Solution: A fit for purpose Hydraulic Electric solution for a Surface Controlled Subsurface Safety Valve, designed with (low voltage/amperage) electrically activated and deactivated latching and unlatching device, and adapted to close virtually instantaneously upon loss of current. Further, the valve would contain a separate electrically energized recocking mechanism, to open and rearm the valve. The valve would have a much longer design life, higher cyclic integrity and therefore high reliability than known products.   4) All Electric-Hydraulic redundant Solution: A fit for purpose Hydraulic Electric solution for a Surface Controlled Subsurface Safety Valve, designed with (low voltage/amperage) electrically activated and deactivated latching and unlatching device, and adapted to close virtually instantaneously upon loss of current. The valve would contain a separate electrically energized recocking mechanism. Further, the valve would contain a separate and redundant hydraulically energized recocking mechanism to open and rearm the valve. Both the hydraulic and electric recocking mechanism would be independent and redundant. The valve would have a much longer design life, higher cyclic integrity and therefore higher reliability than known products.       
 
         [0032]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.