Abstract:
A subsurface safety valve assembly for controlling fluid flow in a wellbore. In one embodiment, the subsurface safety valve assembly includes a tubular member having a longitudinal bore extending therethrough, a flapper removably connected to the tubular member. The flapper is configured to pivot against the tubular member between an open position and a closed position. The subsurface safety valve assembly further includes a flow tube disposed inside the tubular member and a shear sleeve having an upper end and a lower end. The upper end of the shear sleeve is positioned against a lower end of the flow tube to form a first seal between the upper end of the shear sleeve and the lower end of the flow tube.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    Embodiments of this invention are generally related to safety valves. More particularly, embodiments of this invention pertain to subsurface safety valves configured to control fluid flow through a production tubing string.  
           [0003]    2. Description of the Related Art  
           [0004]    Surface-controlled, subsurface safety valves (SCSSVs) are commonly used to shut in oil and gas wells. Such SCSSVs are typically fitted into a production tubing in a hydrocarbon producing well, and operate to block the flow of formation fluid upwardly through the production tubing should a failure or hazardous condition occur at the well surface.  
           [0005]    SCSSVs are typically configured as rigidly connected to the production tubing (tubing retrievable), or may be installed and retrieved by wireline, without disturbing the production tubing (wireline retrievable). During normal production, the subsurface safety valve is maintained in an open position by the application of hydraulic fluid pressure transmitted to an actuating mechanism. The hydraulic pressure is commonly supplied to the SCSSV through a control line which resides within the annulus between the production tubing and a well casing. The SCSSV provides automatic shutoff of production flow in response to one or more well safety conditions that can be sensed and/or indicated at the surface. Examples of such conditions include a fire on the platform, a high/low flow line pressure condition, a high/low flow line temperature condition, and operator override. These and other conditions produce a loss of hydraulic pressure in the control line, thereby causing the flapper to close so as to block the flow of production fluids up the tubing.  
           [0006]    Most surface controlled subsurface safety valves are “normally closed” valves, i.e., the valves utilize a flapper type closure mechanism biased in its closed position. In many commercially available valve systems, the bias is overcome by longitudinal movement of a hydraulic actuator. In some cases the actuator of the SCSSV includes a concentric annular piston. Most commonly, the actuator includes a small diameter rod piston, located in a housing wall of the SCSSV.  
           [0007]    During well production, the flapper is maintained in the open position by a flow tube down hole to the actuator. From a reservoir, a pump at the surface delivers regulated hydraulic fluid under pressure to the actuator through a control conduit, or control line. Hydraulic fluid is pumped into a variable volume pressure chamber (or cylinder) and acts against a seal area on the piston. The piston, in turn, acts against the flow tube to selectively open the flapper member in the valve. Any loss of hydraulic pressure in the control line causes the piston and actuated flow tube to retract, which causes the SCSSV to return to its normally closed position by a return means. The return means serves as the biasing member, and typically defines a powerful spring and/or gas charge. The flapper is then rotated about a hinge pin to the valve closed position by the return means, i.e., a torsion spring, and in response to upwardly flowing formation fluid.  
           [0008]    In recent completion techniques, a SCSSV may be run with the production tubing into the hole prior to a cementing operation. Once the cement is cured, the desired formations are perforated through the tubing. Using this technique, however, exposes the SCSSV to the cement during the cementing operation, which may cause the SCSSV to fail prematurely.  
           [0009]    Therefore, a need exists for an apparatus and method for protecting the SCSSV from cement infiltrating the SCSSV during the cementing operation.  
         SUMMARY OF THE INVENTION  
         [0010]    Various embodiments of the present invention are generally directed to a subsurface safety valve assembly for controlling fluid flow in a wellbore. In one embodiment, the subsurface safety valve assembly includes a tubular member having a longitudinal bore extending therethrough, a flapper removably connected to the tubular member. The flapper is configured to pivot against the tubular member between an open position and a closed position. The subsurface safety valve assembly further includes a flow tube disposed inside the tubular member and a shear sleeve having an upper end and a lower end. The upper end of the shear sleeve is positioned against a lower end of the flow tube to form a first seal between the upper end of the shear sleeve and the lower end of the flow tube.  
           [0011]    Various embodiments of the present invention are also directed to a system for protecting a well completion equipment from at least one of cement or fluids during a cementing operation. In one embodiment, the system includes a sleeve removably disposed inside the well completion equipment and a dart configured to pull the sleeve away from the well completion equipment after the cementing operation is complete. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0013]    [0013]FIG. 1 illustrates a schematic of a production well having a subsurface safety valve installed in accordance with an embodiment of the invention.  
         [0014]    [0014]FIG. 2 illustrates a cross-sectional view of the subsurface safety valve assembly in an open position in accordance with an embodiment of the invention.  
         [0015]    [0015]FIG. 3 illustrates a shear sleeve in accordance with an embodiment of the invention in greater detail.  
         [0016]    [0016]FIG. 4 illustrates a seal formed by a flow tube positioned against a hydraulic chamber housing in accordance with an embodiment of the invention.  
         [0017]    [0017]FIG. 5 illustrates the shear sleeve in a position following the completion of a cementing operation in accordance with an embodiment of the invention.  
         [0018]    [0018]FIG. 6 illustrates a system for protecting a well equipment from cement or other fluids during the cementing operation in accordance with an embodiment of the invention.  
         [0019]    [0019]FIG. 7 illustrates the manner in which a sleeve is coupled to a well equipment in accordance with an embodiment of the invention.  
         [0020]    [0020]FIG. 8 illustrates o ring grooves defined on the upper nipple in accordance with an embodiment of the invention.  
         [0021]    [0021]FIG. 9 illustrates the manner in which a dart connects to the sleeve in accordance with an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    A detailed description will now be provided. Various terms as used herein are defined below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term, as reflected in printed publications and issued patents. In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawings may be, but are not necessarily, to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the invention. One of normal skill in the art of subsurface safety valves will appreciate that the various embodiments of the invention can and may be used in all types of subsurface safety valves, including but not limited to tubing retrievable, wireline retrievable, injection valves, or subsurface controlled valves.  
         [0023]    [0023]FIG. 1 illustrates a subsurface safety valve assembly  10  placed in a typical well completion schematic  12  in accordance with an embodiment of the invention. A land well is shown for the purpose of illustration; however, it is understood that the subsurface safety valve assembly  10  may also be used in offshore wells. FIG. 1 further illustrates a wellhead  20 , a master valve  22 , a flow line  24 , a casing string  26  and a production tubing  28 . In operation, opening the master valve  22  allows pressurized hydrocarbons residing in the producing formation  32  to flow through a set of perforations  34  and into the well  12 . The cement seals an annulus  35  between the casing  26  and the production tubing  28  in order to direct the flow of hydrocarbons. Hydrocarbons (illustrated by arrows) flow into the production tubing  28  through the subsurface safety valve assembly  10 , through the wellhead  20 , and out into the flow line  24 .  
         [0024]    [0024]FIG. 2 illustrates a cross-sectional view of the subsurface safety valve assembly  10  in an open position, i.e., prior to the completion of a cementing operation. An upper nipple  36  and a lower sub  38  serve to sealingly connect the safety valve assembly  10  to the production tubing (not shown). The safety valve assembly  10  is generally maintained in the open position by hydraulic pressure. Hydraulic pressure is supplied by a pump (not shown) in a control panel (not shown) through a control line (not shown) to the safety valve assembly  10 . The hydraulic pressure holds a flapper closure mechanism  18  within the safety valve assembly  10  in the open position.  
         [0025]    As the safety valve assembly  10  is hydraulically actuated, the safety valve assembly  10  includes a hydraulic chamber housing  40  and a piston  42  therein, as shown in FIG. 4. The piston  42  is typically a small diameter piston which moves within a bore of the housing  40  in response to hydraulic pressure from the surface. Alternatively, the piston  42  may be a large concentric piston which is pressure actuated. It is within the scope of the present invention, however, to employ other less common actuators such as electric solenoid actuators, motorized gear drives and gas charged valves (not shown). Any of these known or contemplated means of actuating the subsurface safety valve assembly  10  of the present invention may be used.  
         [0026]    In accordance with an embodiment of the invention, the safety valve assembly  10  further includes a shear sleeve  200 . The shear sleeve  200  is configured to eliminate or reduce the amount of cement and/or fluids from entering the safety valve assembly  10 . FIG. 3 illustrates the shear sleeve  200  in greater detail. At one end (e.g., the top end), the shear sleeve  200  is positioned against a lower end of the flow tube  44 , thereby forming a seal  210  sufficient to keep the cement from entering the safety valve assembly  10 . Seal  210  may be formed by pressing the upper end of the shear sleeve  200  against the lower end of the flow tube  44 . Seal  210  may be any type of sealing mechanism, such as a metal to metal seal or an elastomeric seal. In one embodiment, a temporary holding mechanism, such as a pin  250 , holds the shear sleeve  200  in place at a groove  255  defined on a portion of the outside diameter of the shear sleeve  200 . Other temporary holding mechanisms, such as shear screw, collet and the like, may also be used to hold the shear sleeve  200  in place. In another embodiment, the safety valve assembly  10  further includes a retention sub  225  disposed between the shear sleeve  200  and the lower sub  38 . The retention sub  225  has an inside diameter that is larger than an outside diameter of the shear sleeve  200 . The larger diameter of the retention sub  225  may be configured to either provide sufficient space for the cement to accumulate or for the movement of the shear sleeve  200  when the flow tube  44  is actuated, which will be described in detail in the following paragraphs. As shown in FIG. 3, the shear sleeve  200  may be coupled to the retention sub  225  by a threaded ring  235  and an o ring  230 . The threaded ring  235  may also be used to drive the sleeve  200  against the flow tube  44  to create seal  210 .  
         [0027]    In yet another embodiment, an upper end of the flow tube  44  may be positioned, e.g., pressed, against the hydraulic chamber housing  40 , thereby forming seal  410 , as shown in FIG. 4. Seal  410  is configured to eliminate or reduce the amount of cement from entering the top portion of the safety valve assembly  10 . Like seal  210 , seal  410  may be any type of sealing mechanism, including metal to metal seal or elastomeric seal. In this manner, the shear sleeve  200  in combination with the retention sub  225 , seal  210  and seal  410  are configured to substantially eliminate or reduce the amount of cement and/or fluids from entering the safety valve assembly  10 .  
         [0028]    In operation, the safety valve assembly  10  mounted on the production tubing  28  is run into the wellbore prior to the cementing operation. After the cementing operation is complete, the piston  42  is actuated to push the shear sleeve  200  through the retention sub  225  to the lower sub  38 . The piston  42  is actuated by application of hydraulic pressure through the control line  16 . The piston  42 , in turns, acts upon the flow tube  44 , translating the flow tube  44  longitudinally to such an extent that the pin  250  is sheared. The flow tube  44  continues to push the shear sleeve  200  toward the lower sub  38  until a snap ring  510 , which was previously disposed in a recess  520  defined inside the threaded ring  235 , snaps into a groove  530  defined on the outside diameter of the shear sleeve  200 . (See FIG. 5). The snap ring  510  is configured to hold the shear sleeve  200  in place after the flow tube  44  moves the shear sleeve  200  away from the flapper mechanism  18 . Other holding mechanisms may also be used to hold the shear sleeve  200  in place after the flow tube  44  moves the shear sleeve  200  away from the flapper mechanism  18 . The shear sleeve  200  may be pushed all the way to the bottom of the lower sub  38 . In this manner, after the cementing operation is complete, the shear sleeve  200  is shifted to a location that would not interfere with the operation of the safety valve assembly  10 , thereby eliminating the need to retrieve the shear sleeve  200  to the well surface. After the shear sleeve  200  is shifted away from the flapper mechanism  18 , the pressure (or energy) may be released from the piston  42 , thereby causing a power spring  46  to move the flow tube  44  longitudinally upward, allowing the flapper mechanism  18  to close.  
         [0029]    [0029]FIG. 6 illustrates another way to protect a safety valve assembly  610  from being infiltrated by cement or other fluids during the cementing operation. That is, FIG. 6 illustrates a cross-sectional view of the safety valve assembly  610  disposed between an upper nipple  636  and a lower sub  638 . A sleeve  650  is disposed inside the safety valve assembly  610 . The sleeve  650  may be commonly referred to as a hold open sleeve. The sleeve  650  may extend from the upper nipple  636  to the lower sub  638 , and beyond. The sleeve  650  may be made from a disposable material, such as, aluminum, plastic, brass, steel and the like. The sleeve  650  includes a collar  710  defined on a portion of the outside diameter of the sleeve  650 , as shown in FIG. 7. In one embodiment, the collar  710  is a shear out collar. FIG. 7 further illustrates recess  720  defined on an inside portion of the lower sub  638 . The collar  710  and recess  720  are configured to hold the sleeve  650  in place inside the safety valve assembly  610  during the cementing operation. In one embodiment, recess  720  may be defined in an inside portion of a retention sub  730 , which is coupled to the lower portion of the lower sub  638 . FIG. 8 illustrates that the upper nipple  636  may define o ring grooves  810  configured to provide one or more seals, thereby preventing cement and or other fluids from seeping into the top portion of the safety valve assembly  610 .  
         [0030]    [0030]FIG. 6 further illustrates a dart  660  configured to pull the sleeve  650  away from the safety valve assembly  610  after the cementing operation is complete. An upper outside portion of the dart  660  defines a shoulder  910 , as shown in FIG. 9. FIG. 9 also illustrates a lip  920  defined on a portion of the inside diameter of the sleeve  650 . The outside diameter of the shoulder  910  is greater than the inside diameter of the lip  920 . In this manner, the lip  920  performs as a no go sub, and the shoulder  910  is configured to catch or latch on to the lip  920  when the dart  660  is actuated, which will be described in detail in the following paragraphs.  
         [0031]    In operation, the safety valve assembly  610  mounted on the production tubing  28  along with the sleeve  650  are run into the wellbore prior to the cementing operation. During the cementing operation, the sleeve  650  protects the safety valve assembly  610  from the cement or other fluids contained inside the tubing. After the cementing operation is complete, the dart  660  is used to pull the sleeve  650  away from the safety valve assembly  610  to allow the safety valve assembly  610  to operate without any interference from the sleeve  650 . In this manner, it is no longer necessary to retrieve the sleeve  650  following completion of the cementing operation. The dart  660  is may be pumped down through the production tubing  28  following the cement as the cementing operation is being completed. The dart  660  is generally actuated or driven by cement completion pumps (not shown). When the sleeve  650  is pulled away, the collar  710  collapses, thereby no longer holding the sleeve  650  inside the safety valve assembly  610 . In one embodiment, the sleeve  650  may be pulled all the way down to a rat hole or the bottom of the well. After the sleeve  650  is positioned away from safety valve assembly  610 , the safety valve assembly  610  is free to operate in a normal fashion. Following the completion of the cementing operation, the pressure (or energy) may be released from the piston  42 , causing the power spring to move the flow tube longitudinally upward, thereby allowing the flapper mechanism  18  to close.  
         [0032]    Although the invention has been described in part by making detailed reference to specific embodiments, such detail is intended to be and will be understood to be instructional rather than restrictive. It should be noted that while embodiments of the invention disclosed herein, particularly those embodiments described with reference to FIG. 6 et seq., are described in connection with a subsurface safety valve assembly, the embodiments described herein may be used with any well completion equipment, such as a packer, a sliding sleeve, a landing nipple and the like.  
         [0033]    Whereas the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, might be made within the scope and spirit of the present invention.