Abstract:
An integral multistage safety valve is designed to provide a second level of protection should a first stage fail. The valve may be used in oil and/or gas wells. The interior portion of the multiphase safety valve is designed so as to reduce turbulence and pressure loss through the valve when the valve is in an open position. The valves may be independently operable, or operable with a single control line. The multi-stage valve reduces the number of body joints required to construct two identical valves thereby reducing cost and potential leak paths and increasing reliability of the system.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention is for multiple safety valves for location within an oil or gas well that can be activated to open or close and thus prevent, or permit upward flow of fluids within the well for example in case of an emergency. 
         [0003]    2. Description of Related Art 
         [0004]    Downhole safety valves are known that include a housing, a flapper valve and a remotely controlled actuator for closing the normally open valve in case of an emergency. See for example U.S. Pat. No. 7,392,849. Also serially arranged valves in a downhole tool are also known. Examples of such are shown in U.S. Pat. Nos. 6,394,187; 7,673,689; 4,846,281; 4,605,070; and 6,152,229. These valves are complicated in design and are not compact as is critical in the art. Furthermore the internal flow passage for the fluids are not of a single diameter and many contain obstruction shoulders or changes in diameter that result in turbulent flow or pressure drops. 
         [0005]    Threaded joints are in common use in hydrocarbon producing wells. During design qualification of subsurface safety valves, a body joint must be designed qualified and verified which is an expensive process, because of the consequences of a leak in a valve of this type. Typical solutions would be to provide valves with two body joints and a pup joint between which adds two additional body joints. The present invention reduces the number of body joints in an integral valve to four or five and utilizes the same body joint. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The invention disclosed and claimed in this application is for subsurface multiple stage safety valves that are highly reliable, compact, simple to manufacture and include at least two complete, separately functioning safety valves. In accordance with another aspect of the invention, dual control lines are provided which allows for individual operation of each safety valve. This allows the operator the option of operating one valve and keeping the other as a stand-by or operating both valves simultaneously. The principles of the invention can be applied to pressure equalizing or non-pressure equalizing closing systems. Due to the internal design of the valve, the internal flow path is substantially of uniform diameter thus eliminating turbulence and pressure drops due to internal obstructions and irregularities. Furthermore the exterior diameter of the tool is substantially constant. The tool includes a minimum of body joints which increases the reliability of the tool and simplifies construction. 
         [0007]    Another advantage of the valve is the reduction of body joints necessary for its construction. Reducing the number of body joints reduces potential leak paths of hydrocarbons from the inside. Fewer joints also reduces the cost of the body joint. 
         [0008]    Another embodiment of the present invention is to operate both valves with a single control line, which controls the sequence of openings and closures. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0009]      FIG. 1  is a longitudinal sectional view of an embodiment of the invention. 
           [0010]      FIGS. 2   a  and  2   b  are cross sectional views of an embodiment of the multiple stage safety valve in the closed position. 
           [0011]      FIGS. 3   a  and  3   b  are cross sectional views of an embodiment of the multiple stage safety valve in the open position. 
           [0012]      FIGS. 4 and 5  are cross sectional views of an example of a piston operated sleeve. 
           [0013]      FIG. 6  is a cross sectional view of the safety valve having a single surface control line. 
           [0014]      FIG. 7  is a view similar to  FIG. 6  showing a flow restrictor in the control line branch going to the first valve. 
           [0015]      FIG. 8  is a cross-sectional view of a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Initially, in order to better understand the invention, the prior art will be discussed. Currently in order to provide redundancy, two valves are simply joined together by a pup joint. The upper valve is connected to production tubing by a threaded connection and the lower valve is connected to lower production tubing by a threaded connection. This results in six body joints. As discussed above these body joints increase the likelihood of leak passages and increase the cost of fabrication. 
         [0017]    Referring to  FIG. 1 , an embodiment of the present invention is illustrated. The integral multiple stage safety valve includes five tubular sections  11 ,  12 ,  13 ,  14  and  15  connected to each other by any suitable known methods such as internal and external threads. Upper connection body  11  may be connected to any tubular to be placed within the well. A first spring housing  12  is connected at one end to the upper connection body and at the other end to an integral chamber housing  13  which interconnects the two separate safety valves  60  and  70  as shown in  FIGS. 2   a  and  2   b  according to an embodiment of the invention. Housing  13  includes an interior flow path  57  of substantially constant diameter and generally equal to the interior diameter of sleeve  19 . Second spring housing  14  is connected to a reduced diameter portion  52  of the integral chamber housing  13  by threads as an example. Lower connection body  15  is attached by any known manner to a reduced diameter portion  39  of second spring housing  14  at one end and may be connected to a tubular at its lower end  63 . This design results in four body joints. 
         [0018]    As shown in  FIGS. 4 and 5 , each safety valve includes a piston  18 , a sleeve  19  with an enlarged connection portion  34 , a flapper valve element  33  pivotably connected at  32  to the spring housing, a coil spring  38  that biases the flapper valve element against a valve seat  31  and a coil spring  20  that surrounds sleeve  19 . 
         [0019]    As shown in  FIG. 4 , a conventional mechanism for operating each safety valve includes a piston  18  having a seal  55  on its outer surface. Piston  18  at its lower end is received by an enlarged connection portion of sleeve  19 . Spring  20  abuts a shoulder  56  on the sleeve  19  and is captured at its other end within spring housing  12  as shown at  61  in  FIG. 5 . 
         [0020]    Pressurized hydraulic fluid may be introduced above piston  18  at inlets  51  by separate conduits that extend to the surface. Fluid introduced above piston  18  will cause piston  18  to move downwardly as shown in  FIG. 1 , while compressing spring  20  as shown in  FIG. 3   a . The lower end of sleeve  19  will push open flapper valve  33 . Conversely, a decrease in the pressure will cause sleeve  19  to move upwardly by the force of the compressed spring which will cause flapper valve  33  to close thereby preventing any upward flow of fluid through the central passageway  16  of the safety valve. As discussed above safety valves  60 ,  70  may be independently operated by providing separate hydraulic lines for inlets  51 . 
         [0021]      FIG. 5  illustrates an example of a typical flapper valve that may be utilized with the invention. Lower portion  39  of spring housings  12  and  14  are provided with a valve seat  31 . Flapper valve members  33  are pivotably connected at one side to the spring housings  12  and  14 . The pivot  32  includes a coil spring  38  or the like which biases the valve member  33  against valve seat  31  as is known in the art. 
         [0022]    As shown in  FIG. 6 , both valves may be activated by a single control line  80  that extends to the surface. A branch line  83  may extend to the inlet  51  of the upper valve  60  while line  80  connects to inlet  51  of lower valve  70 . A flow restrictor  82  may be located in either branch line  83  or in flow line  80  downstream of branch line  83  as shown in  FIG. 7  and  FIG. 6  respectively. The positioning of flow restrictor  82  will delay opening of the valve as pressure is applied through control line  80 . In the configuration shown in  FIG. 6 , valve  60  will open first followed by valve  70  and in the configuration shown in  FIG. 7  valve  70  will open first followed by valve  60 . 
         [0023]    As pressure in the control line is reduced, the valve having the flow restrictor in its control line will close second while the other will close first. 
         [0024]      FIG. 8  illustrates a second embodiment of the invention which includes two independent safety valves similar to those disclosed in  FIG. 1  Each safety valve may include an actuator piston, a flow sleeve, a flapper valve element and a coil spring. 
         [0025]    In this embodiment, the safety valve includes six tubular sections  111 ,  112 ,  113 ,  116 ,  117  and  118 . First tubular section  111  has an upper portion which may be threadably connected to production tubing in a known manner. 
         [0026]    The lower portion of first tubular member includes a piston chamber in which piston  136  is received. Fluid under pressure is introduced into the piston chamber via an inlet  127 . Piston  112  acts on a flow sleeve  129  to open flapper valve  115  in the manner discussed above. 
         [0027]    The second tubular section  112  is connected to tublar section  111  at a threaded joint  120 . A third tubular section  113  is connected to second tubular section  112  at a threaded joint  121 . 
         [0028]    A fourth tubular section  116  also has a piston chamber in which is mounted a piston  126  which is adapted to move flow sleeve  131  which will open flapper valve  125  in the same manner as discussed above. A fifth tubular section  117  carries flow sleeve  131  and spring  132  and is connected to the fourth tubular section  116  by a threaded joint as shown it  123 . Hydraulic lines  127  and  114  are connected to a source of hydraulic fluid under pressure at the well head. 
         [0029]    A sixth tubular member  118  is connected to the fifth tubular section  117  at a threaded joint shown at  124 . The lower portion of the sixth tubular member includes a threaded female connector adapted to receive a threaded portion of a production tubular. 
         [0030]    Third tubular member  113  and fourth tubular member  116  in this embodiment form a chamber housing that consists of two tubular members. 
         [0031]    The tubular members are connected together in a similar manner at  120 ,  121 ,  122 ,  123  and  124 . Each joint includes a female threaded portion of the tubular member at its upper portion and a male threaded member at its lower end which is threadably connected to the female portion of the tubular member below it. 
         [0032]    The outside diameter of the tubular members in the embodiments of  FIGS. 1 and 8  are substantially the same as are the diameters of the inner flow passages. This embodiment results in five tubular joints. 
         [0033]    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.