Abstract:
A wireline retrievable injection valve for an oil or gas well has an internal valve that is initially moved to open a flapper safety valve and also opens to allow fluid flow through the valve. The internal valve includes a sleeve that opens the flapper safety valve and shields the flapper safety valve from fluid. In this manner the flapper valve is protected from being caused to “flutter” or “chatter” due to pressure variations in the fluid flow, which may damage the seat.

Description:
[0001]    This application is a continuation-in-part of a U.S. application Ser. No. 13/863,063 filed on Apr. 15, 2013, which is a continuation-in-part of U.S. application Ser. No. 13/669,059 filed on Nov. 5, 2012 which claims priority to provisional application Ser. No. 61/639,569 with a filing date of Apr. 27, 2012. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention is directed to an injection valve typically used in conjunction with an injection well. Injection wells are drilled for example in close proximity to hydrocarbon producing wells that have peaked in terms of their output. Fluid for example water is pumped under pressure into an injection well to maintain the pressure of the underlying formation as the well is produced. Injected water acts to force the hydrocarbons into adjacent producing wells thus increasing the yield. 
         [0004]    2. Description of Related Art 
         [0005]    U.S. Pat. No. 7,866,401 discloses an injection safety valve having a restrictor, also known as an orifice, create a pressure differential so as to move a flow tube past a flapper valve. The diameter of the restrictor is fixed. 
         [0006]    A problem with injection valves is a phenomenon known to those of normal skill in the art as “chattering”. Chattering occurs when the injection rate is insufficient to allow the valve to fully open, whereby the flow across the fixed orifice (the standard in injection valves) is too low to compress the power spring and shift the flow tube into a position to hold the flapper into the fully open and protected position. 
         [0007]    Chattering causes the flapper to intermittently and rapidly slam into the flapper seat causing premature failure of either the flapper and/or seat. Such failure can cause an unsafe well condition necessitating premature, immediate shut in of the well, and expensive well remediation, sometimes costing tens of millions of dollars in the instance of subsea wells. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    One embodiment of the invention includes providing a tubing retrievable injection valve having a full bore internal diameter when running and retrieving the valve. A “slick-line” or “wireline” retrievable “nozzle assembly” having an orifice is carried by and affixed in the wellbore by a lock assembly. The nozzle assembly is retrievable without removing the injection valve. Consequently the diameter of the nozzle may be changed on the surface. The injection valve also has a temporary lock out feature so that the valve may be placed in the well in a lock out mode. In certain situations where the flow rate of the water may vary, an embodiment of the invention includes a nozzle assembly with a variable orifice to provide an infinitely variable downhole nozzle. The nozzle is designed to generate a pressure drop sufficient to hold the flapper valve fully open. This prevents the flapper valve from “chattering” and isolates the flapper valve from fluid flow during injection both of which are harmful to the flapper valve assembly. 
         [0009]    Additionally, in yet further embodiment of the invention, a pair of opposite pole magnets are provided. One magnet is attached to an upper sleeve of the nozzle assembly and a second magnet is attached to a middle sleeve member which carriers a variable orifice. In the run-in position, the flapper valve is locked out and the variable orifice insert permits flow of liquid in both directions. In the set position within the well, the upper sleeve and middle sleeve are locked together and injection into the well is permitted. Once the flowrate is decreased at the surface, the variable orifice insert resets into the fully closed position while a return spring returns the flow tube to the initial position allowing the flapper to close. Once injection resumes, the differential pressure across the variable orifice insert is very high because it&#39;s held in a closed position by the strong magnets. Hence the variable orifice insert moves to a position which opens the flapper valve before any flow is established through the injection valve. In this manner, no flapper chattering is possible. As the injection flow rate is increased, the variable orifice insert will open a greater area in response to the flow rate to allow more flow to pass through the internal restriction. As the restriction is opened by flow, the magnet force is decreased allowing very low operational differential pressure during operation. The operating differential pressure must be above the opening differential pressure for the flow tube and flapper valve to stay open during injection. When the injection flowrate is decreased, the flapper will close thus protecting the valve surface from produced injection water. 
         [0010]    The variable output nozzles are designed so that as flow occurs, the flow tube will first move in a direction to open the flapper valve and then the output area of the nozzle will increase with increased flow rates. 
         [0011]    The nozzle assembly can either be run pre-installed in the injection valve prior to running or after the injection valve has been set, utilizing wireline/slickline operations to insert and or remove the nozzle assembly from the injection valve. 
         [0012]    A further embodiment of the invention is directed to a wireline retrievable injection valve that includes a flapper valve at one end and an axially movable sleeve within which is mounted to a second valve. The second valve is pressure responsive and includes a variable orifice. 
         [0013]    According to another embodiment of the invention, the valve may be designed as a flapperless injection valve thus simplifying the design and construction of the valve. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0014]      FIG. 1  is a cross sectional view of an embodiment of the valve in a lock out, running position. 
           [0015]      FIG. 2  is a cross sectional view of an embodiment of the valve in a pre-injection position with the valve member closed. 
           [0016]      FIG. 3  is a cross-sectional view of the retrievable orifice selective lock assembly. 
           [0017]      FIG. 4  is a perspective view of the retrievable nozzle selective lock assembly. 
           [0018]      FIG. 5  is a cross sectional view of a valve showing the retrievable nozzle selective lock assembly located within the valve body. 
           [0019]      FIG. 6  is a cross sectional view of a valve in an open injection position. 
           [0020]      FIG. 7  is a cross-sectional view of a second embodiment of a retrievable nozzle selection lock assembly according to the invention. 
           [0021]      FIG. 8  is a cross-sectional view of the embodiment of  FIG. 7  shown in a fully open condition. 
           [0022]      FIG. 9  is a cross-sectional view of a third embodiment of a retrievable nozzle selective lock assembly according to the invention. 
           [0023]      FIG. 10  is a cross-section view along line  10 - 10  of  FIG. 11  of a fourth embodiment of a retrievable nozzle selective lock assembly according to the invention. 
           [0024]      FIG. 11  is an end view of the retrievable nozzle assembly of  FIG. 10 . 
           [0025]      FIG. 12  is a cross-sectional view of the nozzle core member of the embodiment of  FIG. 10 . 
           [0026]      FIG. 13  is a cross-sectional view of an embodiment of the valve according to the invention with the variable nozzle assembly of the embodiment shown in  FIG. 10  in the closed position. 
           [0027]      FIG. 14  is a cross-sectional view of the embodiment shown in  FIG. 13  with the flapper valve in the open position. 
           [0028]      FIG. 15  is a cross-sectional view of the embodiment shown in  FIG. 13  with the flapper valve in the open position and the variable orifice in the open position. 
           [0029]      FIG. 16  is a cross-sectional view of a further embodiment of the invention showing the valve in the open position. 
           [0030]      FIG. 17  is a cross-sectional view of the axially movable valve assembly with the secondary valve in the open position. 
           [0031]      FIG. 18  is a cross-sectional view taken along line H?  18 - 18  of  FIG. 17 . 
           [0032]      FIG. 19  is a cross-sectional view of the axially moveable valve assembly with the secondary valve in the closed position. 
           [0033]      FIG. 20  is a cross-sectional view of a flapperless safety valve according to an embodiment of the invention. 
           [0034]      FIG. 21  is a schematic representation of an injection well. 
           [0035]      FIG. 22  is a schematic showing of an injection valve positioned within a tubular string of an injection well. 
           [0036]      FIG. 23  is a view similar to  FIG. 16  showing the flapper valve in the closed position. 
           [0037]      FIG. 24  is a perspective view of a further embodiment of a retrievable variable outlet assembly according to the invention. 
           [0038]      FIG. 25  is a cross-sectional view of the embodiment of  FIG. 24  showing the variable outlet in a closed position. 
           [0039]      FIG. 26  is a cross-sectional view of the embodiment of  FIG. 24  showing the variable outlet in an open position. 
           [0040]      FIG. 27  is a view showing the position of the outer sleeve in the run-in position. 
           [0041]      FIG. 28  is a view showing the position of the inner movable valve member in the run-in position. 
           [0042]      FIG. 29  is a view showing the resetting position of the outer sleeve in the resetting position. 
           [0043]      FIG. 30  is a view showing the position of the inner movable valve member in the resetting position. 
           [0044]      FIG. 31  is a view showing the position of the outer sleeve in the operational position. 
           [0045]      FIG. 32  is a view showing the position of the inner movable valve in the operational position. 
           [0046]      FIG. 33  is cross sectional view of the variable orifice insert positioned in the injection valve housing showing the valve in the run-in position. 
           [0047]      FIG. 34  is a cross sectional view of the variable orifice insert in the valve housing in the injection position. 
           [0048]      FIG. 35  is a graph that depicts the performance of a variable orifice nozzle insert vs. a fixed orifice. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    Referring to  FIG. 1 , an embodiment of the injection valve  10  includes a pressure containing body comprising an upper valve body member  11 , a tubular middle valve body member  12  suitably attached to the upper valve body member  11  by threads at  29 , for example, and a lower valve body member  13  which is connectable to a tubular at its downhole end. Valve body members  12  and  13  are secured to each other by threads for example at  34 . 
         [0050]    The injection valve  10  further includes an upper flow tube having a first section  17  and a second section  14  which are secured together. Section  17  has an interior nipple profile at  16  for receiving a tool. Section  14  has an elongated sleeve portion  19  that extends to valve seat  26  when the valve is in the position shown in  FIG. 1 . Elongated sleeve portion  19  includes a plurality of slots  32  as shown in  FIG. 1 . Ridges  33  are formed on the inner surface of sleeve  19  around slots  32  thus forming a collet. A shiftable lower flow tube  31  is positioned within the elongated sleeve portion  19  of the upper flow tube. Shiftable lower flow tube  31  has two annular grooves  35  and  36  on its outer periphery located so as to form a profile for engagement with ridges  33  on the inner surface of elongated sleeve portion  19 . Shiftable flow tube  31  also has shifting profiles  39  and  38  at each end thereof. 
         [0051]    Middle body member  12  has a reduced diameter portion  25  that carries an annular valve seat  26 . A flapper valve  27  is pivotably connected at  28  to valve seat  26  and is resiliently biased to a closed position on valve seat  26  as is known in the art. 
         [0052]    A coil spring  18  is positioned about elongated sleeve portion  19  and is captured between shoulder  14  of the upper flow tube and an internal shoulder  41  provided within middle valve body member  12 . 
         [0053]    In the temporary lock out running position shown in  FIG. 1 , shiftable flow tube  31  is positioned within the valve body so as to extend beyond valve seat  26  thereby maintaining flapper valve  27  in an open position. 
         [0054]    When the valve is positioned within the well at the desired location, a suitable running tool is lowered into the well and engages the upper shifting, profile  39  of shiftable flow tube  31  and the flow tube is moved upwardly, to the position shown in  FIG. 2 . The uphole end portion  91  of the shiftable lower flow tube  31  will abut a shoulder portion  92  of the upper flow tube  15  as shown in  FIG. 2 . In this position, the resiliently biased flapper valve will be in the closed position. 
         [0055]    The retrievable nozzle selective lock assembly (RNSLA) will now be discussed with reference to  FIGS. 3 and 4 . The RNSLA  50  includes a sleeve formed by generally cylindrical members  51 ,  52 ,  56  and,  53  having an interior flow passage  61 . An inner tubular member  56  is located within cylindrical member  52  and carries nozzle  53 . A plurality of selective locking dogs  58  are located around a portion of its periphery as shown in  FIG. 4 . Leaf springs  59  are positioned under locking dogs  58 . RNSLA  50  includes an annular packing assembly  55 . A replaceable and retrievable orifice nozzle  53  is releaseably attached to the body portion of the RNSLA and includes an orifice  54 . Nozzle  53  may be replaced on the surface with another nozzle having a different size orifice  54 . 
         [0056]      FIG. 5  illustrates the position of the RNSLA within the injection valve prior to the injection stage. RNSLA may be lowered into the valve body by a suitable tool to a position where the selective locking dogs  58  engage the selective nipple profile  16  in upper flow tube  15 . At this point the RNSLA will be physically connected to the upper flow tube; however flapper valve  27  is still in the closed position. 
         [0057]    The next step in the process is to pump a fluid such as water under pressure into the valve body. As the fluid flows through the RNSLA, a pressure drop will occur across orifice  54  which will cause the RNSLA and upper flow tube assembly  15 ,  14 , as well as shiftable flow tube  31  to move downhole as shown in  FIG. 6 . 
         [0058]    This movement will compress spring  18 . The downhole portions of both the upper flow tube and lower flow tube will be forced into contact with flapper valve  27  and as they are moved further by the pressure differential, they will open the flapper valve to the position as shown in  FIG. 6 . 
         [0059]    As long as the fluid is being pumped the injection valve will remain open. However when the pumping stops, compressed spring  18  will move the RNSLA and the upper and lower flow tubes back to the position shown in  FIG. 5  in which the flapper valve is in the closed position. 
         [0060]      FIG. 7  illustrates a second embodiment of the invention. In this case a variable output nozzle assembly  100  replaces the nozzle  53  shown in  FIGS. 3 and 4 . 
         [0061]    Variable output nozzle assembly  100  includes an outer tubular cylindrical casing  101 . An axially moveable cylindrical sleeve  103  having an enlarged portion  107  is positioned within casing  101  and has an end face  114  that extends outwardly of casing  101 . Sleeve  103  has an interior flow passage  105  and also has a plurality of outlet ports  104  that are axially and radially spaced about its longitudinal axis. Sleeve  103  terminates in an end face  116  that includes an outlet orifice  115 . A coil spring  102  is positioned between the inner surface of casing  101  and the outer surface of sleeve  103  as shown in  FIG. 7 . In the relaxed position of  FIG. 7 , one end of the coil spring  102  abuts against shoulder  108  on enlarged portion  107  of sleeve  103  and the other end abuts against end face  109  of the casing  101 . 
         [0062]    At lower flow rates, the pressure drops across orifice  115  will be sufficient to move the lower flow tube to a position keeping flapper valve  27  open. As the flow rate increases, sleeve  103  is moved axially to sequentially move outlet ports  104  past the end face  109  of casing  101  as shown in  FIG. 8 , thereby allowing more fluid to exit the nozzle to proceed downhole of the flapper valve. 
         [0063]      FIG. 9  illustrates a variation from the shape and location of the outlet ports. In this embodiment outlet ports may be relatively large circular openings  114  that are axially offset with respect to one another. Openings  114  may also be elliptical or wedged shape or of any geometric shape. 
         [0064]    The spring constants of springs  18  and  102  are chosen so that as fluid flow begins, the RNSLA will first move in a downhole direction opening the flapper valve before sleeve  103  moves in a downhole direction. 
         [0065]      FIGS. 10-12  illustrate yet a further embodiment of the invention. 
         [0066]    In this embodiment the variable output nozzle assembly includes a first fixed portion including a cylindrical tubular casing  124  having a solid conical core member  139  supported therein by a plurality of struts  129  as shown in  FIGS. 11 and 12 . An outer tubular sleeve member  120  is fitted over casing  124  and includes a constricted portion  122  and conical portions  131  and  132  on either side of constricted portion  122 . Conical member  139  has a first enlarged portion  130  followed by a tapered cone portion  123 . Outer sleeve member  120  includes a thin walled portion  121  that extends to an annular shoulder  126  such that an annular space  133  is formed between casing  124  and thin walled portion  121 . A coil spring  125  is positioned within space  133  such that one end of the spring abuts against a shoulder  134  on enlarged portion  126  of thin walled portion  121  and abuts against a shoulder  135  provided on tubular casing  124 . Thin wall portion  121  is detachably secured to outer sleeve member  12  at  140  for example by threads. In the position shown in  FIG. 10 , the outer surface of core member  139  engages constriction  122  so as to prevent flow. 
         [0067]    As the flow rate of fluid is increased, outer sleeve member  120  will move to the right as viewed in  FIG. 10 . Due to the tapering of cone section  123 , the outlet area of the nozzle at  122  will increase as the flow rate increases. Thus at lower flow rates sufficient force will be provided to maintain the flapper valve in the open position as well as at high flow rates. 
         [0068]    The embodiments according to  FIGS. 7-12  provide an infinitely variable nozzle which will minimize pressure drop over a range of injection flow rates. They provide full open flapper protection over the full range of injection rates thus eliminating flapper chatter due to partial valve opening during injection. 
         [0069]    The variable output nozzles of  FIGS. 7-12  can be substituted for the nozzle  53  shown in  FIG. 3  so that they can be placed and retrieved as a part of the RNSLA shown in  FIGS. 3 and 4 . 
         [0070]      FIGS. 13-15  shown the sequential opening of the flapper valve and the variable orifice as flow is initiated in the well according to the embodiment of the variable orifice shown in  FIG. 10 . The difference between  FIGS. 5 and 6  and  FIGS. 13-15  is that the nozzle assembly  53  of  FIGS. 5 and 6  has been replaced by the nozzle assembly of  FIG. 10 . 
         [0071]    In the position shown in  FIG. 13 , the flapper valve  27  is closed and the outer surface of core member  139  engages constriction  122  so as to prevent flow through the nozzle. The lower ends of upper flow tube  19  and lower flow tube  31  are positioned adjacent the flapper valve  27 . As fluid flow begins the upper and low flow tube along with the variable orifice nozzle assembly will move downwardly to the position shown in  FIG. 14  due to fluid pressure thereby compressing spring  18 . The spring constants for spring  18  an spring  125  are selected so that during initial fluid flow the upper and lower flow tube as well as the variable orifice nozzle assembly will move to the position shown in  FIG. 14  with the variable orifice  122  still in a closed position. However, as fluid pressure and flow increases, outer sleeve member  120  will move downwardly with respect to tubular casing  124  in which cone member  139  is fixed to the position shown in  FIG. 15 . In this position fluid will flow through variable orifice  122 . 
         [0072]      FIG. 16  illustrates a further embodiment of a wireline retrievable valve, as is well known by those with ordinary skill in the art, shown with the flapper valve in an open, injection position. Valve  200  includes a valve body having an upper lock adapter  201 , and intermediate body housing  202  and a lower body housing  203  in which a conventional flapper valve element  224  is rotatably mounted. Valve element  224  is spring biased to a closed position as shown in  FIG. 23 . Valve  200  also includes an inlet  205  and outlet  226 . 
         [0073]    An axially movable valve assembly  250  shown in  FIGS. 17 and 19  is positioned within the valve body and includes an inlet portion  204 , an intermediate portion  221  and a sleeve portion  223 . A spring  211  is captured between a shoulder  240  formed in the outer surface of inlet portion  204  and a step  241  formed in the interior surface  213  of intermediate body housing  202 . A tear drop body member  206  similar to body  130  shown in  FIG. 12  is supported within inlet portion  204  by a plurality of struts  207 . An axially movable nozzle  215  is positioned within inlet portion  204  and intermediate portion  221  of the valve assembly. Body  206  and movable nozzle  215  form a secondary valve having a variable annular fluid passageway  262  as shown in  FIG. 17 . 
         [0074]    Nozzle  215  has a converging inlet section  216 , a throat portion  261  and a diverging outlet section  208 . Nozzle  215  moves axially with the second valve assembly between shoulder  230  in inlet portion  204  and a shoulder  231  formed on intermediate portion  221  of the second valve assembly as shown in  FIGS. 17 and 19 . A spring  214  is positioned between a shoulder  210  on the outer surface of the nozzle and a step  209  on the intermediate portion  221 . Axial movement of the nozzle  215  in a downward direction will compress spring  214  as shown in  FIG. 17 . Nozzle  215  and body  206  form a valve. 
         [0075]    Second valve assembly  250  includes an elongated sleeve  223  coupled to intermediate portion  221  for example by threads. Sleeve  223  is adapted to move downwardly to open flapper valve  224  as shown in  FIG. 16  when fluid is pumped into the well via tubing  403  shown in  FIG. 21 . Further downward movement of sleeve  223  is restrained by a shoulder  225  formed in lower body housing  203 . 
         [0076]      FIG. 21  shows the location of the valve  406  within a well. A well bore  607  extends down to a formation  405  where the injected fluid is to be delivered. A tubular string  403  is connected to the well head  402  which typically includes a plurality of valves  409 . A packer  404  is placed between the tubular string  403  and the well casing. 
         [0077]    In operation. injection fluid is pumped through the well head into tubular string  403  in which valve  406  is located. As shown in  FIG. 22 , valve  406  can be selectively positioned within the tubing string by a wireline nipple  407  for the tubulars  403  and by wireline lock  411  having dogs  412  that cooperate with a groove  413  in the nipple in a manner well known in the art. Wireline lock  411  has packing  412  to seal the lock within the nipple  407 . 
         [0078]    Fluid pressure will initially cause second valve assembly  250  to move downwardly to the position shown in  FIG. 16  such that sleeve  223  moves flapper valve to the open position shown in  FIG. 16 . Continued fluid flow will cause nozzle  215  to move downwardly away from body  206  as shown in  FIG. 17  to thereby allows fluid flow through second valve assembly  250 . 
         [0079]    Yet a further embodiment of the invention is illustrated in  FIG. 20 . This is an embodiment of the injection valve without a flapper valve. The valve  300  includes a main body housing  301  and a lower body housing  322  attached to main body housing  301  via threads  324  as an example. 
         [0080]    Main body portion  301  has an upper connection  325  suitable for connection to a wireline lock  411  for example. The valve includes an inlet  309  and outlet  323  for the injection fluid. A solid tear-shaped body  302  is fixed within the main body housing  301  by a plurality of struts  303 . A nozzle member  304  includes a converging inlet  308  and a diverging outlet  311 . A valve seat  305  is formed between the conveying and diverging portions of the nozzle and cooperates with body  302  to form a variable constricted flow passage through the valve as nozzle  304  moves axially. Nozzle  304  is moved downwardly against spring  306  in spring chamber  307  by a pressure differential. Spring  306  is captured between a shoulder  310  on the exterior surface of the nozzle and a step  312  formed on the upper end of lower body housing  322 . 
         [0081]    When fluid is pumped down to the valve, nozzle  304  will move downwardly to open up an annular fluid passageway between body  302  and nozzle  304 . When fluid flow is terminated, spring  306  which is compressed as nozzle  304  is moved downwardly will shift nozzle  304  in an upward direction thus bringing surface  305  into contact with body  302  thereby closing the annular fluid passageway and preventing flow back of fluid. 
         [0082]      FIG. 24-34  depict a further embodiment of the dual barrier valve of the invention. 
         [0083]      FIG. 24  illustrates a retrievable nozzle select lock assembly (RNSCA)  500  which includes a variable orifice insert similar to that shown in  FIGS. 13 and 14  at  19 ,  31 , and  124 . The RNSCA is designed to be positioned within an injection valve which includes an upper valve body member  11 , a middle valve body member  12  and a lower valve body member  13  which includes a flapper valve assembly  26 ,  27 . 
         [0084]    The RNSCA includes an upper sleeve  501  have a standard internal fishing neck profile  510 . A middle sleeve  508  is attached to upper sleeve  501  by a plurality of pins  506 . A first set of magnets  502  is positional between the upper and middle sleeves. Middle sleeve  508  terminates in a tapered valve seat  516 . An outer sleeve member  521  is axially movable with respect to middle sleeve  508 . A pair of magnets  503  are attached to outer sleeve member  521  and move with the sleeve  521 . Magnets  502  and  503  have opposite poles that attract each other. Pin  512  is secured to middle sleeve  508  and is positioned within a 
         [0085]    J-slot  542  formed in outer sleeve  521 . 
         [0086]    A gap  504  is formed between upper sleeve  501  and outer sleeve  521 . A slightly compressed spring  507  is positioned between middle sleeve  508  and outer sleeve  521  as shown in  FIG. 25 . 
         [0087]    The RNSCA includes a plurality of seals  532  and a locking tab  533 . A lower sleeve  515  is attached to outer sleeve  521  by one or more pins  513 . Lower sleeve  515  supports inner valve member  520  by a plurality of struts  514 . A spring guide sleeve  518  surrounds middle sleeve  508 . 
         [0088]      FIGS. 27 and 28  show the portion of inner vale member  520  in the run in position. Pin  512  is located in the hook portion of the J-slot of outer sleeve  521 . In this position inner valve member  520  is slightly spaced from valve seat  516  so that as the dual valve assembly is lowered into the well, fluid in the well may escape to the well head via an annular orifice  551  between valve seat  516  and valve number  520  as shown in  FIG. 28 . 
         [0089]    In the resetting position of  FIGS. 29 and 30 , outer sleeve  521  and lower sleeve  515  are movable down hole by fluid flow within the valve body and pin  512  is positional with the slot  542  as shown in  FIG. 29 . 
         [0090]    This allows outer sleeve  521  and valve body  520  to move upwardly thereby closing the valve. The valve is now ready for operation as shown in  FIG. 32 . Water under a given pressure will move lower sleeve  515  in a downward direction to open flapper valve  27 . As shown in  FIG. 26  increased pressure will act to move valve body  520  away from valve seat  516  to allow injection of water into the well. 
         [0091]      FIGS. 33 and 34  show the variable orifice insert positioned within an injection valve housing which includes upper body member  11 , middle body member  12  and lower body member  13 . A power spring  570  is positioned between a flange  571  which is attached to upper flow tube  572  and the flapper support  26 . As the variable orifice insert moves in a down hole direction. spring  570  is compressed as shown in  FIG. 34 . 
         [0092]      FIG. 33  shows the valve in the run-in position with pin  512  positioned within slot  542  as shown in  FIG. 27 .  FIG. 34  shows the valve in the resetting position where a low resetting flowrate will develop to fully stroke and lock the flow tubes together. Power spring  570  is compressed by shoulder  571  of upper flow tube  572 . Pin  512  moves to the position shown in  FIG. 29 . When the flowrate is decreased the variable orifice insert resets into the fully closed position as shown in  FIGS. 31 and 32 . Power spring  570  returns the upper flow tube  572  to the initial position of  FIG. 33  along with lower flow tube  31 . 
         [0093]    In this position the flapper valve  27  and the variable orifice insert are both in the fully closed position thus providing a dual barrier check valve for any fluid flowing out of the well. When injection resumes, the differential pressure developed across the insert is relatively high because it&#39;s held closed by the magnets. The variable orifice insert opens the flapper valve before any flow is established through the tool. 
         [0094]    Consequently no flapper chattering is possible. As the flow rate is increased, the variable orifice inset will open to allow flow to pass through the variable orifice. As the orifice is opened by the flow, the magnetic force is decreased allowing very low operational differential pressure during injection operation. The operating differential pressure must be above the opening differential pressure for the flow tube and flapper system to stay open during injection. When the injection flowrate is decreased below a certain valve, the flapper will close protecting the surface from produced injection water. 
         [0095]    The opening of the valve due to fluid flow is resisted by the spring force as it is displaced, by the spring pre load-force and by the magnetic force. These forces balance each other with the result that a low operating differential pressure is maintained which results in higher injection efficiency. 
         [0096]      FIG. 35  illustrates the performance of the variable orifice nozzle insert of the present invention vs. the fixed orifice of the prior art. 
         [0097]    The horizontal axis is the injection flowrate and the vertical axis represents the differential pressure across the orifice. 
         [0098]    With a fixed orifice nozzle, as the flowrate increases and the pressure differential is below 20 psi, the flapper element will chatter as shown in the shaded area until the opening differential pressure is above 20 psi. 
         [0099]    Also the fixed orifice will take significantly higher flow to attain the required opening differential pressure. Also, the fixed orifice will require an even higher flow for re-setting the flow tube. Potentially, the re-setting differential pressure might not be achieved at all rendering the system useless. 
         [0100]    In contrast, the variable nozzle of the present invention does not open until the flapper valve is moved to an open and protected position thereby completely eliminating chatter. 
         [0101]    The variable orifice allows the user to re-set the valve with minimal flow and will consequently always operate above the flapper chattering zone. 
         [0102]    Magnets  502  and  503  may be made of rare earth materials. The various sleeves and housing may be formed of austenitic stainless steels. The portion of the assembly susceptible to erosion, for example, the valve body  520  and lower sleeve  515  could be made of erosion resistant material such as tungsten carbide, ceramic material, hard faced carbon steel, hipped zirconium and stellite. 
         [0103]    All of the embodiments may be deployed or retrieved using a wireline or slickline and are easily redressable and repairable. Furthermore, when injection flow is stopped the valve automatically will close, thereby protecting the upper completion from back flow or a blowout condition. 
         [0104]    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.