Abstract:
A system for securing well tools, such as gas lift valves, into a latching profile within a wellbore. A gas lift valve is provided having a latching arrangement wherein an apertured back-up ring is used to provide stability for the locking lugs throughout the process of latching and unlatching the gas lift valve.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to devices and methods for securing a well tool within a tubular portion of a wellbore. In particular aspects, the invention relates to a latching arrangement for releasably securing a gas lift valve within a side pocket mandrel. 
         [0003]    2. Description of the Related Art 
         [0004]    Secure and reliable latching arrangements are important for releasably securing devices within wellbore arrangements. Gas lift valves are one such device that is used to assist the flow of hydrocarbons to the surface in a wellbore. The gas lift valve transmits a gas, such as air which has been pumped down the annulus, into the flowbore of the production tubing to increase the flow of hydrocarbons through the production tubing and toward the surface of the well. Typically, a gas lift valve is inserted into a side pocket mandrel in a production string using a kickover tool, as is well known in the art. A latching arrangement is needed to secure the gas lift valve within a latching profile in the side pocket mandrel. If the valve is not properly latched into place, it may not function properly. In addition, a latching arrangement that malfunctions may cause the valve to become stuck in the side pocket mandrel so that it cannot be removed without significant damage to the valve or the surrounding wellbore components. 
         [0005]    Prior art latching arrangements for gas lift valves are shown in U.S. Pat. No. 4,265,306 issued to Stout and U.S. Pat. No. 4,554,972 issued to Merritt. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention provides a system for securing well tools, such as gas lift valves, into a latching profile within a wellbore. In a described embodiment, a gas lift valve is provided having a latching arrangement wherein an apertured back-up ring is used to provide stability for the locking lugs throughout the process of latching and unlatching the gas lift valve. In addition, the structure of the backup ring provides a positive retractive force for urging of the locking lugs radially inwardly during withdrawal of the gas lift valve. An axially facing wall of the aperture of the backup ring exerts a compressive force upon the lower axial side of the locking lug, causing a sliding contact between a chamfered surface on the lug and a shoulder on the latching profile. This sliding contact moves the locking lug radially inwardly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
           [0008]      FIG. 1  is a side, cross-sectional view of an exemplary side pocket mandrel and gas lift valve having an improved latching system, in accordance with the present invention. 
           [0009]      FIG. 2  is a side, cross-sectional view of the devices shown in  FIG. 1 , now with the gas lift valve being inserted into the side pocket mandrel. 
           [0010]      FIG. 3  is a side, cross-sectional view of the devices shown in  FIGS. 1-2 , now in a fully latched position. 
           [0011]      FIG. 4  is a side, cross-sectional view of the devices shown in  FIGS. 1-3 , now beginning to be withdrawn from the side pocket mandrel. 
           [0012]      FIG. 5  is a side, cross-sectional view of the devices shown in  FIGS. 1-4 , now further withdrawn from the side pocket mandrel. 
           [0013]      FIG. 6  is a side, cross-sectional view of the devices shown in  FIGS. 1-5 , now withdrawn from the side pocket mandrel. 
           [0014]      FIG. 7  is an axial cross-sectional view of the gas lift valve  12  taken along lines  7 - 7  in  FIG. 1 . 
           [0015]      FIG. 8  is an isometric view of an exemplary back-up ring used in the gas lift valve shown apart from other components. 
           [0016]      FIG. 9  is an axial cross-sectional view of the gas lift valve  12  taken along lines  9 - 9  in  FIG. 2 . 
           [0017]      FIG. 10  is an enlarged cross-sectional detail view depicting a locking lug member and the back-up ring. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The general operation of gas lift valves and side pocket mandrels is well known in the art and described in further detail in U.S. Pat. No. 7,360,602 issued to Kritzler et al. and U.S. Pat. No. 7,228,897 issued to Holt, Jr. et al. Each of these patents is owned by the assignee of the present application and each is hereby incorporated by reference in its entirety. As is known in the art, the side pocket mandrel  10  is a pocket or recess which lies substantially parallel to and alongside of the central flowbore of a string of production tubing within a wellbore. 
         [0019]      FIG. 1  illustrates an exemplary side pocket mandrel  10  and a gas lift valve  12  that can be removably latched within the mandrel  10 . The side pocket mandrel  10  includes a housing  14  that defines a central axial bore  16 . It is noted that, within the context of this discussion the terms “axial” and “axially” will refer to the direction defined by the longitudinal axis of the axial bore  16 , and which is illustrated by the arrows  79  in  FIGS. 1 and 2  as well as arrows  82  in  FIGS. 4-6 . The bore  16  of the side pocket mandrel  10  has an enlarged diameter latching profile  18 . It is noted that the transition between the bore  16  and the latching profile  18  presents sloped shoulders  20 ,  22 . Fluid openings  24  are disposed through the housing  14  proximate the lower end of the bore  16  to permit a gas that is pumped down into the external annulus  26  to enter the bore  16 . 
         [0020]    In  FIG. 1 , the gas lift valve  12  is depicted in an initial run-in position prior to being disposed into and latched within the bore  16 . Those of skill in the art will understand that a kickover tool, of a type known in the art is used to dispose the gas lift valve  12  into the bore  16 . For clarity, the kickover tool is not depicted in the drawings. 
         [0021]    The gas lift valve  12  includes a latch head  28  that is threadedly affixed to a generally cylindrical expander shaft  30 . The shaft  30  features a primary shaft portion  32  which presents a substantially uniform diameter along its length and an enlarged diameter annular portion  34 . The lower end of expander shaft  30  is affixed to a bottom sub  36 . A latch housing  38  radially surrounds the expander shaft  30  and is secured to the expander shaft  30  by a frangible shear member, such as shear pin  40 , which passes through both the shaft  30  and the latch housing  38 . A radially enlarged spring chamber  42  is defined between the latch housing  38  and the primary shaft portion  32 . An axially compressible spring  44  is disposed within the spring chamber  42 . 
         [0022]    A further enlarged lug chamber  46  is defined below the spring chamber  42  between the shaft  30  and the latch housing  38 . In a preferred embodiment, a number of openings (one shown)  48  are disposed through the latch housing  38  within the lug chamber  46 . A back-up ring  50  is disposed within the lug chamber  46  immediately below the spring  44 . The back-up ring  50  contains apertures  52 . In a presently preferred embodiment, there are three apertures  52 , although there may be more or fewer than three, if desired. A locking lug  54  is disposed within each of the apertures  52 . It can be seen from  FIG. 1  that, during initial run-in to the side pocket mandrel  10 , the locking lugs  54  (one show) also reside partially within the window  48  of the latch housing  38  and abut the radially enlarged portion  34  of the expander shaft  30 . 
         [0023]    The structure and operation of an exemplary back-up ring  50 , apertures  52  and locking lugs  54  are better understood with further reference to  FIGS. 7-9 . As depicted in  FIG. 8 , the ring  50  features a generally cylindrical ring body  56  with an inwardly directed flange  58  at one axial end. The apertures  52  are entirely defined within the ring body  56  so is as to each present a pair of axially facing walls  60 ,  62  and a pair of angularly facing walls  64 ,  66 . In a currently preferred embodiment, the apertures  52  are generally rectangular in shape. 
         [0024]    Each of the locking lugs  54  includes a central lug body  68  with a substantially flat radially outward face  67  and chamfered edge portions  69  (see  FIG. 10 ). Each of the lugs  54  also has a pair of ears  70  which extend radially outwardly from the body  68 . The locking lugs  54  are shaped and sized to reside within the apertures  52  in a complimentary fashion. The lug members  54  each have a curved radially inner surface  71  which will abut the outer radial surfaces  34  or  32  of the expander shaft  30 , as  FIGS. 7 and 9  show. The ears  70  of each locking lug  54  function to prevent the locking lug  54  from being moved radially outwardly through the windows  48  of the latch housing  38 . When the locking lug  54  is disposed within the aperture  52 , the axially facing walls  60 ,  62  prevent the lug member  54 , as depicted in  FIG. 10 . The axially facing walls  60 ,  62  abut axial faces  72 ,  74 , respectively of the lug member  54 . As a result, the lug member  54  can move radially inwardly and outwardly with respect to the backup ring  50  (as illustrated by the phantom lines of  54 ′ in  FIG. 10  illustrating a radially outwardly extended position). However, the lug member  54  is prevented from appreciably rotating away in any substantial manner from the axially facing wall  62 , (in the direction illustrated by arrow  76 ) by the presence of the axially facing wall  60 . The lug member  54  is also prevented from appreciably rotating away from the wall  60  (in the direction indicated by arrow  78 ) in any substantial manner by the presence of wall  62 . A substantial rotation of the lug member  54  with respect to the walls  60  or  62  would be an amount of rotation that would preclude the lug member  54  from operating properly to move radially inwardly or outwardly to selectively latch the gas lift valve  12  into the side pocket mandrel  10 . In addition, the angularly facing walls  64 ,  66  prevent angular rotation of the lug members  54 , as  FIGS. 7 and 9  illustrate. 
         [0025]    The operation to insert the gas lift valve  12  into the side pocket mandrel  10  and latch it within is illustrated by  FIGS. 1-3  as well as  7  and  9 . Beginning with the configurations shown in  FIGS. 1 and 7 , a downward compression force (illustrated by arrow  79 ) is applied to the latch head  28  and latch housing  38 . This downward force  79  compresses the spring  44  between the latch housing and the backup ring  50 , as  FIG. 2  depicts. The latching lugs  54  are moved from the lower end of windows  52 , as illustrated in  FIG. 1 , to the upper end of the windows  52 , as shown in  FIG. 2 . In addition, the downward force moves the lug members  54  from abutting the diametrically expanded section  34  of the expander shaft  30  (as shown in  FIGS. 1 and 7 ) to a position wherein the curved faces  71  of the lug members  54  abut the reduced diameter portion  32  of the shaft  30  (see  FIGS. 2 and 9 ). This permits the lug members  54  to be moved radially inwardly by sliding contact between a chamfered edge  69  of the lug with a sloped shoulder  80  (see  FIG. 2 ) within the bore  16  of the side pocket mandrel  10 . Once the lug members  54  have been moved radially inwardly, the compression force gas lift valve  12  is moved downwardly to the position depicted in  FIG. 3  wherein the latching lug members  54  are located within the latching profile  18  of the gas lift mandrel  10 . At this point the downward force  79  is removed. The compression spring  44  will move the backup ring  50  axially downwardly with respect to the latch housing  38  and expander shaft  30 . The inner radial surfaces  71  of the lug members  54  will once again be abutting the expanded diameter portion  34  of the expander shaft  30 . As a result, the lug members  54  will extend outwardly into the latching profile  18 , thereby latching the gas lift valve  12  in place against inadvertent removal during operation. 
         [0026]      FIGS. 4-6  illustrate removal of the gas lift valve  12  from the side pocket mandrel  10 . When it is desired to remove the gas lift valve  12 , an upward pulling force, or removal force) is applied to the latch head  28  (illustrated by arrow  82 ). As is known, the removal force is typically applied to the latch head by a suitable pulling tool (not shown). It is noted that the removal force  82  must be sufficient to shear the shear member  40 . The force  82  first moves the gas lift valve  12  upwardly to the position shown in  FIG. 4  wherein the upper chamfered edge  69  of the locking lugs  54  comes into contact with the shoulder  20  of the latching profile  18 . However, the lugs  54  cannot be moved radially inwardly at this point due to their abutting relation with the expanded diameter portion  34  of the expander shaft  30 . The removal force  82  then shears the shear pin  40 , as shown in  FIG. 5 . When this occurs, the latching head  28  and expander shaft  30  are freed to move with respect to the surrounding latch housing  38 . The radially expanded portion  34  of the expander shaft  30  will engage the flange  58  of the backup ring  50 , thereby drawings it axially upwardly. The radially expanded portion  34  of the expander shaft  30  is also moved above the locking lugs  54 , thereby allowing them to be moved radially inwardly to the position shown in  FIG. 5 , due to sliding contact with the shoulder  20 . It is noted that the lower axially facing wall  60  of the backup ring  50  will exert a positive compressive force against the lower axial face  72  of the locking lugs  54 . This compressive force will ensure that there is sliding contact between the upper chamfered edge  69  of the lugs  54  and the shoulder  20  of the bore  16 . This sliding contact will move the lugs  54  radially inwardly. As the lugs  54  are moved inwardly, they are prevented from axial rotation with respect to the latch housing  38  by sliding contact with the axially facing walls  60 ,  62  of the backup ring  50 . At this point, the gas lift valve  12  is freed to be removed completely from the side pocket mandrel  10 , as further depicted in  FIG. 6 . 
         [0027]    The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.