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BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to the use of O-ring seals, typically formed from elastomer, as shear members. In particular aspects, the invention relates to devices that utilize O-rings as shear members to resist the movement of an axially sliding sleeve.  
         [0003]     2. Description of the Related Art  
         [0004]     There is a variety of tools and devices used within a wellbore that incorporate sliding sleeves, or arrangements where one tubular member is slidably moved with respect to another tubular member to accomplish some function, such as actuation of a valve or a releasable disconnect. Traditionally, shear pins or other frangible members have been used to releasably secure these components together until it is desired to cause them to slide.  
         [0005]     However, the use of frangible members to hold sleeve components together is problematic where the components are subject to high vibration. Vibration can rupture a frangible pin, thereby prematurely releasing the connection that holds the sleeve members together. This results in an undesired activation of the tool. One example of a tool that is normally subjected to high vibration during use is a coiled tubing shear release joint. These tools are used to provide a selective separation point in a continuous length of coiled tubing. The release joint may be activated by shearing of a shearable member, such as a frangible shear pin, to allow separation of release joint components. However, substantial vibration occurs during normal operation of coiled tubing production, and this vibration might cause the shear pin to fail prematurely, thus undesirably activating the release joint.  
         [0006]     The present invention addresses the problems of the prior art.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention provides devices and methods for releasably securing components of a device having a sliding sleeve arrangement to prevent premature actuation due to vibration. In a currently preferred embodiment, the invention utilizes standard elastomeric O-rings as shear members. The O-ring shear members reside within spaces formed between two slidable sleeve members. The O-rings are sheared cross-sectionally to allow the sleeve members to move axially with respect to one another. An exemplary coiled tubing shear release joint is described that incorporates a shear disconnect assembly which uses elastomeric O-rings as shear members. Multiple O-ring seals can be used as shear members to increase the shear value of the device. The use of O-rings as shear members helps prevent premature sliding of sleeve components in response to high vibration. Because the O-rings are resilient, they absorb vibration and do not shear during vibration, the connection between the two sleeve components will not be released prematurely.  
         [0008]     To the inventors&#39; knowledge, elastomeric O-rings have not been heretofore utilized as shear members for the releasable securing of sliding sleeve arrangements. The conventional intended use for elastomeric O-ring members has been as fluid seals. As a result, it has been desired that O-ring members remain intact to provide for good fluid sealing rather than to deliberately destroy them.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  depicts an exemplary sliding sleeve arrangement that incorporates O-ring seals as shear members.  
         [0010]      FIG. 2  illustrates the sliding sleeve arrangement shown in  FIG. 1  now with the O-ring seals sheared.  
         [0011]      FIG. 3  is a side, cross-sectional view depicting an exemplary coiled tubing shear release joint that incorporates O-ring seal shear members, in accordance with the present invention.  
         [0012]      FIG. 4  is an enlarged view of shear disconnect assembly portions of the release joint shown in  FIG. 3 .  
         [0013]      FIG. 5  is an enlarged view of the shear disconnect assembly portions shown in  FIG. 4 , now with the shear members having been sheared.  
         [0014]      FIG. 6  is a further enlarged view depicting details of an exemplary shear collar and O-ring shear member.  
         [0015]      FIG. 7  is a side, cross-sectional view of the coiled tubing shear release joint shown in  FIG. 3 , with the release now activated. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     The present invention relates broadly to the use of typical O-ring seals as shear members in tools and devices that feature axially sliding sleeves. Many devices that incorporate axially sliding sleeves are used in oil wells.  
         [0017]      FIGS. 1 and 2  illustrate an exemplary the general instance of a sliding sleeve apparatus  10  that incorporates elastomeric O-ring seals as a shear mechanism. The sliding sleeve apparatus  10  includes a radially outer sleeve  12  that partially surrounds a radially inner piston  14 . The outer sleeve  12  defines a series of annular grooves  16  inscribed upon its interior surface  18 . The inner piston  14  also defines a series of annular grooves  20  upon its outer surface  22 . In the initial secured position, shown in  FIG. 1 , the grooves  20  on the inner piston  14  are aligned with the grooves  16  on the outer sleeve  12 . O-ring members  24  reside within the spaces created by the alignment of grooves  16  and  20 . While there are five O-ring members  24  shown, it will be understood that there may be more or fewer depending upon the amount of shear resistance desired. Each of the exemplary O-ring shear members  24  presents a substantially rounded cross-section, as shown, although other cross-sectional shapes may be utilized (i.e., square, rectangular, or other). In the position shown in  FIG. 1 , the inner piston  14  is secured in place with respect to the outer sleeve  12  by the O-rings  24 , which prevent axial movement. In the case of vibration of the apparatus  10 , the O-rings  24  are not ruptured.  
         [0018]     The inner piston  14  may be moved with respect to the outer sleeve  12  by hydraulic actuation, a mechanical shifting tool, or in other ways known in the art. In order to move the inner piston  14  with respect to the outer sleeve  12 , it is necessary to impart an axial force to the inner piston  14  that is greater than the shear resistance provided by the O-rings  24 . When this amount of force is applied, the O-rings  24  split into ring portions  24   a ,  24   b , as shown in  FIG. 2 , and the inner piston  14  is freed to move with respect to the outer sleeve  12 . Ring portions  24   a  remain within the grooves  20  while ring portions  24   b  remain inside the grooves  16 . Thus, it can be seen that a O-ring  24  will shear or be separated into two substantially annular pieces, as the ring  24  is separated along its cross-sectional area.  
         [0019]      FIGS. 3-7  depict an exemplary coiled tubing shear release joint  30  that is constructed in accordance with the present invention. The shear release joint  30  is typically used within a wellbore (not shown) to create a separation point in coiled tubing. Thus, the shear release joint  30  includes an upper mandrel  32  with a box-type threaded connection  34  at its upper end  36  to be affixed to an upper section  38  of coiled tubing. The upper section  38  of coiled tubing typically extends to the surface of the wellbore. The mandrel  32  defines an axial flowbore  40  along its length. In addition, several lateral windows  42  (one shown) are disposed through the body of the mandrel  32 .  
         [0020]     A tubular housing  44  radially surrounds the mandrel  32 . The upper end of the housing  44  provides a fishing neck  45 . The inner surface  46  of the housing  44  includes several annular recesses  48 . Dogs  50 , reside loosely within the windows  42  of the mandrel  32 . Although there is only one dog  50  visible in  FIG. 4 , it will be understood by those of skill in the art that there is typically two to four such dogs  50 —one for each window  42 . Each of the dogs  50  presents a radially outer face  52  that is shaped to provide teeth  54  that rest within the recesses  48  of the housing  44 . As a result, the housing  44  and the mandrel  32  are secured to one another.  
         [0021]     A shear sleeve  56  is disposed within the bore  40  of the mandrel  32  and abuts the inner surfaces  58  of the dogs  50 , thereby holding them firmly in place so that the teeth  54  of the dogs  50  engage the recesses  48 . The shear sleeve  56  has a ball seat  59  at its upper end. The lower end of the shear sleeve  56  is retained in place within the mandrel  32  by a shear disconnect assembly, generally shown at  60  in  FIG. 3 . The structure and function of the shear disconnect assembly  60  is more clearly understood by reference to  FIGS. 4 and 5 , and will be described in detail shortly.  
         [0022]     Referring once again to  FIG. 3 , the lower end of the housing  44  is connected by threaded connection  62  to a bottom sub  64 . The bottom sub  64 , in turn, has a lower end with a pin-type threaded connection  66  by which the bottom sub  64  is secured to a lower section  68  of coiled tubing. An axial flowbore  70  is defined along the length of the bottom sub  64 .  
         [0023]     With reference to  FIGS. 4 and 5 , the shear disconnect assembly  60  includes an inner collar  72  that surrounds a lower portion of the shear sleeve  56 . An outer collar, or shear pin retaining ring,  74  radially surrounds the inner collar  72 . One or more standard frangible shear pins  76  are preferably disposed tangentially through the outer collar  74  and inner collar  72  to releasably secure those components together.  
         [0024]     Below the outer collar  74  are three metallic, annular shear collars  78 ,  80 ,  82 . Each of the three shear collars  78 ,  80 ,  82  has a similar configuration, which is illustrated in the further enlarged view provided by  FIG. 6 . Each shear collar  78 ,  80 ,  82  surrounds an elastomeric O-ring shear member  84 ,  86 ,  88 , respectively, and each of the O-ring shear members  84 ,  86 ,  88  resides within a groove  90 ,  92 ,  94 , respectively, that is formed within the outer surface of the shear sleeve  56 . It is noted that the radially outer surface of each of the shear collars  78 ,  80 ,  82  is interengaged with the mandrel  32  via a toothed or threaded surface  96 . As a result of this interengagement, the shear collars  78 ,  80 ,  82  will move in concert with the mandrel  32 .  
         [0025]      FIG. 6  depicts in closer detail the single shear collar  82  surrounding O-ring shear member  88  and groove  94 . The structural features shown in detail here apply equally to the shear collars  78  and  80 . It is noted that the shear collar  82  has a substantially flat inner side  98  that abuts the outer surface of the mandrel  56 . An arcuately curved inner surface  100  extends upwardly and outwardly from the leading, cutting edge  102  of the inner side  98 . The O-ring member  88  is trapped within the groove  94  by the curved inner surface  100 . It is noted that the inner surface  100  might alternatively be angled rather than curved. In either case, the currently preferred angle of departure for the surface  100  is approximately 5°.  
         [0026]     To activate the release joint  30 , a ball  104  (shown in  FIG. 7 ) is dropped through the upper coiled tubing section  38  and comes to rest on ball seat  59  of the shear sleeve  56 . Fluid pressure is then increased behind the ball  104  until the force upon the shear sleeve  56  exceeds the shear value of the O-ring shear members  84 ,  86 ,  88 . At that point, the shear sleeve  56  moves axially downwardly with respect to the mandrel  32  as the shear members  84 ,  86 ,  88  within the shear disconnect assembly  60  are sheared. Downward movement of the shear sleeve  56  with respect to the mandrel  32  causes the leading edge  102  of each of the shear collars  78 ,  80 ,  82  to engage each of the respective O-ring shear members  84 ,  86 ,  88  and cut them through their annular cross-sections, in a manner similar to the O-rings  24  described earlier (i.e., each of the shear members  84 ,  86 ,  88  is divided into two ring portions). Additionally, the standard frangible shear pin  76  is sheared by movement of the inner collar  72  with respect to the outer collar  74 . The elastomeric shear members  84 ,  86 ,  88  absorb vibration of the components during operation and prevents premature axial movement of the shear sleeve  56  with respect to the mandrel  32  via an unintended rupture of the shear pin  76 .  
         [0027]     As the shear sleeve  56  is moved downwardly to the position shown in  FIG. 7 , the dogs  50  are freed to move radially inwardly, and no longer engage the recesses  48  of the housing  44 . The housing  44  becomes disconnected from the mandrel  32 . The mandrel  32  and shear sleeve  56  can now be withdrawn from the wellbore, leaving the housing  44  and bottom sub  64  in the hole. The fishing neck  45  of the housing  44  remains available for later engagement by a fishing tool.  
         [0028]     The shear disconnect assembly  60  may be assembled by first placing the mandrel  32  inside of the housing  44 . The dogs  50  are then slid into place within the windows  42  of the mandrel  32 . The outer collar  74  is slid over the shear sleeve  56  and the shear pin  76  is inserted through the outer collar  74  and inner collar  72 . Next, the first O-ring shear member  84  is disposed into groove  90 . The first shear collar  78  is then disposed over the shear sleeve  56  to trap the O-ring shear member  84  within its groove  90 . The second O-ring shear member  86  is then disposed within groove  92 . The second shear collar  80  is disposed over the shear sleeve  56  and brought into abutting relation to the first shear collar  78  to trap member  86  within the groove  92 . The third O-ring shear member  88  is then disposed within groove  94 , and the third shear collar  82  is slid over the shear sleeve  56  and brought into an abutting relation to the second shear collar  80 . This action traps O-ring shear member  88  within groove  94 . This, then completes the assembly of the shear disconnect assembly  60 . Next, the shear sleeve  56 , with affixed O-rings  84 ,  86 ,  88  and shear collars  78 ,  80 ,  82 , is slid into the mandrel  32  so that the shear sleeve  56  is disposed beneath (i.e., radially within) the dogs  50 , thereby holding them in place to secure the mandrel  32  to the housing  44 . A spanning wrench may be used to tighten threaded connections and to axially preload the O-ring shear members  84 ,  86 ,  88 . The bottom sub  64  is then secured to the housing  44 .  
         [0029]     It is noted that one can use additional O-ring seal members as shear members to increase the shear value of a connection or reduce the number of shear members in order to reduce the shear value of a connection. However, the shear value achieved by the use of additional shear members is not uniformly cumulative, as might have been expected. In practice, it has been observed, for example, that a single elastomeric shear element might provide a total shear resistance of about 1000 psi. The addition of a second, similar shear member will provide a total shear resistance of about 1,950 psi. The addition of a third shear member will provide a total shear resistance of about 2,750. Thus, the additional shear resistance resulting from the addition of a shear member is less than additive, indeed, only about 95% additional resistance is added. In determining the number of shear members to use for a given connection, one should take account of the conditions within the well in which the connection is expected to operate. Higher temperatures will make the O-rings easier to shear, and thus, the use of additional O-rings is desirable.  
         [0030]     Those of skill in the art will recognize that elastomeric shear members might be used in many different types of devices that incorporate sliding sleeves that must be releasably secured to one another and released upon the application of a predetermined amount of axial force. Examples of wellbore tools that might make use of elastomeric shear members are sliding sleeve production valves and actuating tubes used to open a subsurface safety valve. It is further noted that the shear release joint  30 , described above, might be used to provide a releasable disconnect joint for tubular members other than coiled tubing. For example, the release joint might be adapted for use with standard production tubing rather than coiled tubing.  
         [0031]     It is noted that relatively pliable or substantially elastic materials other than elastomers can be used to form the shear members  24 ,  84 ,  86 ,  88 . Suitable alternative materials would have to be suitably pliable and non-brittle in order to absorb expected vibratory energy from the device into which they are incorporated. Yet, these materials must still be able to provide the shear resistance necessary to retain the components in place until a predetermined amount of axial force is applied to the components to overcome that shear resistance. For example, annular members fashioned of plastics, polymers, resins, TEFLON®, or KEVLAR® would provide vibration resistance as well as provide suitable shear resistance for use as a shear member in a sliding sleeve device. A currently preferred type of material is standard N-butyl nitrile elastomer, of the type used to form conventional O-ring seals. These type of O-rings generally come in two hardnesses: 70 durometer and 90 durometer, both of which are suitable for use as a shear member. It is further noted that the shear member need not be annular in shape either, although that shape presently appears to be quite advantageous in use and is currently preferred.  
         [0032]     The inventors have found that annular elastomeric shear members provide an unexpectedly high degree of shear resistance. It is believed that this significant shear resistance is due to the fact that the annular shear member must be sheared through its cross-section along its entire annular structure. In the above-described examples, the O-ring shear members  24 ,  84 ,  86 ,  86  are sheared by the action of a cutting edge that is incorporated into one or both of the sleeve members that enclose the shear members. In the case of the sliding sleeve assembly  10 , the O-ring shear members  24  are sheared, or annularly divided, by the edges of the grooves  16 , which are formed on the outer sleeve  18 , and the edges of the grooves  20  that are formed on the inner piston  14 . In the instance of the coiled tubing release joint  30 , each O-ring shear member, such as  88 , is sheared or divided by the forward cutting edge  102  of the radially outlying shear collar.  
         [0033]     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.

Summary:
Devices and methods for releasably securing components of a device having a sliding sleeve arrangement to prevent premature actuation due to vibration. In a currently preferred embodiment, the invention utilizes standard elastomeric O-rings as shear members. The O-ring shear members reside within spaces formed between two slidable sleeve members. The O-rings are sheared cross-sectionally to allow the sleeve members to move axially with respect to one another. An exemplary coiled tubing shear release joint is described that incorporates a shear disconnect assembly which uses elastomeric O-rings as shear members. Multiple O-ring seals can be used as shear members to increase the shear value of the device. The use of O-rings as shear members helps prevent premature sliding of sleeve components in response to high vibration. Because the O-rings are resilient, they absorb vibration and do not shear during vibration, the connection between the two sleeve components will not be released prematurely.