Abstract:
A tool equalizes a packer or bridge plug before it can release the slips and sealing element of the packer or bridge plug with a reconfigurable grip tool. In one configuration the grip tool is latched only into the equalizing mechanism for the packer or bridge plug. Having equalized the pressure and while still latched to the equalization mechanism the tool is reconfigured with a force and locked into a second configuration. From that position the grip tool can latch and move the release mechanism for total release and retrieval to the surface. Release force undermines a ratchet lock for the slips to allow extension as the sealing element extends axially and radially retracts. If the slips fail to release with undermining of the ratchet lock then a set down force can be applied to re-engage the lower slip cone to push it from the lower slips for a release.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of this invention is sequential equalization and then packer or bridge plug release with discrete mechanisms that are sequentially accessed with extension of the equalization and release tool and more particularly with a feature allowing forcible retraction of a lower slip cone from the lower slips should the slips fail to release with operation of the release mechanism. 
       BACKGROUND OF THE INVENTION 
       [0002]    Packers and bridge plugs serve as wellbore isolation devices. The main difference is that bridge plugs have no passage through a mandrel and are an absolute barrier, while packers have a mandrel passage and are usually associated with a valve to control flow between zones that are isolated from each other when the packer is set. In either case, these devices when set will have some differential pressure across them and the standard procedure for safe operation is to equalize the pressure across the packer or bridge plug first before release of the slip and seal assembly of the packer or bridge plug. 
         [0003]    Very old designs involved a single movement of a mechanism to accomplish both tasks. This movement was in a single direction where the initial movement first equalized and continued movement in the same direction then released the slips and seal elements of the packer or plug. One potential problem with such a design is if the slips and seal of the packer or plug are released before the equalization has fully finished there could be a large enough force left on the packer to send it moving in a direction toward the surface which could send the tubular string attached to such packer moving out of the hole and create a dangerous condition. Accordingly subsequent designs sought to make the equalizing step discrete from the release step by using two discrete mechanisms and a grip tool that is initially blocked from grabbing the release mechanism as it initially grabs the equalizing mechanism by a plurality of dogs that act as travel stops. After the grip tool engages the equalizing mechanism and picks it up to equalize, a recess is presented opposite the dogs acting as a travel stop so that on a subsequent jarring down movement after equalization, the release mechanism is gripped because the dogs acting as a travel stop have gone into the recess so that a subsequent jarring up motion then releases the slips and sealing element of the packer. This system is described in detail in Bishop U.S. Pat. No. 8,322,413. Some problems inherent to this design are that wellbore debris could deposit near the dogs or their associated recess so that the packer release mechanism could not be gripped by the grip tool making release of the packer difficult if not impossible and dictating a milling operation for removal of the packer. Another issue with the Bishop &#39;413 design was that once the lock ring below the slips was released to allow the packer to extend in a downhole direction for retraction of the upper and lower slips and sealing element there was still an issue as attempts were made to bring up the packer of the slips either not releasing their grip on the surrounding tubular or the slip cone not extending far enough away from the slips or getting pushed back under the slips as the packer was moved uphole causing the packer to get stuck. 
         [0004]    To address these issues a grip tool was designed that eliminates the need for the dogs that act as a travel stop by having a grip tool that is initially only capable of reaching the equalizing mechanism. After equalization a further force applied in the same direction as for the equalizing results in a reconfiguration of the grip tool and locking the grip tool in the reconfigured position. In the locked reconfigured position, the grip tool is capable of engaging with the packer or plug release mechanism with an applied force. After such latching the applied force direction is reversed and the tool is released with an undermining of the ratchet lock used initially to hold the set position. In the event of a failure to release just relying on the stored potential energy of the set packer element an option is provided to re-engage the lower ratchet lock and transfer a downhole force to the lower slip cone to push the lower slip cone downhole from under the slips so as to provide another opportunity to get the slips and packer seal to release. An emergency release is provided to be able to remove the grip tool if the equalizing and release mechanisms fail to operate so that the grip tool and associated wireline can be removed from the borehole before fishing is attempted. 
         [0005]    These and other features will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while keeping in mind that the full scope of the inventions described herein are to be determined by the appended claims. 
         [0006]    Retractable slips are illustrated in U.S. Pat. No. 4,813,486 while retrievable bridge plugs and associated running tools are discussed in U.S. Pat. No. 5,366,010. Also relevant to telescoping tools are U.S. Pat. No. 6,349,770; completion method with telescoping perforation and fracturing tool U.S. Pat. No. 7,604,055; Downhole telescoping tool with radially expandable members WO 2011028812 and method and apparatus for accommodating telescoping action U.S. Pat. No. 3,354,950. 
       SUMMARY OF THE INVENTION 
       [0007]    A tool equalizes a packer or bridge plug before it can release the slips and sealing element of the packer or bridge plug with a reconfigurable grip tool. In one configuration the grip tool is latched only into the equalizing mechanism for the packer or bridge plug. Having equalized the pressure and while still latched to the equalization mechanism the tool is reconfigured with a force and locked into a second configuration. From that position the grip tool can latch and move the release mechanism for total release and retrieval to the surface. Release force undermines a ratchet lock for the slips to allow extension as the sealing element extends axially and radially retracts. If the slips fail to release with undermining of the ratchet lock then a set down force can be applied to re-engage the lower slip cone to push it from the lower slips for a release. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIGS. 1 a -1 d    show a bridge plug in the run in position in section; 
           [0009]      FIGS. 2 a -2 b    show a section view of the grip tool in the initial configuration where the equalizing sleeve assembly can be gripped; 
           [0010]      FIGS. 3 a -3 b    is the view of  FIGS. 2 a -2 b    with the grip tool latched in a second and longer configuration so that it can reach the release sleeve; 
           [0011]      FIGS. 4 a -4 b    is the view of  FIGS. 3 a -3 b    with the grip tool engages to the release sleeve and ready to release the packer or bridge plug; 
           [0012]      FIGS. 5 a -5 d    show a section view of the bridge plug in the set position; 
           [0013]      FIGS. 6 a -6 e    is the view of  FIGS. 5 a -5 d    in the released position and ready for removal from the borehole; and 
           [0014]      FIG. 7  is an exterior view at the top of the bridge plug showing the alternating finger structure for the equalizing sleeve and the release sleeve. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]      FIGS. 1 a -1 d    will be used to provide a quick review of the major bridge plug components with the understanding that the configuration is virtually the same for a packer except that the mandrel has a flowpath through it. The illustrated bridge plug  10  has a seal assembly  12  with an embedded upper band spring  14  and a lower embedded band spring  16 . An upper cone  18  and lower cone  20  flank upper slips  22  and lower slips  24 . An inner mandrel  26  has a through passage  28  that provides a flow path starting from ports  30 , through passage  28 , to openings  32  shown in  FIG. 1 b   . Ports  34  are closed by sleeve  36  straddling o-rings  38  and  40 . Sleeve  36  is connected to equalizer sleeve  42  at thread  44 . Sleeve  42  has an exterior profile  46  which is initially retained by the grip tool shown in  FIGS. 2-4 . The grip tool can be lowered into the  FIG. 2  position on wireline, slickline, coiled or rigid tubing. When used with wireline or slickline, the assembly further features a jar tool of a type known in the art for force application as needed in opposed directions as will be explained below. Equalizing the set plug  10  happens with movement of sleeve  36  away from overlapping at least o-ring  40 . This happens when the top end  48  of sleeve  42  is picked up with the grip tool and raised against travel stop  50  as shown in  FIG. 3   a.    
         [0016]    Packer or plug release sleeve  52  has a similar exterior profile  54  as the previously described profile  46  except the locations for the multiple profiles  54  that appear on ends of a finger structure  56  shown in  FIG. 7  are circumferentially offset from the profiles  46  that appear on another set of axial fingers  58  shown in  FIG. 7 . The release sleeve  52  initially traps collet heads  60  in groove  62  to prevent movement of upper mandrel  64  that is secured to inner mandrel  26  at thread  66 . Mandrel body  68  is connected to support collet body  70  at thread  72 . Lower collet  74  is connected at thread  76  to the lower end of mandrel body  68 . Opposed arrows  78  and  80  represent the location a well-known setting tool applied force for setting the plug  10 . A wireline setting tool such as the E-4 sold by Baker Hughes Incorporated of Houston TX can be used to set the plug  10 . The setting axially compresses the plug  10  to force out the slips  22  and  24  and the sealing assembly  12  in a known manner. An upper ratchet ring  82  will then engage a profile  84  on mandrel body  68  that starts out located further downhole before the setting of the plug  10  as shown in  FIG. 1 b   . At the lower end a lower collet  74  has an exterior profile  86  engaged to profile  88  and held engaged by the placement of surface  90  of inner mandrel  26 . A recess  92  can be selectively aligned with profiles  86  and  88  to release them from each other when the plug  10  is released. Profile  88  is on lock ring  96 . Lower cone  20  has a ratchet profile  94  configured to allow ratchet profile  86  to ratchet over it when profile  86  moves uphole for release but when profiles  86  and  94  are re-engaged there is only force transmission into the lower cone  20  and no ratcheting action. This feature comes into play if the slips  22  and  24  do not release when recess  92  aligns with lower collet  74 . In that event the mandrel body  68  is moved down to engage profiles  86  and  94  for tandem movement which has the result of pushing the lower cone  20  down and away from lower slips  24  to effect the release of the plug  10 . This new feature goes beyond typical lock ring arrangements that simply are defeated in an attempt to release the packer. At times the potential energy in the packer element is insufficient to extend the sealing element and slip arrangement. Alternatively, on the way out of the hole the slips can re-engage the surrounding tubular as the lower cone works its way back under the lower slips. The arrangement of ratchet profiles allows addressing such events by engaging profiles  86  and  94  for tandem downhole oriented movement to break the slips loose for another attempt to get the plug or packer to come out of the hole. 
         [0017]    The grip tool  100  is illustrated in  FIGS. 2-4 . Its purpose is to initially equalize the plug or packer  10  from the set position and then release and retrieve it. It is delivered in a variety of ways as mentioned above but a wireline (not shown) connected at  102  is preferred. Upper housing  104  advances until surfaces  106  and  108  shoulder out as shown in  FIG. 2 a   . Vent ports  110  allow fluid displacement from internal chamber  114  going over the shear stud  112  that is shown un-sheared. Normally, the E-4 wireline setting tool mentioned above is secured to the shear stud to apply a force in the direction of arrow  80  as shown in  FIG. 1 a    and discussed above. Normally the small diameter part of the shear stud  112  is supposed to be the shear location but sometimes the stud remains whole so that internal chamber  114  is sized to accept the whole shear stud  112  for those situations. Shear pins  116  allow for release of the tool  100  from the plug or packer  10  in the event the packer fails to equalize and release so that the wireline (not shown) and the tool  100  can be removed so that a fishing tool can be attached to profile  118  or alternatively the plug or packer  10  can be milled out. 
         [0018]    The profile  46  is initially gripped as outer collet support ring  120  and the grip collet ring  122  that is concentrically mounted to support ring  120  are deflected radially outwardly over the profiles  46  that exist at ends of extending fingers  58  as shown in  FIG. 7  and snaps back by the time surfaces  106  and  108  shoulder out. This initial movement can be accomplished with a downward jarring to get surfaces  106  and  108  to connect. A subsequent upward jarring with the collet ring  122  supported by ring  120  against the profile  46  results in movement of sleeve  36  away from o-ring  40  to open ports  34  for equalization of pressure through passage  28  as described above. The open position for sleeve  36  is also shown in  FIG. 6 a -6 b    where o-ring  38  has also been uncovered as the plug  10  is being removed. 
         [0019]    Having equalized pressure across the seal assembly  12  a further upward jar force is applied to tool  100  while still engaged to the profile  46  so that shear pins  124  fail as seen by comparing  FIGS. 2 and 3 . With pins  124  sheared the upward applied force results in telescopingly extending the tool  100  in an axial direction and locking in the extension with a snap ring  126  extending radially into surrounding groove  127  as shown in  FIG. 3 a   . This creates a gap between surfaces  128  and  130  which were previously abutting. It also locks in a greater distance between surface  108  and grip surface  132  such that when surface  108  acts as a travel stop when jarring down again the position of surface  132  will be below profiles  54  that are on fingers  56 . As shown in  FIG. 4 a   , an upward jar force then applied will pull up profiles  54  for the release of the plug or packer  10 . Sleeve  52  is pulled up to the point of engaging ring  134  after shearing screws  136 , which is best seen in comparing  FIGS. 3 and 4 . Movement of sleeve  52  releases collet heads  60  from their respective groove  62  which then allows upper mandrel  64  to move in the direction of arrow  138 . With upper mandrel  64  moving, inner mandrel  26  moves up to present recess  92  even up with locked profiles  86  and  88  so that they can then separate under the potential energy in the sealing element  12  to push the lower cone  20  out from under the lower slips  24 . A pickup force on the tool  100  should then get surfaces  140  and  142  to shoulder out as shown in  FIG. 6 c    so that the tool  100  can remove the plug  10  from the borehole. As explained above, if the plug  10  does not release this way, jarring down on tool  100  brings profiles  86  and  94  back together for tandem movement in a downhole direction to force the lower cone  20  downhole and out from under the lower slips  24 . 
         [0020]    Those skilled in the art will appreciate that the extendable nature of the tool overcomes a risk of debris preventing the dogs in U.S. Pat. No. 8,322,413 from retracting. Such a failure of the dogs to retract into a recess will prevent plug or packer release as the tool in that patent would be precluded from reaching the release sleeve. By providing an extendable tool that is run in to release the packer or plug the exposure of components to wellbore debris is minimized thereby insuring operability when needed to equalize and release the packer. Instead of the dog design of the past, the telescoping feature of the tool  100  allows for a simple way to integrate the ability to change the reach of the tool to sequentially equalize and then release the plug or packer. The use of the ratchet profiles that lock together for tandem movement in a downhole direction provides a backup way to get the slips and sealing element to release in the event that jarring up on the release sleeve and reliance on the potential energy in the sealing element  12  does not allow the slips and sealing element to extend axially so that they retract radially to allow plug removal. 
         [0021]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: