Abstract:
A positioning tool engages a profile with retaining members such as dogs so that a pulling force can be applied for a predetermined time as a signal that the tool is at the proper location. The time delay is a fluid system that drives fluid through a narrow restriction. The restriction is variable to allow unloading of the resistance from the fluid system while the dogs are still adequately supported. As a result the dogs are released from the profile without regional overstressing. A lock can prevent the tool from resetting to limit its use to locating at a single location. The lock holds the hydraulic system in a defeated position so that even if the dogs engage another profile when locked they will immediately exit that profile.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is an indicating tool that lands one or more dogs in a recess to give a surface signal of its location and more particularly features of such tools that protect the dogs that engage the downhole recess as the tool is released after giving the surface signal indication. 
       BACKGROUND OF THE INVENTION 
       [0002]    Position indicating tools for subterranean use are illustrated in U.S. Pat. No. 7,284,606. The elements of this tool are a series of dogs that find a groove generally after passing that groove and being brought back up into engagement. Once the dogs engage a force is placed on the string. This force moves the string up against resistance of fluid that is forced from one reservoir to another through a restriction orifice. The orifice provides a time delay that is sufficiently long to realize at the surface that the tool is properly located before a release of the stress on the dogs in the groove starts to happen. The idea is that the delay is long enough to allow surface personnel to reduce the pulling force so that at the time there is a release the applied force on the dogs is also reduced. 
         [0003]    In field applications there still seemed to be severe wear on the dogs causing them to have to be replaced at more frequent intervals than was desired. One of the problems was that surface personnel would forget or react too slowly in reducing the applied force at the time of release so that no decrease in the wear rate of the dogs could be achieved. Even if the applied pulling load was reduced at the time of release, there was still an issue of the hydraulic system still operating to force fluid through the orifice as relative movement between a mandrel being pulled on and the dogs still in the groove continued to stress the dogs as progressively less contact area supported the dogs in the surrounding groove as well as on the mandrel at a location under the dogs. Despite the reduced pulling force, the progressive decrease in contact support area on various locations on the dog as it was being released, increased those localized stresses. As a result pieces of the dog were still subject to overstress to the point where pieces of the dog near such overstressed local regions would simply be sheared off. This required frequent maintenance to the dogs generally by a replacement of parts. 
         [0004]    Another issue with the prior tool was that if there were many indicating recesses in the wellbore, there was a possibility that the tool would engage them on the way out and to get the tool to release the same metering procedure as initially undertaken would need to be repeated. This could take time and that results in additional expense to the operator. 
         [0005]    Other tools in the past that would only shift a given downhole sliding sleeve once and could not re-latch if the sleeve had been shifted close enough to a travel stop are shown in U.S. Pat. No. 5,636,694. However, there was no mechanism on the tool itself that kept it from re-engaging after a given sleeve shift. What prevented this tool from re-engaging a sleeve it had just shifted was that the sleeve in question had moved to the desired position. This tool would still engage other similarly configured sleeves as it had a reset capability. 
         [0006]    The present invention improves on the design of the position locating tool in U.S. Pat. No. 7,284,606 and modifies it in several respects. It unloads the hydraulic system while the dogs are still sufficiently supported to minimize the shearing issues with the dogs. The unloading occurs with the dogs still sufficiently supported so that stress will not intensify at the time of release to the extent that localized failure can occur. An optional feature allows the tool to be a single time operation by disabling the metering system by virtue of holding the shifted position of parts after a single use so that the metering system is disabled and the tool is prevented from resetting. While the dogs can go into other recesses in the disabled condition, the metering system is not operative and the dogs will simply jump back out of any such grooves when a minimal uphole force is applied to the tool body on the way out of the subterranean location. These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is given by the associated claims. 
       SUMMARY OF THE INVENTION 
       [0007]    A positioning tool engages a profile with retaining members such as dogs so that a pulling force can be applied for a predetermined time as a signal that the tool is at the proper location. The time delay is a fluid system that drives fluid through a narrow restriction. The restriction is variable to allow unloading of the resistance from the fluid system while the dogs are still adequately supported. As a result the dogs are released from the profile without regional overstressing. A lock can prevent the tool from resetting to limit its use to locating at a single location. The lock holds the hydraulic system in a defeated position so that even if the dogs engage another profile when locked they will immediately exit that profile. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a half section of the tool in the position where a pulling force is started with the dog in the locating groove; 
           [0009]      FIG. 2  is the view of  FIG. 1  with the hydraulic system about to release while the dog is still adequately supported in the locating groove; 
           [0010]      FIG. 3  is the view of  FIG. 2  with the dog released and the relative movement of the components optionally locked; 
           [0011]      FIG. 4  is the view of  FIG. 1  but enlarged to show the tapered pin of the hydraulic system in the in initial position; 
           [0012]      FIG. 5  is the view of  FIG. 2  with the tapered pin of the hydraulic system having the larger portion just coming out of the bore; 
           [0013]      FIG. 6  is the view of  FIG. 3  with the smaller portion of the tapered pin out of the restricted bore in the hydraulic system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    As shown in  FIG. 1  a subterranean string  10  has one or more locating grooves  12  that accept one or more dogs  14  that extend from an outer dog housing  16  through one or more openings  18 . The dogs  14  are biased outwardly and retained from coming out of the outer housing  16  in a way that is known in the art and described in U.S. Pat. No. 7,284,606. Dogs  14  have internally oriented raised surfaces  20  and  22  that can reside in contact with surfaces  24  and  26  for run in. Surfaces  24  and  26  are located on mandrel  28 . In the run in position, if an obstacle is encountered running downhole, the dogs  14  move against a bias (not shown) to duck into recesses  30  and  32  so that the obstruction can be cleared. At the same the mandrel  28  can move down taking housing  17  with it as will be explained below. After the obstruction is cleared the dogs  14  go back to the  FIG. 1  position. As seen in  FIGS. 2 and 3  the dogs  14  retract toward surfaces  32  and  34  after the uphole pulling occurs on mandrel  28  for a predetermined time as will be fully explained below. 
         [0015]    The hydraulic system  36  can be seen in a larger scale in  FIGS. 4-6 . Mandrel  28  and outer housing  16  define a first variable volume chamber  38  that has seals  40  and  42 . Passage  44  leads to variable volume chamber  46  that is in part defined by a floating piston  48  having a seal or seals  50 . A spring  52  pushes on piston  48  and is located in chamber  54 . The purpose of biased piston  48  is to act as the thermal expansion compensator for the hydraulic fluid in the cavities  38  and  46  and the passage  44  that connects them. Pin  56  has at least two different diameters  58  and  60  best seen in  FIG. 6 . A ring  62  is attached to an end of the pin  56  at diameter  60  and is designed to engage a shoulder  64  as a travel stop when mandrel  28  is pulled uphole for the metering function. When running in, ring  62  also rests on shoulder  63  to take down housing  17  with mandrel  28  so that housings  17  and  16  separate until the dogs  14  clear an obstruction when running in and the dogs  14  can then pop out under bias (not shown) to put the housings  16  and  17  back together again. With the dogs  14  landed in recess  12  and an upward force put on the mandrel  28  the volume of chamber  38  decreases while the volume of chamber  46  increases as hydraulic fluid has to pass through passage  44 . 
         [0016]    The metering process is illustrated in a comparison of  FIGS. 1-3 . In  FIG. 1  the dogs  14  are in the recess  12  and fully supported at surfaces  20  and  22  such that the uphole corner  66  of the dogs  14  is firmly in the recess  12  and against surface  68 . As the pulling force is applied from the surface to the mandrel  28 , it starts coming up. There is resistance to mandrel  28  rising as hydraulic fluid has to be forced from cavity  38  into cavity  46  through passage  44 , which at the time has the larger diameter  60  still in bore  44  to provide heightened resistance to fluid flow. This is intended so as to give time for surface personnel to realize that the proper location has been reached. Thus far the metering operation is unchanged from the operation of the previous design in U.S. Pat. No. 7,284,606, but what happens next is very different. 
         [0017]      FIG. 2  shows the position of the dogs  14  at the onset of release of the dogs  14  from the recess  12 . Surfaces  20  and  22  are still substantially supported to the tune of preferably at least 50% of their surface area, off of surfaces  24  and  26 . The dogs have yet to start inward retraction from the recess  12  because surfaces  24  and  26  are still precluding that movement. Accordingly, there is still unchanged contact between the upper end  66  of the dogs  14  and the corresponding surface  68  in the recess  12 . Looking at  FIG. 5  at this time the very end of the larger diameter  60  in bore  44  to mark the imminent disappearance of resistance to fluid flow through passage  44 , which will happen as soon as the larger diameter portion  60  exits bore  44  leaving only the smaller diameter  58  in bore  44  which offers, relatively, very little resistance to flow through passage  44  from chamber  38  to chamber  46 . 
         [0018]    When the larger diameter portion  60  comes out of passage  44  the mandrel  28  can rapidly accelerate uphole. As the mandrel  28  accelerates uphole it is no longer pushing the uphole segment  66  of the dogs  14  against surface  68  of the recess  12 . Similarly, surfaces  32  and  34  rapidly present themselves opposite surfaces  20  and  22 . Comparing this to the operation of the prior tool, the metering system in the prior tool maintained resistance to uphole movement of mandrel  28  as surfaces  22  and  24  rode off the end of surfaces  24  and  26  and down the respective adjacent ramps  70  and  72 . This tended to break off pieces, in the old design, of surfaces  20  or  22  on the dogs  14  on one side and the transition between surfaces  24  and  70  or  26  and  72  on the other side. Additionally, as the dogs in the prior design moved in radially the contact area while under pulling load between the upper end  66  and the corresponding surface  68  in recess  12  was reduced so that either or both tended to break as the stress concentrated there before the total release of the dogs  14 . 
         [0019]    In the present invention the metering system  36  becomes disabled when the small diameter portion  58  is all that remains in passage  44 . This is calculated to occur before the stress rises to an unacceptable level at the upper end  66  and recess surface  68  or at surface  20  and opposed surface  24  or at surface  22  and opposed surface  26 . By disabling the metering system before too much stress builds up, shearing or fracture failures at those loading locations are minimized if not eliminated. Instead what happens is that dogs  14  are rapidly undermined and at worst there is some impact load of the lower end  74  against shoulder  76  or sleeve  16  and preferably against the two of them together as the movement of the sleeve  16  is preferably stopped where it draws up even to shoulder  76 . 
         [0020]    As an option the mandrel  28  can have a c-ring  78  in a groove  80  and sleeve  17  can have a recess  82 . As seen by comparing the  FIG. 5  and the  FIG. 6  positions, the c-ring  78  that comes up with mandrel  28  lines up with recess  82  and snaps into it locking sleeve  17  to mandrel  28 . There is an uphole bias on sleeve  17  that is not shown that basically is disabled when the c-ring  78  snaps into recess  82 . Without the locking feature the tool is built to reset as sleeve  17  is pushed by the unseen spring in an uphole direction against sleeve  16  so that surfaces  20  and  22  can again come into alignment with surfaces  24  and  26  for landing in the same or another recess such as  12 . However, with sleeve  17  locked in a further downhole position than during run in, the downhole bias on sleeve  16  cannot be offset and such downhole bias ensures that surfaces  20  and  22  stay offset from supporting surfaces  24  and  26  so that the dogs  14  cannot land and stay in another recess such as  12 . It should be noted that the uphole bias on sleeve  17  and the downhole bias on sleeve  16  were in the previous design of U.S. Pat. No. 7,284,606 were accomplished respectfully by springs  36  and  40  in that patent that is fully incorporated in this application as if fully set forth. 
         [0021]    Those skilled in the art can appreciate that variations of the locking concept to prevent the dogs  14  from catching and metering in another groove are possible as alternatives to the c-ring  78  catching in groove  82 . One such alternative is a ratchet design or a multi-sided ratchet ring known as a body lock ring to name a few alternatives. The change in resistance in the metering system  36  is preferably accomplished with the elongated element having differing diameters  58  and  60  but other techniques can be used to resist flow in passage  44  and then suddenly decrease it or eliminate it. For example, some combination of a fixed orifice and a rupture disc in parallel paths between chambers  38  and  46  can bring about the same result. 
         [0022]    It should also be noted that without the locking system for housing  17  that the release of the dogs  14  in the manner described above will bring up housing  17  so that the larger diameter  60  will again be in passage  44  and the dogs  14  will be supported on surfaces  24  and  26  and ready to land in another recess  12  to repeat the metering process. 
         [0023]    Note also that section  58  having the smaller cross-sectional area can also be eliminated and flow can be restricted with segment  60  either in or out of passage  44 . However, having portion  58  still in the passage  44  when portion  60  comes out allows segment  58  to act as an alignment guide for the elongated member  56  so that if the tool is allowed to reset the member  56  can retain alignment and simply go right back into passage  44  without getting cocked or bent. 
         [0024]    While the preferred contact area of surfaces  20  and  22  respectively on surfaces  24  and  26  is at least 50% by area at the time segment  60  exits passage  44 , that number can change depending on the material of dogs  14  and mandrel  28  and the geometry of the dogs  14 . The objective being that stress is limited to levels that will not cause rapid wear or part destruction from normal operations. The idea being to release the metering system  36  before stresses can concentrate to levels that cause stress cracks or shear off portions of the dogs  14  or supporting structures on the mandrel  28  or the profile  12 . 
         [0025]    Another optional feature is to provide a pressure relief feature  39  to chamber  38  to prevent overpressure of that chamber if the mandrel  28  is pulled up too fast from the surface. Preferably this pressure relief can be through the wall of the housing  17  and can be in the form of a resettable pressure relief valve (not shown). Of course, setting off this relief device will defeat the metering function as resistance to rapid upward movement of the mandrel  28  will disappear as the dogs  14  move radially inwardly. In that sense the device will revert to operation as in U.S. Pat. No. 7,284,606 until the pressure relief device resets such as when the rapid pulling force on mandrel  28  is relaxed. If there is a lockout feature after a single use then the device will have to be brought out of the hole and be reset before the dogs  14  can engage another groove or the same groove  12  in the wellbore. 
         [0026]    As another option to preventing the dogs  14  from re-engaging other grooves after an initial release, which can be in addition to locking sleeve  17  as shown in  FIGS. 3 and 6 , the dogs  14  themselves can be held retracted by magnetic or band spring or other radially inward oriented force to hold the dogs retracted in recesses  32  and  34 . The dogs  14  can be magnetized or have a magnetic strip on their underside or the strip can be in the recesses  34  or  32 . 
         [0027]    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.