Abstract:
An overshot tool includes a grapple, a torque sub rotationally fixed to the grapple and a deformable member in operable communication with the torque sub. The torque sub is responsive to torsional movement thereof. A method for retrieving a fish with the tool is also included.

Description:
BACKGROUND 
       [0001]    When tools get stuck downhole or become unserviceable for other reasons, they may also not be easily removable simply by pulling them out of the hole with the string above but may require the use of a fishing device such as an overshot tool. As one of ordinary skill in the art will recognize, an overshot tool generally extends over an outside diameter of a stuck tool or stub, grabs onto that tool or stub and allows an operator to pull the tool or stub to surface with the overshot tool. Generally such overshot tools further include seals to maintain pressure integrity. 
         [0002]    Overshot tools have long been a valuable part of the fishing arsenal and have worked well for their intended purpose. Improvements, however, are always welcomed by the art. 
       SUMMARY 
       [0003]    An overshot tool includes a grapple, a torque sub rotationally fixed to the grapple and a deformable member in operable communication with the torque sub. The torque sub is responsive to torsional movement thereof. 
         [0004]    A method for retrieving a fish includes overshooting the fish with an overshot tool including a grapple, a torque sub rotationally fixed to the grapple, a top sub axial length adjustably attached to the torque sub, and a deformable member in operable communication with the torque sub. The method further includes actuating the grapple to contact the fish and adjusting an axial length of the top sub and torque sub to deform the deformable member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0006]      FIG. 1  is a schematic quarter section view of an embodiment of an overshot tool in a run in position; 
           [0007]      FIG. 2  is a schematic quarter section view of the embodiment illustrated in  FIG. 1  in an actuated position. 
       
    
    
     DETAILED DESCRIPTION  
       [0008]    In order to enhance understanding of the invention, Applicants have elected to describe first the components of the tool followed by a discussion of its operation. Referring to  FIG. 1 , each component of the device will be introduced. This is followed by reference to  FIGS. 1 and 2  together, wherein operation of the device is discussed. 
         [0009]    Overshot tool  10  comprises a bottom sub  12  attached at an uphole end thereof to a grapple  14  comprising a grapple housing  16  and grapple extension  18  (one or more individual extension pieces arranged annularly around the tool). The grapple further includes a contact layer  20  to interface between grapple extension(s)  18  and a stub  22  of a device or casing being overshot. At an uphole end of grapple  14 , a torque sub  24  is positioned and fixedly connected to the grapple  14 . The Torque sub  24  is telescopically operably connected to a top sub  26  meaning that the total length of the torque sub and the top sub together is adjustable. In one embodiment, the adjustability occurs at an interface between torque sub  24  and top sub  26 . This interface is, as illustrated, a position directing and following arrangement  28  wherein the telescopic nature of the connection is torsionally based. In such embodiment, a helical profile  30  such as a screw thread or ball thread etc. on one of the torque sub  24  or top sub  26  is followable by a following feature  32  such as a thread or ball, etc. at the other of the torque sub  24  or top sub  26 . Application of torque to top sub  26 , then, results in a telescopic difference in overall length of the combined torque sub  24  or top sub  26 . 
         [0010]    Addressing pressure holding capability is, at an inside dimension of sub  24  and sub  26 , an actuatable seal  34  that is responsive to the telescopic length of the torque sub  24 /top sub  26  combination. When the overall length of sub  24  and sub  26  is shortened, the seal  34  is actuated to contact, and in some embodiments fully seal with, stub  22 . Conversely, when the overall length of subs  24 / 26  is increased, the seal  34  is radially retracted/axially lengthened such that a light contact or even a clearance condition is achieved relative to the stub. A stop feature  36 , which may be a ring as shown, is disposed at the torque sub to prevent over-compression of the seal  34 . It should be noted that the axial dimension of the stop feature  36  is specific to the particular diameter of the stub  22  being overshot and must be adjusted accordingly prior to being run in the hole. For example, a stub with a smaller diameter would require an axially shorter stop, all other things being equal; a stub that has a larger diameter requires a shorter stop ring the greater the radial displacement of the seal. 
         [0011]    In one embodiment, to improve fluidity of operation and because as illustrated the top sub contacts the seal  34 , a thrust bearing  40  is disposed at an uphole end housing  42  of the seal  34 . The thrust bearing  40  allows transmission of the compressive force of the torsionally telescopic motion while reducing transmission to seal  34  of the torsional stress of operation of the tool  10 . A downhole end housing  44  of seal  34  is fixedly attached to torque sub  24  and no bearing at this location is needed. 
         [0012]    A backoff stop  46  is supported in top sub  26  to prevent the top sub  26  from unscrewing from the torque sub  24  during the process of unsetting the seal  34 . More specifically, during the unsetting process, when the top sub  26  is torqued to the left to relieve the pressure on the seal, That same left handed torque would cause a separation of the top sub  26  from the torque sub  24 . As this is undesirable, the backoff stop  46  is positioned to prevent this occurrence. The backoff stop in one embodiment and as shown is a ball disposed in a groove  48  between the top sub and torque sub. The backoff stop (ball)  46  translates in the groove  48  only so much before causing a binding interference between the torque sub  24 , ball  46  and top sub  26 . Once the binding interference occurs, unscrewing of the top sub  26  from the torque sub  24  is stopped. And finally, a stop bushing  50  is fixedly connected to top sub  26  to present a no go shoulder  52  whereby the overshot tool  10  will move downhole over the stub  22  only until an uphole end  54  of the stub  22  contacts shoulder  52 . 
         [0013]    Each of the components of tool  10  having been identified, reference is now made to  FIGS. 1 and 2  simultaneously for a discussion of the operation of the tool. 
         [0014]    Initially, it is to be understood that the target stub  22  is ready for retrieval, any dressing or other preconditions or pre-operations having been previously met or undertaken, respectively. 
         [0015]    The overshot tool  10  is made up at the surface and run into the hole via appropriate string (not shown). Downhole advance continues until end  54  of stub  22  contacts shoulder  52  of stop bushing  50 . At this point, the grapple  14  is actuated in a conventional way (as illustrated, by gravity) to compress contact layer  20  against the target stub  22 . This portion of the operation is the one relied upon to pull the stub (etc.) to surface as will be recognized by one of ordinary skill in the art. 
         [0016]    Once the grapple  14  is secured to the stub  22 , right hand rotation of the top stub  26 , which may be effected by rotation of the string from surface, providing the string is rotatable) or by a seal rotation device (whether or not the string is of a rotatable type), causes the overall length of the top sub  26  and torque sub  24  combination to diminish. It is to be appreciated that nothing inherent in the tool itself prevents the tool being configured oppositely to have a left hand rotation, if desired. This action causes a compressive load to be placed upon the seal  34 , which then radially displaces into contact with the stub  22 . This contact may be a sealing contact. The seal is capable of maintaining a high pressure differential once properly actuated. After completion of the foregoing, the fish (stub  22 ) can be pulled to surface. 
         [0017]    The overshot tool  10  can also be released from the stub if desired by opposite rotation to unactuate the seal  34  and then bumping down on the tool to release the grapple. In the illustrated embodiment the reverse rotation would be left hand rotation as the embodiment of the tool described has right hand threads. 
         [0018]    In one embodiment, seal  34  is a metal seal configured to have a predisposition to deform in a specific radial direction. To achieve this predisposition, one embodiment of the seal includes a plurality of lines of weakness disposed at the seal wherein at least one of the plurality of lines of weakness is toward an inside surface of the seal and at least one of the plurality of lines of weakness is toward an outside surface of the seal. The direction of deformation will be, when grooves are the lines of weakness, to close the grooves. Where alternate lines of weakness are created, the direction will be the same but material will flow or otherwise be modified in position during the deformation because the space occupied by a specific volume of material will become smaller thereby necessitating a change in position of the material. In one embodiment, the plurality of lines of weakness is three or more lines of weakness. In an embodiment utilizing three lines of weakness, the radial deformation of the seal will be toward the surface having two lines of weakness and away from the surface having one line of weakness. Alternative configurations of the seal include each of those discussed within U.S. Pat. No. 6,896,049, which is incorporated in its entirety herein by reference. 
         [0019]    While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.