Abstract:
A technique utilizes a fishing tool and method for retrieving a fish from a downhole location without removal of a downhole completion. The fishing tool comprises a housing and a piston slidably mounted in the housing. Grip legs are engaged with the piston such that movement of the piston in a first direction along the housing moves the grip legs to a disengaged position for receiving the fish. Subsequent movement of the piston in a second direction causes the plurality of grip legs to move to an engaged position with the fish. The grip legs can be moved between the disengaged and engaged positions after the fishing tool is moved through the completion.

Description:
BACKGROUND 
       [0001]    In a variety of well applications, completions are deployed in wellbores that have wellbore casings along the wellbore wall. Sometimes, downhole tools are lost within the casing but beyond the tubing associated with the completion. The lost well tool can become a restriction and block or limit the flow of production fluid up through the completion. The well tool also can create complications for subsequent downhole operations. 
         [0002]    Retrieval of the well tool can be accomplished via a fishing operation in which a fishing tool is deployed downhole from a surface rig. The fishing tool comprises a latching or attachment end designed to engage the well tool, i.e. fish, to be retrieved. However, deploying a fishing tool past the completion can be very complicated. Often, a work-over rig is used to first retrieve the completion and then the fishing operation is conducted to retrieve the fish. This results in an expensive and time-consuming process for retrieving the well tool. As a result, the well tool is sometimes left downhole in spite of the potential for production flow blockage and additional complications during subsequent operations downhole 
       SUMMARY 
       [0003]    In general, the present invention provides a fishing tool and method for retrieving a fish from a downhole location. The design of the fishing tool enables it to be moved downhole through a completion, thereby avoiding the need to remove the completion. The fishing tool comprises a housing and a piston slidably mounted in the housing. A plurality of grip legs are engaged with the piston such that movement of the piston in a first direction along the housing causes the grip legs to move to a disengaged position for receiving the fish. Subsequent movement of the piston in a second direction causes the plurality of grip legs to move to an engaged position with the fish. Actuation of the grip legs can be conducted after the fishing tool is moved through the completion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
           [0005]      FIG. 1  is a front elevation view of a fishing tool system being deployed into a wellbore to retrieve a fish, according to an embodiment of the present invention; 
           [0006]      FIG. 2  is a front elevation view of the fishing tool system with a fishing tool actuated to a disengaged position to retrieve the fish, according to an embodiment of the present invention; 
           [0007]      FIG. 3  is a front elevation view of the fishing tool system with the fishing tool actuated to an engaged position latched onto the fish, according to an embodiment of the present invention; 
           [0008]      FIG. 4  is an orthogonal, cut away view of an embodiment of a fishing tool used with the fishing tool system of  FIG. 1 , according to an embodiment of the present invention; 
           [0009]      FIG. 5  is an orthogonal, cut away view of a housing used in the fishing tool of  FIG. 4 , according to an embodiment of the present invention; 
           [0010]      FIG. 6  is an orthogonal, cut away view of a piston used in the fishing tool of  FIG. 4 , according to an embodiment of the present invention; and 
           [0011]      FIG. 7  is an edge view of a gripping leg used in the fishing tool of  FIG. 4 , according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
         [0013]    The present invention relates to a system and methodology for performing a fishing operation. The system and methodology utilize a fishing tool that can be moved past a completion located in a wellbore. The fishing tool is easily adapted for different size wellbores and completions while being amenable for attachment at the end of many types of fishing assemblies. 
         [0014]    For example, the fishing tool can be rigged up at the end of a fishing tool assembly deployed downhole on a coiled tubing string. In one embodiment, the coiled tubing string is run in hole with the fishing tool attached while fluid is pumped downhole through the coil tubing string and fishing tool. The pumped fluid prevents accumulation of debris inside the fishing tool. Once the fishing tool is moved past the completion, the pumping rate is increased to actuate the fishing tool to a disengaged position. For example, the fishing tool can be actuated to move grip legs outwardly toward or against the surrounding casing wall until the fish is reached. In this example, the fishing tool is moved slowly into engagement with the fish until a pressure increase is indicated at the surface. At this point, the pumping of fluid down through the fishing tool is stopped to enable the grip legs to retract to an inward, engaged position, as described in greater detail below. 
         [0015]    Referring generally to  FIG. 1 , one example of a well system  20  is illustrated according to an embodiment of the present invention. In this example, well system  20  comprises a fishing tool assembly  22  having a fishing tool  24  that is being delivered downhole into a well via a conveyance  26 , such as a coiled tubing conveyance. The fishing tool  24  is moved downhole through a completion  28  and towards a well tool  30 , i.e. fish, which is to be retrieved. 
         [0016]    The completion  28  is located in a wellbore  32  that is lined with a well casing  34 . As illustrated in  FIG. 1 , wellbore  32  extends down from surface equipment  36  positioned at a surface location  38 . Surface equipment  36  may comprise a rig for deploying fishing tool  24  and conveyance  26 . Fishing tool  24  is appropriately sized for movement through and past the completion  28  to enable retrieval of the fish  30  from a section of the wellbore  32  below completion  28  without removing completion  28 . During movement downhole, a fluid may be pumped down through conveyance  26 , e.g. coil tubing, and through fishing tool  24 , as indicated by arrows  40 . The flow of fluid prevents debris from accumulating in fishing tool  24  during run in of the fishing tool. 
         [0017]    In the embodiment illustrated, fishing tool  24  comprises a latching mechanism  42  designed for attachment with fish  30 . The latching mechanism  42  may comprise a plurality of grip legs  44  that are mounted for cooperation with a fishing tool housing  46 . During deployment of fishing tool  24  through completion  28 , the grip legs  44  are held in an inward or engaged position to enable movement of the fishing tool through the confines of completion  28 . Once the fishing tool  24  is moved past the distal or lower end of completion  28 , fishing tool  24  is actuated to a disengaged position, as illustrated in  FIG. 2 . 
         [0018]    The disengaged position can be adjusted according to the type of fish to be retrieved and the corresponding latching mechanism  42 . In the example illustrated, however, the disengaged position is achieved by moving grip legs  44  outwardly toward casing  34 . Movement of grip legs  44  to the disengaged position is enabled by increasing the flow of fluid (see arrows  40 ) down through conveyance  26  and fishing tool  24 . As illustrated in  FIG. 2 , the grip legs  44  may be pivoted outwardly into contact with casing  34  to ensure engagement with fish  30  regardless of the orientation of fish  30  within wellbore  32 . The grip legs  44  can be biased to this outward, disengaged position by, for example, springs  48 . 
         [0019]    Upon actuation of grip legs  44  to the outward position, fishing tool  24  is lowered onto fish  30 . The fishing tool  24  is then actuated to the engaged position in which grip legs  44  move inwardly to close over fish  30 , as illustrated in  FIG. 3 . Actuation to the engaged position enables retrieval of fish  30  and can be induced by stopping the downward flow of fluid through conveyance  26  and fishing tool  24 . 
         [0020]    Referring generally to  FIG. 4 , one embodiment of fishing tool  24  is illustrated in greater detail. In this embodiment, fishing tool  24  comprises housing  46  and grip legs  44  having connection ends  50  that are selectively moved into and out of housing  46 . In  FIG. 4 , connection ends  50  are illustrated as pulled into housing  46  which forces the grip legs  44  to pivot inwardly to the inward, engaged position. When connection ends  50  are moved out of housing  46 , springs  48  cause the grip legs  44  to pivot outwardly to the disengaged position (see  FIG. 2 ). 
         [0021]    As illustrated, fishing tool  24  also comprises a piston  52  slidably mounted within housing  46  and connected to grip legs  44 . When piston  52  moves relative to housing  46  in one direction, grip leg connection ends  50  are forced out of housing  46  to enable pivoting of grip legs  44  to the outward, disengaged position. Upon movement of piston  52  in another/opposite direction, connection ends  50  are pulled into housing  46  and grip legs  44  are forced inwardly to the inward, engaged position. Piston  52  may be biased in a direction that pulls connection ends  50  into housing  46  by a suitable spring  54  positioned within housing  46 . 
         [0022]    The fishing tool is operated hydraulically with a flow of liquid that can be placed under increased or decreased pressure as necessary to actuate the fishing tool. The fishing tool is designed to enable liquid flow therethrough to clear debris from the fishing tool during movement downhole. When the liquid flow is increased, however, pressure builds up against piston  52  and moves piston  52  within housing  46  against the bias of spring  54 . The piston movement pushes grip legs  44  out of housing  46  so the grip legs can expand toward the casing walls to swallow the fish. As the fishing tool  24  swallows the fish via continued downward movement of conveyance  26 , the fish tends to push against piston  52  which restricts flow and provides a pressure increase indication to the surface. At this time, the flow of fluid down through the fishing tool  24  is stopped and spring  54  moves piston  52  in an opposite direction, drawing connection ends  50  back into housing  46 . As the connection ends  50  are pulled back into housing  46 , the grip legs  44  are pivoted inwardly into a locked position on the fish  30 . 
         [0023]    Housing  46  may be constructed in various sizes and configurations depending on the specific fishing applications. One example of housing  46  is illustrated in  FIG. 5  and comprises a generally cylindrical housing having a connection end  56  for connection to a variety of fishing assemblies. By way of example, connection end  56  may be a threaded connection end for threaded engagement into a fishing assembly. Opposite connection end  56 , housing  46  comprises a locking end  58  into which connection ends  50  of grip legs  44  are drawn to lock the grip legs into the engaged position. 
         [0024]    As illustrated, the housing  46  comprises an abutment ring  60  against which spring  54  is trapped by piston  52 . A passage  62  extends axially through the abutment  60  and has one or more O-rings  64  that seal against a shaft portion  66  of piston  52 , as illustrated best in  FIG. 6 . 
         [0025]    As further illustrated in  FIG. 6 , piston  52  comprises a head portion  68  on one end of shaft portion  66  and a connection region  70  disposed on an opposite end of shaft portion  66 . An axial flow passage  72  extends through piston  52  to enable fluid flow therethrough. In some embodiments, the maximum rate of flow that can be moved through flow passage  72  without shifting piston  52  is adjustable via a variable port  74 . Variable port  74  can be interchangeable or otherwise variable to increase or decrease the amount of fluid that can be flowed through fishing tool  24  without shifting fishing tool  24  to the disengaged position. 
         [0026]    Head portion  68  comprises a pressure surface  76  against which pressure is applied to move piston  52  against spring  54  and thereby actuate fishing tool  24  to the disengaged position. Pressure is applied by increasing the fluid flow downhole beyond the capacity of flow passage  72  such that pressure increases against surface  76  and shifts piston  52  relative to housing  46 . Head portion  68  may further comprise an O-ring  78  that is positioned to form a seal with the interior of housing  46 . 
         [0027]    Connection region  70  may be constructed in a variety of configurations depending on the desired method of attaching grip legs  44 . By way of example, connection region  70  may comprise a plurality of pivots designed for connection with corresponding pivots  80  of grip legs  44 , as further illustrated in  FIG. 7 . By way of example, the grip legs  44  may be pivotably mounted to connection region  70  in a manner that captures connection ends  50  between connection region  70  and the surrounding locking end  58  of housing  46  when connection ends  50  are drawn into housing  46 . Furthermore, springs  48  can be connected between connection region  70  and grip legs  44 ; or the springs can simply be positioned to act against grip legs  44  in a manner that pivots the grip legs outwardly when piston  52  axially moves connection ends  50  out of the locking constraints of housing  46 . 
         [0028]    Grip legs  44  can be formed in a variety of configurations depending on the environment in which they are used and the types of well tools to be retrieved. In the example illustrated, each grip leg  44  comprises an elongate body  82  extending from its connection end  50 . The elongate body  82  may comprise a plurality of teeth  84  that function to securely grip and hold the fish  30 . By way of example, the teeth  84  may be oriented in an upward direction toward housing  46  to further facilitate the gripping and holding of fish  30 . 
         [0029]    In operation, the design of fishing tool  24  enables movement of the fishing tool past completions located in wellbore  32 . Application of sufficient fluid flow downhole to the fishing tool  24  increases pressure against pressure surface  76  of piston  52  so that piston  52  is shifted against the bias of spring  54 . Upon sufficient movement of piston  52  relative to housing  46 , grip legs  44  become free of locking end  58  of housing  46  and transition to a disengaged position. Conveyance  26  is then used to move grip legs  44  over the fish  30 , and the pressure against piston  52  is released. This allows spring  54  to shift piston  52  in an opposite direction along housing  46 , thereby drawing connection ends  50  of grip legs  44  back into housing  46 . Movement of connection ends  50  into housing  46  forces grip legs  44  to pivot inwardly and lock onto fish  30  for retrieval from the wellbore. The fish  30  can be released simply by pumping fluid at a sufficient rate to again create adequate pressure against piston  52  to shift the piston relative to housing  46  and move grip legs  44  to the disengaged position. 
         [0030]    The present system and methodology can be used to enable fishing operations in a variety of well configurations. The system and methodology further enable fishing operations to be conducted in a more time efficient and cost efficient manner by avoiding the need for removal of completions. Additionally, fishing tool  24  can be utilized with a variety of fishing tool assemblies, and the size and component configuration can be adjusted based on factors related to the fish to be retrieved, the wellbore environment, the completion equipment, and the other equipment utilized in the fishing operation. 
         [0031]    Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.