Abstract:
A plug counter including a housing sized to receive and pass plugs. A helix sleeve rotatably positioned relative to the housing. The helix sleeve including a helical track having a plurality of consecutive turns. A key positionable relative to the helical track and responsive to movement of the helix sleeve in a first rotational direction, wherein the key prevents further movement of the helix sleeve in the first rotational direction after a selected number of plugs pass through the plug counter. Also included is a downhole tool including

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of an earlier filing date from U.S. Non Provisional application Ser. No. 12/564,539 filed Sep. 22, 2009, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    In the Drilling and completion industries it is often desirable to affect tools or formations at a great distance from a surface located facility such as a rig. One example of an operation intended to affect a formation is a fracturing operation. In order to perform such an operation, hydraulic pressure is built within a tubing string until the pressure exceeds formation capability for holding that pressure and fractures form in the formation. This type of operation is most effective if done in small incremental sections of a borehole for reasons related to control and distribution of fractures to serve the ultimate purpose of the borehole. Such purposes include hydrocarbon production, Carbon Dioxide sequestration, etc. 
         [0003]    In the art, fracturing discrete locations of the borehole tends to require a number of tools related to the pressuring of discrete locations. Such tools increase expense initially and generally create other issues to be overcome after the fracturing process is complete such as removal of the tools that enabled the pressuring of a discrete location. Where multiple fracturing locations are contemplated, generally a staged system must be built and administered correctly for it to work. One such system uses progressively larger seat diameters from the toe back to surface and then progressively increasing diameter balls. While the system works well, it is limited by the number of different size balls that can be used. Tolerance is also required in any system (due to such things as irregular shape of tubing secondary to borehole irregularity), which therefore further limits the number of diameters usable in a particular system. 
         [0004]    Since fracturing and other operations where it is desirable to isolate discrete locations continue to become more prevalent and ubiquitous, alternate systems for accessing and manipulating the downhole environment is always well received. 
       SUMMARY 
       [0005]    A plug counter including a housing sized to receive and pass plugs; a helix sleeve rotatably positioned relative to the housing, the helix sleeve including a helical track having a plurality of consecutive turns; and, a key positionable relative to the helical track and responsive to movement of the helix sleeve in a first rotational direction, wherein the key prevents further movement of the helix sleeve in the first rotational direction after a selected number of plugs pass through the plug counter. 
         [0006]    A downhole tool including a housing having a support and one or more plug passage recesses; a movable plug seat positionable to be supported by the support or aligned with the one or more plug passage recesses; a helix sleeve rotatable in response to movement of the movable plug seat, the helix sleeve having a helical track including a plurality of consecutive turns; and, a key responsive to movement of the helix sleeve and configured to prevent further movement of the helix sleeve and movable plug seat after a selected number of movable plug seat movements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0008]      FIGS. 1-4  illustrate a cross sectional view of one embodiment of the tool disclosed herein in four different positions; 
           [0009]      FIGS. 5-8  illustrate in partial transparent view a counter portion of the tool disclosed herein in four different positions corresponding to the positions shown in  FIGS. 1-4 ; 
           [0010]      FIG. 9  is a perspective view of an alternate moveable seat substitutable in the tool; and 
           [0011]      FIG. 10  is a schematic view of a portion of an alternate housing of the tool  10  shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1-4 , a plug counter tool  10  is illustrated in longitudinal cross section in four different positions to make apparent not only its structural constituents but its operation as well. It is initially noted that the term “plug” as used herein is intended to encompass tripping balls, darts, and similar structures that can be propagated through a borehole and/or tubing string to reach remote locations therewithin. The plug counter tool embodiments disclosed herein facilitate the use of a single size plug (or fewer sizes, if desired, in a particular application) for multiple actuation sequences. For example, where multiple fracture points are desired in a borehole, traditional fracturing would require a number of different diameter plugs used sequentially from smaller to larger as operations progress up the hole. With the tool embodiments described herein only one size plug is needed. 
         [0013]    Referring directly to  FIG. 1 , an outer housing  12  includes a support  14  to support a moveable plug seat  16 , which in the case of  FIG. 1  is presented by a set of collet fingers  18 . The support  14  and movable seat  16  operate together to catch a plug  20  after which the plug is passed or denied passage as discussed hereunder. The fingers  18  are supported by support  14  while the collet fingers are in the position shown in  FIG. 1 . Support for the fingers  18  is dependent upon the position of collet  22 , which is dependent upon the ability of a spring  24  to hold the collet  22  in the position shown in  FIG. 1 . More specifically, when a plug is seated in the seat  16  pressure can and will in operation be built uphole of the plug. The spring rate of the spring  24  selected dictates the amount of fluid pressure that can be resisted before the collet  22  moves in a downhole direction and the fingers  18  become unsupported. The spring  24  is a compression spring and as illustrated is a coil spring. It will hold the collet  22  in the illustrated position until a plug  20  engages the seat  16  and sufficient fluid pressure uphole of the plug overcomes the spring force of spring  24  and compresses the same. As the spring  24  is overcome by fluid pressure, the collet  22  moves in a downhole direction (to the right in the Figure) and moves the fingers  18  off of the support  14 . Just downhole of the support  14  is a plug passage recess  28  that will allow radial expansion of the fingers  18  (see  FIG. 2 ) by an amount sufficient to allow passage of the plug  20  through the seat  16 . After passage of the plug, fluid pressure equalizes across the seat  16  and the collet  22  returns to the position of  FIG. 1  under the bias of the spring  24 . 
         [0014]    Connected to the collet  22  is j-slot sleeve  30 . Sleeve  30  moves axially of the tool  10  along with the collet  22 . At a downhole end of the housing  12 , an anti-rotation sleeve  32  is attached to the housing. Sleeve  32  does not move relative to housing  12  in any way once the tool is assembled. Anti-rotation sleeve  32  includes one or more pin openings  34  into which one or more pins  36  will be individually inserted. Each pin  36  will thus be fixed to the anti-rotation sleeve  32  and extend into an alignment groove  38  of which there will be one or more in the j-slot sleeve  30 . The one or more pins  36  and respective alignment grooves  38  ensure that the j-slot sleeve  30  is not rotatable but is permitted to move only axially during operation of the tool  10 . Upon movement of the collet  22  induced by fluid pressure uphole of plug  20  as described above, the j-slot sleeve  30  will cycle back and forth axially of the tool  10 . 
         [0015]    Radially inwardly of the anti-rotation sleeve  32  and rotatable relative thereto is a helix sleeve  40  exhibiting a helical track  42  at an outside surface thereof. The helix sleeve  40  includes one or more j-slot followers  44  (one shown), which may be a part of the helix sleeve  40  or may be a separate component that is engaged with the helix sleeve  40 . In either event, the j-slot follower(s)  44  are configured to contact angled surfaces  46  and  48  of a j-slot  50  (see  FIG. 5 ) disposed at the j-slot sleeve  30  upon axial movement of the j-slot sleeve  30 . Because followers  44  are fixed to the helix sleeve  40 , the helix sleeve  40  will move rotationally about the j-slot sleeve  30  as the followers  44  move along each angled surface  46  or  48 . The impetus for this movement is the axial cycling of the j-slot sleeve  30  as described above. Each time a plug  20  lands at the seat  16 , thereby allowing pressure to build from uphole against the plug  20 , and hence urging the collet  22  to a position aligning the fingers  18  with recess  28 , the followers  44  will contact and slide along one of the angled surfaces  46 . This will cause a measured rotation of the helix sleeve  40 . Because the spring  24  is compressed during this pressure induced axial movement, energy is stored that will be used to urge the followers  44  along the next adjacent angled surface  48  pursuant to the j-slot sleeve  30  moving uphole under spring bias, causing another measured rotation of the helix sleeve  40 . The spring  24  induces such movement only after the plug  20 , against which fluid pressure had been applied, is released. 
         [0016]    As the helix sleeve  40  rotates, a key  52  that is engaged with the helical track  42  moves leftwardly in the drawing closer to an end  54  of a keyway  56 . It is to be appreciated that although the illustrated embodiment moves in an uphole direction, the tool  10  can easily be configured to allow movement of the key  52  in a downhole direction by reversing the helix angle of the helical track  42  and reversing the surface angles of surfaces  46  and  48 . As illustrated in  FIGS. 1 and 5 , the key  52  is in a position that will allow the greatest number of plugs to pass before preventing passage of the next plug to be seated.  FIGS. 4 and 8  show the key in the position where the next plug to seat will not pass. 
         [0017]    As configured the tool  10  will pass a number of plugs and then prevent further passage of plugs because the helix sleeve  40  is prevented from rotating by the contact between key  52  and an end  54  of keyway  56 . The prevention of rotation of the helix sleeve  40  correspondingly prevents the j-slot sleeve  30  from cycling downhole sufficiently to allow the fingers  18  to reach the recess  28 . Consequently the plug  20  cannot pass. This position is illustrated best in  FIG. 8  where key  52  is at end  54  and follower  44  is at surface  46  but it cannot slide on surface  46  because the key will no longer allow rotation of the helix sleeve  40  due to having run out of helical track  42 . It is to be understood, then, that the maximum number of plugs that are passable through tool  10  are fixed by design during manufacture by the length of the helical track  42  and the keyway  56 . This is not to say however that this maximum number of plugs is the only number of plugs that will be passable before a plug is denied passage. Rather, because the key is placable in the keyway  56  as the tool is being run into the hole, at any point on the helical track  42  that is exposed to the keyway  56 , any number from the maximum number down to a single plug may be selected. 
         [0018]    More specifically, the key  52  is a component of the tool  10  that is removable and replaceable at any point along the keyway  56  where the helical track  42  crosses the keyway  56 . The helix sleeve  40  itself may be marked to show how many plugs will pass before denying passage to make it a simple operation in the field for a rig worker to place the key in the keyway  56  to select a number of plug passages to facilitate a particular operation. It should be noted that because of the high pressures generally encountered in the wellbore for operations related to seating plugs and the potential operations that might be effected by pressuring up on such a plug, for example fracturing at about 10,000 psi, the key  52  should be robust in size and construction as it is, in the end, the key that stops movement of the balance of the components. 
         [0019]    Another feature of the tool  10  is that if for any reason, after plug passage has been denied, it is necessary to pass the denied plug, the follower(s)  44  may be released by, for example, shearing and the collet will be able to move to the recess  28  allowing the plug to pass. This is accomplished by pressuring up higher on the tubing to greater than a threshold pressure that is set prior to running the tool  10  in the hole by the number and strength of the followers  44  employed in the tool  10 . Thereafter all plugs will pass and no further counting will be possible with the tool  10  without removal thereof from the hole and replacement of one or more followers  44 . 
         [0020]    Referring to  FIGS. 9 and 10 , an alternate embodiment of the tool disclosed above is illustrated. The embodiment operates similarly to the tool  10  and identically operating components are not discussed again. The tool is distinct in that a dog-based seat structure  122 , having a plug seat  116 , is substituted for the collet  22  in the  FIG. 1  embodiment. For clarity, numerals are mimicked in the  100  series. In normal operation the dogs function, as do the fingers  18  from the previous embodiment. The housing  112  is also distinct in that an additional plug passage recess  150  is provided uphole of the support  114  so that in reverse flow, the one or more dogs  118  can be moved into alignment with the recess  150  to allow passage of one or more plugs in the uphole direction as part of a reverse circulation operation to remove the plugs from the borehole. In order for the structure  122  to move uphole, a plug that had been passed in normal operation of the tool  110  is moved in reverse circulation into a seat  117  on the backside of seat  116 . The pressure of reverse circulation acts on the plug in the same manner as in the original operation but in the opposite direction. A spring  152  is disposed uphole of the structure  122  and will be compressed against a top sub  154  at a selected force from fluid pressure on the plug. Movement of the structure  122  in the uphole direction mirrors that of movement in the downhole direction and aligns the dogs  118  with the recess  128 , which allows the plug to pass. While an embodiment could eliminate spring  152  and simply allow the structure  122  to stay in the uphole position, including the spring  152  provides the added benefit that the device will automatically revert to a functional state after passage of the plug in the uphole direction so that normal operation of the tool  110  could be resumed if desired. 
         [0021]    While one or more 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.