Abstract:
A selective plug including a body; and a rotator configuration in operable communication with the body capable of causing the plug to selectively pass a number of borehole restrictions to reach and engage a target restriction and method.

Description:
BACKGROUND 
       [0001]    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, CO2 sequestration, etc. 
         [0002]    In the art, fracturing discrete locations of the borehole tends to require a number of tools that 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 required in any system and therefore limits the number of diameters that will be functional even further. 
         [0003]    Since fracturing and other operations where discrete locations are desired to be isolated or accessed continue to become more prevalent and ubiquitous, alternate systems for accessing and manipulating the downhole environment is always well received. 
       SUMMARY 
       [0004]    A selective plug including a body; and a rotator configuration in operable communication with the body capable of causing the plug to selectively pass a number of borehole restrictions to reach and engage a target restriction. 
         [0005]    A method for conducting borehole operations including determining where in a borehole an operation is desired; setting a selective plug; and deploying the selective plug into the borehole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Referring now to the drawings wherein like elements are numbered alike in the Figures: 
           [0007]      FIG. 1  is a schematic cross sectional view of a selective plug described herein; 
           [0008]      FIG. 2  is a schematic cross sectional view of another embodiment of a selective plug described herein; 
           [0009]      FIG. 3  is a schematic cross sectional view of yet another embodiment of a selective plug as described herein; 
           [0010]      FIG. 4  is a perspective partial phantom view of the embodiment of  FIG. 3 ; and 
           [0011]      FIG. 5  is another perspective cross sectional view of the embodiment of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , a selective plug  10  is illustrated. The plug  10  is settable to pass through a number of restrictions (one shown as  12 ) in a borehole. Generally the restriction  12  will protrude radially inwardly from a casing  14  but the invention is not limited to cased boreholes but rather is usable in any borehole configuration where restrictions are employed. The plug itself comprises a body  16  sized to be able to pass through restrictions in the borehole in which the plug is intended to be employed. The body supports a seal member  18  at an outside surface  20  thereof, the seal member intended to provide a pressure tight interaction with the target restriction  12 . The degree of sealing required depends upon the degree of pressure that is intended to be applied to the borehole system, the higher the intended pressure the higher the contact force of the seal member  18  with the restriction  12  and hence the more robust the pressure seal. 
         [0013]    The body  16  further includes openings  22  (two shown but more may be disposed about the periphery of the body  16 ). The openings  22  allow for the through passage of rotationally secured keys  24 . The keys are interactive with the restrictions(s)  12  as a rotational axis  26  of each key comes into proximity with the restriction  12 . As can be viewed in  FIG. 1 , one of the keys  24  is illustrated in contact with the restriction  12 . Each of the keys  24  includes a biasing arrangement  25  at the rotational axis  26  to cause the key to move to a position where engagement with a next restriction will occur. The other side of the key is in communication with a ratchet housing  28  where a plurality of ratchet teeth  30  are positioned. The keys and the ratchet housing together form an incrementing configuration. It is to be appreciated that a number of ratchet teeth are illustrated but that in a commercial embodiment there may be many more. The number of ratchet teeth must be enough to allow incremental movement of the ratchet housing  28  through all of the restrictions that will be passed through. In one embodiment, there will be at least as many teeth as all the restrictions in a particular or a hypothetical borehole. Either way the point is that with enough teeth  30  it is possible to set the plug to pass as many restrictions as desired even if the target restriction is the deepest one in the borehole. This will be more clear when operation of the plug is discussed. 
         [0014]    Finally, the ratchet housing  28  includes a dampener  32  comprising in one embodiment, a fluid chamber  34  and a piston  36  bifurcating the fluid chamber  34 . The piston includes a flow passage  38  having a relatively restricted dimension through which fluid may pass from one end of the piston to the other end of the piston thereby moving the fluid in the fluid chamber  34  from one side of the piston to the other during operation of the plug  10 . The function of the dampener  32  is to slow the reaction of the keys  24  when they rotate due to contact with a restriction  12 . This causes a pressure spike uphole of the plug  10  that can be detected to verify that the plug  10  has encountered a restriction. Counting the verification events then provides confidence that when the plug does land without passing a restriction, it is the correct target restriction. It is to be appreciated that although the dampener provides for desirable functionality, it is not required for the plug to operate with respect to its primary objective, which is to selectively pass a number of restrictions and to not pass a target restriction. The plug  10  will do so whether or not a pressure spike is produced or received at a remote location. 
         [0015]    In embodiments that do include the dampener  32  a variation of its structure allows for easier setting of the plug  10  by including a check valve  40 , which provides a much greater flow area for movement of the piston  36  in a setting direction than it does for piston movement during operation of the plug  10 . 
         [0016]    Finally the plug  10  includes a selection indicator  42 . An operator uses the indicator to set the plug  10  to bypass a number of restrictions that will cause the plug to set in the target restriction. 
         [0017]    Operation of the plug illustrated in  FIG. 1  begins with the setting of the number of restrictions that are to be passed in a borehole. The ratchet housing  28  is moved within the body  16  to set one or more of the keys  24  in a position between two of the teeth  30 . Selecting a position means that a leading end  44  of ratchet housing  28  is spaced a certain distance from an inside surface  46  of body  16 . When the distance is absorbed by movement of the ratchet housing  28  pursuant to the action of keys  24  while passing restrictions  12 , the ratchet housing  28  is physically prevented from moving further and hence the keys are physically prevented from rotating further. Whatever key  24  that is in contact with a target restriction  12  at this time will prevent further advancement of the plug  10  and the borehole is ready for pressurization to whatever extent has been designed into the plug  10 . The distance between end  44  and surface  46  is slowly absorbed by the movement of the ratchet housing  28  because as each key  24  engages a restriction, a force is placed upon the key. Because the key is allowed to move about a rotational axis  26  the force acting on the key  24  from the restriction is transmitted through the key to rotational axis  26 . The rotational axis  26  changes the direction of the force to apply it to one of the plurality of teeth  30  thereby pushing the ratchet housing  28  toward surface  46 . This action continues until the angle of the key  24  has exhausted it force providing potential through rotation. As will be appreciated from the Figure, at least one other of the keys  24  is offset from the first discussed key  24 . This allows the second key  24  to engage the next one of the plurality of teeth  30  when the first discussed one of the plurality of teeth is still resting on a crown of the last actuated one of the plurality of teeth. Following another rotational change in key  24  position the first key will come off the crest of the tooth it was resting on and drop into the next trough between two of the plurality of teeth  30 . From this position the key is again positioned to have effect on the ratchet housing  28  at the next restriction  12 . The number of keys that are being used to move the ratchet housing  28  at a given restriction can be as few as one or as many as is practicable in the space available in the body  16  depending upon desires for particular applications. The keys each return to the position where engagement with teeth and restriction is possible via the biasing arrangement  25  such as a torsion spring. 
         [0018]    As noted above, the ratchet housing  28  is moved such that end  44  moves away from surface  46  during setting of the plug  10 . In embodiments where dampener  32  is employed a specific embodiment of the dampener  32  includes the check valve  40  noted above. Due to the increased flow area that is gained through the check valve  40 , an operator moving the ratchet housing  28  for setting purposes will not have to work as hard as he or she would if the check valve were not present (which is certainly contemplated in some embodiments). 
         [0019]    In another embodiment of a selective plug  110 , referring to  FIG. 2 , the same ultimate goal of producing a plug that will bypass a selected number of restrictions before remaining in one for some period of time is accomplished. Similar to the foregoing embodiment there are a number of restrictions  12  in a borehole that may be cased or open providing there is a mechanism for providing restrictions  12 . In the embodiment of  FIG. 2 , a body  116  includes one or more openings  122  (one shown) where in each of which is a key  124  that is articulated to the body  116  at pivot  150 . The key further includes an articulated lever  152  that is configured to engage one of a plurality of teeth  130 . As illustrated there are two keys  124   a  and  124   b  and two accompanying levers  152   a  and  152   b.  These are spaced axially from one another to enable the counting function of the plug  110 . It is important to note that the one or more keys that are included in the plug  110  are in one embodiment arranged around the body  116 . It is not intended that the reader presume that because the illustrated keys  124  are axially arranged that all of the possible keys  124  that may be incorporated in the embodiment would be axially arranged. It is also not necessarily required that there be axially spaced keys but rather that there be a mechanism to hold the spring  158  while a key that has urged the ratchet housing  128  toward the right hand side of the drawing in  FIG. 2  moves to a reset position, having emerged from the compression of the restriction  12 . This will be further described hereunder. The body  116  further includes one or more dogs  154  that are extendible radially outwardly of the body  116  under circumstances of actuation of the plug  110 . 
         [0020]    The teeth  130  are positioned upon a ratchet housing  128 . The ratchet housing further includes a one or more dog supports  156  thereon that at a particular position of the ratchet housing  128  will support the dogs  154  in a radially outwardly extended position. This position is achieved when the ratchet housing  128  is fully stroked within the body  116  by having passed through the selected number of restrictions  12 . To ensure that the ratchet housing  128  moves by only one tooth increment per restriction passed, a biasing arrangement  158  is included such as a compression spring that bears against one end of the body  116  and one end of the ratchet housing  128  as illustrated. These components make up an incrementing configuration for this embodiment. 
         [0021]    Finally, at an uphole end of the ratchet housing, a wiper  160  is disposed to enable the plug  110  to be moved through the borehole using fluid pressure applied from uphole and a selection indicator  142  to assist the operator in setting the plug  110  to bypass a denied number of restrictions. 
         [0022]    In operation, the plug  110  is initially manually set at a surface location by an operator. The ratchet housing  128  is positioned relative to the body  116  such that a selected number of teeth  130  are required to be ratcheted through before the dog support  156  moves to support the dogs  154 . The number of teeth is the same as the number of restrictions through which the plug is being set to pass before it is to hold its position to support another operation such as a fluid pressure build up uphole of the plug  110  for tool actuation or fracturing, etc. Because the biasing arrangement  158  applies a force on the ratchet housing  128  in a direction to the left in the drawing  FIG. 2 , the lever  152  is caught in a trough of the teeth  130 . The lever is hence urged by the tooth it is engaged with against the key  124   a  causing the key to pivot radially outwardly of the body  116 . The radial dimension of the one or more keys  124  is greater than the restrictions that the plug  110  will encounter during its trip downhole. The key(s)  124  will thus land on the restrictions  12  that it/they arrive at and be urged radially inwardly by the restriction. The radially inward urging causes the lever  152   a  to apply a force to the tooth with which it is engaged overcoming the oppositely acting force from the biasing arrangement  158  and thereby moving the ratchet housing  128  toward end  162  of body  116 . The movement is incremental but is for a sufficient distance to allow lever  152   b  to engaged its next-in-line tooth  130  to hold the new position that the key  124   a  and lever  152   a  passing through the restriction have achieved for the ratchet housing  128 . Because of the positioning of the keys  124   a  and  124   b  or the length of levers  152   a  and  152   b,  the keys  124   a  and  124   b  and  152   a  and  152   b  together act as an escapement to facilitate maintenance of the ratchet housing  128  in its incremental position. The key  124   a  will move radially outwardly again based upon a torsion spring disposed at pivot  150  or similar making it ready to engage the next restriction  12 . The same is true for key  124   b.  The described sequence continues until the dog support  156  arrives at the dogs  154  and supports them. The next restriction through which the plug  110  is moved will encounter the supported dogs  154 . Since the dogs  154  do not yield to the restriction  12 , the plug  110  will maintain its position in the target restriction to allow whatever fluid pressure holding operation is desired. 
         [0023]    In yet another embodiment, referring to  FIGS. 3-5 , a selective plug  210  having the same capabilities as the plugs described hereinbefore is illustrated. This embodiment includes a body  216  having a flared end  264 . The flared end is in one embodiment includes ramped surfaces  266  and  268 . Surface  266  assists in directing the plug  210  trough a restriction by avoiding a sharp shoulder that otherwise might catch on a portion of the restriction  12  while surface  268  cooperates with a collet  270  in the operation of the plug  210  as will be further elucidated hereunder. A wiper  260  is positioned at an opposite end of the body  216  from the flared end  264 . 
         [0024]    Upon the body  216  is mounted a key  224  that is interactive with a rotator  276  in operation of the plug  210 . The key  224  further provides a seat  274  for a biasing arrangement  258 . The biasing arrangement will in one embodiment comprise a compression spring such as a coil spring as shown. The biasing arrangement  258  acts between the seat  274  and the collet  270 , urging the two apart from one another. 
         [0025]    The rotator  276  is disposed between the collet  270  and the body  216  and provides, in one embodiment, the selectivity in target restriction in cooperation with key  224 . A selection indicator  242  is also provided for purposes identical to those described above. 
         [0026]    Before making reference to  FIGS. 4 and 5  to illustrate the rotator  276  and the key  224  interaction, it is helpful to understand the high level operation of the plug. The plug  210  will be set by positioning the rotator  276  relative to the key  224  and then introduced to the borehole. When the plug  210  encounters a restriction  12 , the collet  270  lands on the restriction  12  and a load is transferred into the collet  270 . The load provides a greater force than does the biasing arrangement  258  and so the collet moves relative to the body  216  allowing the flared end  264  of the body  216  to move through the restriction and at the same time unsupport one or more collet fingers  278 . Once the fingers  278  are unsupported they will flex radially inwardly causing the outside diameter of the collet  270  at fingers  278  to become smaller than the restriction and therefore move therethrough. At each restriction this movement is possible thereby allowing the plug  210  to pass through an unlimited number of restrictions. To limit the number of restrictions through which the plug  210  will pass and thereby select a target restriction upon which the plug  210  will seat for a period of time, the rotator  276  and key  224  are included in the plug  210 . 
         [0027]    Referring now to  FIGS. 4 and 5 , understanding of the rotator  276  and key  224  and how they interact to produce an incrementing configuration will improve. In FIG.  4 , the collet  270  has been illustrated in phantom to allow a viewer to see the rotator  276 . Rotator  276  is, in one embodiment, configured with a J-slot  280  on an outside dimension surface thereof and a plurality of step profile teeth  282  on an inside dimension surface thereof ( FIG. 5 ). The Jslot  280  interacts with a lug  284  attached to the collet  270 . Each time the collet  270  is urged against the bias of biasing arrangement  258 , the lug  284  contacts an angled surface  286  of the Jslot  280  and causes the rotator  276  to rotate a small degree. Each time the collet  270  moves back toward the flared end  264 , the lug will contact another angled surface  288  and the rotator will rotate another small increment. Based upon the position of the step profile  282  relative to the key  224 , a selected number of restrictions  12  will be passed before the key  224  engages a step of the step profile  282  and prevents the collet  270  from cycling. Upon this condition, the next restriction encountered by the plug  210  will not be passed but the plug  210  will seat thereon and whatever operation was intended may be carried out. 
         [0028]    Finally it is to be understood 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.