Abstract:
A downhole tool includes, a body having a recess, a first seal bore, a second seal bore, and a tool disposed at the body that is responsive to differential pressure across a piston. The downhole tool is configured to allow a differential pressure to form across the piston in response to a first plug sealing to and located at the first seal bore by the recess and preventive of forming a pressure differential across the piston in response to a second plug sealing to and located at the second seal bore by the recess.

Description:
BACKGROUND 
       [0001]    Tubular systems typically employ tools that actuate in response to hydraulic pressure being applied to a piston. Elastomeric seals, such as o-rings disposed at the pistons, for example, allow the pistons to move in relation to a housing while maintaining seals therebetween. After actuation of the tool the elastomeric seals have, by design, completed their task and will not be required to hold differential pressure thereacross. In some situations, however, subsequent borehole activity may cause a differential pressure to exist across the seals. This situation may occur when plugging a portion of a wellbore to prevent production therefrom in an application directed to hydrocarbon recovery, for example. Continued differential pressure across the elastomeric seals places higher functional and structural demands on the seals. Systems and methods to avoid placing these additional demands on the seals would therefore be well received in the art. 
       BRIEF DESCRIPTION 
       [0002]    Disclosed herein is a downhole tool. The downhole tool includes, a body having a recess, a first seal bore, a second seal bore, and a tool disposed at the body that is responsive to differential pressure across a piston. The downhole tool is configured to allow a differential pressure to form across the piston in response to a first plug sealing to and located at the first seal bore by the recess and preventive of forming a pressure differential across the piston in response to a second plug sealing to and located at the second seal bore by the recess. 
         [0003]    Further disclosed herein is a method of sealing a downhole tool. The method includes, positioning a first plug with a recess of the downhole tool, sealably engaging a first seal bore with the first plug, pressuring up against the first plug, and building a pressure differential across a piston of the downhole tool. The method further includes, removing the first plug from engagement with the downhole tool, positioning a second plug with the recess, sealably engaging a second seal bore with the second plug, and preventing building of a pressure differential across the piston. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0005]      FIG. 1  depicts a partial cross sectional view of a downhole tool seal arrangement disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0006]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the FIGURES. 
         [0007]    Referring to  FIG. 1 , an embodiment of a downhole tool sealing arrangement disclosed herein is illustrated generally at  10 . The downhole tool sealing arrangement  10  includes, a setting tool  14  that is responsive to hydraulic pressure acting upon a piston  18 . A tubular  22  has a first seal bore  26  and a second seal bore  30  that longitudinally straddle one or more openings  34 , with a single opening being illustrated in this embodiment, through a wall  38  thereof. The seal bores  26 ,  30  are sealingly receptive to one or more plugs  42  runnable within the tubular  22 . The first seal bore  26  is positioned downstream of the opening  34  while the second seal bore  30  is positioned upstream of the opening  34 . A packer  46 , illustrated in this embodiment, positioned uphole of the setting tool  14  and the opening  34 , is settable by movement of the piston  18  in an uphole direction. 
         [0008]    The foregoing structure is operated by first running one of the plugs  42  into sealing engagement with the first seal bore  26 . One or more recesses  50  (with just one recess being illustrated herein) in the tubular  22  can be engaged by a collet  52  (Note: dogs or other engagement devices could also be employed in place of or in addition to the collet) of the plug  42  to positionally locate the plug  42  in sealing engagement with a surface  53  of the first seal bore  26 . Hydraulic pressure can then build against the plug  42 , in this case from the uphole direction, and pressurize the piston  18  through the opening  34 . The piston  18  then moves in an upward direction and engages a ring  54  of the packer  46  and sets the packer  46  into sealing and anchoring engagement with a borehole  58 , casing, or other downhole structure. A ratchet arrangement  62  can be employed to maintain the packer  46  in the set position even after pressure on the setting tool  14  has been reduced. 
         [0009]    The existence of the second seal bore  30  and the positioning of the second seal bore  30 , specifically the second seal bore  30  being located uphole of the first seal bore  26  and the opening  34 , provides benefits over typical systems. Typical systems employ only the first seal bore  26  and not the second seal bore  30 , or require a second recess or set of recesses with a smaller dimensioned second seal bore which restricts the inner dimension of the system. Consequently, operators of typical systems can isolate the borehole  58  below the first seal bore  26  only by sealingly engaging the first seal bore  26 . In doing so however, elastomeric seals  64 , employed in the setting tool  14 , such as o-rings for sliding seals of pistons, for example, form a portion of the isolating seal. The sealing requirements for isolating the borehole  58  below the tool  14  are usually more demanding than simply sealing the piston  18  sufficiently to allow actuation of the setting tool  14 . As such, typical systems can require more durable and more expensive materials to be used in the elastomeric seals  64 . In the instant invention, for example, the elastomeric seals  64  need not form a portion of an isolating seal since the plug  42  can be sealed to the second seal bore  30 . Since, in this case, an inside  70  of the tubular  22  and an annular space  74 , defined between the borehole  58  and an outer surface  78  of the tubular  22  below the packer  46  are essentially at the same pressure, the elastomeric seals  64  experience no differential pressure thereacross during isolation. The elastomeric seals  64  in the downhole tool seal arrangement  10  disclosed herein has no additional performance requirements beyond what is required to sealingly engage the piston  18  during actuation of the setting tool  14 . It should also be noted that when one of the plugs  42  is sealingly engaged with the second seal bore  30  the piston  18  and the elastomeric seals  64  are also isolated from hydrostatic pressure. 
         [0010]    Furthermore, a surface  82  of the second seal bore  30  can be dimensioned substantially the same as the surface  53  of the first seal bore  26 . In so doing, the plugs  42  that seal to each of the first seal bore  26  and the second seal bore  30  can have similar sealing elements  86  that are dimensioned alike. Additionally, neither of the surfaces  53 ,  82  will create a restriction to flow through the tubular  22  that is greater than the other. The plugs  42  then that seal to the first seal bore  26  can differ from the plugs  42  that seal to the second seal bore  30  only in a longitudinal length between the collet  52  and the sealing elements  86 . 
         [0011]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.