Abstract:
Disclosed herein is a downhole tubular sealing system. The system includes, a tubular runnable in a downhole wellbore, a swellable seal disposed at the tubular that is sealable with the downhole wellbore when swelled, and at least one releasable member in operable communication with the tubular and the swellable seal. The at least one releasable member configured to longitudinally fix the swellable seal to the tubular when nonreleased and to longitudinally disengage the swellable seal from the tubular when released.

Description:
BACKGROUND 
     It is common in multi-stage completions in downhole hydrocarbon wells to sealingly engage a wellbore at multiple locations to allow individualized stimulation treatment of each of the separate stages. The casing from surface and between each of the separated stages undergoes longitudinal expansion and contraction due to temperature changes of the casing. An example of when such temperature changes may occur is during stimulation treatment when fluid pumped downhole is a much lower temperature than the prevailing downhole temperatures. The longitudinal expansions and contractions can stress the casing, the seals and walls of the wellbore causing damage to one or more systems of the well operation. Systems and methods to prevent such damage are well received in the art. 
     BRIEF DESCRIPTION 
     Disclosed herein is a downhole tubular sealing system. The system includes, a tubular runnable in a downhole wellbore, a swellable seal disposed at the tubular that is sealable with the downhole wellbore when swelled, and at least one releasable member in operable communication with the tubular and the swellable seal. The at least one releasable member configured to longitudinally fix the swellable seal to the tubular when nonreleased and to longitudinally disengage the swellable seal from the tubular when released. 
     Further disclosed herein is a method of sealing a tubular to a downhole structure. The method includes, positioning the tubular with a swellable seal disposed thereat within a downhole wellbore, swelling the swellable seal into sealing engagement with the downhole structure, longitudinally unfixing the swellable seal from the tubular, and slidably sealingly engaging the swellable seal with the tubular 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a quarter cross sectional view of a sealing system disclosed herein in a non-sealed configuration; 
         FIG. 2  depicts a quarter cross sectional view of the sealing system of  FIG. 1  with the seal sealingly engaged with a downhole wellbore; 
         FIG. 3  depicts a quarter cross section view of the sealing system of  FIG. 1  with releasable members in a released and translated configuration; 
         FIG. 4  depicts a quarter cross sectional view of an alternate sealing system disclosed herein in a non-sealed configuration; 
         FIG. 5  depicts a quarter cross sectional view of the sealing system of  FIG. 4  with the seal sealingly engaged with a downhole wellbore; and 
         FIG. 6  depicts a quarter cross sectional view of the sealing system of  FIG. 4  with releasable members in a released and translated configuration. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     A downhole tubular sealing system disclosed herein allows a swellable seal initially longitudinally fixed to a tubular to be positioned within a downhole wellbore. Once downhole, the swellable seal can be swelled into sealing engagement with walls of the wellbore. Release members that initially longitudinally fix the swellable seal to the tubular can be released, thereby allowing the swellable seal to remain in sealing engagement with the wellbore walls while also allowing the tubular to longitudinally move in relation to the swellable seal while maintaining sealing integrity with the swellable seal. 
     Referring to  FIG. 1 , an embodiment of a downhole tubular sealing system  10  disclosed herein is illustrated within a downhole wellbore  12 . The sealing system  10  includes, a tubular  14 , illustrated in this embodiment as a casing, a swellable seal  18  and at least one releasable member  22  (two being shown) longitudinally fixing the swellable seal  18  to the tubular  14 . In this view the sealing system  10  is shown positioned within the wellbore  12  in a run-in configuration and as such is not in sealing engagement with the wellbore  12  as the swellable seal  18  is in an unswelled condition. 
     Each of the releasable members  22  has a point end  26 , a shaft  28 , and a head end  30 . The point ends  26  engage with recesses  34  in an outer surface  38  of the tubular  14  while the shafts  28  slidable engage with through holes  42  (more easily seen in  FIG. 2 ) in the swellable seal  18  and through holes  46  in dams  50 . The releasable members  22  thereby longitudinally fix the swellable seal  18  to the dams  50  and the tubular  14  in response to the point ends  26  being engaged with the recesses  34 , as is the case when the releasable members  22  are in the nonreleased configuration. The head ends  30  of each releasable members  22  is encased in the swellable seal  18  such that some of the swellable material of the swellable seal  18  is positioned between broad flanges  54  of the head ends  30  and portions  58  of the dams  50  (more easily seen in  FIG. 2 ) that include the holes  46 . With this configuration, swelling of the swellable seal  18  causes the releasable members  22  to move radially outwardly as a thickness of a portion of the swellable seal  18  between the flange  54  and the dam  50  increases. Sizing of the components are set so that the point ends  26  of the releasable members  22  withdraw from the recesses  34  prior to the swellable seal  18  reaching its full swell dimensions, thereby assuring release of the releasable members  22  in response to swelling of the swellable seals  18 . 
       FIG. 2  illustrates the swellable seal  18  in a swelled condition. In this condition the swellable seal  18  is sealingly engaged with the wellbore  12 . Additionally, the releasable members  22  are shown in a released configuration so that the swellable seal  18  can sealingly slide along the tubular  14 . The swellable seal  18  in this view has not been longitudinally displaced from the run-in position along the tubular  14 , and therefore the point ends  26  are still longitudinally aligned with the recesses  34 . 
     In  FIG. 3 , the swellable seal  18  is still swollen and in sealing engagement with the wellbore  12  and the releasable members  22  are in a released configuration. Additionally, the swellable seal  18 , the releasable members  22  and the dams  50  have been longitudinally displaced along the tubular  14  in the direction of arrow  62 . The swellable seal  18  remains sealingly engaged with the tubular  14  during the longitudinal displacement. 
     Referring to  FIGS. 4-6 , an alternate embodiment of a downhole tubular sealing system  110  disclosed herein is illustrated. Unlike in the system  10  in the system  110  the releasable members  122  do not release in response to swelling of the swellable seal  118 . Instead, the releasable members  122  are force failing members such as, shear screws or lock rings, for example, with shear screws being illustrated in this figure. The releasable members  122  longitudinally fix the dams  150  directly to the tubular  114  until a large enough longitudinal force between the dams  150  and the tubular  114  shears the screws  122 . These longitudinal forces may be generated by contraction or expansion of the tubular  114  due to temperature changes thereof while the swellable seal  118  is swelled and sealingly engaged with the wellbore  112 . The swellable seal  118  is contained on the tubular  114  between the dams  150 . 
     In  FIGS. 4 and 5  the shear screws  122  are shown intact and threadably engaged in at least holes  142  in the dams  150  and holes  146  in surface  138  of the tubular  114 . In  FIG. 4  the swellable seal  118  is unswelled, and in  FIG. 5  the swellable seal  118  is swelled and sealingly engaged with the wellbore  112 . 
     Referring to  FIG. 6 , the shear screws  122  have been sheared such that screw portions  122 A are movable with the dams  150 , while screw portions  122 B are movable with the tubular  114 . In alternate embodiments the screw portions  122 B may not be connected to the tubular  114 , but instead may be free to travel to where ever they happen to go. As illustrated, the swellable seal  118  and dams  150  have been moved longitudinally from their original position along the tubular  114  in a direction according to arrow  162 . 
     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.