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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of the filing date of, and priority to, U.S. patent application No. 61/811,523, filed Apr. 12, 2013, the entire disclosure of which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates in general to a tubular string such as casing string, and in particular to a system and method for rotating casing string. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    In the oil and gas industry, advances in horizontal drilling have allowed drillers to drill extended reach horizontal sections of wellbores. In some cases, during the installation of a casing string into such an extended reach horizontal section, the casing string needs to be rotated to allow the casing string to be installed to the desired depth. However, rotating the casing string sometimes requires the application of torsion to the casing string using a tool. Such an application of torsion may increase the amount of torque retained in one or more connections between different components of the casing installation system. Additionally, after the torsion has been applied, attempting to disconnect the tool from the casing installation system may increase the risk of breaking connections between tubulars in the casing string. Therefore, what is needed is a system, apparatus or method that addresses one or more of the foregoing issues, or one or more other issues. 
       SUMMARY 
       [0004]    In a first aspect, there is provided a system that includes a tool, a hanger connected to the tool, and a plurality of tubulars connected to the hanger and adapted to be positioned within a wellbore that traverses a subterranean formation. Each of the tubulars is connected to at least one other tubular. The tool, the hanger, and the plurality of tubulars, are rotatable in response to at least the application of torsion to the tool. The tool, the hanger, and the plurality of tubulars, are rotatable without transferring torque to the connection between the tool and the hanger. 
         [0005]    In an exemplary embodiment, the hanger is a casing hanger, and the plurality of tubulars is a casing string. 
         [0006]    In another exemplary embodiment, the tool, the hanger, and the plurality of tubulars, rotate in response to at least: the application of a tensile load across the tool; and the application of torsion to the tool during the application of the tensile load across the tool. 
         [0007]    In certain exemplary embodiments, any trapped torsion between any of the respective connections between any two of the tubulars in the plurality of tubulars is released in response to the application of a compressive load across the tool. 
         [0008]    In an exemplary embodiment, after the application of torsion to the tool, the connection between the tool and the hanger is capable of being broken without breaking any of the respective connections between any two of the tubulars in the plurality of tubulars. 
         [0009]    In a second aspect, there is provided a method that includes positioning a tubular string within a wellbore that traverses a subterranean formation, the tubular string including a plurality of tubulars, each of the tubulars being connected to at least one other tubular. A hanger is connected to the tubular string. Torsion is applied to the tubular string to rotate the tubular string. To apply torsion to rotate the tubular string, a tool is connected to the hanger, and torsion is applied to the tool, in order to apply torsion to the hanger and thus to the tubular string, without transferring torque to the connection between the tool and the hanger. 
         [0010]    In an exemplary embodiment, the tubular string is a casing string, and the hanger is a casing hanger. 
         [0011]    In another exemplary embodiment, the tool includes a tubular member, and connecting the tool to the hanger includes connecting the tubular member to the hanger. Torsion is applied to the tool, in order to apply torsion to the hanger and thus to the tubular string, without transferring torque to the connection between the tubular member and the hanger. 
         [0012]    In certain exemplary embodiments, the method includes applying a compressive load across the tool to release any trapped torsion between any of the respective connections between any two of the tubulars in the tubular string. 
         [0013]    In an exemplary embodiment, the method includes breaking the connection between the tool and the hanger without breaking any of the respective connections between any two of the tubulars in the tubular string. 
         [0014]    In another exemplary embodiment, applying torsion to the tubular string further includes applying a tensile load across the tool. Torsion is applied to the tool, in order to apply torsion to the hanger and thus to the tubular string, during applying the tensile load across the tool. 
         [0015]    In a third aspect, there is provided an apparatus for rotating a tubular string within a preexisting structure. The apparatus includes a first tubular member, a second tubular member extending within the first tubular member, a third tubular member extending within the first tubular member. The apparatus includes a first configuration in which: the third tubular member is in a first position relative to each of the first and second tubular members; torque is permitted to be transmitted between the second and third tubular members to connect the apparatus to, or disconnect the apparatus from, a fourth tubular member adapted to be connected to the tubular string; and torque is not permitted to be transmitted between the first and third tubular members. The apparatus includes a second configuration in which: the third tubular member is in a second position relative to each of the first and second tubular members; torque is not permitted to be transmitted between the second and third tubular members; and torque is permitted be transmitted between the first and third tubular members to rotate the tubular string. 
         [0016]    In an exemplary embodiment, the preexisting structure is a wellbore that traverses a subterranean formation, the fourth tubular member is a casing hanger, and the tubular string is a casing string. 
         [0017]    In another exemplary embodiment, the apparatus includes a torsion nut connected to the first tubular member, and the third tubular member extends through the torsion nut. When the apparatus is in the second configuration, torque is permitted to be transmitted between the first and third tubular members via at least the torsion nut. 
         [0018]    In certain exemplary embodiments, the third tubular member includes a first plurality of keys or slots, and a second plurality of keys or slots axially spaced from the first plurality of keys or slots. 
         [0019]    In an exemplary embodiment, the second tubular member includes a third plurality of keys or slots for complementary engagement with the first plurality of keys or slots when the apparatus is in the first configuration. The torsion nut includes a fourth plurality of keys or slots for complementary engagement with the second plurality of keys or slots when the apparatus is in the second configuration. 
         [0020]    In another exemplary embodiment, the apparatus includes a torsion nut connected to one end of the first tubular member, wherein the third tubular member extends through the torsion nut. The first tubular member includes a fifth plurality of keys or slots at the other end thereof for transmitting torque to the tubular string to rotate the tubular string. 
         [0021]    In certain exemplary embodiments, the apparatus includes the fourth tubular member, the fourth tubular member including a sixth plurality of keys or slots adapted to complementarily engage the fifth plurality of keys or slots of the first tubular member. When the fourth tubular member is connected to the tubular string, torque is adapted to be transmitted to the tubular string via the fourth tubular member. 
         [0022]    In an exemplary embodiment, the apparatus includes a first annular groove formed in the outside surface of the third tubular member, wherein the first annular groove is generally aligned with an end of the torsion nut when the apparatus is in the first configuration, and a second annular groove formed in the outside surface of the third tubular member and axially spaced from the first annular groove, wherein the second annular groove is generally aligned with the end of the torsion nut when the apparatus is in the second configuration. 
         [0023]    In another exemplary embodiment, the first and second tubular members include internal and external shoulders, respectively. The apparatus further includes an annular support that is sandwiched between the external shoulder of the second tubular member and the internal shoulder of the first tubular member when the apparatus is in the first configuration. 
         [0024]    Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed. 
     
    
     
       DESCRIPTION OF FIGURES 
         [0025]    The accompanying drawings facilitate an understanding of the various embodiments. 
           [0026]      FIG. 1  is a diagrammatic view of an apparatus according to an exemplary embodiment, the apparatus including a tool, a casing hanger and a tubular string. 
           [0027]      FIG. 2  is an exploded perspective view of the tool and the casing hanger of  FIG. 1 , according to an exemplary embodiment. 
           [0028]      FIG. 3  is a sectional view of the tool and the casing hanger of  FIGS. 1 and 2 , according to an exemplary embodiment. 
           [0029]      FIG. 4  is a view similar to that of  FIG. 3 , but depicts the tool in another configuration, according to an exemplary embodiment. 
           [0030]      FIG. 5  is a view similar to that of each of  FIGS. 3 and 4 , but depicts the tool in yet another configuration, according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    In an exemplary embodiment, as illustrated in  FIG. 1 , an apparatus is generally referred to by the reference numeral  10  and includes a hanger, such as a casing hanger  12 , to which a tool  14  is connected. A tubular string  16  is connected to the casing hanger  12 , and is positioned within a preexisting structure such as, for example, a wellbore  18  that traverses one or more subterranean formations. In an exemplary embodiment, the tubular string  16  is a casing string, which extends within the wellbore  18  to facilitate oil and gas exploration and production operations. The tubular string  16  includes a plurality of tubulars, each of which is connected to at least one other tubular in the tubular string  16 . For example, as shown in  FIG. 1 , the plurality of tubulars in the tubular string  16  includes at least tubulars  16   a ,  16   b  and  16   c . The tubular  16   a  is connected to the casing hanger  12  to define a connection  20   a , the tubular  16   b  is connected to the tubular  16   a  to define a connection  20   b , and the tubular  16   c  is connected to the tubular  16   b  to define a connection  20   c . In an exemplary embodiment, each of the connections  20   a ,  20   b  and  20   c  is a threaded engagement, with the threaded engagement being sufficiently tight so as to render the tubular string  16  operable for its intended purposes within the wellbore  18  (e.g., conveying fluids through the tubular string  16 , holding pressure within the tubular string  16 , providing structural support to the wellbore  18 , one or more other intended purposes, or any combination thereof). In an exemplary embodiment, each of the connections  20   a ,  20   b  and  20   c  is a box and pin connection, with the box and pin connection being sufficiently tight so as to render the tubular string  16  sufficiently operable for its intended purposes within the wellbore  18  (e.g., conveying fluids through the tubular string  16 , holding pressure within the tubular string  16 , providing structural support to the wellbore  18 , one or more other intended purposes, or any combination thereof). 
         [0032]    In an exemplary embodiment, as illustrated in  FIG. 2  with continuing reference to  FIG. 1 , the tool  14  includes a first tubular member, such as an outer torsion sleeve (or outer sleeve  22 ), a second tubular member, such as a casing hanger/running tool connection sleeve (or inner sleeve  24 ), a third tubular member, such as a landing tool/running tool pup (or pup  26 ), and a torsion nut  28 . The tool  14  further includes an annular support  30 , a plurality of torsion keys  32 , a plurality of torsion keys  34 , and a plurality of torsion keys  36 . In an exemplary embodiment, the annular support  30  is a bushing. In an exemplary embodiment, the annular support  30  is a high-capacity axial bearing assembly. 
         [0033]    In an exemplary embodiment, as illustrated in  FIGS. 2 and 3  with continuing reference to  FIG. 1 , the outer sleeve  22  includes a plurality of openings  22   a  formed in the bottom end thereof; respective internal threaded connections are formed in the openings  22   a . The torsion keys  32  include respective external threaded connections, which threadably engage with the internal threaded connections in the respective openings  22   a , thereby connecting the torsion keys  32  to the outer sleeve  22 . In an exemplary embodiment, the torsion keys  32  are connected to the outer sleeve  22  using fasteners, or are integrally formed with the outer sleeve  22 . The outer sleeve  22  further includes an internal threaded connection  22   b  at the end portion thereof opposing the openings  22   a , and an internal shoulder  22   c  positioned axially between the openings  22   a  and the internal threaded connection  22   b.    
         [0034]    As shown in  FIGS. 2 and 3 , and under conditions to be described below, the outer sleeve  22  is adapted to engage the casing hanger  12  so that the torsion keys  32  extend into respective openings  12   a  formed in an external shoulder  12   b  (see  FIG. 2 ) of the casing hanger  12 , and so that an upper end portion  12   c  of the casing hanger  12  extends within the outer sleeve  22 . An internal shoulder  12   d , and an internal threaded connection  12   e  adjacent thereto, are formed in the upper end portion  12   c  of the casing hanger  12 . The casing hanger  12  further includes a flange  12   f , which is adapted to engage a wellhead housing (not shown), under conditions to be described below. 
         [0035]    The inner sleeve  24  extends within the outer sleeve  22 , and includes an external threaded connection  24   a  at the lower end thereof, an external shoulder  24   b  adjacent the external threaded connection  24   a , and an external shoulder  24   c  above the external shoulder  24   b . Under conditions to be described below, the external threaded connection  24   a  is adapted to threadably engage, and threadably disengage from, the internal threaded connection  12   e  of the casing hanger  12 . Similarly, the external shoulder  24   b  is adapted to engage, and disengage from, the internal shoulder  12   d  of the casing hanger  12 , and the external shoulder  24   c  is adapted to engage, and disengage from, the annular support  30 . The torsion keys  34  are positioned proximate the external shoulder  24   c , and are circumferentially spaced around, and connected to, the inner sleeve  24 . In an exemplary embodiment, the torsion keys  34  are connected to the inner sleeve  24  via fasteners  38 , which extend radially inwardly into the inner sleeve  24 . In an exemplary embodiment, the torsion keys  34  are connected to the inner sleeve  24  via other types of fasteners, or are integrally formed with the inner sleeve  24 . 
         [0036]    The pup  26  extends within the outer sleeve  22 , and includes slots  26   a  formed in the lower end thereof, an internal shoulder  26   b , and an external shoulder  26   c . Axially-spaced annular grooves  26   d  and  26   e  are formed in the outside surface of the pup  26  proximate the upper end portion thereof. The torsion keys  36  are positioned adjacent the external shoulder  26   c , and are circumferentially spaced around, and connected to, the pup  26 . In an exemplary embodiment, the torsion keys  36  are connected to the pup  26  via fasteners  40 , which extend radially inwardly into the pup  26 . In an exemplary embodiment, the torsion keys  36  are connected to the pup  26  via other types of fasteners, or are integrally formed with the pup  26 . The pup  26  extends through the torsion nut  28 , which includes an external threaded connection  28   a , which is threadably engaged with the internal threaded connection  22   b  of the outer sleeve  22 , thereby connecting the torsion nut  28  to the outer sleeve  22 . The torsion nut  28  further includes a flange  28   b , which engages the upper end of the outer sleeve  22 . Slots  28   c  are formed in the lower end of the torsion nut  28 . In several exemplary embodiments, as indicated in  FIGS. 2 and 3 , the tool  14  may include annular sealing elements, such as o-rings, which are axially-spaced from one another along the tool  14  and sealingly engage components thereof. 
         [0037]    In operation, in an exemplary embodiment, with continuing reference to  FIGS. 1 ,  2  and  3 , the apparatus  10  facilitates oil and gas exploration and production operations. More particularly, the flange  12   f  of the casing hanger  12  engages a wellhead housing (not shown), and the tubular string  16  hangs from the casing hanger  12 , being positioned within the wellbore  18 . In an exemplary embodiment, each of the connections  20   a ,  20   b  and  20   c  is a threaded engagement, with the threaded engagement being sufficiently tight so as to render the tubular string  16  operable for its intended purposes within the wellbore  18  (e.g., conveying fluids through the tubular string  16 , holding pressure within the tubular string  16 , providing structural support to the wellbore  18 , one or more other intended purposes, or any combination thereof). In an exemplary embodiment, the tubular string  16  is in tension at least in part because it hangs from the casing hanger  12 . The casing hanger  12  suspends the tubular string  16  within the wellbore  18 , thereby causing the tubular string  16  to be in tension. In several exemplary embodiments, at any time during the operation of the apparatus  10 , the tool  14  may or may not be connected to the casing hanger  12 . 
         [0038]    During operation, in several exemplary embodiments, it is desired to rotate the tubular string  16  about its longitudinal axis while the tubular string  16  is in tension and positioned within the wellbore  18 . The rotation of the tubular string  16  may be desirable in order to, for example, allow the tubular string  16  to be installed to the desired depth in the subterranean formation(s) through which the wellbore  18  extends. To so rotate the tubular string  16 , the tool  14  is connected to the casing hanger  12 . 
         [0039]    To connect the tool  14  to the casing hanger  12 , the tool  14  is assembled in accordance with the foregoing, and then is moved downwards, as viewed in  FIG. 3 . As a result, the upper end portion  12   c  of the casing hanger  12  extends within the outer sleeve  22 , as shown in  FIG. 3 . The inner sleeve  24  is moved downward within the outer sleeve  22 , as viewed in  FIG. 3 , so that the external threaded connection  24   a  may be threadably engaged with the internal threaded connection  12   e  of the casing hanger  12 . The inner sleeve  24  may be so moved by moving the pup  26  downward, as viewed in  FIG. 3 , so that the torsion keys  34  extend into the respective slots  26   a  of the pup  26 . The pup  26  may be rotated, which rotation, due to the extension of the torsion keys  34  into the respective slots  26   a , transmits torque from the pup  26  to the inner sleeve  24 , causing the inner sleeve  24  to rotate and thus the external threaded connection  24   a  to be threadably engaged with the internal threaded connection  12   e , thereby connecting the inner sleeve  24  to the casing hanger  12 . The inner sleeve  24  continues to be rotated until the inner sleeve  24  is sufficiently connected to the casing hanger  12 , thereby connecting the tool  14  to the casing hanger  12 . At this point, the outer sleeve  22  engages the casing hanger  12  so that the torsion keys  32  complementarily engage, and fully extend into, the respective openings  12   a  of the casing hanger  12 . Further, the external shoulders  24   b  and  24   c  engage the internal shoulder  12   d  and the annular support  30 , respectively. Still further, the annular support  30  is sandwiched between the external shoulder  24   c  of the inner sleeve  24  and the internal shoulder  22   c  of the outer sleeve  22 . Still further, the annular groove  26   e  is generally axially aligned with the upper end of the torsion nut  28 , thereby providing an external visual indication that the inner sleeve  24  is sufficiently connected to the casing hanger  12 . In the configuration shown in  FIG. 3 , no tensile load is applied across the tool  14 . 
         [0040]    In an exemplary embodiment, as illustrated in  FIG. 4  with continuing reference to  FIGS. 1 ,  2  and  3 , a tensile load is applied across the tool  14 . More particularly, the pup  26  is forced to move upwards, relative to the outer sleeve  22 , the inner sleeve  24  and the torsion nut  28 , until the torsion keys  36  complementarily engage, and fully extend into, the respective slots  28   c  of the torsion nut  28 , as shown in  FIG. 4 . Thus, the pup  26  shoulders out when the torsion keys  36  are keyed into the respective slots  28   c . As shown in  FIG. 4 , the annular groove  26   d  is generally axially aligned with the upper end of the torsion nut  28 , thereby providing an external visual indication that the pup  26  has shouldered out against the torsion nut  28 , and thus a tensile load is being applied across the tool  14 . 
         [0041]    The tensile load of the tubular string  16  is transferred from the suspended tubular string  16  to the casing hanger  12  via the connection  20   a  (see  FIG. 1 ), from the casing hanger  12  to the inner sleeve  24  via the threaded engagement between the external threaded connection  24   a  and the internal threaded connection  12   e , from the inner sleeve  24  to the outer sleeve  22  via the respective engagements between the external shoulder  24   c  and the annular support  30 , and between the internal shoulder  22   c  and the annular support  30 , from the outer sleeve  22  to the torsion nut  28  via the threaded engagement between the external threaded connection  28   a  and the internal threaded connection  22   b , and from the torsion nut  28  to the pup  26  via the shouldering out of the pup  26  against the torsion nut  28 . In the configuration shown in  FIG. 4 , the tensile load of the tubular string  16  is applied across the tool  14 ; as a result, the apparatus  10  is in tension while the tubular string  16  is positioned within the wellbore  18 . 
         [0042]    After applying the tensile load of the tubular string  16  across the tool  14 , torsion is applied to the tubular string  16 , while the tubular string  16  is in tension and positioned within the wellbore  18 , in order to rotate the tubular string  16  within the wellbore  16 . More particularly, when the apparatus  10  is in the configuration shown in  FIG. 4  and tension is applied across the tool  14 , the pup  16  is rotated about its longitudinal axis, thereby applying torsion to the tool  14 . The applied torsion is transmitted from the pup  26  to the torsion nut  28  via extension of the torsion keys  36  into the respective slots  28   c , from the torsion nut  28  to the outer sleeve  22  via the threaded engagement between the external threaded connection  28   a  and the internal threaded connection  22   b , from the outer sleeve  22  to the casing hanger  12  via the extension of the torsion keys  32  into the respective openings  12   a , from the casing hanger  12  to the tubular  16   a  via the connection  20   a  (see  FIG. 1 ), from the tubular  16   a  to the tubular  16   b  via the connection  20   b  (see  FIG. 1 ), from the tubular  16   b  to the tubular  16   c  via the connection  20   c  (see  FIG. 1 ), etc. In response to this applied torsion, the tubular string  16  rotates about its longitudinal axis within the wellbore  18  while remaining in tension. The applied torsion is not transmitted or transferred to the connection between the tool  14  and the casing hanger  12 , that is, the threaded engagement between the external threaded connection  24   a  and the internal threaded connection  12   e.    
         [0043]    In several exemplary embodiments, so long as tension is applied across the tool  14  while the tool  14  is connected to the casing hanger  12 , the tool  14  is capable of carrying the tensile load of, and rotating, the tubular string  16 , without transferring torque to the connection between the tool  14  and the casing hanger  12 , that is, the threaded engagement between the external threaded connection  24   a  of the inner sleeve  24  and the internal threaded connection  12   e  of the casing hanger  12 . Thus, the amount of torque necessary to disconnect the inner sleeve  24  (and thus the tool  14 ) from the casing hanger  12  is not increased as a result of applying torsion to the tool  14 , the casing hanger  12  and the tubular string  16 . 
         [0044]    In an exemplary embodiment, when a compressive load is applied across the tool  14 , the pup  26  moves downward, as viewed in  FIGS. 3 and 4 , and un-keys from the torsion nut  28 . That is, the torsion keys  36  no longer extend into the respective slots  28   c , as shown in  FIG. 3 . As a result, any trapped torsion between any two of the tubulars (e.g., the tubulars  16   a  and  16   b , or the tubulars  16   b  and  16   c ) in the tubular string  16  is released. Moreover, any trapped torsion between any two of the above-described pairs of components used to transmit or transfer torque from the pup  16  to the tubular  16   c  is released. For example, any trapped torsion in any of the connections  20   a ,  20   b  and  20   c  is released. In an exemplary embodiment, a compressive load may be applied across the tool  14  by forcing the pup  26  to move downward, as viewed in  FIG. 3 . In an exemplary embodiment, a compressive load may be applied across the tool  14  by permitting the apparatus  10  to be dropped into, or landed in, the wellhead profile, and/or manipulating the apparatus  10  or components thereof so that the apparatus  10  drops into, or lands in, the wellhead profile. The pup  26  continues to move downward until it keys into the inner sleeve  24 , that is, the torsion keys  34  complementarily engage, and fully extend into, the respective slots  26   a  of the pup  26 , as shown in  FIG. 3 . 
         [0045]    In an exemplary embodiment, as illustrated in  FIG. 5  with continuing reference to  FIGS. 1 ,  2 ,  3  and  4 , after the pup  26  has keyed into the inner sleeve  24 , the tool  14  may be disconnected from the casing hanger  12 . To disconnect the tool  14  from the casing hanger  12 , the pup  26  is rotated, which rotation, due to the extension of the torsion keys  34  into the respective slots  26   a , transmits torque from the pup  26  to the inner sleeve  24 , causing the inner sleeve  24  to rotate and thus break the connection between the tool  14  and the casing hanger  12 , that is, the threaded engagement between the external threaded connection  24   a  and the internal threaded connection  12   e . Accordingly, continued rotation of the pup  26  causes the external threaded connection  24   a  to be threadably disengaged from the internal threaded connection  12   e . As a result, the tool  14  is disconnected from the casing hanger  12 . During or after the rotation effecting this disconnection, the pup  26  may be forced upwards until the annular groove  26   d  is generally axially aligned with the upper end of the torsion nut  28 , thereby providing an external visual indication that the inner sleeve  24 , and thus the tool  14 , is fully disconnected from the casing hanger  12 . This external visual indication is shown in  FIG. 5 . Since the tool  14  is disconnected from the casing hanger  12 , the tool  14  may be lifted off of the casing hanger  12  so that that the torsion keys  32  no longer extend into the respective openings  12   a  of the casing hanger  12 . 
         [0046]    During the above-described disconnection of the tool  14  from the casing hanger  12 , the connection between the tool  14  and the casing hanger  12  may be broken without breaking the connection  20   a  (see  FIG. 1 ), and without breaking any of the respective connections between any two of the tubulars in the tubular string  16 , such as the connection  20   b  or  20   c  (see  FIG. 1 ). This is possible because the tool  14  permitted torsion to be applied to the tubular string  16 , in order to rotate the tubular string  16  within the wellbore  18  as described above, without transferring torque to the connection between the tool  14  and the casing hanger  12 . In several exemplary embodiments, use of the tool  14  to rotate the tubular string  16  eliminates, or at least reduces, the risk that the connection  20   b  or  20   c , or any other connections between any two tubulars in the tubular string  16 , may be broken before the connection between the tool  14  and the casing hanger  12  is broken. As a result, all connections between the tubulars in the tubular string  16  (including the connections  20   b  and  20   c ), and the connection  20   a , remain sufficiently tight so as to render the tubular string  16  operable for its intended purposes within the wellbore  18  (e.g., conveying fluids through the tubular string  16 , holding pressure within the tubular string  16 , providing structural support to the wellbore  18 , one or more other intended purposes, or any combination thereof). 
         [0047]    In several exemplary embodiments, the tubular member, to which the tool  14  is adapted to be connected, may not be a casing hanger; instead of the casing hanger  12 , the tool  14  may be connected to another type of hanger, or another tubular member, in a manner similar to the manner in which the tool  14  is connected to the casing hanger  12 . In several exemplary embodiments, the tubular member substituted for the casing hanger  12 , as well as the tool  14 , may be positioned anywhere along the tubular string  16 , and may be characterized as part of the tubular string  16 . Since the tool  14  is part of the tubular string  16 , the tool  14  is operable to, for example, convey fluids through the tubular string  16 , hold pressure within the tubular string  16 , provide structural support to the wellbore  18 , or any combination thereof. Alternatively, in several exemplary embodiments, the tubular member substituted for the casing hanger  12 , as well as the tool  14 , may be positioned inline between the tubular string  16  and another tubular string, or may define a portion of the tubular string  16  upstream of the tool  14  and another portion of the tubular string  16  downstream of the tubular member substituted for the casing hanger  12 . Since the tool  14  is positioned inline between the tubular string  16  and another tubular string, or defines upstream and downstream portions of the tubular string  16 , the tool  14  is operable to, for example, convey fluids through the tubular string  16 , hold pressure within the tubular string  16 , provide structural support to the wellbore  18 , or any combination thereof. 
         [0048]    In several exemplary embodiments, the tool  14  enables a customer to rotate the tubular string  16  while installing it in the wellbore  18 . This helps to reduce the risk of the tubular string  16  (such as casing string) getting stuck during installation. This also allows the customer to install the tubular string  16  (such as casing string) into long horizontal wellbore sections. In several exemplary embodiments, after the mandrel casing hanger has been landed in the wellhead profile and the tool  14  is in compression, the connection between the tool  14  and the casing hanger  12  is the lowest torqued connection in the entire tubular string  16 . When, for example, a left hand torque is applied to the entire tubular string  16 , the tool  14  will start to back off from the casing hanger  12  and allow for the tool  14  to be removed from the wellbore  18 . In several exemplary embodiments, the operation of the apparatus  10 , including the rotation of the tubular string  16 , does not increase the amount of torque retained in the respective connections between adjacent tubulars in the tubular string  16 . Moreover, in several exemplary embodiments, disconnecting the tool  14  from the casing hanger  12  (or from another tubular member) does not increase the risk of breaking any of the respective connections between adjacent tubulars in the tubular string  16 . 
         [0049]    In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms. 
         [0050]    In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear. 
         [0051]    In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. 
         [0052]    Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.

Summary:
In one aspect, a system includes a tool, a hanger connected to the tool, and a plurality of tubulars connected to the hanger and adapted to be positioned within a wellbore. The tool, hanger, and tubulars are rotatable in response to at least the application of torsion to the tool, and without transferring torque to the connection between the tool and the hanger. In another aspect, a method includes positioning a tubular string within a wellbore, connecting a hanger to the tubular string, and applying torsion to the tubular string to rotate the tubular string. To apply torsion to rotate, a tool is connected to the hanger, and torsion is applied to the tool without transferring torque to the connection between the tool and the hanger. In another aspect, there is provided an apparatus for rotating a tubular string in a preexisting structure, such as a wellbore.