Patent Abstract:
A packer that is usable with a subterranean well includes an assembly to circumscribe one out of multiple tubular arrays that are inserted through the packer. The packer also includes a member that is separable from the assembly to configure the assembly for connection to the tubular array. The member includes a first seal between the member and the tubular array and a second seal that is located between the member and the shell. The first seal is separate from the second seal. The assembly includes a slip to engage a casing of the well and a sealing element to seal an annulus of the well.

Full Description:
BACKGROUND 
   The invention generally relates to a modular retrievable packer. 
   A packer is a device that is used in an oilfield well to form a seal for purposes of controlling production, injection or treatment. In this manner, the packer is lowered downhole into the well in an unset state. However, once in the appropriate position downhole, the packer is controlled from the surface of the well to set the packer. As an example, for a mechanically-set packer, a tubular string that extends from the surface to the packer may be moved pursuant to a predefined pattern to set the packer. For a hydraulically-set packer, fluid inside the tubular string may be pressurized from the surface, creating a tubing pressure differential to set the packer. 
   In its set state, the packer anchors itself to the casing wall of the well and forms a seal in the annular region between the packer and the interior surface of the casing wall. This seal subdivides the annular region to form an upper annular region above the packer that is sealed off from a lower annular region below the packer. The packer also forms a seal for conduits that are inserted through the packer between the upper and lower annular regions. As examples, one of these conduits may communicate production fluid from a production zone that is located below the packer, one of the conduits may communicate control fluid through the packer, one of the conduits may house electrical wiring for a submersible pump, allow production or injection through two different reservoir zones, etc. 
   As a more specific example,  FIG. 1  depicts a well that includes a packer  20 . As shown, the packer  20  may be connected to a tubular string  16  that extends downhole into the well. The packer  20  forms an annulus seal with the interior surface of a wall of a casing string  12  that circumscribes the packer  20 . The packer  20  typically includes at least one seal assembly  24  to form the annulus seal and at least one set of slips  22  to anchor the packer  20  to the casing string  12 . In this manner, when run into the well, the seal assembly  24  and the slips  22  are radially retracted to allow passage of the packer  20  through the central passageway of the casing string  12 . However, when the packer  20  is in the appropriate downhole position, the packer  20  is set to place the packer  20  in a state in which the seal assembly  24  and slips  22  are radially expanded. When radially expanded, the slips  22  grip the interior surface of the wall of the casing string  12  to physically anchor the packer  20  in position inside the well. The radial expansion of the seal assembly  24 , in turn, seals off the annular space between the string  16  and the casing string  12  to form a sealed annular region above the seal assembly  24  and a sealed annular region below the seal assembly  24 . 
   The packer  20  may be hydraulically actuated for purposes of controlling the packer  20  from the surface of the well to set the packer  20 . This means that pressure may be communicated through fluid inside the string  16  to the packer  20 . In response to this pressure reaching a predefined threshold level, pistons (not shown in  FIG. 1 ) move to radially expand the slips  22  and apply compressive forces on the seal assembly  24  to radially expand the assembly  24 . A retention mechanism of the packer  20  serves to hold the packer  20  in the set state when the pressure that is used to set the packer  20  is released. 
   One or more mandrels  21 , or tubular elements, may extend through the packer  20  for purposes of providing communicating paths through the packer  20 . Depending on the particular application of the packer  20 , a particular mandrel  21  may contain one or more communication paths, such as paths to communicate production fluid, electrical lines, or control fluid through the packer  20 . For example, in a particular application, a single mandrel  21  may extend through the packer  20  for purposes of communicating production fluid from a tubular string  23  located below the packer  20  to the string  16  located above the packer  20 . However, in other applications, more than one mandrel  21  may be extended through the packer  20 . Thus, one mandrel  21  maybe used for purposes of communicating electrical or hydraulic lines, for example, and another mandrel  21  may be used for purposes of communicating production fluid through the packer  20 . 
   The packer  20  may be retrievable, and thus may include a release mechanism that when engaged, releases the retention mechanism of the packer  20  to radially retract the slips  22  and seal assembly  24  to permit retrieval of the packer  20  to the surface of the well. 
   The packer  20  establishes two general seals: an interior seal between the interior of the packer  20  and the exterior of the one or more mandrels  21  that are extended through the packer  20 ; and an exterior seal between the exterior of the packer  20  and the interior surface of the wall of the casing string  12 . Because the mandrel configuration may change depending on the particular application of the packer, a given packer design may need to be modified to accommodate the particular application. Thus, for example, the packer  20  may have a first design for an application in which a single mandrel extends through the packer  20 . However, the design of the packer  20  must be redesigned for an application in which two mandrels are extended through the packer  20 . In this manner, the exterior profiles and structure that are presented by two mandrels are significantly different from the exterior profiles and structures that are associated with one mandrel, thereby requiring a substantial redesign of the packer&#39;s interior sealing rings and structure that establishes the packer&#39;s interior seal. Furthermore, the design of the packer  20  may need to be redesigned to accommodate different size mandrels or additional mandrels that are inserted through the packer  20 . 
   Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are set forth above. 
   SUMMARY 
   In an embodiment of the invention, a packer that is usable with a subterranean well includes an assembly to circumscribe one out of multiple tubular arrays that are inserted through the packer. The packer also includes a member that is separable from the assembly to configure the assembly for connection to the tubular array. The member includes a first seal between the member and the tubular array and a second seal that is located between the member and the shell. The first seal is separate from the second seal. The assembly includes a slip to engage a casing of the well and a sealing element to seal an annulus of the well. 
   Advantages and other features of the invention will become apparent from the following description, drawing and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a packer of the prior art. 
       FIGS. 2 and 3  are schematic diagrams of a packer in accordance with an embodiment of the invention depicting a state of the packer when run into a well. 
       FIGS. 4 ,  5  and  6  are schematic diagrams depicting the packer in accordance with the invention in a state in which the packer is set. 
       FIGS. 7 ,  8  and  9  are schematic diagrams depicting the packer in accordance with the invention in a state after the packer has been unset for purposes of retrieval of the packer from the well. 
       FIGS. 10 and 11  are schematic diagrams of a packer in accordance with another embodiment of the invention depicting a different mandrel configuration. 
   

   DETAILED DESCRIPTION 
   An embodiment of a packer in accordance with the invention is depicted in its run in state in  FIGS. 2 and 3 .  FIG. 2  depicts an upper section  100 A of the packer, and  FIG. 3  depicts the lower section  100 B of the packer. In this run in state, the packer is ready to be run into a well to the appropriate position at which the packer may be set, as described further below. 
   The packer includes one or more internal tubes, or mandrels, that extend through the packer for purposes of establishing one or more communication paths through the packer. In the embodiment that is depicted in  FIGS. 2 and 3 , the packer includes an internal tubing, or mandrel  25 , that extends through the packer for purposes of establishing fluid communication between a tubular member  26  that extends above the packer and a tubular member (not shown in  FIG. 2  or  3 ) that extends below the packer. 
   The packer forms a seal between the packer and the exterior surface(s) of the one or more mandrels. Thus, the different mandrel configurations require different seals. However, the packer has a design that minimizes the number of components that must be changed to reconfigure the packer from a first configuration for use with a particular mandrel configuration (such as the mandrel configuration depicted in  FIGS. 2 and 3 ) to a second mandrel configuration for use with a different mandrel configuration (a two mandrel configuration, for example). 
   In some embodiments of the invention, the ability of the packer to be easily reconfigured flows from the modular design of the packer. Referring to  FIGS. 2 and 3 , in some embodiments of the invention, the packer includes an internal and generally circularly cylindrical shell  34 . The shell  34  has a central passageway through which the internal mandrel  25  extends. Mounted on the exterior of the shell  34  are components that are associated with anchoring the packer to the casing wall and forming a seal between the packer and the casing wall. In this manner, these components may include, for example, a set of slips  70  (one slip being depicted in  FIGS. 2 and 3 ) that are spaced regularly around the periphery of the packer to anchor the packer to the casing string, and these components may also include an elastomer seal assembly  36  ( FIG. 2 ) that circumscribes the shell  34  and is compressed to seal off the well annulus. As further described below, also mounted on the exterior of the shell  34  are various pistons and other devices used to set and unset the elastomer seal assembly  36  and the slips  70 , as described below. Thus, the shell  34  forms a basic structure of a shell assembly that includes the shell  34  and components that are associated with anchoring the packer to the casing wall and forming a seal between the casing wall and the packer. 
   For purposes of facilitating the redesign of the packer for different mandrel configurations, unlike conventional packers, sealing rings do not directly bridge the space between the interior surface of the shell  34  and the exterior surface of the mandrel  25 . The inclusion of such sealing rings that form direct seals between the shell  34  and mandrel  25  hinders the reconfiguration of the packer, as specific grooves must be formed in the exterior surface of the mandrel  25  and/or in the interior surface of the shell  34  to accommodate these sealing rings. Thus, for example, the grooves and general design of the shell for a one mandrel design would be different than the design of the shell for a two mandrel design. This means a different shell would have to be used for each configuration. However, unlike conventional packers, the packer has a different design in which seals between the shell  34  and mandrel(s) are established by separate components, called sealing bulkheads with the diversity to change the internal configuration without changing most of the components on the shell. 
   In this manner, for the embodiment of the packer  20  depicted in  FIGS. 2 and 3 , the packer includes an upper sealing bulkhead  32 . This upper sealing bulkhead  32  includes a first sealing ring to form a seal between the bulkhead  32  and the mandrel  25  and a second sealing ring to form a seal between the bulkhead  32  and the shell  34 . Similarly, the packer includes a lower sealing bulkhead  80  (see  FIG. 3 ) that includes a third sealing ring to form a seal between the bulkhead  80  and the mandrel  25  and includes a fourth sealing ring to form a seal between the bulkhead  80  and the shell  34 . Thus, no sealing rings extend directly between the shell  34  and the mandrel  25 , i.e., no seals are formed directly between the shell  34  (and shell assembly) and the mandrel  25 . 
   Due to this arrangement, a different mandrel configuration is accommodated by simply changing the sealing bulkheads and sealing rings, as compared to redesigning the packer&#39;s shell assembly or another part of the packer associated with the anchoring and annulus sealing functions of the packer. In this manner, a particular set of upper and lower sealing bulkheads are used with one mandrel configuration, another set of upper and lower sealing bulkheads are used with a two mandrel configuration, a third set of upper and lower sealing bulkheads are used with mandrel configurations with mandrels having different diameters, etc. Thus, because only the sealing bulkheads and sealing rings are dependent on the mandrel configuration, design time and costs associated with reconfiguring the packer for different mandrel configurations are minimized. 
   Turning now to a more detailed description of the packer and more particularly referring to  FIG. 2 , in some embodiments of the invention, the upper sealing bulkhead  32  includes an annular groove  32   c  that holds a corresponding elastomer sealing ring  33  (an O-ring, for example) to form a seal between the upper sealing bulkhead  32  and the exterior surface of the mandrel  25 . The upper sealing bulkhead  32  also includes an annular groove  32   b  that holds an elastomer sealing ring  38  (an O-ring, for example) to form a seal between the upper sealing bulkhead  32  and the shell  34 . Thus, with these two sealing rings  33  and  38 , the upper sealing bulkhead  32  forms a seal between the shell  34  and the mandrel  25 . 
   The upper sealing bulkhead  32  has a lower annular inclined surface  32   a  that forms a shoulder that, in turn, abuts an upper annular contact surface of the elastomer seal assembly  36 . As described below, when the packer is set, a piston of the packer exerts an upward force on the elastomer seal assembly  36 , forcing the elastomer seal assembly  36  against the surface  32   a  and causing the seal assembly  36  to radially expand. 
   In some embodiments of the invention, the packer is hydraulically actuated by fluid pressure that is applied through a central passageway  39  of the mandrel  25 . For purposes of establishing fluid communication between pistons of the shell assembly and the central passageway  39 , the mandrel  25  includes radial fluid ports  31  that extend through the sidewall of the mandrel  25 . In this manner, the pressure on the fluid in the central passageway  39  is increased to actuate the pistons to set the packer. Afterwards, the applied pressure is decreased, or bled off. As described below, the packer includes a retention mechanism to hold the packer in its set state, even after the applied fluid pressure is released. 
   As also described below, the packer may be retrieved by exerting an upward force of sufficient magnitude on a tubular string that is connected to the mandrel  25  and extends to the surface of the well. In this manner, a sufficient upward force on the mandrel  25  engages a release mechanism of the packer to release the slips  70  ( FIG. 3 ) and elastomer seal assembly  36  to permit radial retraction of these devices and the retrieval of the packer to the surface of the well. 
   In some embodiments of the invention, the force to radially expand the elastomer seal assembly  36  is applied by an upper piston assembly  42  that circumscribes the shell  34 . The piston assembly  42  includes an upper sleeve  42   a  that circumscribes the shell  34  and has an upper annular inclined surface  42   h  to contact a lower annular contact surface of the seal assembly  36 . For purposes of preventing the inadvertent setting of the packer, the upper sleeve  42   a  is initially held in place to the shell  34  via one or more shear screws  43 . In this manner, when the packer is set, enough upward force is applied on the piston assembly  42  to shear the shear screws  43  to permit compression of the elastomer seal assembly  36  by the piston assembly  42 . 
   In addition to the upper sleeve  42   a , the upper piston assembly  42  includes an intermediate sleeve  42   b  that is located below and is connected to the upper sleeve  42   a . The intermediate sleeve  42   b , in turn, circumscribes the shell  34 , and is located above and is connected to a lower sleeve  42   c  of the piston assembly  42 . This lower sleeve  42   c  also circumscribes the shell  34 . The lower end of the lower sleeve  42   c , in turn, includes a piston head  42   f  ( FIG. 3 ) that is in fluid communication with an expandable chamber  54 . 
   Referring to  FIGS. 2 and 3 , an annular region that is defined radially between the exterior surface of the mandrel  25  and the inner surface of the shell  34  and longitudinally between the upper  32  and lower  80  sealing bulkheads communicates fluid between the radial ports  31  of the mandrel  25  and the chamber  54 . Due to this communication, an upward force is exerted on the upper piston assembly  42  in response to the fluid inside the central passageway  39  being pressurized. After the shear pins  43  shear, this upward force causes upward movement of the piston assembly  42  that, in turn, applies a compressive force to radially expand the seal assembly  36 . 
   Referring to  FIG. 3 , in some embodiments of the invention, the packer includes a lower piston assembly  50  that circumscribes the shell  34  and resides below the expandable chamber  54 . In this manner, the piston assembly  50  includes a piston head  50   a  that is in fluid communication with the chamber  54 . Because the piston head  50   a  is located below the chamber  54 , when sufficient pressure is applied to the fluid inside the central passageway  39 , the piston assembly  50  moves in a downward direction. As described below, this movement of the piston assembly  50  causes the radial expansion of the slips  70 . 
   More particularly, the piston assembly  50  is formed from a generally circularly cylindrical sleeve that circumscribes the shell  34 . The piston assembly  50  is initially held in place to the shell  34  by one or more shear screws  51 . However, after sufficient fluid pressure is applied to expand the chamber  54 , the shear screws  51  shear, thereby freeing the piston assembly  50  to move in a downward direction. 
   The sleeve that forms the piston assembly  50  is connected to a generally circularly cylindrical upper cone assembly  64  that circumscribes the shell  34 . The upper cone assembly  64  moves downwardly with the piston assembly  50  to apply force to the slips  70  for purposes of causing the slips  70  to radially expand. In this manner, in the depiction of the packer of  FIG. 3 , the cone assembly  64  includes a lower inclined annular face  64   c  that contacts the inclined faces of the slip  70 . Thus, when the lower piston assembly  50  moves in a downward direction, the inclined face  64   c  of the cone assembly  64  pushes against the corresponding inclined faces of the slips  70  to force the slips  70  in radially outward directions. Each slip  70  is held in position by a spring-biased connection  70   a  that radially retracts the slip  70  when the cone assembly  64  is not pushing against the slip  70 . 
   In some embodiments of the invention, a generally circularly cylindrical outer sleeve  67  circumscribes the upper cone assembly  64 . The sleeve  67  has openings through which the slips  70  extend. The sleeve  67  is initially secured to the upper cone assembly  64  via one or more shear screws  65 . In this manner, after the lower piston assembly  50  exerts sufficient force against the cone assembly  64 , the shear screws  65  shear, thereby allowing movement of the upper cone assembly  64  and thus, the extension of the slips  70 . 
   A lower cone assembly  76  abuts a lower inclined annular surface of each slip  70 . In this manner, the lower cone assembly  76  is circumscribed by the outer sleeve  67  and includes an inclined annular surface  76   c  that mates with corresponding inclined surfaces of the slips  70  to produce a force to radially extend the slips  70  when the lower piston assembly  50  moves in a downward direction. The lower cone assembly  76  is secured to the mandrel  25  via one or more shear screws  89 . 
   As described further below, the shear screws  89  shear in response to a sufficient upward force that is exerted on the mandrel  25  to cause the packer to transition from a set state to an unset state for retrieval from the well. In this manner, when the packer is set, the lower cone assembly  76  is fixed in position. Thus, the application of an upward force on the mandrel  25  causes the shear screws  89  to shear, thereby freeing the mandrel  25  to move relative to the lower cone assembly  76 . The release of the packer from its set state is further described below. 
   Among the other features of the packer, the packer may include a pin and slot arrangement to permit a limited movement between the upper  64  and lower  76  cone assemblies and the outer sleeve  67 . Such movement permits movement for purposes of setting the slips  70 , but the range of movement is limited for purposes of disengaging the packer from its set state, as described further below. The pin and slot arrangement includes one or more upper slots  90  that are formed in the outer sleeve  67  above the slips  70  and one or more lower slots  94  that are formed in the outer sleeve  67  below the slips  70 . Each upper slot  90  is associated with a pin  91  that radially extends from the upper cone assembly  64  into the associated upper slot  90 . Each lower slot  94  is associated with a pin  95  that radially extends from the lower cone assembly  76  into the associated lower slot  94 . 
   The lower sealing bulkhead  80  is generally circularly cylindrical, circumscribes the mandrel and is circumscribed by the shell  34 . The lower sealing bulkhead  80  includes an interior annular groove  80   a  that holds an elastomer sealing ring  81  (an O-ring, for example) that forms the seal between the interior surface of the bulkhead  80  and the exterior surface of the mandrel  25 . The lower sealing bulkhead  80  also includes an exterior annular groove  80   b  that holds an elastomer sealing ring  83  (an O-ring, for example) that forms the seal between the exterior surface of the bulkhead  80  and the interior surface of the shell  34 . In some embodiments of the invention, the lower sealing bulkhead is secured to the shell  34  via one or more screws  97 . 
   Referring to  FIGS. 2 and 3 , for purposes of maintaining the set state of the packer after the release of the fluid pressure in the central passageway  39 , the packer includes a sleeve  46  that is generally circularly cylindrical and circumscribes the lower portion of the upper piston assembly  42  and the upper portion of the lower piston assembly  50 . The sleeve  46  forms a set retention mechanism by forming a non-retractable extension between the upper  42  and lower  50  piston assemblies; and this extension is increased in response to the upper movement of the upper piston assembly  42  and the lower movement of the lower piston assembly  50 . 
   More specifically, a lower end  46   b  ( FIG. 3 ) of the sleeve  46  is attached to the lower piston assembly  50 ; and an upper end  46   a  ( FIG. 2 ) of the sleeve  46  is connected in a ratchet-type arrangement with the upper piston assembly  50 . The upper portion  46   a  of the sleeve  46  includes teeth that engage exterior mating teeth of a ratchet ring  48  (FIG.  2 ). The ratchet ring  48  is circumscribed by the upper end  46   a  of the sleeve  46  and circumscribes the upper piston assembly  42 . More specifically, interior ratchet teeth of the ratchet ring  48  interact with exterior ratchet teeth  42   g  of the upper piston assembly  42 . The interior ratchet teeth of the ratchet ring  48  and the ratchet teeth  42  have profiles to permit the ratchet teeth  42   g  (and upper piston assembly  42 ) to move in an upward direction relative to the ratchet ring  48 , but these profiles do not permit the ratchet teeth  42   g  (and upper piston assembly  42 ) to move in a downward direction relative to the ratchet ring  48 . Due to this arrangement, when pressure is applied to the fluid to drive the piston assembly  42  in an upward direction and drive the lower piston assembly  50  in a downward direction, the sleeve  46  maintains the positions of the upper  42  and lower  50  piston assemblies, while allowing more movement in the upper and lower directions of the upper  42  and lower  50  piston assemblies, respectively. Thus, when pressure is released from the fluid in the central passageway, the piston assemblies  42  and  50  maintain the forces on the elastomer seal assembly  36  and the slips  70  to keep the packer in the set state. 
     FIGS. 4 ,  5  and  6  depict upper  120 A, intermediate  120 B and lower  120 C sections of the packer in the packer&#39;s set state. Referring to these figures, in its set position, the elastomer seal assembly  36  is expanded radially in an outward direction. Furthermore, the teeth  42   g  of the lower piston assembly  42  engage the ratchet ring  48  at a lower position so that the piston assemblies  42  and  50  are located by a distance apart that does not change when pressure is released from the fluid inside the central passageway. As depicted in  FIG. 5 , in the set position, the slip  70  is expanded so that teeth  70   b  of the slip  70  may engage the inner surface of the surrounding well casing string. As depicted in  FIG. 4 , in this position of the upper piston assembly  42 , the shear screws  43  have been sheared, thereby allowing free movement of the upper piston assembly  42 . Furthermore, in the depicted position of the lower piston assembly  50  in  FIG. 5 , the shear screws  51  have been sheared thereby allowing downward movement of the lower piston assembly  50 . 
   Referring to  FIG. 6 , in the set position of the packer, a collet ring  82  of the packer has a shoulder  85  that engages a corresponding inner shoulder of the lower cone assembly  76 . The collet ring  82  is pressed into this engagement by a retaining ring  84  that is positioned in a corresponding annular groove formed in the outer surface of the mandrel  25 . The collet ring  82  is located below and abuts the shell  34 . Thus, due to this arrangement, the collet ring  82  prevents movement of the shell  34  with respect to the mandrel  25 . The movement of the mandrel  25  with respect to the lower cone assembly  76 , in turn, is prevented via the shear screws. 
     FIGS. 7 ,  8  and  9  depict upper  140 A ( FIG. 7 ) intermediate  140 B ( FIG. 8 ) and lower  140 C ( FIG. 9 ) sections of the packer after the packer has been released from its set state. In this manner, the release of the packer from its set state occurs in response to the application of a sufficient upward force to the tubing that is connected to the mandrel  25 . This force, in turn, shears screws of the packer, discussed below, to release the actuating mechanisms of the packer to retract the elastomer seal assembly  36  and retract the slips  70 . 
   More particularly, in some embodiments of the invention, the upper force on the mandrel  25  shears the shear screws  89  that connect the lower cone assembly  76  to the mandrel  25 . Due to this released connection, the retaining ring  84  slides upwardly with the mandrel  25 , thereby freeing the collet ring  82  to radially retract. This radial retraction of the collet ring  82 , in turn, permits movement of the shell  34  with the mandrel  25 . When the shell  34  moves in an upward direction, the shell contacts an upper shoulder  27  (see  FIG. 7 ) of the upper sealing bulkhead  32 , to cause movement of the upper sealing bulkhead  32  away from the elastomer seal assembly  36 , thereby releasing pressure on the upper seal assembly  36 . Due to the upward motion of the upper sealing bulkhead  32 , the shell  34  further slides in an upward direction until a shoulder  34   a  of the shell  34  contacts a corresponding shoulder  42   h  ( FIG. 7 ) of the upper piston assembly  42 . This contact pulls the upper piston assembly  42 , the sleeve  46  and the lower piston assembly  50  an upward direction to release the applied pressure on the slips  70 . Furthermore, the pins  91  reach the upper limit of their respective slots  90  to pull the upper cone assembly  64  and the sleeve  65  in an upward direction to release pressure on the slip  70   b.    
   Different sealing bulkheads may be used in other embodiments of the invention. For example,  FIGS. 10 and 11  depict upper  150 A and lower  150 B sections of a packer in accordance with another embodiment of the invention. In this embodiment, two mandrels pass through the packer: a primary mandrel  173  and a secondary mandrel  174 . As an example, the primary mandrel  173  may be used for purposes of communicating production fluids, and the secondary mandrel  174  may be used as a bypass line or for purposes of providing a path for electrical and/or hydraulic communication lines through the packer. In this embodiment of the invention, the upper sealing bulkhead  32  is replaced with an upper sealing bulkhead  160  (FIG.  10 ), and the lower sealing bulkhead  80  is replaced by a lower sealing bulkhead  180 . 
   Referring to  FIG. 10 , the upper sealing bulkhead  160  has an opening  178  to receive the primary mandrel  173  and an opening  176  to receive the secondary mandrel  174 . An interior annular groove  162  that circumscribes the opening  178  holds an elastomer sealing ring  164  (an O-ring, for example) that forms a seal between the sealing bulkhead  160  and the primary mandrel  173 . An interior annular groove  170  that circumscribes the opening  176  holds an elastomer sealing ring  172  (an O-ring, for example) that forms a seal between the sealing bulkhead  160  and the secondary mandrel  174 . The sealing bulkhead  160  also includes an interior annular groove  166  that circumscribes the shell  34  and holds an elastomer sealing ring  168  (an O-ring, for example) that forms a seal between the sealing bulkhead  160  and the shell  34 . 
   Referring to  FIG. 11 , the lower sealing bulkhead  180  has an opening  194  to receive the primary mandrel  173  and an opening  192  to receive the secondary mandrel  174 . An interior annular groove  182  that circumscribes the opening  194  holds an elastomer sealing ring  184  (an O-ring, for example) that forms a seal between the sealing bulkhead  180  and the primary mandrel  173 . An interior annular groove  189  that circumscribes the opening  192  holds an elastomer sealing ring  190  (an O-ring, for example) that forms a seal between the sealing bulkhead  180  and the secondary mandrel  174 . The sealing bulkhead  180  also includes an exterior annular groove  186  that is circumscribed by the shell  34  and holds an elastomer sealing ring  188  (an O-ring, for example) that forms a seal between the sealing bulkhead  180  and the shell  34 . 
   In the preceding description, directional terms, such as “upward” and “downward,” were used for reasons of convenience to describe the packer and its associated components. However, such orientations are not needed to practice the invention, and thus, other orientations are possible in other embodiments of the invention. For example, in some embodiments of the invention, the packer may be used in a horizontal or lateral well bore. 
   While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.

Technology Classification (CPC): 4