Patent Publication Number: US-9903176-B2

Title: Expandable packer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of pending U.S. patent application Ser. No. 13/942,456, filed Jul. 15, 2013, which is a continuation of U.S. patent application Ser. No. 13/523,656, filed Jun. 14, 2012, now U.S. Pat. No. 8,499,844, which is a continuation of U.S. patent application Ser. No. 12/389,090, filed Feb. 19, 2009, now U.S. Pat. No. 8,201,636, which claims benefit of U.S. provisional patent application Ser. No. 61/029,634, filed Feb. 19, 2008. Each of the aforementioned related patent applications is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the invention generally relate to expandable tubing assemblies and expanding such assemblies to seal a surrounding annulus. 
     Description of the Related Art 
     Drilling a bore into the earth enables access to hydrocarbons in subsurface formations. The process of drilling a borehole and of subsequently completing the borehole in order to form a wellbore requires the use of various tubular strings. Methods and apparatus utilized in the oil and gas industry enable placing tubular strings in a borehole and then expanding the circumference of the strings in order increase a fluid path through the tubing and in some cases to line the walls of the borehole. Some of the advantages of expanding tubing in a borehole include relative ease and lower expense of handling smaller diameter tubing and ability to mitigate or eliminate formation of a restriction caused by the tubing. 
     Many applications require creating a seal around one of the tubular strings in the wellbore such that fluid flow through a surrounding annulus is blocked. Various types of conventional packers exist that may be set for this purpose without expanding an inside diameter of the tubing. Further, expandable tubing may include a band of elastomeric material disposed on its outer surface to facilitate sealing. However, these bands produce sealing that is localized only at the band and often unreliable due to too low of a seal pressure being achieved. 
     Therefore, there exists a need for apparatus and methods that enable improved sealing around tubing that has been expanded. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention generally relate to expansion of tubing to create a seal in an annulus surrounding the tubing. A method in one embodiment expands a packer assembly that includes tubing with a sealing element disposed on an outside surface thereof. The sealing element defines thick bands alternating with thin bands that protrude from the outside surface of the tubing less than the thick bands. The method includes expanding the tubing such that relatively greater expansion occurs at where the thin bands are located compared to where the thick bands are located. 
     A method of expanding a packer assembly for one embodiment includes running tubing with a sealing element disposed on an outside surface thereof into a wellbore. The method includes placing the sealing element into engagement with a surrounding surface. Further, creating undulations in a diameter of the tubing occurs based on alternating first and second properties of the sealing element along a length of the tubing. 
     An expandable packer assembly according to one embodiment includes tubing having unexpanded and expanded positions. A sealing element disposed on an outside of the tubing defines thick bands alternating along a length of the tubing with thin bands that protrude from the outside of the tubing less than the thick bands. An inner diameter of the tubing along the length is uniform in the unexpanded position and undulations in the inner diameter are at the thin bands in the expanded position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a cross-section view of an expandable packer in a pre-expansion run-in position with a profiled sealing material disposed around base tubing. 
         FIG. 2  is a cross-section view of the expandable packer in an expanded position within a surrounding structure such as casing. 
         FIG. 3  is a schematic illustration showing amplitude of undulations created in the base tubing upon expanding as a result of the profiled sealing material. 
         FIG. 4  is a graph depicting sealing pressure performance as a function of the amplitude. 
         FIG. 5  is a schematic illustration showing a thickness deviation ratio and pitch defined by topography of the profiled sealing material. 
         FIG. 6  is a graph depicting sealing pressure performance as a function of the pitch. 
         FIG. 7  is a graph depicting sealing pressure performance as a function of the thickness deviation ratio. 
         FIGS. 8 and 9  are plots of data from seal pressure tests of the expandable packer at about 22° C. and 100° C., respectively. 
         FIG. 10  is a cross section view of the expandable packer during an expansion operation with an exemplary expander tool such as an inflatable device with a locating mechanism. 
         FIGS. 11A and 11B  are views illustrating an expansion tool for use with the expandable packer. 
         FIGS. 12A and 12B  are views illustrating the expansion tool disposed in the expandable packer. 
         FIGS. 13A and 13B  are views illustrating an expansion tool disposed in the expandable packer. 
         FIGS. 14A and 14B  are views illustrating an expansion tool disposed in the expandable packer. 
         FIGS. 15A and 15B  illustrate an expandable packer in a casing. 
         FIGS. 16A and 16B  illustrate another embodiment of the expandable packer. 
         FIGS. 17A and 17B  illustrate another embodiment of the expandable packer. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention generally relate to expansion of tubing to create a seal in an annulus surrounding the tubing. The tubing includes a sealing material selected to cause forming of undulations in a diameter of the tubing upon expansion of the tubing. The tubing with the sealing material provides improved sealing performance. 
       FIG. 1  illustrates an exemplary expandable packer  100  in a pre-expansion run-in position with a profiled sealing material  102  disposed on an outside of base tubing  104 . The sealing material  102  may include an elastomeric material wrapped/molded/positioned around the tubing  104  continuous along a length of the tubing  104  that may include all or part of the tubing  104 . Along this length of the tubing  104  where the sealing material  102  extends, a property (e.g., thickness, compressibility, hardness or swelling extent) of the sealing material  102  varies to achieve post expansion results as described further herein. Consistency of the profiled sealing material  102  can use hard, soft or swellable elastomeric material or a combination thereof to achieve desired high pressure sealing for cased hole or open-hole conditions. In some embodiments, the variation of the sealing material  102  occurs along a section of the tubing  104  at least in part due to discontinuity of the sealing material  102 . For example, a longitudinal break in the sealing material  102  may leave the tubing  104  without the sealing material  102  at the break. 
     By way of example since thickness is suitable for illustration, the profiled sealing material  102  defines a topography that alternates lengthwise over the tubing  104  between thick bands  106  of the sealing material  102  that occupy a greater annular area than thin bands  108  of the sealing material  102 . Each of the bands  106 ,  108  circumscribe the tubing  104  to form a ring shape oriented transverse to a longitudinal bore of the tubing  104 . The expandable packer  100  may utilize any number of the bands  106 ,  108  and in some embodiments has at least one of the thick bands  106  disposed between two of the thin bands  108 . 
     Machining of the sealing material  102  from an initially uniform thickness may create differences in the thickness of the bands  106 ,  108 . Further, separate additional outer sleeves may add to thickness of the sealing material  102  at the thick bands  106 . Tailored molding of the sealing material  102  offers another exemplary approach to provide the differences in the thickness between the bands  106 ,  108  of the sealing material  102 . 
     For some embodiments, a gripping structure or material may be located on the outside of the tubing  104  such that when the tubing  104  is expanded the gripping structure or material moves outward in a radial direction and engages a surrounding surface (e.g., casing or open borehole) to facilitate in anchoring the tubing  104  in place. As an example, the expandable packer  100  includes a grit  110  disposed on the outside of the tubing  104 . The grit  110  such as tungsten carbide or silicon carbide may adhere to any portion of the tubing  104  that is to be expanded. In some embodiments, the sealing material  102  at one or more of the thin bands  108  include the grit  110  that is coated on or embedded therein. 
       FIG. 2  shows the expandable packer  100  in an expanded position within a surrounding structure such as an open borehole or casing  200 . Upon expansion, the tubing  104  plastically deforms selectively creating undulations  109  resulting in high pressure sealing. The grit  110 , if present, also embeds in the casing  200  upon expansion to aid in hanging the expandable packer  100 . The undulations  109  occur as a result of and where the thin bands  108  of the sealing material  102  permit relatively greater radial expansion of the tubing  104 . While not expanded as much, the tubing  104  corresponding to where the thick bands  106  of the sealing material  102  are located also deforms in a radial outward direction to place the thick bands  106  into engagement with the casing  200 . Design of the sealing material  102  thus creates a specific pattern of the undulations  109  after expansion. 
     Expansion of the tubing  104  may occur utilizing an inflatable expander having a flexible bladder that is pressurized into contact with the inside of the tubing  104 . For some embodiments, a compliant (i.e., not a fixed diameter during expansion) cone or a compliant rotary expander tool can achieve expansion of the tubing  104 . Further, hydroforming techniques using only fluid pressure to act directly against an inside surface of the tubing  104  may expand the tubing  104 . Such hydroforming of the tubing  104  employs seals spaced apart inside the tubing  104  such that hydraulic pressure may be applied to an interior volume of the tubing  104  between the seals. 
     One potential cause for loss of sealing occurs if the fluid pressure in the annulus between the tubing  104  and wellbore causes the tubing  104  to collapse, thereby pulling the sealing element  102  away from its sealing engagement with the casing  200 . The undulations  109  tend to increase collapse resistance of the tubing  104  compared to tubing which has been expanded to have a constant diameter. Thus, the increase in collapse resistance benefits sealing ability of the sealing element  102 . Further, the undulations  109  at least reduce any potential decreases in seal load as a result of elastic recovery of the tubing  104  immediately after expansion. The undulations  109  may experience less elastic recovery than when a longer length of the tubing  104  is expanded, thereby mitigating effect of the elastic recovery causing removal of the seal load. While it is believed that these mechanisms enhance sealing performance as determined by test data results described herein, other factors without limitation to any particular theory may alone or in combination cause the improvements in the sealing performance obtained. 
       FIG. 3  schematically illustrates amplitude (A) of the undulations  109  created in the tubing  104  upon expanding. In particular, the amplitude as identified represents extent of localized radial deformation defined as difference between an inner diameter of the tubing  104  adjacent the undulation  109  and an outer diameter of the tubing  104  at a peak of the undulation  109 . The undulations  109  created in part due to the profiled sealing material  102  influence sealing performance of the expandable packer  100 . 
       FIG. 4  in particular shows a graph depicting sealing pressure performance as a function of the amplitude characterized as a generic unit length. The sealing pressure performance for this amplitude based analysis occurs as a result of discrete localized sealing engagement at only the undulations  109  without sealing engagement extending over a substantial length of the tubing  104 . The results shown demonstrate that sealing pressure achievable trends higher along an amplitude curve  400  with increase in the amplitude. Selection of the amplitude can alter sealing pressure achievable by several multiples. It is to be noted that this illustrates one embodiment of a sealing arrangement where the undulations  109  are formed and only the thin bands  108  contact and create a seal with the surrounding structure. In another embodiment, upon expansion, the undulations  109  are formed but only the thick bands  106  contact and create a seal with the surrounding structure. In a further embodiment, upon expansion, the undulations  109  are formed and the thin bands  108  contact the surrounding structure while only the thick bands  106  create a seal with the surrounding structure. In yet a further embodiment, upon expansion, the undulations  109  are formed whereby both the thin bands  108  and the thick bands  106  contact and create a seal with the surrounding structure. 
     Several design factors of the sealing element  102  influence generation of the undulations  109  and resulting seal created by the expandable packer  100 . Factors that can influence the amplitude achieved and enable creation of the amplitude that is sufficiently high to provide the seal performance desired include a thickness deviation ratio between the thick and thin bands  106 ,  108  of the sealing element  102 , a pitch of the sealing element  102  as defined by distance between the thick bands  106 , the number of undulations  109 , the number of bands  106 ,  108  and the material and dimensional properties of the tubing  104 , such as yield strength, ductility, wall thickness and diameter. These design factors in combination with the radial expansion force applied by the expander tool control the amplitude of the undulation  109 . 
       FIG. 5  illustrates a max height (H1) of the thick band  106  protruding from the tubing  104  and an intermediate height (H2) determined by protrusion of the thin band  108 . The thickness deviation ratio equals H1/H2. The pitch (P) as shown represents longitudinal distance between the max heights of two consecutive ones of the thick bands  106 . The pitch and the thickness deviation ratio play an important role for high pressure sealing through radial expansion of the packer assembly  100 . 
       FIG. 6  shows a graph depicting sealing pressure performance as a function of the pitch characterized as a generic unit length. The dimension of the pitch in combination with the physical and dimensional parameters of the material has an effect on the curvature of the undulations  109  being formed. For a given material and a given set of dimensions a shorter pitch results in a less undulation and a longer pitch results in a greater undulation. By varying the parameters, the curvature of undulation is altered. Shorter pitch results in lower sealing pressure as sufficient values for the amplitude cannot be generated during expansion. Further, broadening out of the undulation  109  along the tubing  104  as occurs when the pitch increases beyond that required to achieve the amplitude desired can decrease sealing pressure. A pitch curve  600  demonstrates that the sealing pressure increases with increase in the pitch up to a threshold for the pitch at which point further increase in the pitch reduces the sealing pressure. For any given application with specific criteria such as pre-expansion diameter and wall thickness of the tubing  104 , analytical/empirical models may enable selection of the pitch to achieve a maximum seal performance as identified by point  601  along the pitch curve  600 . 
       FIG. 7  illustrates a graph depicting sealing pressure performance as a function of the thickness deviation ratio. The seal pressure performance improves when the ratio increases (i.e., increasing the maximum height of the thick bands  106  of the sealing element  102  and/or decreasing the intermediate height provided by the thin bands  108  of the sealing element  102 ). As the thickness deviation ratio increases from one to two to provide the thick band  106  protruding twice as far as the thin band  108 , the sealing pressure achievable increases along a ratio curve  701  by a factor greater than two. Further increases in the thickness deviation ratio result in slower continued increase in the sealing pressure. For some embodiments, the ratio is selected to be between 1.25 and 5.0, between 1.5 and 2.5, or between 1.75 and 2.25. 
     As a comparative example, point  700  on the ratio curve  701  corresponds to prior sealing elements having a uniform thickness across a length that is expanded into sealing engagement such that no undulations exist. Such prior sealing elements can, based on location of the point  700 , only maintain sealing at pressures below about 1800 pounds per square inch (psi) (12,410 kilopascal (kPa)). 
       FIGS. 8 and 9  show plots of data from seal pressure tests of the expandable packer  100  at about 22° C. and 100° C., respectively. The expandable packer  100  was tested up to 6500 psi (44,815 kPa) without sealing failure which illustrates the ability to select attributes to create undulations as set forth herein to obtain a much higher seal pressure as compared to prior sealing elements which by comparison would only maintain pressures of about 1800 psi. Downward trending  800  occurs over time once each of the pressures tested is initially reached as a result of equilibration as the sealing material  102  further compresses. In addition, drop offs  802  at certain times in the plots occur due to intentional pressure relief prior to further pressurization and not any failure of the sealing by the expandable packer  100 . 
       FIG. 10  illustrates the expandable packer  100  during an expansion operation with an exemplary expander tool  900  such as an inflatable device having a bladder  902  that is capable of being fluid pressurized to expand the tubing  104 . For some embodiments, the expander tool  900  includes a locating mechanism  904 . The locating mechanism  904  includes dogs  906  biased outward to engage recesses  908  at selected locations along an inside of the tubing  104 . Mechanical engagement between the dogs  906  and each of the recesses  908  provides resistance from further relative movement of the expander tool  900  within the tubing  104 . Other mechanical devices such slips or other forms of retractable grippers may be used in place of the dogs  906 . 
     The selected locations thus identify when the expander tool  900  has been located where desired such as when moving the expander tool  900  from its position at a last expansion cycle to a subsequent length of the tubing  104  for expansion. Use of the locating mechanism  904  helps ensure that a length of the tubing  104  is not missed in the expansion process. Any missed sections may have trapped fluid that inhibits expansion of the missed sections. Attempts to later expand missed sections may force such trapped fluid to collapse surrounding sections of the tubing  104  previously expanded. 
     In operation, expansion of the expandable packer  100  does not require expensive high pressure pumps on a rig as a mobile pump using relatively less volume can operate the expander tool  900 . The expander tool  900  also works reliably over multiple expansion cycles especially given that expansion ratios may be controlled to be less than 50%. 
       FIGS. 11A and 11B  are views illustrating an expansion tool  225  for use with the expandable packer  100 . The expansion tool  225  includes a mandrel  230 , elastomeric sections  235  and optional spacer bands  240 . Generally, the expansion tool  225  is actuated by applying an axial force to elastomeric sections  235  by a force member, such as a hydraulic jack, which causes the elastomeric sections  235  to compress and expand radially outward, as shown in  FIG. 11B . In turn, the outward expansion of the elastomeric sections  235  causes a surrounding tubular to expand radially outward. It is to be noted that the bands  240  may also expand radially outward but not as much as the elastomeric sections  235 . In one embodiment, a first end  245  of the expansion tool  225  is movable and a second end  255  is fixed. In this embodiment, the force is applied to the first end  245  which causes the first end  245  to move toward the second end  255 , thereby compressing the elastomeric sections  235 . In another embodiment, the first end  245  and the second end  255  are movable and the forces are applied to both ends  245 ,  255  to compress the elastomeric sections  235 . In a further embodiment, the second end  255  is fixed to the mandrel  230  and the first end  245  is movable. In this embodiment, the force is applied to the first end  245  while substantially simultaneously pulling on the mandrel  230  to move the second end  255  toward the first end  245 , thereby compressing the elastomeric sections  235 . 
     The elastomeric sections  235  may be made from rubber or any other type of resilient material. The elastomeric sections  235  may be coated with a non-friction material (not shown) such as a composite material. The non-friction material is used to reduce the friction between the elastomeric sections  235  and the surrounding tubular. Further, the non-friction material may protect the elastomeric sections  235  from damage or wear which may occur due to multiple expansion operations. 
     The bands  240  in between the elastomeric sections  235  are used to separate elastomeric sections  235 . The bands  240  may be made from any suitable material, such as thin metal, composite material or elastomeric material having a hardness that is different from the elastomeric sections  235 . 
       FIGS. 12A and 12B  are views illustrating the expansion tool  225  disposed in the tubing  104  of the expandable packer  100 . For clarity, the thick bands  106  and the thin bands  108  of the sealing material  102  are not shown. The expansion tool  225  may be used to expand the expandable packer  100  into an expanded position within a surrounding structure such as an open borehole or casing (not shown). Upon expansion, the tubing  104  is plastically deformed to selectively create the undulations  109  which result in a high pressure seal, as shown in  FIG. 12B . The expansion tool  225  may be located in the expandable packer  100  in any manner. In one embodiment, the expansion tool  225  is located in the expandable packer  100  such that the elastomeric sections  235  are positioned adjacent the thin bands  108  and the bands  240  are positioned adjacent the thick bands  106 . Upon activation of the expansion tool  225 , the elastomeric sections  235  expand radially outward which causes the tubular  104  to plastically deform and form the undulations  109 . While not expanded as much, the tubing  104  corresponding to where the thick bands  106  of the sealing material  102  are located also deforms in a radial outward direction to place the thick bands  106  into engagement with the casing. It is to be noted that the undulations  109  tend to increase collapse resistance of the tubing  104 . Thus, the increase in collapse resistance benefits the sealing ability of the sealing element  102 . Further, the undulations  109  at least reduce any potential decreases in seal load as a result of elastic recovery of the tubing  104  immediately after expansion. The undulations  109  may also experience less elastic recovery than when a longer length of the tubing  104  is expanded, thereby mitigating effect of the elastic recovery causing removal of the seal load. 
       FIGS. 13A and 13B  are views illustrating an expansion tool  325  disposed in the tubing  104  of the expandable packer  100 . The expansion tool  325  includes a mandrel  330 , elastomeric sections  335 ,  345 ,  355  and optional bands  340 . The expansion tool  325  operates by applying an axial force to elastomeric sections  335 ,  345 ,  355  which causes the elastomeric sections  335 ,  345 ,  355  to compress and expand radially outward. 
     The expansion tool  325  may be used to expand the expandable packer  100  into an expanded position within a surrounding structure such as an open borehole or casing (not shown). For clarity, the thick bands  106  and the thin bands  108  of the sealing material  102  are not shown. As illustrated, the elastomeric sections  335 ,  345 ,  355  are tapered down (or tiered) from one end  355  to another end  345 . The reducing diameter of the elastomeric sections  335 ,  345 ,  355  may be stepwise (as illustrated), or it may be a continuous reducing diameter, such as cone shaped. The taper in the elastomeric sections  335 ,  345 ,  355  may be used to drive fluid out of the annulus between the casing and the sealing material on the expandable packer  100 , thereby preventing any pipe collapse due to trapped fluid expansion. The bands  340  between the elastomeric sections  335 ,  345 ,  355  are not tapered. However, in one embodiment, the bands  340  may have a taper in a similar manner as the elastomeric sections  335 ,  345 ,  355 . 
       FIG. 13B  illustrates the expansion tool  325  inside the tubing  104  during the expansion process. The first portion of the tubing  104  that is juxtaposed with the thicker elastomeric section  335  expands first and additional axial force is applied to expand the elastomeric sections  345 ,  355  to subsequently expand the remaining portions of the tubular  104  similar to the first portion. In other words, the expansion process along the short length of the tubular  104  is progressive. As shown, the tubing  104  is plastically deformed to selectively create the undulations  109  which result in a high pressure seal between the expandable packer  100  and the surrounding structure. It is to be noted that the resulting undulations  109  are also tapered (or tiered) similar to the elastomeric sections  335 ,  345 ,  355 . The expansion tool  325  may be positioned in the expandable packer  100  in any manner. In one embodiment, the expansion tool  325  is located in the expandable packer  100  such that the elastomeric sections  335 ,  345 ,  355  are positioned adjacent the thin bands  108  and the bands  340  are positioned adjacent the thick bands  106 . 
       FIGS. 14A and 14B  are views illustrating an expansion tool  425  disposed in the tubing  104  of the expandable packer  100 . The expansion tool  425  includes a mandrel  430 , elastomeric sections  435 ,  445 ,  455  and optional bands  440 . The expansion tool  425  operates by applying an axial force to elastomeric sections  435 ,  445 ,  455  which causes the elastomeric sections  435 ,  445 ,  455  to compress and expand radially outward. The expansion tool  425  may be used to expand the expandable packer  100  into an expanded position within a surrounding structure. For clarity, the thick bands  106  and the thin bands  108  of the sealing material  102  are not shown. As illustrated, the elastomeric sections  435  and  455  are tapered down from the elastomeric section  445  to create a profiled shape. The way the tubular expands by utilizing the profiled shape of the elastomeric sections  435 ,  445 ,  455  will drive fluid out of the annulus between the casing and the sealing material on the expandable packer  100 , thereby preventing trapped fluid expansion in the annulus. As shown in  FIG. 14B , the tubing  104  plastically deforms. It is to be noted the undulations may be formed in the tubing  104  in a similar manner as set forth in  FIGS. 1 and 2 , thereby resulting in a high pressure sealing between the expandable packer  100  and the surrounding structure. 
       FIGS. 15A and 15B  illustrate an expandable packer  500  in the casing  200 . The expandable packer  500  includes a profiled sealing material  502  disposed on an outside surface of a base tubing  504 . The sealing material  502  may be the same material as the material of the base tubing  504 . For instance, a portion of the wall of the base tubing  504  may be cut to form the sealing material  502 . The wall of the base tubing  504  may be machined on a portion of the outer diameter and/or a portion of the inner diameter.  FIG. 16A  illustrates a portion of the inner diameter of the tubing  504  having been machined to form thick bands  506  and thin bands  508 . Additionally, optional elastomeric elements  510  may be placed around an outer surface of the tubing  508 .  FIG. 16B  illustrates the tubing  504  shown in  FIG. 16A  after expansion.  FIG. 17A  illustrates a portion of the inner diameter of the tubing  504  having been machined to form thick bands  506  and thin bands  508 .  FIG. 17B  illustrates the tubing  504  shown in  FIG. 17A  after expansion. 
     Returning back to  FIG. 15A , in another embodiment, the sealing material  502  may be different material placed around the tubing  504 , such as a soft metal with low yield strength, high malleability and ductility. Along this length of the tubing  504  where the sealing material  502  extends, a property (e.g., thickness, compressibility, or hardness) of the sealing material  502  may vary to achieve desired expansion results. As illustrated, the sealing material  502  defines a topography that alternates lengthwise over the tubing  504  between thick bands  506  of the sealing material  502  that occupy a greater annular area than thin bands  508  of the sealing material  502 . Each of the bands  506 ,  508  circumscribe the tubing  504  to form a ring shape oriented transverse to a longitudinal bore of the tubing  504 . The expandable packer  500  may utilize any number of the bands  506 ,  508  and in some embodiments has at least one of the thick bands  506  disposed between two of the thin bands  508 . Additionally, in some embodiments, a grit (not shown) or other grip enhancing formations, such as slips, may be disposed on the outside of the tubing  504 , as set forth herein. 
       FIG. 15B  shows the expandable packer  500  in an expanded position within a surrounding structure such as an open borehole or casing  200 . Upon expansion, the tubing  504  plastically deforms selectively creating undulations  509  resulting in high pressure sealing. The undulations  509  occur as a result of and where the thin bands  508  of the sealing material  502  permit relatively greater radial expansion of the tubing  504 . While not expanded as much, the tubing  504  corresponding to where the thick bands  506  of the sealing material  502  are located also deforms in a radial outward direction to place the thick bands  506  into engagement with the casing  200 . In this manner, a metal to metal seal may be generated and retained due to residual plastic strain on the tubing  504 . It should be noted that the casing  200  may also be deformed elastically to enhance the metal to metal seals. Further, it should be noted that the undulations  509  tend to increase collapse resistance of the tubing  504  which benefits the sealing ability of the sealing element  502 . In another embodiment, the seal between the expandable packer  500  and the casing  200  may be a combination of metal to metal and elastomeric seals. 
     It is also to be noted that the expansion tools  225 ,  325 ,  425  may be used to form the undulations in the expandable packer  100 ,  500 . In addition, the expansion tools  225 ,  325 ,  425  may be used to form undulations in other types of tubulars, such as plain pipe with or without sealing elastomers. 
     For some embodiments, the expandable packer provides a straddle packer, a liner hanger packer, a bridge plug, a scab liner, a zonal isolation unit or a tie back shoe. The expandable packer enables hanging of liners while providing high pressure sealing. The grit or slips of the expandable packer enhance anchoring capability and may be coated on part of the tubing separate from the sealing element. Further, in any embodiment, the sealing material may be a swellable elastomeric material. 
     In a further embodiment, a force member may be used to place the tubing of the expandable packer in a compressive state prior to expansion of the expandable packer by placing the tubing in axial compression. While the tubing is in the compressive state, the expandable packer may be expanded such that the tubing plastically deforms to selectively create the undulations as set forth herein. An example of axial compression enhanced tubular expansion is described in US Patent Publication No. 2007/0000664, which is herein incorporated by reference. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.