Abstract:
A multi-layer deformable composite construction. In a described embodiment, a method of expanding a structure in a wellbore includes the steps of: positioning the structure in an unexpanded configuration in the wellbore, the structure including a wall made up of multiple layers; expanding the structure to an expanded configuration while permitting relative displacement between the layers; and then preventing relative displacement between the layers.

Description:
BACKGROUND  
         [0001]    The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a multi-layer composite construction for use in a well.  
           [0002]    It is well known to expand structures, such as screens, pipe, wellbore junctions, etc., in a well. Expansion of the structures after being positioned in a wellbore enables the structures to pass through restrictions in the wellbore, enlarge flow areas therethrough, and provides other benefits as well.  
           [0003]    Unfortunately, an expanded structure typically has a relatively low collapse resistance. This is due to several factors. One factor is that the structure must be made weak enough to be expanded downhole. If the structure is too strong, it cannot be inflated or swaged outward using conventional expansion techniques.  
           [0004]    Another contributing factor is that materials which have sufficient elasticity to permit them to be deformed to the degree necessary for expansion downhole are also relatively easy to deform in collapsing the structure. If the material thickness is increased to provide increased collapse resistance, then the material must withstand even greater deformation in the expansion process. In addition, greater material thickness results in a larger overall structure, which may defeat the purpose for making the structure expandable.  
           [0005]    From the foregoing, it can be seen that it would be quite desirable to provide improved expandable structures for use in a wellbore, and improved methods for constructing and using such structures.  
         SUMMARY  
         [0006]    In carrying out the principles of the present invention, in accordance with an embodiment thereof, a multi-layer deformable composite structure is provided which solves the problems in the art described above. Methods of expanding the structure in a wellbore are also provided.  
           [0007]    The structure includes a wall made up of multiple layers. While the structure is being expanded, the layers are able to displace relative to each other. This permits the structure to be expanded without transmitting shear forces between the layers. When the structure is expanded, the layers are prevented from displacing relative to each other, thereby permitting shear forces to be transmitted between the layers, and increasing the structure&#39;s resistance to collapse.  
           [0008]    In one aspect of the invention, a method of expanding a structure in a wellbore of a subterranean well is provided. The method includes the steps of: positioning the structure in an unexpanded configuration in the wellbore, the structure including a wall made up of multiple layers; expanding the structure to an expanded configuration in the wellbore; and bonding the layers to each other after the positioning and expanding steps.  
           [0009]    In another aspect of the invention, another method of expanding a structure in a wellbore of a subterranean well is provided. The method includes the steps of: positioning the structure in an unexpanded configuration in the wellbore, the structure including a wall made up of multiple layers; expanding the structure to an expanded configuration while permitting relative displacement between the layers; and then preventing relative displacement between the layers.  
           [0010]    In yet another aspect of the invention, a system for expanding a structure in a wellbore of a subterranean well is provided. The system includes the structure with a wall having multiple layers. The structure is expanded from an unexpanded configuration to an expanded configuration by initially permitting relative displacement between the layers, and then preventing relative displacement between the layers.  
           [0011]    There may be cases where it is advantageous to “crush” or deform the structure and then bond the layers together prior to running the structure into the well. In this manner, the structure would be easier to manufacture because it would require less horsepower to deform to its compressed or unexpanded configuration. For instance, the crushed shape could be made by physically compressing/crushing or drawing.  
           [0012]    After the layers are drawn/crushed, they could be assembled and then fastened together to prevent the layers from moving relative to one another. The downhole inflation/expansion forces would be higher, but that can be worked around by using high-pressure intensifiers (e.g., the drill pipe pressure may be increased significantly to inflate the structure downhole). The strains may be low enough that the structure can be reinflated as a structure of one wall thickness, instead of as a multilayer structure. This would eliminate the complexity of bonding or otherwise securing the layers together downhole.  
           [0013]    These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    FIGS.  1 A-C are schematic cross-sectional views of a method embodying principles of the present invention;  
         [0015]    [0015]FIG. 2 is an enlarged scale cross-sectional view of a lower portion of a wellbore junction used in the method of FIG. 1;  
         [0016]    [0016]FIG. 3 is an enlarged scale cross-sectional view of a first method of attaching a liner to the wellbore junction;  
         [0017]    [0017]FIGS. 4A &amp; B are enlarged scale cross-sectional views of a second method of attaching a liner to the wellbore junction;  
         [0018]    [0018]FIGS. 5A &amp; B are enlarged scale cross-sectional views of a third method of attaching a liner to the wellbore junction;  
         [0019]    [0019]FIGS. 6A &amp; B are enlarged scale cross-sectional views of a method of compressing and expanding the wellbore junction;  
         [0020]    FIGS.  7 - 10  are enlarged scale cross-sectional views of alternate methods of transmitting shear forces between adjacent layers of the wellbore junction; and  
         [0021]    [0021]FIG. 11 is a schematic cross-sectional view of a liner hanger embodying principles of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]    Representatively illustrated in FIGS.  1 A-C is a method  10  which embodies principles of the present invention. In the following description of the method  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used only for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention.  
         [0023]    In the method  10  as viewed in FIG. 1A, an enlarged underreamed cavity  12  is formed in a wellbore  14 . An expandable structure  16  is then positioned in the cavity  12 . When the structure  16  is expanded, the cavity  12  provides space in the wellbore  14  for the enlarged structure.  
         [0024]    As depicted in FIG. 1A, the structure  16  is a wellbore junction, used to provide for drilling multiple branch wellbores extending outwardly from the wellbore  14 . The structure  16  forms a protective lining for the wellbore  14  at the junction, isolating the intersecting wellbores from a formation  18  surrounding the junction.  
         [0025]    However, it should be understood that the method  10  as illustrated in the figures and described herein is merely an example of one application of the principles of the invention, and many other uses of these principles are possible. For example, it is not necessary for the underreamed cavity  12  to be formed in the wellbore  14 . It is not necessary for the expandable structure  16  to be a wellbore junction, since other expandable structures, such as tubing, casing, liner, screens, other well tools, etc., may also benefit from the principles of the invention. In short, the specific details of the method  10  are given to enable a person skilled in the art to understand how to make and use the invention, but are not to be take n as limiting the invention in any manner.  
         [0026]    In FIG. 1A, the structure  16  is depicted in an unexpanded configuration. Preferably, the structure  16  is fabricated in an initial configuration, and then compressed into the unexpanded configuration as described more fully below. However, it is not necessary for the structure  16  to be compressed from an initial configuration into an unexpanded configuration in keeping with the principles of the invention. Instead, the unexpanded configuration could be the initial configuration of the structure  16 , for example.  
         [0027]    In FIG. 1B, the structure  16  is depicted after it has been expanded. The structure  16  may be expanded using any of those methods known to those skilled in the art. For example, pressure may be applied to the interior of the structure via a tubular string  28  to thereby inflate the structure. Alternatively, or in addition, a swaging tool may be displaced through the structure  16  to apply an outwardly directed expansion force to the interior of the structure.  
         [0028]    Note that the expanded structure  16  has a larger outer dimension than the inner diameter of the wellbore  14 , thus the desirability of forming the underreamed cavity  12  in the wellbore. However, if the structure  16  in its expanded configuration is no larger than the wellbore  14 , then the cavity  12  is not needed. For example, the structure  16  could be a casing string, in which case it could be expanded in the wellbore  14  without forming the cavity in the wellbore.  
         [0029]    Cement  20  is flowed into the wellbore  14  about the structure  16  to secure the structure in the wellbore and prevent fluid migration through an annulus  22  between the structure and the wellbore. The cement  20  may be flowed into the annulus either prior to, or after, the structure  16  is expanded. Preferably, the cement  20  is flowed into the cavity  12  at a relatively very slow rate, to prevent voids from being formed in the annulus  22  in the cavity.  
         [0030]    To provide for cement flow through the structure  16  during the cementing process, the structure may be provided with a cementing shoe or float shoe. The shoe may be expandable, such as the shoe described in copending application Ser. No. 10/121,471, filed Apr. 11, 2002 and entitled EXPANDABLE FLOAT SHOE AND ASSOCIATED METHODS, the entire disclosure of which is incorporated herein by this reference. However, it should be understood that it is not necessary for the structure  16  to be provided with a cementing shoe, or for the shoe to be expandable if one is provided.  
         [0031]    Upper and lower end connections (e.g., where the casing string  28  connects to the structure  16 ) of the structure are preferably multi-layered as well. The end connections of the structure  16  (whether they terminate or have a casing string attached to the bottom) transition from a large diameter down to a smaller diameter in the unexpanded configuration, thus this transition area will be subjected to “crushing/re-inflating” strains as high as in the main body of the structure. Note that multiple ones of the structure  16  may be interconnected in the casing string  28 , and these structures may be expanded simultaneously, sequentially, or in any order desired.  
         [0032]    Having a conduit for flow through the structure  16  is preferable not only for cementing purposes, but for circulating and well control while tripping in the hole. Likewise, the ability to run multiple expandable structures  16  on one casing string  28  will be enhanced by providing a conduit through the upper structures  16  to the lower structures.  
         [0033]    As depicted in FIG. 1C, multiple branch wellbores  24  are drilled through a bottom wall  26  of the structure  16 . To drill the wellbores  24 , cutting tools, such as mills, drills, etc., are passed through the structure  16  to drill through the bottom wall  26  and into the earth below the structure. The cutting tools may be guided by deflection devices, such as whipstocks, alignment devices, etc., installed in the expanded structure  16 .  
         [0034]    One or more windows  30  may be provided in the bottom wall  26  of the structure  16 , as depicted in FIG. 2, so that it is not necessary to mill through the bottom wall prior to drilling the wellbores  24 . An easily drilled through membrane or other closure  32  may be used to prevent flow through the window  30  during the expansion and/or cementing processes. The membrane  32  is then drilled through, or otherwise disposed of, when the wellbores  24  are drilled.  
         [0035]    Note that, although in the method  10  as described herein, the wellbores  24  are drilled outwardly from the bottom wall  26  of the structure  16 , it will be readily appreciated that one or more of the wellbores could be drilled outwardly through a sidewall of the structure.  
         [0036]    To line the wellbores  24 , a liner string  34  may be connected to the structure  16 . Preferably, the liner string  34  is sealed to the structure  16 , so that the interior of the structure remains isolated from the formation  18  surrounding the intersection of the wellbores  14 ,  24 . As depicted in FIG. 3, the liner string  34  is provided with an outwardly extending flange  36  which sealingly engages the interior of the bottom wall  26 . The seal between the flange  36  and the bottom wall  26  may be a metal-to-metal seal, or it may be provided by an elastomer or nonelastomer seal, an adhesive sealant, or any other type of seal.  
         [0037]    The flange  36  is depicted in FIG. 3 as one method of attaching the liner string  34  to the structure  16 . Other methods are described below. However, it will be readily appreciated that many alternative methods may be used in keeping with the principles of the invention. For example, the liner string  34  could be provided with outwardly extending keys or dogs which engage an internal profile of the structure  16 , or the liner string could be provided with a liner hanger which is set in a bore of the structure  16 , etc. A suitable liner hanger is described in U.S. Pat. No. 6,135,208, the entire disclosure of which is incorporated herein by this reference. Thus, it should be understood that the principles of the invention are not limited by the details of the specific liner string attachment methods described herein.  
         [0038]    In FIGS. 4A &amp; B, another method of connecting a liner string  38  to the structure  16  is representatively illustrated. In this method, a flanged bushing  40  is installed in the bottom wall  26 . Preferably, the flanged bushing  40  is sealed to the bottom wall  26 , similar to the manner in which the flange  36  is sealed to the bottom wall as described above.  
         [0039]    A lower tubular portion  42  of the bushing  40  extends through the bottom wall  26 . After the corresponding branch wellbore  24  is drilled, the liner string  38  is conveyed through the bushing  40  and is expanded in the wellbore, as depicted in FIG. 4B. An upper end of the liner string  38  is positioned within the lower tubular portion  42  of the bushing  40  when the liner string is expanded.  
         [0040]    Preferably, expansion of the liner string  38  also causes the tubular portion  42  to expand outward, so that an inner diameter of the expanded liner string is at least as large as an inner diameter of the bushing  40 . Thus, expansion of the liner string  38  may also expand the portion  42  of the bushing  40 , connect the liner string to the structure  16 , and form a seal between the top of the liner string and the bushing. For this purpose, the upper end of the liner string  38  may be configured similar to the liner hanger described in the U.S. Pat. No. 6,135,208 referred to above.  
         [0041]    Another method of connecting a liner string  44  to the structure  16  is representatively illustrated in FIGS. 5A &amp; B. In this method, the bottom wall  26  of the structure  16  is provided with an outwardly extending tubular portion  46 . After the corresponding branch wellbore  24  is drilled, the liner string  44  is positioned in the branch wellbore, so that an upper end of the liner string is within the tubular portion  46 , as depicted in FIG. 5A.  
         [0042]    The liner string  44  is then expanded, as depicted in FIG. 5B. Expansion of the liner string  44  also causes expansion of the tubular portion  46 , in a manner similar to that in which the tubular portion  42  of the bushing  40  is expanded as described above and illustrated in FIG. 4B. Preferably, this expansion of the liner string  44  secures the liner string to the structure  16 , and forms a seal therebetween.  
         [0043]    Note that the method depicted in FIGS. 5A &amp; B eliminates the step of installing the bushing  40  in the bottom wall  26 , since the tubular portion  46  is integrally formed on the bottom wall of the structure  16 . However, the tubular portion  46  is vulnerable to damage due to the cutting tools and other equipment passing therethrough while the wellbore  24  is being drilled. For this reason, it may be desirable to install the bushing  40  in the bottom wall  26  of the structure  16  as depicted in FIGS. 5A &amp; B, so that the tubular portion  46  is protected from damage during the drilling process. Thus, the bushing  40  may serve as a wear bushing which is removed after the drilling process and prior to installing the liner string  44 .  
         [0044]    Referring additionally now to FIGS. 6A &amp; B, a cross-sectional view of the structure  16  is representatively illustrated, taken along line  6 - 6  of FIG. 1A. In FIG. 6A, the structure  16  is depicted in its initial and expanded configurations. In FIG. 6B, the structure  16  is depicted in its unexpanded configuration.  
         [0045]    As mentioned above, the structure  16  may be fabricated in an initial configuration (FIG. 6A), and then compressed into an unexpanded configuration (FIG. 6B). After positioning in the wellbore  12 , the structure  16  is then expanded, so that it resumes its initial configuration, which is also its expanded configuration (FIG. 6A). Alternatively, the structure  16  could be initially fabricated in its unexpanded configuration (FIG. 6B), and then expanded to its expanded configuration (FIG. 6A).  
         [0046]    In its unexpanded configuration, a sidewall  48  of the structure  16  is subjected to multiple fairly small radius folds, so that the structure has a “cloverleaf” shape, i.e., the sidewall is circumferentially corrugated. As depicted in FIG. 6B, the sidewall  48  has four outer lobes or corrugations. However, it should be understood that any number of corrugations may be used, and the sidewall  48  may have any shape, in keeping with the principles of the invention.  
         [0047]    If the sidewall  48  were made up of only a single thickness of material, a relatively large amount of elongation of the material would be required at the radii of the folds or corrugations. Since shear stresses due to the bending of the material would be transmitted through the entire thickness of the material, the convex side of a fold would be in tension while a concave side of the fold would be in compression. The thicker the material in the sidewall  48 , the greater the tension and compression produced by the radii of the folds or corrugations.  
         [0048]    It would be beneficial to reduce the amount of elongation produced in the sidewall  48  material. This would reduce any coldworking of the material produced when the structure  16  is compressed and expanded, reduce the forces needed to compress and expand the structure, expand the range of materials which may be used (i.e., including materials having lower elongation limits), and would provide other benefits.  
         [0049]    Accordingly, the sidewall  48  is preferably made up of multiple layers  50 ,  52 ,  54 ,  56 . Although four layers are depicted in FIGS. 6A &amp; B, any number of layers may be used. The layers  50 ,  52 ,  54 ,  56  are preferably each made of steel or another metal, although other materials may be used, in keeping with the principles of the invention.  
         [0050]    The layers  50 ,  52 ,  54 ,  56  are initially free to displace relative to one another, so that shear forces due to expanding and compressing the structure  16  are not transmitted between the layers (other than via friction between the layers). Thus, significantly less elongation of each layer  50 ,  52 ,  54 ,  56  is required in compressing and expanding the sidewall  48  as compared to a single-thickness sidewall.  
         [0051]    However, transmission of shear forces between the layers  50 ,  52 ,  54 ,  56  is desirable once the structure  16  has been expanded, in order to resist forces tending to collapse the structure. As will be appreciated by one skilled in the art, transmission of shear forces between the layers  50 ,  52 ,  54 ,  56  will provide greater resistance to bending of the sidewall  48 , and will thereby aid in maintaining the structure  16  in its expanded configuration.  
         [0052]    In order to enable transmission of shear forces between the layers  50 ,  52 ,  54 ,  56  after expansion of the structure  16 , the layers may be bonded or mechanically interlocked to each other during and/or after the expansion process. FIGS.  7 - 10  representatively illustrate various methods of accomplishing this result. However, it should be clearly understood that other methods may be used, without departing from the principles of the invention.  
         [0053]    In FIG. 7, interlocking profiles  58  are formed on facing surfaces of the layers  52 ,  54 . These profiles  58  may be ridges, grooves, ramps, dovetails, tongues and grooves, etc., or any other type of profile which may serve to transmit a shear force between the layers  52 ,  54 . The profiles  58  may serve to substantially increase friction between the layers  52 ,  54  when the structure  16  is expanded.  
         [0054]    In the initial or unexpanded configuration of the structure  16 , the profiles  58  may be spaced apart, the profiles subsequently engaging each other when the structure is expanded. Alternatively, the profiles  58  may be configured so that, although they are initially in contact with each other, they do not transmit shear forces between the layers  52 ,  54  until the structure  16  is expanded. Any other method of mechanically interlocking the layers  52 ,  54  to each other may be used, in keeping with the principles of the invention.  
         [0055]    In FIG. 8, a granular material  60 , such as an aggregate or a crystalline material, is positioned between the layers  50 ,  52 . The material  60  substantially increases friction between the layers  50 ,  52 , so that the layers are interlocked when the structure  16  is expanded.  
         [0056]    In FIG. 9, an adhesive or chemical bond  62  prevents relative displacement between the layers  50 ,  52 . The adhesive  62  may be positioned between the layers  50 ,  52  either before or after expansion of the structure  16 . For example, the adhesive  62  could be a thermally-activated adhesive which is positioned between the layers  50 ,  52  prior to expansion. After expansion, a heat source is positioned within the structure  16  to activate the adhesive  62  to bond the layers  50 ,  52  to each other.  
         [0057]    As another example, the layers  50 ,  52  could be spaced apart after expansion of the structure  16 . The adhesive  62  (for example, an epoxy) could then be pumped between the layers  50 ,  52  and allowed to harden. Any other method of adhering or bonding the layers  50 ,  52  to each other may be used, in keeping with the principles of the invention.  
         [0058]    In FIG. 10, the adhesive  62  is initially contained within frangible beads or capsules  64  positioned between the layers  50 ,  52 . For example, the capsules  64  could be made of glass or a ceramic material. The layers  50 ,  52  would initially be spaced apart.  
         [0059]    When the structure  16  is expanded, the layers  50 ,  52  are displaced toward each other, thereby breaking the capsules  64  and releasing the adhesive  62  from the capsules. The adhesive  62  then bonds the layers  50 ,  52  to each other. Any other method of releasing an adhesive between the layers  50 ,  52  during or after the expansion process may be used, in keeping with the principles of the invention. For example, use of capsules which are thermally- or time-activated/degraded, or use of thermally- or time-activated adhesives, such as epoxies.  
         [0060]    Alternatively, the adhesive  62  could initially be external to the capsules  64  in the space between the layers  50 ,  52 . In this case, the capsules  64  could contain an adhesive system component, such as a catalyst or hardening agent for the adhesive  62 . When the capsules  64  are broken by displacement of the layers  50 ,  52 , the catalyst or hardening agent could then come into contact with the adhesive  62 , thereby causing the adhesive to harden or otherwise bond the layers to each other.  
         [0061]    Furthermore, other methods may be used to increase the collapse resistance of the expanded structure  16 . For example, one or more inner layers (e.g., layers  54 ,  56 ) may be yielded during the expansion process, without yielding one or more outer layers (e.g., layers  50 ,  52 ), or at least yielding of the inner layer(s) may be greater than yielding of the outer layer(s). This would produce residual hoop or circumferential compression in the inner layer(s) and residual hoop or circumferential tension in the outer layer(s).  
         [0062]    This result may be accomplished by any of a variety of methods. For example, the inner layer(s) may be made thinner than the outer layer(s), as depicted in FIGS. 6A &amp; B, so that greater hoop stress is generated in the inner layer(s) during the expansion process. Alternatively, the inner layer(s) may be made of a material having a lower yield strength than the outer layer(s). As another alternative, the layers may have different moduli of elasticity, or other different material properties. In this case, it may be desirable to make the inner layer(s) thicker than the outer layer(s).  
         [0063]    However, it should be understood that the layers may have any relationship between their thicknesses as desired, or as dictated by the material properties of the layers an their desired condition after expansion. For example, one layer may be made of a material selected for its corrosion resistance or other property substantially unrelated to its strength or stress condition after expansion, in which case the layer may be made thinner or thicker than any other layer.  
         [0064]    There may be cases where it is advantageous to “crush” or deform the structure  16  and then bond the layers  50 ,  52 ,  54 ,  56  together prior to running the structure into the well. In this manner, the structure  16  would be easier to manufacture because it would require less horsepower to deform to its compressed or unexpanded configuration. For instance, the crushed or unexpanded configuration could be made by physically compressing/crushing or drawing.  
         [0065]    After the layers  50 ,  52 ,  54 ,  56  are drawn/crushed, they could be assembled and then fastened together to prevent the layers from moving relative to one another. The downhole inflation/expansion forces would be higher, but that can be worked around by using high-pressure intensifiers (e.g., the drill pipe pressure may be increased significantly to inflate the structure downhole). The strains may be low enough that the structure  16  can be reinflated as a structure of one wall thickness, instead of as a multilayer structure. This would eliminate the complexity of bonding or otherwise securing the layers  50 ,  52 ,  54 ,  56  together downhole.  
         [0066]    Referring additionally now to FIG. 11, another expandable structure  70  incorporating principles of the present invention is representatively illustrated. The structure  70  is a liner hanger which may be used at the top end of the liner string  38  depicted in FIG. 4B, or at the top end of the liner string  44  depicted in FIG. 5B, to attach and seal the liner string to the structure  16 .  
         [0067]    The liner hanger  70  includes multiple layers  72 ,  74 ,  76  which are initially substantially free to expand or compress without transmitting shear forces between the layers. The liner hanger  70  is conveyed into the well in a compressed or unexpanded configuration, and then expanded downhole, for example, as depicted in FIGS. 4B &amp; 5B. After expansion, the layers  72 ,  74 ,  76  are bonded or adhered to each other, or mechanically interlocked, etc., as described above for the layers  50 ,  52 ,  54 ,  56  of the structure  16 , so that the layers  72 ,  74 ,  76  then transmit shear forces therebetween and/or relative displacement between the layers is prevented, or at least substantially resisted.  
         [0068]    During expansion, an outer layer  72  or  74  may be yielded to an extent greater than that of an inner layer  74  or  76 , so that residual tensile hoop stress remains in an outer layer and residual compressive hoop stress remains in an inner layer after the expansion process is completed. In addition, the layers  72 ,  74 ,  76  may have different material properties, different thicknesses, etc., as described above for the layers  50 ,  52 ,  54 ,  56  of the structure  16 .  
         [0069]    To enhance sealing between the expanded liner hanger  70  and the tubular member  42 ,  46  in which it is expanded, the liner hanger preferably includes a sealing material  78 . The sealing material  78  may be configured as a part of the outer layer  72 , as depicted in FIG. 11, or it may be separately attached externally on the outer layer  72 . The sealing material  78  may be an elastomer, such as a nitrile or fluorocarbon material, it may be a nonelastomer, such as PTFE or PEEK material, or it may be a metal, such as lead, etc.  
         [0070]    Thus, it should be understood that any type of sealing material  78  may be used in the liner hanger  70 , in keeping with the principles of the invention. The sealing material  78  could be incorporated into the outer layer  72 , for example, by providing the outer layer made of a composite material.  
         [0071]    To enhance gripping engagement between the expanded liner hanger  70  and the tubular member  42 ,  46  in which it is expanded, the liner hanger preferably includes grip members or slips  80 . As depicted in FIG. 11, the grip members  80  are triangular in cross-section and are embedded in the sealing material  78 . However, it should be clearly understood that these details are not necessary in keeping with the principles of the invention, since the grip members  80  could be otherwise shaped or otherwise positioned on the liner hanger  70 .  
         [0072]    Although separate sealing material  78  and grip members  80  have been illustrated in FIG. 11, it will be readily appreciated that it is not necessary to provide separate structures to perform the functions of these elements. For example, the grip members  80  could seal against the tubular member  42 ,  46  in which the liner hanger  70  is expanded (such as, by metal-to-metal contact between the grip members and the interior of the tubular member), and the sealing material  78  could grip the tubular member in which the liner hanger is expanded (such as by friction between the sealing material and the interior of the tubular member).  
         [0073]    Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.