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CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/594,628, filed Apr. 25, 2005, incorporated by reference herein in its entirety. The inventions of the present application are related to assignee&#39;s pending patent application Ser. No. 10/763,565 filed Jan. 23, 2004 (68.0418); Ser. No. 10/924,684 filed Aug. 20, 2004 (68.0455); and Ser. No. 11/361,531 filed Feb. 23, 2006 (43.0023). 

   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates generally to the field of well bore zonal isolation tools and methods of using same in various oil and gas well operations. 
   2. Related Art 
   A zonal isolation tool should provide reliable, long-term isolation between two or more subsurface zones in a well. A typical application would be to segregate two zones in an open-hole region of a well, the zones being separated by a layer of low permeability shale in which the zonal isolation tool is placed. A nominal size configuration would be usable in wellbores drilled with an 8-½ inch (21.6 cm) outer diameter bit below 9-⅝ inch (24.5 cm) casing, but the use of zonal isolation tools is not limited to any particular size, or to use in open holes. By segregating open-hole intervals, downhole chokes may be used for production management. Similarly, selective zonal injection may be performed. If distributed temperature sensing is placed in the well, monitoring predictive control is possible. 
   A conventional completion assembly  10  with a zonal isolation tool  12  is illustrated in  FIGS. 1 and 2  for allowing production of two separate flows  4 A and  4 B from an open hole  3 . Assembly  10  may include a production packer  14 , a gravel pack packer  16 , flow control valves  18 , and other components commonly used in downhole completions. Zonal isolation tool  12  may comprise a packer  20 , a pair of anchors  22 , a pair of polished bore receptacles (PBRs)  24 , and an expansion joint  26 . Service tools may include a setting string  28  and an isolation string  30 . 
   Most of the current zonal isolation tools are made with an elastomeric membrane for sealing supported on a metallic support carriage structure for mechanical strength. In some constructions, the zonal isolation tools of this design may be composed of an inner sealing element, an integrated mechanical carriage structure, and an outer elastomeric element for sealing. The carriage can be made entirely of a composite material and thus integrates the mechanical support elements within a laminar structure of the composite body. Although these designs decrease extrusion of the inner elastomeric element through the carriage, further problems remain. One problem manifests itself in certain downhole conditions, for example at high temperatures, where the inner elastomeric element may be prone to extrusion through the support carriage structure when inflated. For support carriages having slats, the slats generally provide good protection against extrusion of the underlying elastomer through the slats, however, high friction coefficient between slats may make inflation/deflation difficult at high hydrostatic pressure. 
   Therefore, while there have been some improvements in zonal isolation tool design, further improvement is desired. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, zonal isolation tools and methods of use are described that reduce or overcome problems in previously known apparatus and methods. 
   Zonal isolation tools of the invention comprise: 
   a) a wellbore sealing member expandable by fluid pressure to contact a wellbore over an initial contact area; 
   b) an inflation valve open during expansion of the sealing member to the initial contact area and closed upon the fluid pressure reaching a predetermined setting; and 
   c) a vent between the sealing member and a wellbore annulus adapted to open after the inflation valve is closed. 
   Certain apparatus embodiments comprise d) a linear compression member adapted to impart compressive load on the wellbore sealing member, and thus form a sealing point at or near a leading edge of the wellbore sealing member. The wellbore sealing member of the zonal isolation tools of the invention may comprise an inner sealing element and an outer sealing element. One or both of the inner and outer sealing elements, or portions of each, may comprise an elastomeric material, which may be the same or different for each member or portion thereof. Zonal isolation tools of the invention may comprise means for preventing substantial radial expansion of the sealing member while running the tool in hole, such as bands, screws, snap rings, poppet valves, and the like. The tool may include means for controlling longitudinal location of a leading edge of a final seal to ensure a sealing point at or near a leading edge of the sealing member, such as a slotted metal or composite cylindrical member having a plurality of individual beams, at least some of the beams having notches near the leading edge of the sealing member. The tools of the invention may comprise one or more anti-extrusion members selectively positioned between the slotted cylinder and the inner sealing element, or between the slotted cylinder and the outer sealing element, or in both positions. Zonal isolation tools of the invention may have a venting port located on a low pressure side of the sealing member, useful to vent any gases accumulating between inner and outer sealing elements. Other embodiments may have one or more flow paths, sometimes referred to as shunt tubes, although they need not be tubular, serving to allow flow of fluids such as gravel slurry, injection fluids, and the like through the zonal isolation tool. The flow paths may have an equivalent flow area as the main flow paths in the zonal isolation tool. If a screen pipe is employed, the screen pipe and isolation tool may be on different centers, which may ease any disruption in the flow transition. The zonal isolation tools of the invention may comprise standard non-expandable end connections. 
   Zonal isolation tools of the invention may comprise a straight pull release mechanism, as well as a connector for connecting an end of the tool to coiled tubing or jointed pipe. Yet other embodiments of the zonal isolation tools of the invention comprise an expandable packer wherein the expandable portion comprises continuous strands of polymeric fibers cured within a matrix of an integral composite tubular body extending from a first non-expandable end to a second non-expandable end of the body. Other embodiments of zonal isolation tools of the invention comprise continuous strands of polymeric fibers bundled along a longitudinal axis of the expandable packer body parallel to longitudinal cuts in a laminar interior portion of the expandable body to facilitate expansion of the expandable portion of the integral composite tubular body. Certain other tool embodiments of the present invention comprise a plurality of overlapping reinforcement members made from at least one of the group consisting of high strength alloys, fiber-reinforced polymers and/or elastomers, nanofiber, nanoparticle, and nanotube reinforced polymers and/or elastomers. Yet other tool embodiments of the present invention include those wherein the reinforcement members have an angled end adjacent a non-expandable first end and adjacent a non-expandable second end to allow expansion of the expandable portion of the sealing member. 
   Another aspect of the invention are methods of using the inventive tools, one method of the invention comprising: 
   positioning a zonal isolation tool of the invention in a wellbore between two zones; 
   inflating the wellbore sealing member by opening an inflation valve to establish an initial sealing area; and 
   axially compressing the wellbore sealing member to achieve a final seal having a point at or near a leading edge of the wellbore sealing member. 
   Certain method embodiments comprise venting the wellbore sealing member to a wellbore annulus after the inflation valve. Certain embodiments comprise beginning axial compression of the wellbore sealing element using a linear compression member before beginning venting of the wellbore sealing member to the wellbore annulus. Yet another method embodiment comprises axially compressing the wellbore sealing element before closing the inflation valve completely, followed by venting the wellbore sealing element to the wellbore annulus. Other methods of the invention include closing the inflation valve after inflating the wellbore sealing member, and subsequently operating a compressible member to axially compress the wellbore sealing member to a final sealing area. Yet other methods of the invention comprise producing fluid from at least one of the two zones. If two fluids are produced simultaneously, the two fluids may be the same or different in composition, temperature, pressure, and fluid mechanical characteristics, such as viscosity, gravity, and the like. Methods of the invention may comprise controlling the position of a leading edge of the final sealing member. 
   Another method of the invention comprises: 
   (a) positioning a zonal isolation tool of the invention in an open-hole wellbore between two zones, and initially inflating (hydroforming) the wellbore sealing member using tubing pressure and then releasing pressure; 
   (b) compressing the wellbore sealing member using tubing pressure to initiate a cup-type seal in the open-hole wellbore; and 
   (c) using annular differential pressure to fully energize the cup-type seal. 
   These and other features of the apparatus and methods of the invention will become more apparent upon review of the brief description of the drawings, the detailed description of the invention, and the claims that follow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The manner in which the objectives of the invention and other desirable characteristics can be obtained is explained in the following description and attached drawings in which: 
       FIG. 1  is a schematic side elevation view, partially in longitudinal cross section, of a completion assembly comprising an embodiment of a zonal isolation tool constructed in accordance with the invention; 
       FIG. 2  is a schematic side elevation view, partially in longitudinal cross section, of the zonal isolation tool of  FIG. 1 , along with a setting string and isolation string; 
       FIG. 3  is a schematic longitudinal side elevation view of a portion of the base structure of the inventive zonal isolation tool of  FIG. 1 ; 
       FIG. 4  is a schematic longitudinal side elevation view of a portion of the base structure of the zonal isolation tool of  FIG. 1  after inflation pressure has been applied; 
       FIG. 5  is a schematic longitudinal side elevation view of a portion of the base structure of the zonal isolation tool of  FIG. 1  with a compressive load being applied; 
       FIGS. 6A-D  are schematic longitudinal cross sectional views of a portion of the base structure of the zonal isolation tool of  FIG. 1  illustrating an operational sequence; 
       FIG. 7  is a schematic longitudinal cross section view of a portion of the zonal isolation tool of  FIG. 1  illustrating the seal element; 
       FIG. 8  is a schematic longitudinal cross section view of a portion of the zonal isolation tool of  FIG. 1  illustrating the seal element after inflation pressure; 
       FIG. 9  is a schematic longitudinal cross section view of a portion of the zonal isolation tool of  FIG. 1  illustrating the seal element after compressive loading is applied; 
       FIG. 10  is a more detailed schematic longitudinal cross section view of the seal element of the zonal isolation tool of  FIG. 1 ; 
       FIG. 11  is an enlarged detailed view of a portion of the seal element of the zonal isolation tool of  FIG. 1 ; 
       FIG. 12  is an enlarged schematic longitudinal cross section view illustrating anti-extrusion sheets used in the zonal isolation tool of  FIG. 14 ; 
       FIG. 13  is a perspective schematic view of the structural undercarriage of the zonal isolation tool of  FIG. 1 ; 
       FIGS. 14A and 14B  are schematic axial cross section views illustrating alternate fluid pathways that may be incorporated in the zonal isolation tool of  FIG. 1 ; and 
       FIGS. 15A ,  15 B, and  15 C are schematic longitudinal cross section views of another embodiment of a zonal isolation tool of the invention. 
   

   It is to be noted, however, that the appended drawings are not to scale and 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. 
   DETAILED DESCRIPTION 
   In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
   All phrases, derivations, collocations and multiword expressions used herein, in particular in the claims that follow, are expressly not limited to nouns and verbs. It is apparent that meanings are not just expressed by nouns and verbs or single words. Languages use a variety of ways to express content. The existence of inventive concepts and the ways in which these are expressed varies in language-cultures. For example, many lexicalized compounds in Germanic languages are often expressed as adjective-noun combinations, noun-preposition-noun combinations or derivations in Romanic languages. The possibility to include phrases, derivations and collocations in the claims is essential for high-quality patents, making it possible to reduce expressions to their conceptual content, and all possible conceptual combinations of words that are compatible with such content (either within a language or across languages) are intended to be included in the used phrases. 
   The invention describes zonal isolation tools and methods of using same in wellbores. A “wellbore” may be any type of well, including, but not limited to, a producing well, a non-producing well, an experimental well, and exploratory well, and the like. Wellbores may be vertical, horizontal, any angle between vertical and horizontal, diverted or non-diverted, and combinations thereof, for example a vertical well with a non-vertical component. Although existing zonal isolation tools have been improved over the years, these improved designs have left some challenging problems. One problem manifests itself at in certain downhole conditions, for example high temperatures, where the inner rubber layer may be prone to extrusion through the support carriage structure when inflated. For zonal isolation tools having slats, the slats generally provide good protection against extrusion of the underlying elastomer through the slats, however, after inflation and deflation the slats may experience permanent deformation. Thus, there is a continuing need for zonal isolation tools and methods that address this problem. 
   Referring now to  FIGS. 3 ,  4  and  5 , a first apparatus embodiment  29  of the invention is disclosed. The drawings are schematic in fashion and not to scale. The same numerals are used to call out similar components. This embodiment includes an elastomeric seal member  34  initially inflated by a fluid entering an inflation port  21  in base pipe  15 . Inflation port  21  aligns with a similar passage  31  in a member  19 , which may be described as an inflation valve, during initial expansion of seal member  34 . Member  19 , along with a moveable piston  13  and a movable sleeve  7  also define an expandable chamber  2 . Moveable sleeve  7  includes a through hole  9 , whose function will become apparent. Base pipe  15  includes another through passage  11  opening into a chamber  23  formed in a stationary sleeve  5 . Moveable piston  13  is able to slide longitudinally downward within stationary sleeve  5 . Passage  31  opens into a large chamber  43  able to accept fluid to expand sealing member  34 . Chamber  43  is sealed by an o-ring or other seal at  39 . 
     FIGS. 4 and 5  illustrate operation of embodiment  29 . Sealing member  34  is initially expanded via fluid pressure entering through inflation port  21  and passage  31  and into chamber  43  to an initial expansion pressure, causing sealing member  34  to engage a wellbore or borehole wall  33 . During this initial expansion, moveable piston  13  and moveable sleeve  7  remain essentially stationary. Once the defined initial pressure is reached in chamber  43 , member  19  moves to the left, blanking or closing inflation port  21 , and through hole  9  opens into the hydroforming chamber  43 , as illustrated in  FIG. 5 . After inflation port  21  is blanked off or closed, a fluid  45  is introduced into chamber  23  via through hole  11 , causing moveable piston  13  and moveable sleeve  7  to the right in  FIG. 5 . This in turn causes sealing member  34  to compress axially and also to form a seal at or near a leading edge  32 . Fluid pressure  35 A is also allowed to vent from the annulus  6  into chamber  43  through passage  9  and pressure  35 B is nearly equal to pressure  35 A, allowing pressure communication as indicated by the arrows from annulus  6  to chamber  43 . Pressures  35 A and  35 B are higher than pressure  37 . Sealing member  34  ( FIG. 5 ) may include an underlying carriage  36  ( FIG. 13 ). After actuation, differential pressure energizes the cup-type seal  34 , vis-à-vis pressure in  35 B is greater than pressure in  37 . It should be noted that the fluid pressure used to activate the sealing member  34  may be transmitted to the sealing member  34  and/or setting pistons  13  by various means. An embodiment receives the tubing pressure via a setting tool  28  fitted with sealing elements (o-rings, packing, or the like). When the sealing members  34  are situated in polished bores both above and below the zonal isolation tool  29  or packer system, a pressure chamber is formed that communicates with the packer element and setting pistons  13 . Pressure is applied thru the setting tool  28  via the surface control equipment at the rig. Another embodiment utilizes the differential pressure between the hydrostatic pressure downhole and a trapped atmospheric chamber (not shown) integral to the packer device. To activate the packer, a setting tool is used to break the seal of the atmospheric trap chamber. Once freed, the pressure differential may be used to hydroform the element, and further to apply the compressive load as claimed. A similar embodiment may compliment or even replace the trapped atmospheric chamber with a pre-charged volume of nitrogen or other gas stored within the packer. The result is to create a large differential pressure at setting depth. Further embodiments may include activation by non pressurizing means, such as mechanical ratcheting via an electric-powered or hydraulic-powered downhole device, such as a tractor run on slickline, e-line, or coiled tubing. 
   The zonal isolation tool  29  of this embodiment uses hydroforming pressure as a first step to energize. Initial inflation will affect a long length of sealing contact, assuring good compliance to the open hole. After initial inflation, a compressive load is applied via linear piston  7  ( FIG. 5 ) to ensure sealing point  32  near the leading end of the sealing element structure. 
   The following are operational considerations, occurring sequentially: (1) the tubing or base pipe  15  must be open to the sealing member; (2) the initial inflation must stop when a defined pressure within sealing member  34  is reached; (3) inflation port  21  must be assuredly blanked from tubing or base pipe  15 ; and (4) a vent must open between sealing member  34  and annulus  6 . As illustrated in  FIGS. 3-5 , in certain embodiments of the invention a linear compressive load from a moveable piston opens a vent such as passage  9  in  FIG. 5 . The operational sequence must happen in the proper order.  FIGS. 6A-D  illustrate this order. For example, if vent  9  is opened prior to port  21  being blanked, then it would become impossible to blank port  21  because open communication would be established. To blank the port  21 , an o-ring must un-seal, then re-seal under dynamic conditions. Despite that limitation, other combinations of this sequence may work in other embodiments of the invention, as disclosed herein. 
   Referring to  FIG. 7 , several circumferential bands  40  may be employed to prevent seal  34  from expanding radially while running in hole.  FIG. 7  illustrates schematically a simplified seal  34  with bands  40 . The right end  38  of seal  34  is fixed while the left end  44  is free to displace axially to the right. A ratchet ring  42  prevents axial movement to the left and thus helps seal  34  retain elastic (potential) energy. Setting pressure is applied inside seal  34  via the packer setting tool  28  ( FIG. 2 ). Bands  40  break when a defined pressure is reached, allowing seal  34  to expand and contact the formation wall  33  ( FIGS. 4 ,  5 ). Another embodiment of this feature may replace or complement the circumferential bands with a poppet valve. 
   As illustrated in  FIG. 8 , the seal centerline in this embodiment lies to the right of the contact centerline. This behavior is conditioned by machining a notch  46  at the left end of carriage  36  ( FIG. 12 ). 
   A setting pressure of approximately 1,500 psi (about 10.3 megaPascals) is used to lengthen the contact length of seal  34  with the formation ( FIG. 8 ). Finally, the setting pressure is increased to approximately 2,500 psi (about 17.2 megaPascals) to: (1) blank port  21  (i.e. isolate inside of sealing member  34  from tubing or base pipe  15  pressure); (2) vent sealing member  34  to annulus  6  through vent  9 ; and (3) axially compress the left end of sealing member  34  to bias sealing point  32 . The cup effect makes each seal unidirectional, as illustrated in  FIG. 9 . When a bidirectional seal is desired, at least two seals are required facing opposite directions. 
   A venting port  60  ( FIG. 10 ) may be placed on the low-pressure side  37  of sealing member  34  to eliminate any atmospheric trap that would be created between the inner sealing element  50  outer sealing element  52 . Total seal length is indicated at  55 , while slotted length is indicated at  56  if a slotted carriage is employed. 
   Carriage  36  is illustrated in  FIG. 13  as a cylinder having one or more machined slots  58  in the axial direction. These slots may be used to create individual beams  57  around the cylinder. The left end of beams  57  may be notched as illustrated in detail in  FIG. 12  to simulate a “simply supported” beam. The right end may not be notched; if it is not, the right end simulates a “cantilevered” beam. Carriage  36  may also be un-slotted, that is, a thin solid tube. 
   Inner sealing element  50  ( FIG. 11 ), sometimes referred to as a bladder, may be an elastomeric cylinder bonded near the ends of carriage  36  to provide inflation capability to sealing member  34 . Inner sealing element  50  allows sealing member  34  to deploy under internal pressure and to self-energize when differential pressure across packer  20  is present. Because inner sealing element  50  may be cold-bonded to metal at  51 , a mechanically energized wedge  53  may be used to improve reliability. Inner sealing element  50  may have a thickness ranging from about 0.10 to about 0.20 inch (from about 0.25 to about 0.5 cm), and may comprise 80 durometer HNBR, although the invention is not so limited, as other materials discussed herein may be employed. 
   Outer sealing element  52  may be a rubber cylinder bonded to the ends of the carriage  36  to provide sealing against the formation. Outer sealing element  52  may have any thickness that provides appropriate tear and wear resistance during conveyance and good conformability to open-hole irregularities. Its thickness may range from about 0.30 to about 0.70 inch (from about 0.76 to about 1.78 cm) to. Outer seal element  52  may also comprise 80 durometer HNBR, and may comprise other materials as discussed herein. 
   Dashed circle “A” in  FIG. 11  refers to a detailed view illustrated in  FIG. 12 . The use of notched beams in support carriage  36  helps control the axial location of the leading edge  32  of the contact point of sealing member  34  with the formation. By allowing some degree of enhanced freedom in radial movement in or near the notched end  46 , the maximum deflection point (contact point with maximum sealing pressure) shifts to the left of the structure, as illustrated schematically in  FIGS. 8 and 9 . This improves the overall sealing performance of sealing elements  50  and  52  under differential pressure and contributes to the long-term reliability of the apparatus of the invention, particularly sealing member  34 . Additionally, individual beams  57  able to expand radially may be more efficient than a continuous metallic cylinder in terms of pressure required to achieve a given expansion and in terms of conforming to irregular open hole geometries. Carriage  36  may be made of, for example, 4130/4140 steel. 
   Anti-extrusion sheets  54  ( FIG. 12 ) are, in the embodiment illustrated, sheet metal cylinders located between carriage  36  and outer sealing element  52  and inner bladder  50  to prevent extrusion through the gaps formed as individual beams  57  in carriage  36  expand and separate. Anti-extrusion sheets  54  may be slotted or un-slotted, and may have any thickness suitable for the intended purpose, but will likely range in thickness from about 0.020 to about 0.050 inch (from about 0.051 to about 0.13 cm). Anti-extrusion sheets may comprise half-hardness low-carbon steel, and if used are welded at  59  to carriage  36  at each end. Un-slotted anti-extrusion sheets may allow removal of inner elastomeric element  50  and a buffer layer. A buffer layer of non-metallic material may be added between the innermost anti-extrusion sheet metal cylinder  54  and inner elastomeric element  50 . A buffer layer may be used to prevent the sharp edges of the sheet metal cylinder from puncturing the relatively thin layer of elastomer used for inner elastomeric member  50 . Suitable buffer layer materials include polyetheretherketone (PEEK), and may be have a thickness ranging from about 0.010 to about 0.030 inch (about 0.025 to about 0.076 cm). 
     FIGS. 14A and 14B  illustrate schematic cross section views at a screen pipe ( FIG. 14A ) and a packer ( FIG. 14B ) of one embodiment of the invention.  FIG. 14A  illustrates shunt tubes  62  for pumping gravel slurry or injection fluids through a zonal isolation tool of the invention, and illustrates that the outer circumference of the screen may have a different center  70  than the inner circumference  72 .  FIG. 14B  illustrates alternate fluid pathways for pumping gravel slurry or injection fluids through a zonal isolation tool of the invention. Three pathways  64  illustrated between a screen base pipe  66  and a packer base pipe  15 , along with three packer setting ports  68 . Maintaining a sufficiently large inner diameter is desirable to achieving full functionality for such alternate fluid pathways. The design illustrated preserves an equivalent area from for transport tubes. It is possible to move the packer and screen base pipes onto different centers, which would ease the disruption in the flow transition. 
     FIGS. 15A ,  15 B, and  15 C illustrate schematically an alternate embodiment of the invention  80 . This embodiment differs from embodiment  29  illustrated in  FIGS. 3-5  in operation. After initial seal pressure is reached in chamber  43  using fluid  41 , a moveable block  76  is moved to the right by fluid pressure  45 , and an O-ring  77  is caused to unseat into a small chamber  78 . In the same movement, inflation port  21  is blanked close, and high pressure fluid in annulus  6  is allowed to pass through chamber  78  into chamber  43 , causing the pressures  35 A and  35 B to become nearly equivalent. Since there is no passage in block  76  to align with inflation port  21  in base pipe  15 , there is less chance in this embodiment that annulus pressure will pass through port  21 , and port  21  is more easily blanked. 
   Apparatus of the invention may be used in an open hole for sandface completions utilizing stand-alone screens. However, the inventive apparatus may also be adapted for use in open-hole gravel pack sand control applications. In the latter role, the inventive apparatus may incorporate the use of alternate path transport and shunt tubes to assist gravel slurry placement. Additionally, the inventive apparatus may be used in sand control applications utilizing expandable screens. Aside from the various sand control applications listed, the inventive apparatus may also be used as an annular barrier, or for compartmentalizing long open-hole sections. 
   The zonal isolation tools of the invention may connect in any number of ways to their wellbore counterparts. Each end of the apparatus of the invention may be adapted to be attached in a tubular string. This can be through threaded connections, friction fits, expandable sealing means, and the like, all in a manner well known in the oil tool arts. Although the term tubular string is used, this can include jointed or coiled tubing, casing or any other equivalent structure for positioning tools of the invention. The materials used can be suitable for use with production fluid or with an inflation fluid. 
   The outer elastomeric elements engage an adjacent surface of a well bore, casing, pipe, tubing, and the like. Other elastomeric layers between the inner and outer elastomeric members may be provided for additional flexibility and backup. A non-limiting example of an elastomeric element is rubber, but any elastomeric materials may be used. A separate membrane may be used with an elastomeric element if further wear and puncture resistance is desired. A separate membrane may be interleaved between elastomeric elements if the elastomeric material is insufficient for use alone. The elastomeric material of outer sealing elements should be of sufficient durometer for expandable contact with a well bore, casing, pipe or similar surface. In some embodiments the elastomeric material may be of sufficient elasticity to recover to a diameter smaller than that of the wellbore to facilitate removal therefrom. The elastomeric material should facilitate sealing of the well bore, casing, or pipe in the inflated state. 
   “Elastomer” as used herein is a generic term for substances emulating natural rubber in that they stretch under tension, have a high tensile strength, retract rapidly, and substantially recover their original dimensions (or even smaller in some embodiments). The term includes natural and man-made elastomers, and the elastomer may be a thermoplastic elastomer or a non-thermoplastic elastomer. The term includes blends (physical mixtures) of elastomers, as well as copolymers, terpolymers, and multi-polymers. Examples include ethylene-propylene-diene polymer (EPDM), various nitrile rubbers which are copolymers of butadiene and acrylonitrile such as Buna-N (also known as standard nitrile and NBR). By varying the acrylonitrile content, elastomers with improved oil/fuel swell or with improved low-temperature performance can be achieved. Specialty versions of carboxylated high-acrylonitrile butadiene copolymers (XNBR) provide improved abrasion resistance, and hydrogenated versions of these copolymers (HNBR) provide improve chemical and ozone resistance elastomers. Carboxylated HNBR is also known. Other useful rubbers include polyvinylchloride-nitrile butadiene (PVC-NBR) blends, chlorinated polyethylene (CM), chlorinated sulfonate polyethylene (CSM), aliphatic polyesters with chlorinated side chains such as epichlorohydrin homopolymer (CO), epichlorohydrin copolymer (ECO), and epichlorohydrin terpolymer (GECO), polyacrylate rubbers such as ethylene-acrylate copolymer (ACM), ethylene-acrylate terpolymers (AEM), EPR, elastomers of ethylene and propylene, sometimes with a third monomer, such as ethylene-propylene copolymer (EPM), ethylene vinyl acetate copolymers (EVM), fluorocarbon polymers (FKM), copolymers of poly(vinylidene fluoride) and hexafluoropropylene (VF2/HFP), terpolymers of poly(vinylidene fluoride), hexafluoropropylene, and tetrafluoroethylene (VF2/HFP/TFE), terpolymers of poly(vinylidene fluoride), polyvinyl methyl ether and tetrafluoroethylene (VF2/PVME/TFE), terpolymers of poly(vinylidene fluoride), hexafluoropropylene, and tetrafluoroethylene (VF2/HPF/TFE), terpolymers of poly(vinylidene fluoride), tetrafluoroethylene, and propylene (VF2/TFE/P), perfluoroelastomers such as tetrafluoroethylene perfluoroelastomers (FFKM), highly fluorinated elastomers (FEPM), butadiene rubber (BR), polychloroprene rubber (CR), polyisoprene rubber (IR), IM, polynorbornenes, polysulfide rubbers (OT and EOT), polyurethanes (AU) and (EU), silicone rubbers (MQ), vinyl silicone rubbers (VMQ), fluoromethyl silicone rubber (FMQ), fluorovinyl silicone rubbers (FVMQ), phenylmethyl silicone rubbers (PMQ), styrene-butadiene rubbers (SBR), copolymers of isobutylene and isoprene known as butyl rubbers (IIR), brominated copolymers of isobutylene and isoprene (BIIR) and chlorinated copolymers of isobutylene and isoprene (CIIR). 
   The expandable portions of the packers of the invention may include continuous strands of polymeric fibers cured within the matrix of the integral composite body comprising elastomeric elements. Strands of polymeric fibers may be bundled along a longitudinal axis of the expandable packer body parallel to longitudinal cuts in a laminar interior portion of the expandable body. This can facilitate expansion of the expandable portion of the composite body yet provide sufficient strength to prevent catastrophic failure of the expandable packer upon complete expansion. 
   The expandable portions of the inventive tools may also contain a plurality of overlapping reinforcement members. These members may be constructed from any suitable material, for example high strength alloys, fiber-reinforced polymers and/or elastomers, nanofiber, nanoparticle, and nanotube reinforced polymers and/or elastomers, or the like, all in a manner known and disclosed in U.S. patent application Ser. No. 11/093,390, filed on Mar. 30, 2005, entitled “Improved Inflatable Packers”, the entirety of which is incorporated by reference herein. 
   Zonal isolation tools of the invention may be constructed of a composite or a plurality of composites so as to provide flexibility. The expandable portions of the inventive tools may be constructed out of an appropriate composite matrix material, with other portions constructed of a composite sufficient for use in a wellbore, but not necessarily requiring flexibility. The composite may be formed and laid by conventional means known in the art of composite fabrication. The composite may be constructed of a matrix or binder that surrounds a cluster of polymeric fibers. The matrix can comprise a thermosetting plastic polymer which hardens after fabrication resulting from heat. Other matrices are ceramic, carbon, and metals, but the invention is not so limited. The matrix can be made from materials with a very low flexural modulus close to rubber or higher, as required for well conditions. The composite body may have a much lower stiffness than that of a metallic body, yet provide strength and wear impervious to corrosive or damaging well conditions. The composite tool body may be designed to be changeable with respect to the type of composite, dimensions, number of cable and fibrous layers, and shapes for differing downhole environments. 
   Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, no clauses are intended to be in the means-plus-function format allowed by 35 U.S.C. § 112, paragraph 6 unless “means for” is explicitly recited together with an associated function. “Means for” clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.

Summary:
Zonal isolation tools and methods of using same are described. The zonal isolation tools include a wellbore sealing member expandable by fluid pressure to contact a wellbore over an initial contact area, an inflation valve open during expansion of the sealing member to the initial contact area and closed upon the fluid pressure reaching a predetermined setting, a vent between the sealing member and a wellbore annulus adapted to open after the inflation valve is closed, and a compressive load imparted to the sealing member via a linear piston to achieve a sealing point at the leading edge of the sealing member. This abstract allows a searcher or other reader to quickly ascertain the subject matter of the disclosure. It will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).