Abstract:
An expandable downhole anchoring tool positionable within a wellbore for use in cooperation with drilling equipment comprises a body including a plurality of angled channels formed into a wall thereof, and a plurality of moveable slips disposed in the same radial plane around the body, wherein the plurality of moveable slips are hydraulically translatable along the plurality of angled channels between a collapsed position and an expanded position. A method of setting an expandable anchor within a wellbore comprises running the anchor into the wellbore in a collapsed position, and expanding the anchor into gripping engagement with the wellbore, wherein the anchor is adapted to expand up to at least 1.5 times a collapsed diameter of the anchor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/549,434 filed Mar. 2, 2004 and entitled “Expandable Down Hole Anchor”, and further, the present application is related to U.S. application Ser. No. 10/719,199, filed Nov. 21, 2003, and entitled “Thru Tubing Tool and Method, now U.S. Patent Publication No. 2004/0149430, both hereby incorporated herein by reference for all purposes. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0003]     Not applicable.  
       FIELD OF THE INVENTION  
       [0004]     The present invention relates generally to expandable anchoring tools for use in drilling operations, and methods of attaching an expandable anchor to a wellbore wall. Further, the present invention relates to methods and apparatus for drilling a secondary borehole from an existing borehole in geologic formations. More particularly, the present invention relates to expandable anchors that can be run into boreholes of varying diameters and then expanded to set against either a cased or open hole to anchor another well tool for conducting downhole well operations.  
       BACKGROUND  
       [0005]     Once a petroleum well has been drilled and cased, it is often necessary or desired to drill one or more additional wells that branch off, or deviate, from the first well. Such multilateral wells are typically directed toward different parts of the surrounding formation, with the intent of increasing the output of the well. The main well bore can be vertical, angled or horizontal. Multilateral technology can be applied to both new and existing wells.  
         [0006]     In order to drill a new borehole that extends outside an existing cased wellbore, the usual practice is to use a work string to run and set a whipstock via an anchor disposed at the lower end thereof. The upper end of the whipstock comprises an inclined face. The inclined face is designed to guide a window milling bit radially outwardly with respect to the casing axis as the milling bit is lowered, so that the milling bit engages and cuts a window in the casing. The lower end of the whipstock is adapted to engage an anchor in a locking manner that prevents both axial and rotational movement.  
         [0007]     Multilateral technology provides operators several benefits and economic advantages. For example, multilateral technology can allow isolated pockets of hydrocarbons, which might otherwise be left in the ground, to be tapped. In addition, multilateral technology allows the improvement of reservoir drainage, increasing the volume of recoverable reserves and enhancing the economics of marginal pay zones. By utilizing multilateral technology, multiple reservoirs can be drained simultaneously. Thin production intervals that might be uneconomical to produce alone become economical when produced together with multilateral technology. Multiple completions from one well bore also facilitate heavy oil drainage.  
         [0008]     In addition to production cost savings, development costs also decrease through the use of existing infrastructure such as surface equipment and the well bore. Multilateral technology expands platform capabilities where slots are limited and eliminates spacing problems by allowing more drain holes to be added within a reservoir. In addition, by sidetracking damaged formations or completions, the life of existing wells can be extended. Laterals may be drilled below a problem area once casing has been set, thereby reducing the risk of drilling through troubled zones. Finally, multilateral completions accommodate more wells with fewer footprints, making them ideal for environmentally sensitive or challenging areas.  
         [0009]     Often however, a well bore is configured such that a tubular string of a smaller diameter is contained within a larger pipe string, casing, or open hole, thereby making it necessary to run well tools through the smaller diameter tubular and thereafter perform downhole operations (such as sidetracking) within the larger area provide by the larger pipe string, casing, or open hole. Expandable tools are generally used for such operations. Disadvantages of known expandable anchors include limited radial expansion capabilities and limited capability of securing the anchor within the larger diameter. As such, prior expandable anchors that support whipstocks for drilling sidetrack boreholes, for example, may be susceptible to small but not insignificant amounts of movement. Hence, it would be desirable to provide an expandable anchor that effectively prevents an anchored whipstock from moving.  
       SUMMARY  
       [0010]     The present invention is directed to an expandable downhole anchoring tool positionable within a wellbore for use in cooperation with drilling equipment. In one embodiment, the expandable downhole anchoring tool comprises a body including a plurality of angled channels formed into a wall thereof, and a plurality of moveable slips disposed in the same radial plane around the body, wherein the plurality of moveable slips are hydraulically translatable along the plurality of angled channels between a collapsed position and an expanded position.  
         [0011]     In another embodiment, the expandable downhole anchoring tool comprises a mandrel, a pair of movable slip housings each having a plurality of angled channels, and a plurality of slips disposed in the same radial plane about the mandrel that translate along the angled channels between a collapsed position and an expanded position, wherein the plurality of slips are disposed between the pair of moveable slip housings in the collapsed position.  
         [0012]     In another aspect, the present invention is directed to a method of setting an expandable anchor within a wellbore comprising running the anchor into the wellbore in a collapsed position, and expanding the anchor into gripping engagement with the wellbore, wherein the anchor is adapted to expand up to at least 1.5 times a collapsed diameter of the anchor.  
         [0013]     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     For a more detailed description of the present invention, reference will now be made to the accompanying drawings, wherein:  
         [0015]      FIG. 1  is a cross-sectional side view of one embodiment of the expandable anchor in a locked and collapsed run-in position;  
         [0016]      FIG. 2  is a cross-sectional end view taken at plane B-B of  FIG. 1 ;  
         [0017]      FIG. 3  is a cross-sectional side view of the expandable anchor of  FIG. 1  in an unlocked and expanded position wherein the slips engage a surrounding wellbore wall;  
         [0018]      FIG. 4  is a cross-sectional end view taken at plane B-B of  FIG. 3 ;  
         [0019]      FIG. 5  is an enlarged cross-sectional view of one embodiment of a locking means of the expandable anchor of  FIG. 1 ;  
         [0020]      FIG. 6  is a cross-sectional side view of the expandable anchor of  FIG. 1  with the slips in a maximum expanded position;  
         [0021]      FIG. 7  is a cross-sectional end view taken at plane E-E of  FIG. 6 ;  
         [0022]      FIG. 8  is a cross-sectional side view of the expandable anchor of  FIG. 1  in a released and collapsed position;  
         [0023]      FIG. 9  is a perspective view of an individual slip of the expandable anchoring tool of  FIG. 1 ;  
         [0024]      FIG. 10  is a front view of the slip of  FIG. 9 , depicting the borehole engaging surface;  
         [0025]      FIG. 11  is a side view of the slip of  FIG. 9 ;  
         [0026]      FIG. 12  is a cross-sectional view taken at plane C-C of  FIG. 11 ;  
         [0027]      FIG. 13  is a cross-sectional view taken at plane D-D of  FIG. 11 ;  
         [0028]      FIG. 14  is a cross-sectional end view taken at plane B-B of  FIG. 11 ;  
         [0029]      FIG. 15  is a cross-sectional side view taken at plane A-A of  FIG. 14 ; and  
         [0030]      FIG. 16  is a cross-sectional view taken at plane F-F of  FIG. 14 . 
     
    
     NOTATION AND NOMENCLATURE  
       [0031]     Certain terms are used throughout the following description and claims to refer to particular assembly components. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”.  
         [0032]     Reference to up or down will be made for purposes of description with “up”, “upper”, or “upstream” meaning toward the earth&#39;s surface or toward the entrance of a well bore; and with “down”, “lower”, or “downstream” meaning toward the bottom of the well bore.  
         [0033]     In the drawings, the cross-sectional side views of the expandable anchor should be viewed from left to right, with the upstream end on the far left side of the drawing and the downstream end on the far right side of the drawing.  
       DETAILED DESCRIPTION  
       [0034]     Various embodiments of the expandable anchor and methods of use will now be described with reference to the accompanying drawings, wherein like reference numerals are used for like features throughout the several views.  
         [0035]      FIGS. 1-8  depict one embodiment of an expandable anchor, generally designated as  800 , in various operational positions. In an embodiment, the expandable anchoring tool  800  may be used, for example, in combination with a whipstock and drilling assembly for sidetracking operations, perhaps below a restriction. It should be appreciated, however, that the expandable anchor  800  may be used in many different types of drilling assemblies. Sidetracking and milling systems provide only some of the representative assemblies within which the expandable anchor  800  may be used, but these should not be considered the only assemblies. In particular, the expandable anchor  800  may be used in any drilling assembly requiring an anchoring tool. Further, it is to be fully recognized that the different teachings of the embodiments disclosed herein may be employed separately or in any suitable combination to produce desired results.  
         [0036]      FIGS. 1-8  provide an operational overview of the expandable anchor  800 . In particular, the expandable anchor  800  is lowered into the casing in the locked and collapsed position shown in  FIGS. 1 and 2 . When the expandable anchor  800  reaches a desired depth, the anchor  800  is unlocked and expanded to a set position shown in  FIGS. 3 and 4  where the slips  820  of the anchor  800  engage a surrounding casing or open borehole wall. The expandable anchor  800  is configured to expand over a range of diameters, and  FIGS. 6 and 7  depict the expandable anchor  800  in its maximum expanded position. Finally, to remove the expandable anchor  800  from the well, the anchor  800  is released from the casing to return to an unlocked and collapsed position as shown in  FIG. 8 .  
         [0037]     Referring now to  FIGS. 1-5 , the expandable anchor  800  comprises a top sub  882  connected via threads  864  to a generally cylindrical mandrel  860  having a flowbore  808  therethrough, which in turn is connected via threads  884  to a nose  880 . In one embodiment, the anchor  800  includes an upper box connection  814  and a lower pin connection  812  for connecting the anchor  800  into a downhole assembly. The upper box connection  814  may be connected to the lower end of a whipstock, for example. If the expandable anchor  800  is the lowermost tool in the downhole assembly, an optional nose protector  890  may be connected to the nose  880  at the lower pin connection  812 . In such an assembly, a pipe plug  897  is connected to the nose  880  to close off the flowbore  808  of the mandrel  860  so that the anchor  800  may be expanded hydraulically.  
         [0038]     The mandrel  860  is the innermost component within the anchor  800 . Disposed around and slidingly engaging the mandrel  860  are a Belleville spring stack  825 , an upper slip housing  821 , one or more slips  820 , and a lower slip housing  822 . One or more recesses  816  are formed in the slip housings  821 ,  822  to accommodate the radial movement of the one or more slips  820 . The recesses  816  include angled channels  818  formed into the wall thereof, and these channels  818  provide a drive mechanism for the slips  820  to move radially outwardly into the expanded positions depicted in  FIGS. 3, 4 ,  6  and  7 . In one embodiment, the expandable anchor  800  comprises three slips  820  as best shown in  FIG. 4 , wherein the three slips  820  are spaced 120° circumferentially in the same radial plane. It should be appreciated, however, that any number of slips  820  may be disposed in the same radial plane around the anchor  800 . For example, the anchor  800  may comprise four slips  820 , each approximately 90° from each other, or two slips  820 , each approximately 180° from each other.  
         [0039]     Referring again to  FIGS. 1-5 , connected via threads  838  to the lower slip housing  822  is a piston housing  835 , which in turn is connected via threads  813  to a shear sub  810  that is releasably coupled to the nose  880  via one or more shear screws  811 . The piston housing  835  forms a fluid chamber  832  around the mandrel  860  within which a piston  830  and a locking means  720  are disposed. The piston  830  connects via threads  836  to the mandrel  860 , and the mandrel  860  includes ports  895  that enable fluid flow from the flowbore  808  into the fluid chamber  832  to actuate the anchor  800  to the expanded positions shown in  FIGS. 3, 4 ,  6  and  7 . In one embodiment, a seal  866  is provided between the piston  830  and the mandrel  860 , a seal  834  is provided between the piston  830  and the piston housing  835  and a seal  839  is provided between the piston housing  835  and the lower slip housing  822 .  
         [0040]      FIG. 5  depicts an enlarged view of the locking means  720 , shown releasably coupled to the piston housing  835  via one or more shear screws  775 . The locking means  720  comprises a lock housing  721  mounted about the mandrel  860  and a lock nut  722 , which interacts with the mandrel  860  to prevent release of the expandable anchor  800  when pressure is released. The outer radial surface of mandrel  860  includes serrations  862  which cooperate with inverse serrations  723  formed on the inner surface of locking nut  722 , as described in more detail below.  
         [0041]      FIGS. 9-16  depict various views of a single slip  820  of the expandable anchor  800 . The slip  820  is shown in isometric view in  FIG. 9 , in front view in  FIG. 10 , and in side view in  FIG. 11  to depict a front surface  521 , a back surface  527 , a top surface  665 , a bottom surface  660 , and two side surfaces  528 . Top surface  665  and bottom surface  660  are preferably angled to assist in returning the slip  820  from an expanded position to a collapsed position. The slip  820  also includes extensions  650  disposed along each side  528  of slip  820 . The extensions  650  preferably extend upwardly at an angle from the back surface  527  of the slip  820  toward the front, borehole engaging surface  521  of the slip  820 . The extensions  650  protrude outwardly from the slip  820  to fit within corresponding channels  818  in the recesses  816  of the slip housings  821 ,  822 . The interconnection between the slip extensions  650  and the body channels  818  increases the surface area of contact between the slips  820  and the slip housings  821 ,  822 , thereby providing a more robust expandable anchor  800  as compared to prior art tools.  
         [0042]     The front borehole engaging surface  521  may comprise, in one embodiment, a multiplicity of radially aligned engagement “threads” and axially aligned “fins” (not shown) that are designed, when the anchor  800  is in the expanded position, to grip the casing or open borehole wall and thereby resist torsional as well as axial loads imposed on the anchor  800  during sidetracking operations. In the embodiment depicted in  FIGS. 9-16 , buttons  700  may be set in the front surface  521  to grippingly engage the casing or open hole wall. In one embodiment, the material for the gripping buttons  700  is tungsten carbide.  
         [0043]      FIGS. 12 and 14  show a cavity  690  in the back surface  527  of the slip  820 , which engages the mandrel  860 . The cavity  690  extends for the full length of the slip  820  and can be of any desired configuration so long as it conforms to a substantial portion of the circumference of the mandrel  860 . If the mandrel  860  is curvilinear, then the cavity  690  will be of conforming curvilinearity so that the mandrel  860  matingly engages the cavity  690 . For example, if the mandrel  860  is essentially round, then the cavity  690  will be essentially hemi-circular as shown in  FIGS. 12 and 14 .  
         [0044]     Referring now to  FIGS. 3 and 4 , the expandable anchor  800  is depicted with the slips  820  in the expanded position, extending radially outwardly into gripping engagement with a surrounding casing or open borehole wall. The anchor  800  has two operational positions within a particular wellbore—namely a collapsed position as shown in  FIGS. 1 and 2  for running the anchor into a wellbore, and an expanded position as shown in  FIGS. 3 and 4  for grippingly engaging a wellbore.  
         [0045]     To actuate the anchor  800 , hydraulic forces are applied to cause the slips  820  to expand radially outwardly from the locked and collapsed position of  FIGS. 1 and 2  to the unlocked and expanded position of  FIGS. 3 and 4 . Specifically, fluid flows down the flowbore  808  and through the ports  895  in the mandrel  860  into the chamber  832  surrounded by the piston housing  835 . When the anchor  800  is the lowermost tool in a drilling assembly, a pipe plug  897  is provide to close off the flowbore  808  through the mandrel  860  to allow fluid pressure to build up within the anchor  800  to actuate it, i.e. expand the anchor  800 . If, however, another tool is run below the anchor  800 , pipe plug  897  is removed so that hydraulic fluid can flow through the anchor  800  to the lower tool. In such an operation, the lower tool includes a similar pipe plug within its bore so that hydraulic pressure can be built up in both the lower tool and the anchor  800  to actuate both tools. In an embodiment, one example of a lower tool that may be run below the anchor  800  is a hydraulically set well reference member described in U.S. Pat. No. 6,543,536 assigned to Smith International, Inc. The well reference member is set first in the wellbore, and then the expandable anchor  800  is set so that drilling through the casing can commence to produce a sidetracked well. Then the anchor  800  and the drilling assembly components connected above the anchor  800  are removed from the well, but the well reference member remains in the wellbore adjacent the window cut in the casing. As such, the well reference member provides a marker for future operations so that a drilling assembly can be lowered and connected to the well reference member in the proper orientation and at the right depth in the wellbore.  
         [0046]     Referring again to  FIGS. 1-5 , pressure will continue to build in the fluid chamber  832  as the piston  830  provides a seal therein until the pressure is sufficient to cause shear screws  811  to shear. Since the piston  830  is connected via threads  836  to the mandrel  860 , the piston  830  will remain stationary while the outer piston housing  835  and the lower slip housing  822  connected thereto will move axially upwardly from the position shown in  FIG. 1  to the position shown in  FIG. 3 . Upward movement of the lower slip housing  822  acts against the slips  820  to drive the slips  820  radially outwardly along the channels  818 . This upward motion will also cause the slips  820  and the upper slip housing  821  to move axially upwardly against the force of the Belleville spring stack  825 .  
         [0047]     Because the outer piston housing  835  is moveable to expand the slips  820  rather than the piston  830 , the anchor  800  design eliminates a redundant piston stroke found in conventional expandable tools, and the expandable anchor  800  maintains approximately the same axial length in the collapsed position of  FIG. 1  and in the expanded position of  FIG. 3 . The expandable anchor  800  also has a shorter mandrel  860  as compared to other anchors, and the slips  820  are nearly unidirectional. Therefore, the Belleville spring stack  825  is provided as a means to store up energy. If the Belleville spring stack  825  were not present, the energy stored in the anchor  800  would be based on how much the mandrel  860  stretches as the slips  820  are set against a wellbore. Although the mandrel  860  is made of a hard metal, such as steel, it still stretches a small amount, acting as a very stiff spring. Therefore, in order to store up energy in the anchor  800 , this spring effect must be weakened or unstiffened to some degree, such as by adding the Belleville spring stack  825 . In so doing, the stroke length required to set the slips  820  is increased since the slips  820  have to move far enough to compress the Belleville spring stack  825 . Thus, the Belleville spring stack  825  is provided to store up energy, which requires the anchor  800  to be stroked further to set it because the spring stack  825  must be fully compressed as shown in  FIGS. 3 and 6 .  
         [0048]     Referring now to  FIGS. 6 and 7 , the anchor  800  is also configured for operation within wellbores having a range of diameters, and the anchor  800  is depicted in its maximum expanded position. In an embodiment, a spacer screw  840  is provided to maintain a space between the lower slip housing  822  and the upper slip housing  821  when the anchor  800  is in its maximum expanded position. During assembly of the anchor  800 , when installing the slips  820 , the upper slip housing  821  and the lower slip housing  822  are abutted against each other, and the extensions  650  in the slips  820  are aligned with the channels  818  in the recesses  816  of the slip housings  821 ,  822 . Then the upper and lower slip housings  821 ,  822  are pulled apart and the slips  820  collapse into the anchor  800  around the mandrel  860 . To ensure that the anchor  800  does not overstroke downhole, the spacer screw  840  stops the upper and lower slip housing  821 ,  822  from abutting together as during assembly, thereby preventing the slips  820  from falling out of the anchor  800 . Thus, in the maximum expanded position, the spacer screw  840  provides a stop surface against which the lower slip housing  822  is prevented from further upward movement so that it remains spaced apart from the upper slip housing  821 . The spacer screw  840  is provided only as a safety mechanism because the slips  820  should engage the wellbore wall in an intermediate expanded position, as shown in  FIGS. 3 and 4 , well before the lower slip housing  822  engages the spacer screw  840 .  
         [0049]     Thus, the expandable anchor  800  is fully operational over a wide range of diameters, and has an expanded position that varies depending on the diameter of the wellbore. As such, the expandable anchor  800  is specifically designed to provide proper anchoring of a drilling assembly to withstand compression, tension, and torque for a range of wellbore diameters. Specifically, the expandable anchor  800  is configured to expand up to at least 1.5 times the collapsed diameter of the anchor  800 . For example, in one embodiment, the expandable anchor  800  has a collapsed diameter of approximately 8.19 inches and is designed to expand into engagement with 9⅝ inch casing up to 13⅜ inch casing, which correlates with an 8½ inch diameter wellbore up to a 12¼ inch diameter wellbore.  
         [0050]     Referring again to  FIG. 5 , once the slips  820  are expanded into gripping engagement with a borehole, to prevent the anchor  800  from returning to a collapsed position until so desired, the expandable anchor  800  is also provided with a locking means  720 . As the piston housing  835  moves, so will a lock housing  721  that is connected thereto via shear screws  775  mounted about the mandrel  860 . The lock housing  721  cooperates with a lock nut  722 , which interacts with the mandrel  860  to prevent release of the anchor  800  when hydraulic fluid pressure is released. Specifically, the outer radial surface of mandrel  860  includes serrations  862 , which cooperate with inverse serrations  723  formed on the inner surface of the locking nut  722 . Thus, as the piston housing  835  moves the lock housing  721  upwardly, the locking nut  722  also moves upwardly in conjunction therewith causing the inner serrations  723  of the locking nut  722  to move over the outer serrations  862  of the mandrel  860 . The serrations  862  on the mandrel  860  are one-way serrations  862  that only allow the locking nut  722  and the components that are connected thereto to move upstream when hydraulic pressure is applied to the anchor  800 . Therefore, because of the ramped shape of the serrations  862 , the locking nut  722  can only move in one direction, namely upstream, with respect to the mandrel  860 . The interacting serrations  723 ,  862  prevent movement in the downstream direction since there is no ramp on the mandrel serrations  862  that angle in that direction. Thus, interacting edges of the serrations  723 ,  862  ensure that movement will only be in one direction, thereby preventing the anchor  800  from returning to a collapsed position until so desired.  
         [0051]     Still referring to  FIG. 5 , in an embodiment, the locking nut  722  is machined as a hoop and then split into multiple segments, and a garter spring  725  is provided to hold the segments of the locking nut  722  around the mandrel  860 . The garter spring  725  resembles an O-ring, except that the spring  725  is made out of wire. The wire is looped around the locking nut  722 , and the ends are hooked together. The garter spring  725  allows the sections of the locking nut  722  to open and close as the locking nut  722  jumps over each individual serration  862  as it moves upwardly on the mandrel  860 . Thus, the garter spring  725  allows the locking nut  722  to slide up the ramp of a mandrel serration  862  and jump over to the next serration  862 , thereby ratcheting itself up the mandrel  860 . The garter spring  725  also holds the locking nut  722  segments together so that the locking nut  722  cannot back up over the serrations  862  on the mandrel  860 .  
         [0052]     Referring now to  FIG. 8 , the expandable anchor  800  is also designed to return from an expanded position to a released, collapsed position. The anchor  800  can be released from gripping engagement with a surrounding borehole by applying an upward force sufficient to allow the slips  820  to retract to the released and collapsed position shown in  FIG. 8 . In particular, the lock housing  721  is connected to the piston housing  835  by shear screws  775 . To return the anchor  800  to a collapsed position, an axial force is applied to the anchor  800  sufficient to shear the shear screws  775 , thereby releasing the locking means  720 . As shown in  FIGS. 1, 3 ,  6  and  8 , a release ring  718  is disposed between the upper slip housing  721  and the mandrel  860 . In one aspect, the release ring  718  provides a shoulder to prevent the upper slip housing  821  from sliding too far downwardly with respect to the slips  820  in the run-in position of  FIGS. 1 and 2 , or after releasing the anchor  800  to the position shown in  FIG. 8 . In another aspect the release ring  718  is configured to allow the mandrel  860  to move a small distance axially before the slips  820  disengage from the wellbore to allow for the shear screws  775  to shear completely. Thus, when an axial force is applied to the mandrel  860 , the release ring  718  allows for the slips  820  to maintain engagement with the wellbore to provide a counter force against which the shear screws  775  can shear. Therefore, the release ring  718  allows for the shear screws  775  to shear completely, which enables the slips  820  to collapse back into the anchor  800 . With the anchor  800  in the released and collapsed position of  FIG. 8 , the anchor  800  can be removed from the wellbore.  
         [0053]     In summary, the various embodiments of the expandable anchor  800  of the present invention may be used as an anchor to grippingly engage a larger diameter tubular or borehole, whether cased or open hole. The various embodiments of the present invention solve the problems of the prior art and include other features and advantages. Namely, the embodiments of the present expandable anchor  800  are stronger and more robust than prior art expandable anchoring tools.  
         [0054]     While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention.