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BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to wellbore completion. More particularly, the invention relates to an apparatus and method for expanding an anchor in a borehole. 
         [0003]    2. Description of the Related Art 
         [0004]    Expandable technology enables a smaller diameter tubular to pass through a larger diameter tubular, and thereafter be expanded to a larger diameter. In this respect, expandable technology permits the formation of a tubular string having a substantially constant inner diameter. When an expandable tubular is run into a borehole, it must be anchored within the borehole at the desired depth to prevent movement of the expandable tubular during the expansion process. Anchoring the expandable tubular within the borehole allows expansion of the length of the expandable tubular in the borehole. During the anchoring operation, an expander tool is typically pushed or pulled through an anchor of the expandable tubular to expand the anchor into contact with the surrounding borehole. The anchor must provide adequate frictional engagement between the expandable tubular and the inner diameter of the borehole to stabilize the expandable tubular against longitudinal axial movement within the borehole during the expansion process of the expandable tubular. 
         [0005]    The expandable tubular used to isolate the area of interest is often run into the borehole after previous strings of casing are already set within the borehole. The expandable tubular for isolating the area of interest must be run through the inner diameter of the previous strings of casing to reach the portion of the open-hole borehole slated for isolation, which is located below the previously set strings of casing. Accordingly, the outer diameter of the anchor and the expandable tubular must be smaller than all previous casing strings lining the borehole in order to run through the casing to the depth at which the open-hole borehole exists. 
         [0006]    Additionally, once the expandable tubular reaches the open-hole portion of the borehole below the previously run casing, the diameter of the open-hole portion of the borehole is often larger than the inner diameter of the casing liner. After being placed at a desired location, to hold the expandable tubular in place within the open-hole portion of the borehole before initiating the expansion process, the anchor must have a large enough outer diameter to sufficiently fix the expandable tubular at a position within the open-hole borehole before the expansion process begins. 
         [0007]    There is a need for an open-hole anchor to support an expandable tubular used to isolate an area of interest within a borehole prior to initiating and during the expansion of the expandable tubular. There is a need for an open-hole anchor which is small enough to run through the previous casing liner in the borehole, capable of expanding to a large enough diameter to frictionally engage the inner diameter of the open-hole borehole below the casing liner, and capable of holding the expandable tubular in position axially and rotationally during the expansion of the length of the expandable tubular. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention generally relates to an apparatus and method for expanding an anchoring device in a borehole. In one aspect, an anchoring device is provided. The anchoring device includes an expandable tubular. The anchoring device further includes a plurality of bands disposed on an outer surface of the expandable tubular. Each band is attached to the tubular at a first connection point and a second connection point, wherein each band is configured to bow radially outward as the expandable tubular shortens in length in response to the expansion of the tubular. 
         [0009]    In a further aspect, a method of attaching an anchoring device in a borehole is provided. The method includes the step of positioning the anchoring device in the borehole, the anchoring device having a tubular and a plurality of bands disposed on an outer surface of the tubular. The method further includes the step of reducing the axial length of the tubular by expanding the tubular radially outward, wherein the reduction of axial length of the tubular causes the bands to bow radially outward into contact with the borehole. 
         [0010]    In a further aspect, an anchoring device is provided. The anchoring device includes a tubular. The anchoring device further includes a first band attached to an outer surface of the tubular at a first connection point and a second connection point. Additionally, the anchoring device includes a second band attached to the outer surface of the tubular at a third connection point and a fourth connection point, wherein the first band bows to a first distance and the second band bows to a second distance when the axial length of the tubular is reduced due to expansion of the tubular and wherein the first band is disposed on top of a portion of the second band. 
         [0011]    In another aspect, an anchoring device is provided. The anchoring device includes a tubular. The anchoring device further includes a first band attached to an outer surface of the tubular at a first connection point and a second connection point, wherein the first connection point is a releasable connection that is configured to release the connection between an end portion of the first band and the tubular. The anchoring device also includes a second band attached to the outer surface of the tubular at a third connection point and a fourth connection point, wherein the first connection point releases the end portion of the first band and the second band bows radially outward when the axial length of the tubular is reduced due to expansion of the tubular. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0013]      FIGS. 1A-1D  are views illustrating an expansion operation of an open-hole anchor in a borehole. 
           [0014]      FIGS. 2A and 3A  are views illustrating an anchor portion prior to expansion of the open-hole anchor, and  FIGS. 2B and 3B  are views illustrating the anchor portion after expansion of the open-hole anchor. 
           [0015]      FIG. 4  is a view illustrating bands of the anchor portion disposed on a portion of a tubular. 
           [0016]      FIG. 5  is a view illustrating the band of the anchor portion having multiple contact points with the borehole. 
           [0017]      FIG. 6  is a view illustrating different lengths of the band. 
           [0018]      FIG. 7  is a view illustrating an anchor with bands bowed radially outward. 
           [0019]      FIG. 8  is a view of an anchor having multiple anchor portions. 
           [0020]      FIG. 9A  is a view illustrating an anchor prior to expansion, and  FIG. 9B  is a view illustrating the anchor portion after expansion. 
           [0021]      FIG. 10A  is a view illustrating an anchor prior to expansion, and  FIG. 10B  is a view illustrating the anchor portion expanded into contact with the borehole. 
           [0022]      FIG. 11  is a view illustrating an anchor with dual bands. 
           [0023]      FIGS. 11A-11D  illustrate different configurations of the dual bands. 
           [0024]      FIG. 12  is a view illustrating an anchor with a spiral band. 
           [0025]      FIG. 13A  is a view illustrating an anchor prior to expansion, and  FIG. 13B  is a view illustrating the anchor after expansion. 
           [0026]      FIG. 14  is a view illustrating an anchor with a double helix band arrangement. 
           [0027]      FIG. 15A  is a view illustrating an anchor prior to expansion, and  FIG. 15B  is a view illustrating the anchor after expansion. 
           [0028]      FIG. 16A  illustrates a view of an anchor prior to expansion. 
           [0029]      FIG. 16B  illustrates a view of the anchor after expansion. 
           [0030]      FIG. 16C  illustrates a view of the anchor in contact with a borehole. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The present invention generally relates to an apparatus and method for expanding an anchoring device in a borehole. The anchor will be described herein in relation to an open hole. It is to be understood, however, that the anchor may also be used inside of a cased borehole without departing from principles of the present invention. To better understand the novelty of the anchoring device of the present invention and the methods of use thereof, reference is hereafter made to the accompanying drawings. 
         [0032]      FIGS. 1A-1D  illustrate an expansion operation of an open-hole anchor  100  (anchoring device) in a borehole  10 . The open-hole anchor  100  of the present invention is lowered into the borehole  10  attached to a running tool  25 . The running tool  25  in  FIGS. 1A-1D  is shown for illustrative purposes. Other running tools may be used to expand the open-hole anchor  100  without departing from principles of the present invention. 
         [0033]      FIG. 1A  illustrates the placement of the open-hole anchor  100  adjacent an under-reamed portion of the borehole  10 . The open-hole anchor  100  is connected to the running tool  25  by a releasable engagement device  30 , such as a latch, collet, slips, thread, shear member or any other suitable mechanism. The open-hole anchor  100  includes an anchor portion  150  and a seal portion  110  disposed around a tubular  125 . The anchor portion  150  is positioned between the engagement device  30  (i.e., fixed point) and an end  105  (i.e., free point) of the tubular  125 .  FIG. 1B  illustrates a first cone  20  expanding the tubular  125  adjacent the anchor portion  150 . The first cone  20  is configured to move relative to the engagement device  30  by a hydraulic or mechanical moving device. As the first cone  20  expands the tubular  125 , the length between the end  105  of the tubular  125  and the engagement device  30  changes from a first length to a second shorter length, which causes the anchor portion  150  to activate. In other words, the tubular  125  becomes axially shorter as the tubular  125  is expanded radially. The reduction in the length of the tubular  125  occurs between the fixed end (engagement device  30 ) and the free end  105 . 
         [0034]      FIG. 1C  illustrates an optional second cone  40  further expanding the open-hole anchor  100 . After the open-hole anchor  100  is attached to the borehole  10  by the anchor portion  150 , the engagement device  30  is released and the running tool  25  is pulled upward to expand (or further expand) the tubular  125  of the open-hole anchor  100  by using the first cone  20  and the second cone  40 .  FIG. 1D  illustrates the removal of the running tool  25  after expansion of the open-hole anchor  100 . 
         [0035]      FIGS. 2A and 3A  are views illustrating the anchor portion  150  prior to expansion of the open-hole anchor  100 , and  FIGS. 2B and 3B  are views illustrating the anchor portion  150  after expansion of the open-hole anchor  100 . As shown, bands  155  are circumferentially spaced around the tubular  125 . The bands  155  are made from thin strips of flexible material, such as metal or composite. The bands  155  may be a rectangle, a square, a circle or any geometric shape. The bands  155  are attached to the tubular at connection points  160  along the longitudinal axis of the tubular  125 . The connection points  160  may be made by welding, gluing or another connection method known in the art. The bands  155  also include a central section that is not attached to the tubular  125 . As shown in  FIGS. 2A and 3A , the bands  155  are in a substantially linear arrangement prior to expansion. The bands  155  are configured to buckle as the length of the tubular  125  moves from the first length to the second shorter length due to the radial expansion of the tubular  125 . In other words, as the length of the tubular  125  reduces, the length between the connection points  160  also reduces, which causes the bands  155  to buckle and bow (or bend) radially outward. Further, the bands  155  are configured to engage the irregularity of the borehole  10 . For instance, if the anchor  100  is positioned in a portion of the borehole  10  that includes an irregular wall, then several bands  155  bow outward into the irregular shaped wall portion and other bands  155  bow outward into the regular shaped wall portion. In other words, the bands  155  conform to the shape of the wall of the borehole  10 . 
         [0036]    The distance between the connection points  160  define the length of the bands  155 . The length of the bands  155  may be used to define the outer diameter of the anchor portion  150 . For instance, as shown in  FIG. 2B , the largest outer diameter of the anchor portion  150  is defined between connection point  160 A and connection point  160 B, which has the band with the longest length. The smallest outer diameter of the anchor portion  150  is defined between connection points  160 C and  160 D, which has the band with the shortest length. Thus, there is a proportional relationship between the length of the band  155  and the outer diameter of the band  155  after buckling occurs due to the expansion of the tubular  125 . 
         [0037]      FIG. 4  illustrates the bands  155  of the anchor portion  150  disposed on a portion of the tubular  125 . The tubular  125  has an outer diameter B and a reduced outer diameter A. In the embodiment shown, the bands  155  are located on a portion of the tubular  125  that has the reduced outer diameter A. One benefit of having a reduced outer diameter is that the open-hole anchor  100  may have substantially the same outer diameter by the anchor portion  150  and the portion of the tubular  125  adjacent the anchor portion  150 , which may allow the open-hole anchor  100  to move through tight areas of the borehole  10 . Another benefit of having a reduced outer diameter is that the force required to expand the tubular  125  of the reduced outer diameter A will be less than the force required to expand a tubular with a larger diameter. Another benefit of having a reduced outer diameter is that the bands  155  are substantially protected against knocks and abrasion when running the anchor  100  into the borehole  10 . In other embodiments, the bands may be disposed on a portion of the tubular that has not been reduced or an upset portion (or enlarged portion) relative to other portions of the tubular. 
         [0038]      FIG. 5  illustrates the band  155  of the anchor portion  150  having multiple contact points with the borehole  10 . The band  155  may be configured to have a single contact point  170  or multiple contacts points  170 A,  170 B with the borehole  10 . The number of contact points is determined by the length L of the band  155  (e.g., the connection points  160 ). Generally, the longer the length L, the greater amount of contact points. As discussed herein, the outer diameter of the band  155  is proportional to the length of the band  155 . To put it another way, the radius R of the band  155  (i.e., growth) after buckling is directly related to the length L of the band  155 . Thus, the number of contact points with the borehole  10  can be determined based upon the length L of the band  155 . Typically, the more contact points between the band  155  and the borehole  10 , the stronger the anchoring relationship between the anchor portion  150  and the borehole  10 .  FIG. 5  shows two contact points between the band  155  and the borehole  10 , however, there may be any number of contact points without departing from principles of the present invention. Other factors that may affect the radius R and/or the contact points of the band  155  are the radial clearance between the borehole  10  and the tubular  125 , the amount of shrinkage of the tubular  125 , the thickness of the band  155 , the stiffness (and/or the strength) of the material of the band  155  and the characteristics of the borehole  10 . Further, the band  155  (after buckling) may have a symmetrical form as shown or may have an asymmetrical form. 
         [0039]      FIG. 6  is a view illustrating different lengths of the band  155 . As set forth herein, the length L 1 , L 2 , L 3  of the band  155  is proportional to the outer diameter of the band  155  after buckling occurs due to the expansion of the tubular  125 . The length L 1 , L 2 , L 3  of the band  155  is also inversely proportional to the strength of the anchor (e.g., band  155 ). For instance, the band  155  with length L 1  is a stronger anchor than the band  155  with the length L 2 . The reason the band  155  with length L 1  is a stronger anchor is because the band  155  with length L 1  is stiffer or more rigid than the band  155  with the length L 2 . The band  155  that is stiff has a greater collapse resistance and greater load-bearing capability and thus is a stronger anchor. The band  155  with length L 3  illustrates a self-sustaining buckle arrangement in which the length L 3  is divided into two short lengths L 3 A, L 3 B. In essence, the band  155  with length L 3  is divided into two short length bands which are rigid. In sum, the band  155  with length L 1  is the strongest anchor, the band  155  with length L 3  is the next strongest and the band  155  with length L 2  is the weakest of the anchors shown in  FIG. 6 . 
         [0040]      FIG. 7  is a view illustrating an anchor  200  with bands  210  bowed radially outward due to buckling. Each band  210  is connected to a tubular  205  at connection points  215 A,  215 B. As the tubular  205  is expanded, the bands  210  buckle and bow radially outward. In one embodiment, the tubular  205  may include grooves  220  formed on an outer surface of the tubular  205 . The grooves  220  may be used to reduce the required force necessary to expand the tubular  205 . In another embodiment, the tubular  205  is a screen mesh and the bands  210  are configured to anchor the screen mesh in the borehole. 
         [0041]      FIG. 8  is a view of an anchor  250  having multiple anchor portions  230 A- 230 F. Each anchor portion  230 A- 230 F includes bands  240 . Each band  240  is attached to a tubular  235  at connection points  245 A,  245 B. The anchor portions  230 A- 230 F are located between a fixed end  255  and a free end  260 . As the tubular  235  is radially expanded, the length of the tubular  235  is reduced between the fixed end  255  and the free end  260 , and thus the anchor portions  230 A- 230 F bow radially outward. As shown, the amount of expansion that occurs in each anchor portion  230 A- 230 F decreases the further away the anchor portion is from the free end  260 . In other words, anchor portion  230 A bows radially outward further than anchor portion  230 F. 
         [0042]      FIG. 9A  is a view illustrating an anchor  275  prior to expansion, and  FIG. 9B  is a view illustrating the anchor portion  275  after expansion. As shown, the anchor  275  includes bands  290 . Each band  290  is attached to a tubular  285  at connection points  295 A,  295 B. The bands  290  are disposed on the tubular  285  at an angle relative to a longitudinal axis of the tubular  285 . In one embodiment, the band  290  is offset at an angle of 10 degrees relative to a longitudinal axis of the tubular  285 . As shown in  FIG. 9B , the bands  290  are configured to buckle and bow radially outward as the tubular  285  is expanded. 
         [0043]      FIG. 10A  is a view illustrating an anchor  300  prior to expansion, and  FIG. 10B  is a view illustrating the anchor portion  300  expanded into contact with the borehole  10 . As shown, the anchor  300  includes bands  310 . Each band  310  includes grip members  320  on an outer surface of the band  310 . The grip members  320  are configured to grip the borehole  10  upon expansion of the band  310 . The grip members  320  may be abrasive coating, tungsten carbide inserts, knurled edges or another friction enhancing method known in the art. Each band  310  is attached to a tubular  305  at connection points  315 A,  315 B. As shown in  FIG. 10B , the bands  310  are configured to buckle and bow radially outward into contact with the borehole  10  as the tubular  305  is expanded. 
         [0044]      FIG. 11  is a view illustrating an anchor  350  with dual bands. As shown, the anchor  350  includes bands  340 ,  345 . Each band  340  is attached to a tubular  335  at connection points  225 A,  225 B, and each band  345  is attached to the tubular  335  at connection points  330 A,  330 B. As illustrated, the band  340  is disposed on top of band  345  such that the bands  340 ,  345  make an “X” configuration. Similar to other embodiments, the bands  340 ,  345  are configured to buckle and bow radially outward as the tubular  335  is expanded. 
         [0045]      FIGS. 11A-11D  illustrate different configurations of the bands  340 ,  345  shown in  FIG. 11 . It should be understood, however, that the bands  340 ,  345  are not limited to the configurations illustrated in  FIG. 11A-11D . Rather, other configurations may be devised without departing from principles of the present invention.  FIG. 11A  illustrates a configuration of the bands  340 ,  345  in which the band  345  is disposed on top of the band  340 . As such, the band  345  may limit the amount the band  340  bows radially outward. For instance, the band  345  may cause the band  340  to be configured as the band  155  shown in  FIG. 5  (or  FIG. 6  illustrated by L 3 ) in which the band  340  includes multiple contact points. Alternatively, the band  340  may be used to apply a radial force on the band  345  to enhance the amount the band  345  bows radially outward and thus increase the engagement between the anchor and the surrounding borehole. The bands  340 ,  345  may be made of different material or the bands  340 ,  345  may have different thickness which may affect the amount the bands  340 ,  345  bow radially outward. 
         [0046]    As shown in  FIG. 11B , the lengths of the bands  340 ,  345  may be different. For instance, the band  345  may have a length L 1  and the band  340  may have a length L 2 . In the embodiment illustrated, the length L 1  is shorter than the length L 2 . As set forth herein, the length of the band is related to the amount the band will bow due to shrinkage in the tubular. Thus, the band  345  may not bow as much due to the length L 1 . Additionally, the band  345  is disposed on top of the band  340 , which will limit the amount the band  340  bows radially outward or cause the band  340  to be configured as the band  155  shown in  FIG. 5  (or  FIG. 6  under L 3 ) in which the band  340  includes multiple contact points. Alternatively, the length of the band  340  may be selected to cause the band  340  to apply a radial force on the band  345  to enhance the amount the band  345  bows radially outward and thus increase the engagement between the anchor and the surrounding borehole. In other embodiments, the band  345  is longer than the band  340 , which may allow the band  345  to bow out further than the band  340 . 
         [0047]      FIG. 11C  illustrates the bands  340 ,  345  having an overlap length L 3 . The band  345  may be disposed on top of the band  340  at an angle α. The overlap length L 3  is increased as the angle α is decreased. For instance, the angle α may be equal to or slightly greater than 0 degrees to have a substantially complete overlap of the bands  345 ,  340 . The opposite holds true: the overlap length L 3  is decreased as the angle α is increased. For instance, the angle α may be equal to or slightly greater (or slightly less) than 90 degrees to have minimal overlap of the bands  345 ,  340 . The overlap length L 3  of the band  345  may be used to control the amount the band  340  bows radially outward. 
         [0048]      FIG. 11D  illustrates the bands  340 ,  345  disposed at an angle β relative to a longitudinal axis  365  of the tubular. As set forth herein, the shrinkage of the tubular that occurs during the expansion operation is typically along the longitudinal axis  365  of the tubular. Thus, the angle β of the bands  340 ,  345  relative to the longitudinal axis  365  will affect the amount of expansion of the bands  340 ,  345 . For instance, if the angle β is close to 0 degrees, then the band  340  will be substantially in line with the longitudinal axis  365  and thus experience a large percentage of the shrinkage of the tubular and bow radially outward. At the same time, the band  345  will be substantially perpendicular to the longitudinal axis  365  of the tubular and thus experience a small percentage of the shrinkage of the tubular, which may limit the amount the band  345  bows radially outward. If the angle β is close to 90 degrees, then the band  340  will be substantially perpendicular to the longitudinal axis  365  and thus experience a small percentage of the shrinkage of the tubular, which may limit the amount the band  340  will bow outward. At the same time, the band  345  will be substantially in line with the longitudinal axis  365  and thus experience a large percentage of the shrinkage of the tubular and bow radially outward. The amount the bands  340 , 345  bow radially outward may be controlled by a combination of length as described in  FIG. 11B , amount of overlap as described in  FIG. 11C  and the angle relative to the longitudinal axis of the tubular as described in  FIG. 11D . 
         [0049]      FIG. 12  is a view illustrating an anchor  375  with a spiral band  390 . As shown, the anchor  375  includes band  390  that is attached to the tubular  385  in a spiral manner. The band  390  may be one continuous piece or several individual pieces. The band  390  may include any number of connection points  395 A,  395 B. Similar to other embodiments, the spiral band  390  is configured to buckle and bow radially outward as the tubular  385  is expanded. 
         [0050]      FIG. 13A  is a view illustrating an anchor  400  prior to expansion, and  FIG. 13B  is a view illustrating the anchor  400  after expansion. The anchor  400  may be used when the anchor  400  has a fixed point at each end. In this arrangement, an expansion portion  425  may be used to allow for shrinkage in the tubular  405 . More specifically, the tubular  405  has a first fixed point  420  and a second fixed point  430 . The first fixed point  420  may be the releasable engagement device (see  FIG. 1A ), and the second fixed point  430  may be due to differential sticking of the tubular  405  in the borehole or held by another releasable engagement device. As shown, the anchor  400  includes bands  410 . Each band  410  is attached to a tubular  405  at connection points  415 A,  415 B. The anchor  400  also includes the expansion portion  425  that is configured to expand along a longitudinal axis of the tubular  405  as the tubular  405  is radially expanded. The expansion portion  425  may be bellows (as shown) or a slip joint. As the tubular  405  is expanded, the expansion portion  425  elongates along the longitudinal axis of the tubular  405 , which causes the bands  410  to buckle and bow radially outward. 
         [0051]      FIG. 14  is a view illustrating an anchor  450  with a double helix band arrangement. As shown, the anchor  450  includes a first band  455  and a second band  460  that are attached to a tubular  465  in a double helix manner. Each band  455 ,  460  may be one continuous piece or several individual pieces. The bands  455 ,  460  may include any number of connection points. Similar to other embodiments, the bands  455 ,  460  are configured to bow radially outward as the length of the tubular  465  shrinks during the expansion operation. 
         [0052]      FIG. 15A  is a view illustrating an anchor  475  prior to expansion, and  FIG. 15B  is a view illustrating the anchor  475  after expansion. The anchor  475  includes band  485 , which is attached to a tubular  490  at connection points  490 A,  490 B. The anchor  475  further includes a biasing member  480  disposed between the band  485  and the tubular  490 . The biasing member  480  may be an elastomer member, a swelling elastomer, a spring, Bellville washers, a shape memory polymer, a shape memory metal, one or more bands substantially aligned with the band  485  similar to bands  340 ,  345  as described in  FIGS. 11A-11D  or any other known biasing member. The biasing member  480  is configured to apply a radial force on an inner surface of the band  485 , which may encourage the band  485  to bow radial outward during the expansion operation of the tubular  490 . The biasing member  480  is movable from a compressed position ( FIG. 15A ) to a less compressed position ( FIG. 15B ). More specifically, the biasing member  480  is compressed and placed between the band  485  and the tubular  490  when the anchor  475  is fabricated. During the expansion operation of the anchor  475 , the length of the tubular  490  shrinks, which causes the band  485  to bow radially outward. At the same time, the biasing member  480  applies a radial force on the inner surface of the band  485 , which also causes the band to bow radially outward. 
         [0053]      FIG. 16A  illustrates a view of an anchor  500  prior to expansion. The anchor  500  includes a band  510 , which may be made from thin strips of flexible material, such as metal or composite. The band  510  is attached to a tubular  505  at connection points  515 ,  520  along the longitudinal axis of the tubular  505 . As will be discussed herein, the connection point  520  is a releasable connection that is configured to release the connection between the band  510  and the tubular  505  at a predetermined time. 
         [0054]      FIG. 16B  illustrates a view of the anchor  500  after expansion. As shown, the band  485  is bowed radially outward. Similar to the other embodiments, the length of the tubular  490  shrinks during the expansion operation, which causes the band  485  to bow radially outward. As also shown in  FIG. 16B , the band  510  is still connected to the tubular  510  at the connection points  515 ,  520 . 
         [0055]      FIG. 16C  illustrates a view of the anchor  500  in contact with a borehole  525 . At a predetermined point, the connection point  520  is configured to release the connection between the band  510  and the tubular  505 , which allows an end portion of the band  510  to move radially outward into contact with the borehole  525 . In one embodiment, the connection point  520  releases due to a shear force that acts on the connection point  520  which is generated by the shrinkage of the tubular  505  upon expansion of the anchor  500 . The connection point  520  may be formed using spot welding, glue, releasable screws, shear pins or any other temporary connection members known in the art. After the connection point  520  is released, the end portion of the band  510  pivots around the connection point  515  until the end portion contacts the borehole  525 . The end portion may include gripping members or a coating that increases the friction between the end portion and the borehole  525 . Although  FIGS. 16A-16C  illustrate one band  510 , any number of bands may be used in the anchor  500  without departing from principles of the present invention. Additionally, the bands of the anchor  500  may be configured such that the release of the connection point may alternate with adjacent bands. In other words, the connection point  520  may release on one band and the connection point  515  may release the adjacent band. Further, another band may be located under the band  510  and include a releasable connection point that releases around the same time as the connection point  520  and thus resulting in two contact points with borehole  525 . Furthermore, other bands as set forth in  FIGS. 11A-11D  or a biasing member as set forth in  FIGS. 15A-15B  may be placed under the band  510  to encourage engagement of the band  485  with the borehole  525 . 
         [0056]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Summary:
The present invention generally relates to an apparatus and method for expanding an anchoring device in a borehole. In one aspect, an anchoring device is provided. The anchoring device includes an expandable tubular. The anchoring device further includes a plurality of bands disposed on an outer surface of the expandable tubular. Each band is attached to the tubular at a first connection point and a second connection point, wherein each band is configured to bow radially outward as the expandable tubular shortens in length in response to the expansion of the tubular. In a further aspect, a method of attaching an anchoring device in a borehole is provided.