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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of co-pending U.S. Provisional Patent Application Ser. No. 60/658,506, filed on Mar. 4, 2005, which application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a downhole tool. More particularly, the invention relates to a downhole tool that can be actuated in multiple, separate ways. More particularly still, the invention relates to a downhole anchor that can be set either mechanically or hydraulically in casing of a variety of sizes and weights. 
     2. Description of the Related Art 
     When oil and gas wells are drilled, a bore hole is formed in the earth and typically lined with steel pipe that is cemented into place to prevent cave in and to facilitate the isolation of certain areas of the wellbore for the collection of hydrocarbons. Once the steel pipe or casing is cemented into place, the hydrocarbons are typically gathered using a smaller string of tubulars, called production tubing. Due to a variety of issues, including depletion of formations adjacent the wellbore and stuck tools and pipe that prevent continued use of the wellbore, it is often desirable to form another wellbore, not from the surface but from some location along the existing wellbore. This new, or lateral wellbore can be lined with pipe and hydrocarbons can then be collected along its length. It is not uncommon to have more than one lateral, or sidetracked wellbore extending from a single central or parent wellbore. 
     Initiating a new wellbore from a cased, central wellbore requires a hole or window be formed in the casing wall adjacent that location where the new wellbore will commence. Forming windows is typically done with the help of a whipstock which is a wedge-shaped member having a concave face that can “steer” a mill or cutter to a side of the casing where the window will be formed. Whipstocks and their use are well known and an example is shown in U.S. Pat. No. 6,464,002 owned by the same assignee as the present invention and that patent is incorporated by reference herein in its entirety. The whipstock may be run in by itself or to save a trip, the whipstock might be run in with the mill or cutter temporarily attached to its upper edge. In any case, the whipstock has to be anchored in the wellbore at its lower end to keep it in place and to resist the downward force placed upon it as the cutter moves along its length through the casing wall. 
     Various anchors are used with whipstocks and prior art anchors can be mechanically set or hydraulically set. Mechanical anchors include those that require a compressive force to shear a pin and permit the anchor to assume a second, set position. Mechanical anchors work well when the anchor is to be set at the bottom of a wellbore or when there is some type of restriction that has been placed in the wellbore, like a bridge plug. In those instances, there is a stationary surface available to use to generate the compressive force needed to set the mechanical anchor. In other instances, the anchor must be set at some point along the wellbore where there is no surface to act upon in order to create a compressive force. In these instances, the anchors can be set with pressurized fluid, but that requires a different apparatus and the type of anchor actually needed on a job is not always apparent in advance. 
     Because of the uncertainty of equipment needed to best form a window in a casing, there are instances in which the wrong type anchor is on site and delays are created as another more appropriate anchor is found. An additional problem relates to the fact that most prior art anchors offer little flexibility in the size casing in which they can operate. For example, prior art anchors with slip and cone arrangements are designed to increase their outer diameters minimally when they are set and only work properly when they are designed for the specific inner diameter casing in which they are used. Additionally, it is not uncommon to encounter a restriction in the form of garbage as even casing of a smaller inside diameter prior to reaching larger diameter casing where the anchor is to be set. Many prior art anchors that are small enough to fit through the restriction will not expand far enough to become properly set in the larger casing. 
     There is a need for an anchor that is adaptable to be operated either mechanically or hydraulically. There is a further need for an anchor that can be operated in casings of varying diameters. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide an anchor for a wellbore that is adaptable to be operated in at least two separate and distinct ways. In one embodiment, a whipstock anchor is provided that can be operated either mechanically or hydraulically. In another embodiment, the anchor is designed to be set in casing of various inner diameters, even after the unset anchor is run through restrictions. In a further embodiment, there is a method of forming a window in a casing well using the whipstock anchor of the present invention. 
     In another embodiment, an anchor for supporting a downhole tool in a wellbore comprises a first body and second body, the bodies slidably movable relative to each other to increase an outer diameter of the anchor in a set position; a biasing member disposed between the first body and the second body, the biasing member arranged to move the anchor from a run in position to the set position; and a triggering mechanism for initiating the movement of at least one of the bodies to the set position. In another embodiment, the triggering mechanism is readily adaptable to be operated either mechanically or hydraulically. 
     In yet another embodiment, a method of supporting a downhole tool in a wellbore comprises providing the downhole tool with an anchor, the anchor having a first body and second body, the bodies slidably movable relative to each other to increase an outer diameter of the anchor in a set position; a biasing member disposed between the first body and the second body, the biasing member arranged to move the anchor from a run in position to the set position; and a triggering mechanism for initiating the movement of at least one of the bodies to the set position. The method further comprises running the downhole tool and the anchor into the wellbore on a tubular string; activating the anchor, thereby causing the biasing member to move the second body relative to the first body; and setting the anchor in the wellbore. In another embodiment, the method includes supplying a compressive mechanical force to sufficient to cause a shearable connection to fail. Alternatively, a hydraulic force is applied to set the anchor. 
     In another embodiment, the anchor is hydraulically activated and mechanically set. 
     Embodiments of the anchor are suitable for use with any downhole tool requiring support in a wellbore, including, but not limited to, whipstock, packer, plugs, and a wellbore tubular 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a side, section view of a hydraulic version of the anchor of the present invention, shown in a run-in position. 
         FIG. 1A  is an enlarged view of the anchor of  FIG. 1 . 
         FIG. 2  is a side, section view of the anchor of  FIG. 1 , shown in a set position. 
         FIG. 2A  is a schematic view of the anchor and a whipstock shown in a set position. 
         FIG. 3  is a section view of a mechanical version of the anchor. 
         FIG. 4  is an isometric view of the anchor of  FIG. 3 . 
         FIG. 5  is a section view of the anchor along a line  5 - 5  of  FIG. 4 . 
         FIG. 6  is a schematic view of an embodiment of an anchor having dual slip bodies. 
         FIG. 7  is a schematic view of an embodiment of an anchor for setting a packer. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side, section view of a hydraulic version of an anchor of the present invention, shown in a run-in position. The anchor  100  includes an anchor body  105  which is essentially a wedge-shaped, semicircular member with a first surface  106  substantially parallel to the inner wall  200  of surrounding casing and an inner surface  107  having sides that are gradually sloped. The anchor body  105  is connected to a whipstock which is not shown but is typically located directly above the anchor  100 . A slip body  150  is somewhat of a mirror image of the anchor body  105  with inner and outer surfaces that are opposed to the surfaces of the anchor body  105 . The slip body  150  typically includes at least one slip member  160  and is substantially free-floating relative to the anchor body  105 . 
       FIG. 1A  is an enlarged view of the anchor  100  of  FIG. 1 . Due to a shoulder  165  formed at its upper end, the slip body  150  is movable relative to the anchor body  105  by a biasing member such as a compression spring  175 . Spring  175  is disposed between the anchor body  105  and the slip body  150  and is retained by retention members  176 , 177  at each end. The spring  175  acts to move the two bodies  105 , 150  relative to each other in order to set the anchor  100 , as will be shown and discussed herein. A shoulder  112  formed at a lower end of the anchor body  105  permits the anchor body  105  to be moved relative to the slip body  150  due to movement of the spring  175 . 
     As stated, the anchor  100  shown in  FIGS. 1-2  is operable hydraulically. Disposed between the anchor body  105  and the slip body  150  is a trigger assembly generally noted as  209 . The assembly  209  includes not only the compression spring  175  but also a locking mechanism to retain the spring  175  in its compressed, run-in position shown in  FIGS. 1 and 1A . As shown, the locking mechanism is hydraulically activated to release the spring  175 . The spring  175  remains compressed due to a set of collet fingers  201  which are housed within a groove  202  formed in retention member  176 . The fingers  201  are prevented from leaving the groove  202  by a shear piston  205  which supports the inner surface of the collet fingers  201  as shown in  FIG. 1A . The shear piston  205  is retained in its position relative to the collet fingers  201  by a frangible member such as shear pins  210  at its upper end that temporarily tie it to retention member  176 . In this respect, the trigger assembly  209  is only activated when a hydraulic force is applied and cannot be activated by a mechanical force. Advantageously, the anchor  100  cannot accidentally activate when it encounters an obstruction or is inadvertently dropped in the wellbore. In one embodiment, one or more shear pins  210  are circumferentially disposed. In another embodiment, one or more shear pins  210  are disposed axially relative to the each other. 
     At a lower end of the shear piston  205  is a seal piston  220  having a seal member  225  and a piston surface  230  at a lower end thereof. The piston surface  230  is in fluid communication with a fluid line  235  which is visible in  FIG. 1A  and typically runs upwards past the whipstock (not shown) to a tubular string that carries the whipstock and the anchor  100  into the wellbore. Operating a downhole tool with pressurized fluid through a fluid line that bypasses a whipstock is well known in the art and an example of such an arrangement is shown in U.S. Pat. No. 6,364,037 assigned to the same owner as the present application and that patent is incorporated by reference herein in its entirety. Alternatively, pressurized fluid may be supplied to the anchor in any suitable manner known to a person of ordinary skill in the art. 
       FIG. 2  is a side, section view of the anchor  100  of  FIG. 1 , shown in a set position. In this Figure, the compression spring  175  has been permitted to relax and in doing so has pulled the anchor body  105  and the slip body  150  towards each other along their sloped, inner surfaces. The result is an enlarged effective “outer diameter” that puts the slip member  160  in contact with the casing wall  200 , thereby fixing the anchor  100  in the wellbore. The design of the anchor  100  includes two important features. First, the anchor  100  will set at virtually any point along the length of its “throw” or at any point between its run-in position and that point where the compression spring  175  is essentially completely relaxed and the bodies  105 ,  150  can move no further along their respective surfaces. Secondly, (as is visible in  FIG. 4 ) the slip body  150  is formed with one or more tapered surfaces  308 ,  309 ,  310  (also referred to herein as “undercut”) at an end thereof. In one embodiment, the taper surfaces  308 ,  309 ,  310  begin at the slip member  160  and tapers inward. The surfaces are tapered to ensure the slip  160  contacts the casing wall  200  instead of the slip body  150  regardless of the relative positions of the anchor body  105  and slip body  150 . In  FIG. 1A , the slip body  150  is also provided with a tapered surface  108 . In another embodiment, the lower portion of the anchor body  105  also includes one or more sloped surfaces  109 . With the design disclosed herein, the anchor  100  can effectively operate with an increased diameter of as much as 30%. 
     In operation, the anchor  100  is used as follows. When the anchor  100  is at the location in the wellbore where it is to be set, pressurized fluid is introduced into fluid line  235  and onto the piston surface  230  of seal piston  220 . The pressurized fluid forces the piston  220  upwards and into contact with shear piston  205 . In turn, the shear force is exerted to the shear pins  210 . At a predetermined force, shear piston  205  causes the shear pins  210  to fail and the shear piston  205  moves out of contact with the collet fingers  201 , thereby permitting relative movement between the collet fingers  201  and retention member  176 . The retention member  176  is urged away from retention member  177  by the spring  175 . Initially, a sloped side surface of groove  202  causes the collet fingers to bend inward and move out of the groove  202  as the spring  175  moves the retention member  176  away. Thereafter, the expansion force of the spring  175  moves the slip body  150 , which is in contact with the retention member  176 , up the inner surface  107  of the anchor body  105 , thereby moving the slip body  150  outward into contact with the casing wall. During relative movement between the bodies  105 ,  150 , the undercut of the anchor body  105  prohibits the anchor body  105  from interfering with the slip body  150  pushing the slip member  160  outward. Also, the undercut of the slip body  150  becomes generally parallel with the casing wall  200 , which exposes more of the slip members  160  into contact with the casing wall  200 . The foregoing action increases the outer diameter of the anchor  100  until slip member  160  is in contact with casing wall  200 . Preferably, only the slip members  160  of the slip body  150  are in contact with casing wall  200 . In the preferred embodiment, a set down force is applied from the surface to the anchor  100  to fully set the anchor  100  in the casing. 
     After activation, the anchor  100  provides a stable, three point contact  160 ,  260 ,  270  with the casing wall  200  to support the whipstock  250 , as illustrated in  FIG. 2A . During activation, as the slip body  150  moves outward, the anchor  100  forces the whipstock  250  to pivot off its bottom end  260  and the whipstock tip  270  is forced into contact with the casing wall  200 . Thus, a three point contact is created between the slips  260 , pivot point  260 , and the whipstock tip  270 . This three point contact is particularly advantageous for performing low-side exit, i.e., a low side lateral. As shown in  FIG. 2A , due to the pivot action, the weight of the whipstock  250  is directed upwards. When the drill bit or mill is directed toward the casing wall  200  by the whipstock  250 , the weight of the whipstock  250  acting on the bit is significantly reduced, thereby facilitating the exit process. 
       FIG. 3  is a section view of the anchor  100  having a mechanical triggering mechanism. The availability of different triggering or actuation mechanism options while using identical or almost identical parts provides flexibility in choosing the proper actuation technique on site, if necessary. Also, the anchor  100  can be modified with very little effort and very few, if any, additional parts. In this manner, the anchor  100  is readily adaptable to operate either hydraulically or mechanically. In the mechanically operated embodiment, the shear piston  205  is removed along with the shear pins  210  that initially connects the shear pistons  205  to retention member  176 . While the seal piston  230  remains, it has no function when the anchor  100  is triggered mechanically. In place of the shear piston and pins, external shear pins are used that hold the anchor  100  in a set position until it is actuated downhole. While the anchor  100  can be used mechanically or hydraulically with the changes described herein, it will be understood that the anchor  100  could become effectively mechanical or hydraulic using a variety of modifications known to a person of ordinary skill in the art, and those modifications are all within the scope of this invention. 
       FIG. 4  is an isometric view of the anchor arranged with a mechanical triggering mechanism and includes a temporary connection between the two bodies  105 ,  150  in the form of two external shear pins  300 . Each external shear pin  300  extends through an aperture  301  formed in each body  105 ,  150  in an off-center fashion so that they do not penetrate the inner cavity of the anchor  100  where spring  175  is housed. 
       FIG. 5  is a section view of the anchor of  FIG. 4  along a line  5 - 5 . Visible are the external shear pins  300  extending between the bodies  105 ,  150  and fixing them relative to each other. Also visible in the Figure is the tongue and groove arrangement  305  that permits the bodies  105 ,  150  to move past each other as the anchor  100  is set. 
     In practice, the anchor of  FIGS. 3-5  are used as follows. The anchor  100  is transported into a wellbore at the end of a string of tubulars, usually with a mill temporarily attached between the string and an upper end of the whipstock. When the assembly reaches a predetermined depth, it is put into compression by contacting either a bottom of the hole or a bridge plug or some other restriction therebelow. At a predetermined compressive force, the shear pins  300  or other suitable trigger devices will fail and the device is triggered with the compression spring  175  operating to move the bodies  105 ,  150  relative to each other and to increase the outer diameter of the anchor  100  until the slips  160  contacts casing wall  200 . Thereafter, weight can be set down from the surface to further fix the anchor in the wellbore prior to operating the mill and forming the casing window. 
     In another embodiment, the anchor may include dual slip bodies as illustrated in  FIG. 6 . The anchor  400  includes a first anchor body  405  and a first slip body  450 . A second anchor body  425  and a second slip body  452  are disposed on the first slip body  450 . Slip members  460  are provided on the second slip body  452  for engagement with the casing  401 . In this respect, the effective outer diameter of the anchor  400  is further increased when the second slip body  452  is activated. In this manner, an even larger diameter tubular or wellbore may be engaged by the anchor. 
       FIG. 7  shows an embodiment of the anchor  500  used to set a packer  530  in a casing  501 . The packer  530  is run in on a tubular  535 , and the anchor  500  is attached to a lower portion of the tubular  535 . The packer  530  may comprise an elastomeric material such as rubber. The anchor  500  includes an anchor body  505  having at least two inclines for receiving complementary slip bodies  551 ,  552 . As the slip bodies  551 ,  552  move up their respective inclines, the front portion of the slip bodies  551 ,  552  contact and deform the packer  530  into contact with the casing  501 . In this manner, the anchor  500  may be used to simultaneously squeeze and set the packer  530 . It must be noted that the packer may be set using any anchor described herein. In this respect, after the packer is set, set down weight may be applied to compress the packer into sealing engagement with the casing wall. 
     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:
An anchor for a wellbore is adaptable to be operated in at least two separate and distinct ways. In one embodiment, a whipstock anchor is provided that can be operated either mechanically or hydraulically. In another embodiment, the anchor is designed to run through a restriction in a retracted position and thereafter expanded to position a wellbore tool in the wellbore. Preferably, the anchor is expandable to set in wellbores of various sizes and either cased or uncased.