Abstract:
A whipstock/billet anchor can be set in open hole such that one or more slips initially shift laterally near the lower end or below the whipstock/billet while the upper end reacts and gets pushed against the wellbore. Then with the top of the whipstock/billet against the wellbore another slip gets a bite to secure the whipstock/billet in a manner where the wellbore gives it some support near its upper end as a drill bit engages the whipstock/billet to make a lateral. Open and cased hole application is contemplated. The anchor also allows running in and supporting a tubular string below and a tool above with the further option of cocking the tool for better support before securing it.

Description:
FIELD OF THE INVENTION 
   The field of this invention is downhole anchor and more particularly anchors for supporting a whipstock/billet or aluminum kickoff plug and more particularly in open hole environments although cased hole applications are contemplated. 
   BACKGROUND OF THE INVENTION 
   Laterals are kicked off in an open hole well with a whipstock/billet/billet supported on an anchor. The whipstock/billet slide has an inclined face that can direct the gauged hole bit to start a lateral in the proper orientation, the aluminum billet is round with a pocket notched at the top to help start bi-center bits. Known orientation tools are used to insure the proper positioning of the whipstock/billet/billet face. The whipstock/billet, after being properly oriented is normally secured by an anchor assembly, open hole anchors in the past did not have a adjustable fulcrum point, this tool not only anchors the whipstock/billet/billet but also forces the top of the whipstock/billet/billet to the formation wall holding the whipstock/billet/billet secure in the desired direction. Typically the slips that are part of the anchor assembly are actuated to move radially outward. The slips are normally around the periphery of the anchor body and when actuated secure putting the anchor and attached whipstock/billet/billet in the center of a cylindrical wellbore. 
   In open hole applications the slips of the anchor bite into the formation. When anchors in the past were actuated, for example in open hole, the upper end of the whipstock/billet/billet was centered in the surrounding wellbore. When the drill bit was advanced to drill the lateral its interaction with the top of the whipstock/billet/billet that was unsupported by the surrounding well bore can cause vibration on the anchor slips causing them lose the grip on formation. As a result the whipstock/billet/billet was without support and could slip down the well bore. At that point drilling had to stop a sidetrack has to be done above the whipstock/billet/billet process repeated, or the well was plugged back to a kickoff point with cement this adds additional time and incremental increase to the drilling cost. This proved to be troublesome in the past particularly in open hole applications. 
     FIGS. 1 and 2  illustrate the problem with the prior designs.  FIG. 1  shows a whipstock/billet  10  without the running string that would normally deliver it and help set the anchor  12  that is below it.  FIG. 1  illustrates a vertical bore  14  but the same result will occur in a deviated bore. An open hole  14  is illustrated as opposed to a cased hole. The anchor  12  has upper slips  16  and lower slips  18  that are disposed around the outer periphery and generally in a symmetrical manner. The gripper teeth  20  and  24  have opposed orientations to hold the whipstock/billet  10  in wellbore  14  against applied forces that may come in opposed directions. When the setting tool (not shown) is actuated to set the anchor  12  the slips  16  and  18  tend to center the whipstock/billet  10  in the wellbore  14  as indicated by the annular gap  26  shown in  FIG. 2  representing the set position. One reason this occurs is that the slips  16  and  18  are close to each other and move out at the same rates. Those skilled in the art will appreciate that a passage  28  is used for actuation of anchor  12  and after actuation leaves a passage that can provide access to the wellbore below the whipstock/billet  10 . 
   The problem with this design is that the whipstock/billet is a very long and slender structure that is subjected to complex loading when engaged by a rotating bit. When centered in a wellbore it has no lateral support and acts akin to a cantilevered beam subjected to torsion and lateral loads. As a result, grip failures have occurred in the past. 
   The present invention addresses the issue with a grip system with offset grippers that initially push in a given direction laterally below a whipstock/billet so as to cant or cock the opposite end of the whipstock/billet against the wellbore whereupon that position is then locked in by another set of slips spaced from the initial slip or slips vertically as well as circumferentially, in the preferred embodiment. Additionally, the anchor of the present invention can support a downhole tool above and a tubular string below and be actuated to support both while also allowing fluid communication through the tool, such as a whipstock/billet or a billet, to the tubular string below. These and other aspects of the invention will be readily appreciated by those skilled in the art from a review of the description of the preferred embodiment, the drawings and the claims which appear below. 
   SUMMARY OF THE INVENTION 
   A whipstock/billet anchor can be set in open hole such that one or more slips initially shift laterally near the lower end or below the whipstock/billet/billet while the upper end reacts and gets pushed against the wellbore. Then with the top of the whipstock/billet/billet against the wellbore another slip gets a bite to secure the whipstock/billet in a manner where the wellbore gives it full support at the upper end as a drill bit engages the whipstock/billet/billet to make a lateral. Open and cased hole application is contemplated. The anchor also allows running in and supporting a tubular string below and a tool above with the further sidetrack options. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a prior art design anchor in the run in configuration; 
       FIG. 2  is the anchor of  FIG. 1  in the set position showing the whipstock/billet centered in a wellbore; 
       FIG. 3  shows one type of whipstock/billet with a set anchor of the present invention and support the whipstock/billet gets from the wellbore as well as a liner string supported below; 
       FIG. 4  is the same view of  FIG. 3  with a billet type whipstock/billet; 
       FIG. 5  is a section view of the slip assembly for the anchor shown in the run in position; 
       FIG. 6  is the view of  FIG. 5  showing the slips starting to come out; and 
       FIG. 7  shows the slips from  FIG. 6  now in full extension. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The overall assembly is best seen in  FIG. 3 . There a whipstock/billet  30  has a tapered face  32  and a through passage  34  through which a setting tool (not shown) is initially extending for setting the anchor  36  in borehole  38 . Anchor  36  preferably has lower slip sets  40  of which only one is shown and at least one upper slip set  42 . Preferably when there are two slip sets  40  and an upper slip set  42  the circumferential spacing among them is preferably about 120 degrees. This puts the lower slip sets  40  on one side of the anchor  36  with the upper slip set  42  on the other. In fact the angles of separation can vary with the idea being that the lower slips sets being on one half of the circumference and the upper slip sets on the other. The reason for this will be explained below. 
   Looking again at  FIG. 3 , showing the anchor  36  now set, it can be seen that the upper end  44  of the whipstock/billet  30  is pushed against the borehole  38 . This happens when lower slip sets  40  push the lower end  46  of the whipstock/billet  30  to the right which in turn forces the upper end  44  of the whipstock/billet  30  toward the left. After that position is assumed, the upper slip set  42  still has room to move out radially and contact the borehole  38  to in effect lock the whipstock/billet  30  in the cocked position shown in  FIGS. 3 and 4 . The only difference between  FIGS. 3 and 4  is the style of whipstock/billet that is used. 
   In another feature of the present invention, a liner  48  can be run in with the anchor  36  for support in the wellbore  38  at the same time the whipstock/billet  30  is set into position. As with all these applications the use of the present invention can be in open hole or cased hole. 
   Referring now to  FIGS. 5-7  the workings of the anchor assembly  50  will be described. What is shown in  FIGS. 5-7  is the lower end  52  of the whipstock/billet W. What is not shown is the known setting tool that holds down the top of the whipstock/billet while a rod also not shown extends through a lower end  54  of hollow mandrel  56 . While the whipstock/billet W is held from coming uphole by the known setting tool the rod that extends to lower end  54  gets pulled up until a predetermined force is applied at which time a nut on the rod shears off and the setting tool is removed. This setting tool is omitted for drawing clarity and because its operation is well known to those skilled in the art. Instead what will be described is the operation of the anchor assembly  58  as the setting tool is actuated. 
   The setting tool (not shown) acts to push up on lower sub  60 , which in turn pushes on body  62 . Although only one inclined dovetail  64  is illustrated, there can be more than one and at least two that are circumferentially offset are preferred. Dovetail  64  is located axially below pivot point  66 . In the preferred embodiment, the pivot point  66  is situated circumferentially opposite the dovetails  64  so that for example if there are two dovetails  64  and one pivot point  66  an angular spacing of about 120 degrees about the circumference put the two dovetails  64  on an opposite side from the pivot point  66 . Why this matters will be explained below. 
   An upper body  68  is secured to the whipstock/billet W and does not move when the setting tool operates. Upper body  68  features a dovetail  70  on which rides up upper slip  72 . Upper slip  72  is pinned to link  74  at pin  76 . Link  74  is pinned at pivot point  66 . Circumferentially on the other side from pivot point  66  is pivot point  78  which is axially higher. Link  80  is pinned to pivot point  78  and slip  82  is pinned at  84  to link  80 . 
   The operation of the anchor assembly  50  will now be described. As the lower sub  60  is pushed up by the setting tool the dovetails  64  being on the same side circumferentially, when two or more are used, rise and preferentially move the slips  82  radially outwardly. While slip or slips  72  move radially out at the same time because dovetail  64  and pivot  66  move in tandem with body  62 , the fact remains that slips  82  will reach the wellbore wall first because they are lower down the hole than slips  72  and depending on the wellbore orientation they present the heavy side of the assembly that due to gravity will seek the wellbore wall. It should be noted that even in a horizontal run the slips  82  can be oriented toward the high side of the lateral or the low side. When slips  82  are oriented toward the high side of a horizontal lateral they will still be lower and heavier and still cock the whipstock/billet W lower end  52  to the bottom of the horizontal run so that the whipstock/billet tip  44  shown in  FIGS. 3 and 4  will go to the opposite or high side of the lateral at which time the slip  72  will get a bite opposite slip or slips  82  to lock in the cocked position of the whipstock/billet W. This in turn allows the whipstock/billet to get more support in the cased or open hole as its top  44  is firmly against the wellbore. 
   In general, the operation of the anchor  50  is to use axially offsetting slip assemblies disposed on opposed sides circumferentially. The lower slip or slips engage the wellbore first and cock the whipstock/billet or other downhole tool that is connected to the anchor  50 . The cocking, in the case of a whipstock/billet W, puts the upper end hard against the wellbore for support once drilling or milling starts. To help retain that cocked position an upper slip or slips  72  gets a bite on the wellbore to hold the cocked position. With the whipstock/billet thus locked in a cocked position by slips at different elevations with different circumferential orientations, the whipstock/billet W is less likely to break loose at anchor  50  because it has wellbore support and is held in that position. 
     FIGS. 6 and 7  illustrate how the setting tool makes the slips  82  and  72  come out by pushing on lower sub  60 . 
   Preferably there are more lower slips  82  than upper slips  72  with their distribution being such as to shift the center of gravity of the anchor  50  off of the longitudinal axis. This weight and position distribution of the slips assists in getting that cocking motion going and allows the slips  82  to in turn get the whipstock/billet top  44  cocked in an opposite direction for a better lock of the cocked position when slip  72  then gets a bite. 
   Those skilled in the art will appreciate that the present invention works differently than prior through tubing whipstock/billets that have a linkage mounted slip on one side circumferentially and push the whipstock/billet body on the lower end opposite the slip up against the casing after being passed through tubing. In these designs, the whipstock/billet body is simply shoved over by an extending slip. In the present invention the whipstock/billet body is indeed shoved over by a lower slip or slips but the cocked position is then secured by an upper slip or slips making the locked position of the whipstock/billet more secure under the load of a mill or drill. 
   Those skilled in the art will appreciate that whether a whipstock/billet that is meant to divert a bit or mill or a billet that is intended to be partially chewed up in diverting a bit, is used the present invention presents a better way to secure them in open or cased hole and further allows the running in and supporting of a liner string at the same time. The liner can be solid or perforated and the present invention allows an anchor to be set that supports the liner and has the additional flexibility to properly support a whipstock/billet or billet or any other downhole tool. In the case of a whipstock/billet or billet, the anchor wedges the tool against the borehole and locks in that position with offset slips that in the preferred embodiment are axially and circumferentially offset. The liner  86  can be attached to body  62 , for example, as shown in  FIG. 5 . 
   While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the exemplified embodiments set forth herein but is to be limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.