Abstract:
A through tubing retrievable whipstock and installation method is disclosed. In the preferred embodiment, a plurality of anchor links pivot at one end and have wickers on an opposed rounded end. The links are configured to deliver an optimum contact angle with respect to the longitudinal axis of the whipstock in a variety of casing sizes and weights. A lock ring system holds the set position and the upper end is hinged and biased to stay out of the way of the mill or mills and yet be easy to engage by a retrieving tool.

Description:
PRIORITY INFORMATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/329,932 on Oct. 17, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The field of this invention is through tubing retrievable whipstocks, which can be set in the hole below the tubing, preferably in casing of various sizes.  
         BACKGROUND OF THE INVENTION  
         [0003]    The ability to set a whipstock through tubing for milling a window for a lateral is a great time saver. The tubing doesn&#39;t need to be pulled and the resultant time saving translates into substantial cost savings. Various designs of through-tubing whipstocks have been developed, the earlier ones not being retrievable and the later ones incorporating a retrievable feature. U.S. Pat. No. 5,909,770 entitled Retrievable Whipstock uses a pair of pivoting links each connected to a common tension bar, which is pulled up relative to the whipstock body by a known setting tool. The set is held by wedges, which must be undermined to release the whipstock. The tension bar has wickers to dig into the casing below the tubing. In this tool, the best results were obtainable if the angle the pivoting links made with the longitudinal axis of the whipstock was less than about 60-70 degrees. The problem with the tool arose if it were to be used in different size casing. Even casing of the same size but different wall thickness could allow for link rotation in excess of the desired maximum. In response to this issue either adjustable length links were used which had to be correctly set for the anticipated casing condition at the anticipated whipstock location or spare links of the desired length had to be on hand and installed before running in the hole. This turned out to be inconvenient and somewhat imprecise. Accordingly one of the objectives of the present invention is to allow a single tool to set in a variety of internal diameters, with variations in excess of 1.5 inches. Additionally, a simply designed and reliable locking and release system is another objective of the present invention. Furthermore, a more reliable structure to facilitate retrieval while being maintained out of the way of the mill or mills is another objective of the present invention. To accomplish these objectives, some of the features of the present invention comprise specially shaped anchoring links, which anchor through edge wickers. The anchoring links are rotated into position by a tension rod system whose set position is secured with a simple and reliable locking ring system, which is selectively released. The upper end is hinged and biased to stay out of harms way during milling. These and other features of the present invention will become more readily apparent to one skilled in the art from a review of the detailed description of the preferred embodiment, which appears below.  
           [0004]    Relevant whipstock patents include U.S. Pat. Nos.: 5,494,111; 5,195,591; 5,944,101; 5,860,474; 5,423,387; 6,167,961; Re 36,526; 5,796,167; 5,647,437; 5,595,247; 5,566,762; 5,467,819; 5,193,620; 5,647,436; 5,836,387. Also relevant are Baker Oil Tools Products H15050; H15076; H15043 and the TIW TTR Window Milling System and Weatherford Enterra&#39;s Thru-Tubing Window Milling System featuring the Pawl Locking System.  
         SUMMARY OF THE INVENTION  
         [0005]    A through tubing retrievable whipstock and installation method is disclosed. In the preferred embodiment, a plurality of anchor links pivot at one end and have wickers on an opposed rounded end. The links are configured to deliver an optimum contact angle with respect to the longitudinal axis of the whipstock in a variety of casing sizes and weights. A lock ring system holds the set position and the upper end is hinged and biased to stay out of the way of the mill or mills and yet be easy to engage by a retrieving tool. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIGS. 1 a - 1   d  are an elevation view in section of the tool in the run in position;  
         [0007]    [0007]FIGS. 2 a - 2   d  are the view of the tool from FIGS. 1 a - d  but in the set position;  
         [0008]    [0008]FIGS. 3 a - 3   d  show and alternative set position rotated 180 degrees from FIGS. 2 a - 2   d;    
         [0009]    [0009]FIGS. 4 a - 4   d  show the tool in the released position;  
         [0010]    [0010]FIG. 5 is a section through lines  5 - 5  in FIG. 1 a;    
         [0011]    [0011]FIG. 5 is a section through lines  6 - 6  in FIG. 1 a;    
         [0012]    [0012]FIG. 7 is a detailed view of the hinged top shown in section;  
         [0013]    [0013]FIG. 7 a  is a perspective view of the hinged top segment shown in FIG. 7.  
         [0014]    [0014]FIG. 8 is a view through section lines  8 - 8  of FIG. 7;  
         [0015]    [0015]FIG. 9 is a section view of the locking system in the run in position;  
         [0016]    [0016]FIG. 10 is the view of FIG. 9 with the tool in the set position; and  
         [0017]    [0017]FIG. 11 is the view of FIG. 10 with the tool in the released position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Referring to FIGS. 1 a - 1   d,  the whipstock  10  has a lower end  12 . Anchor links  14  and  16  are respectively pinned at pins  18  and  20 . In the run in position shown in FIG. 1 d,  being disposed in the recess  22  of whipstock  10  protects the links  14  and  16 . This allows whipstock  10  to be advanced through tubing (not shown) without risk of snagging the links  18  and  20 , which could result in a premature anchoring of the whipstock  10 . Links  14  and  16  are respectively pinned at pins  24  and  26  to tension rod  28 . Pins  14  and  16  are disposed on a common centerline  30  which is offset from centerline  32  on which are located pins  24  and  26 . When an uphole pull is exerted on tension rod  28  while holding the whipstock  10  fixed, this offset in centerlines  30  and  32 , creates a rotation of links  14  and  16  about their respective pin mounts  24  and  26 , as shown in FIG. 2 d.  Those skilled in the art will appreciate that the length of tension rod  28  may be adjustable. The location of the pins  24  and  26  on their respective links  14  and  16  can be altered. A greater or less number of links, such as  14  can be used. Links such as  14  or  16  can be individually actuated rather than actuated in tandem, although the tandem actuation takes fewer moving parts and is therefore more compact and will operate more reliably. Although the links  14  and  16  are shown to have an elongated shape, they can have other shapes and can be urged to the set position in equivalent ways to use of a tension rod  28 .  
         [0019]    Referring again to FIG. 2 d,  links  14  and  16  each respectively have a dog leg portion  34  and  36  which is has an offset in its longitudinal axis respectively from the upper portion  38  and  40 . Each dogleg portion has respectively a lower arcuate segment  42  and  44 , which can be its edge surface, and on which there is respectively a set of wickers  46  and  48 . Typically, a point of contact  50  will define dashed line  52 , which extends from a pivot pin such as  20 . It is desirable to keep the angle between dashed line  52  and centerline  30  in the preferred angle range of about 60-70 degrees. Since the whipstock  10  will be used in a variety of casing weights and even different sizes, it is possible to obtain the optimum angle between lines  52  and  30  for a range of casing sizes by controlling several variables. One is the radius of the arc on which the wickers  46  or  48  will contact the casing. Another variable is the length of a given link from its pin, such as  18  to its projected contact point  50  with the casing. Yet another variable, which is related to the overall link length, is the degree of offset from an upper portion such as  38  and a dogleg portion, such as  34 . When this geometry problem is solved, the optimum angle between lines  52  and  30  of about 60-70 degrees can be achieved with casing internal variations in different installations of 1.5 inches and more. For example, a single unit can be set in 7 inch casing weighing 39 pounds per foot to 7⅝ inch casing weighing 29.8 pounds per foot with no adjustments or part change-outs. An even broader range of casing sizes can be serviced with a single tool, without alteration. This flexibility makes the whipstock  10  more versatile and reduces the chance for slippage during window milling due to an insufficient grip. Those skilled in the art realize that casing condition at the point of support for the whipstock  10  can be variable. This makes it difficult to know the precise inside casing diameter at the fixation point. The rounded portions, such as  42 , on dogleg segment  34 , compensate for such variability to allow for the optimum grip using the preferred angular relationship between lines  30  and  52 .  
         [0020]    The structure and operation of the setting mechanism will now be described. The tension rod  28  extends along the whipstock  10  on its back side (i.e. opposite from where the milling will take place) and has wedges  54  and  56  connected to it. These wedges will ride on sloping surfaces  58  and  60  to cause rotation of links  14  and  16  when the tension rod  28  is pulled up relative to whipstock  10 , see FIGS. 2 b  and  2   c.  The upper end  61  of the tension rod  28  terminates in transfer block  62 (see FIG. 2 a ). A locking mandrel  64 (see FIGS. 2 a  and  9 ), which is simply a rod with ratchet teeth  66 , extends up-hole from transfer block  62 . Body lock ring  68  has internal serrations  70  and external serrations  72 . It is a longitudinally split ring, the split not being shown in FIG. 9. Locking sleeve  74  has internal serrations  76  and is also longitudinally split but the split is not shown in FIG. 9. Locking sleeve  74  is mounted over lock ring  68 . Body lock housing  78  is mounted over locking sleeve  74  (see FIGS. 2 a  and  9 ) and secures locking sleeve  74  to shoulder  80  on whipstock  10 . During setting, the transfer block  62  is urged uphole, taking with it locking mandrel  64  and tension rod  28 . Lock ring  68  is prevented from moving uphole because serrations  72  engage serrations  76 . However serrations  70  allow serrations  66  on locking mandrel  64  to ratchet up, but not back down. FIG. 10 shows the set and locked position.  
         [0021]    Release occurs when the body lock housing  78  is pulled up, undermining support for locking sleeve  74 . Locking sleeve  74  is substantially weaker than locking ring  68 . The released tension due to retraction of lock housing  78  forces locking sleeve  74  to open up radially because it has a longitudinal split. It could also simply fail by developing another longitudinal split. As shown in FIG. 11, the locking ring  68  merely stays with locking mandrel  64  as it moves downhole. Links  14  and  16  can now rotate back to the position of FIG. 1 d  immediately or upon upward movement of the whipstock  10  with a retrieving tool (not shown).  
         [0022]    This locking system is simple and reliable and releases more easily than prior lock systems, which used rotating lock dogs such as U.S. Pat. No. 5,909,770. The locking system is simple to actuate with a known setting tool as is illustrated in FIGS. 5 and 6. FIG. 5 illustrates that a known setting tool  82  is releasably attached to the transfer block  62  with a mechanism  84  which fails in shear after pulling up the transfer block  62 , while preventing whipstock  10  from moving uphole, until transfer block  62  can no longer move due to contact of links  14  and  16  with the casing (not shown).  
         [0023]    [0023]FIGS. 2 a  and  3   a  show that various orientations for the set position can be obtained. If the whipstock  10  is set in a horizontal lateral, the whipstock  10  can be anchored for a window to be milled looking up (FIG. 2 a ) or looking down (FIG. 3 a ) or any other position in between, using a known MWD tool to determine the whipstock orientation downhole from the surface.  
         [0024]    Another feature of the present invention is the hinged top segment  86  (see FIGS. 2 a  and  7 ). It is attached by a pin  88  extending through holes  90  (see FIG. 8) to mandrel  92 , which is in turn screwed to body lock housing  78 . Plungers  94  each biased by a spring  96  disposed in recess  98  exert a force offset from pin  88  so as to put a rotational force on top segment  86 . Again, if FIG. 2 a  is a horizontal lateral, plungers  94  keep the top segment down at the bottom to keep it out of harms way during milling. The springs  96  only offset the weight of the top segment  86  and beyond that apply a slight residual force to hold it out of the way of the mill. At the same time, the hinged upper segment is easy for the retrieving tool to pry up so that an upward force can be applied to top segment  86  to move up body lock housing  78  and effect the release as described above. In FIG. 3 a,  the biased top segment  86  is held from falling down into the path of the mill but not with so much force as to preclude the release tool from easily getting under top segment  86  to get the needed grip on it for the release of the whipstock  10 . Those skilled in the art will appreciate the difficulty in getting the release tool to grip the top of the whipstock  10 , if there were no hinged top segment  86 . The stiffness of the whipstock would hold the upper end to the casing wall with a sufficient force so as to potentially prevent the retrieving tool from getting it lifted off the casing wall to get under it for a grip. Those skilled in the art will appreciate that the hinged top segment  86  can be replaced with different connections or eliminated altogether in favor of a thinned portion near the upper end of the whipstock  10 , itself, to give the upper end the required flexibility.  
         [0025]    Those skilled in the art will now appreciate the various advantages of the present invention. The anchor system is usable in a range of casing sizes without adjustment. It can compensate for casing wear and allows the force to be retained radially, making the unit less susceptible to release from vibration or shock. Prior systems, which distributed the anchor force equally radially in all directions, had no mechanism for dealing with inside wall dimensional irregularities that arose from casing wear. Cement was squeezed past the anchor on those prior designs to beef up the holding force. Any window orientation can be accommodated with the aid of the hinged flexible upper segment. Links  14  and  16  provide progressive contact with a tooth profile that digs into the casing wall.  
         [0026]    While the preferred embodiment has been described above, those skilled in the art will appreciate that other mechanisms are contemplated to accomplish the task of this invention, whose scope is delimited by the claims appended below, properly interpreted for their literal and equivalent scope.