Patent Abstract:
A self adjusting excluder sub includes a first subassembly; a second subassembly with respect to which the first subassembly is axially movable; and a support disposed at the second subassembly and when actuated being resiliently disposed against the first subassembly while being laterally movable relative to the first and second subassemblies jointly and method.

Full Description:
BACKGROUND 
       [0001]    Whipstocks are well known to the hydrocarbon industry as devices providing a hardened diverter face useful to cause a milling tool run into the downhole environment either behind (single trip) or after (multiple trips) the whipstock to track through a wall of a borehole whether that hole be cased or open. The ability to cause such “side tracks” is important in that it is the basis for multilateral wellbore technology. Multilateral technology has dramatically enhanced the ability of operators to recover hydrocarbon materials from subsurface formations by accessing multiple reservoir areas from a single surface location. This reduces the cost involved with recovering the hydrocarbon materials and in addition, reduces the footprint of a well system at the surface. 
         [0002]    Inherent in the milling of either a casing or the formation or both is the production of debris. Debris in the wellbore is undesirable because it tends to cause malfunctions in well equipment resulting in delays and additional costs in running the well operation. In order to avoid debris falling down the wellbore, debris barrier devices have been employed by the industry. Unfortunately, an effective debris barrier has eluded the art. 
       SUMMARY 
       [0003]    A self adjusting debris excluder sub includes a cup; a cone configured to bias the cup to a sealed position; and a support having an end supporting the cup and an end mounted in the sub to allow lateral movement of the end that supports the cup. 
         [0004]    A self adjusting excluder sub includes a first subassembly; a second subassembly with respect to which the first subassembly is axially movable; and a support disposed at the second subassembly and when actuated being resiliently disposed against the first subassembly while being laterally movable relative to the first and second subassemblies jointly. 
         [0005]    A debris excluder includes a cup having a first perimetrical dimension smaller than a tubular member in which it is intended to be run; and a cone in operable communication with the cup to selectively increase the cup to a second perimetrical dimension. 
         [0006]    A method for milling a window while excluding debris includes shifting a second subassembly relative to a first subassembly in a self adjusting excluder sub; and expanding a cup of the first subassembly with a cone of the second subassembly, the cone mounted on a support articulated from the second assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0008]      FIG. 1  is a cross-sectional view of a debris catcher for use with a whipstock as disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    It has been discovered by the inventors hereof that whipstock debris catchers of the prior art have been thwarted by properties inherent in the whipstock assembly. Because whipstock assemblies are pushed to a side of the primary borehole in which they are anchored opposite of the side of the borehole at which an exit is being milled by the milling tool, debris excluding devices of the prior art can fail to catch all the debris. Further, because the greatest concentration of debris is generated on the side of the whipstock that is being pushed away from the borehole wall, generally, therefore also being the side of the whipstock where a prior art debris catcher is most vulnerable, debris generally escapes capture. 
         [0010]    Referring to  FIG. 1 , a debris catcher arrangement  10  is illustrated that accommodates the lateral movement of the whipstock inherent in milling the casing or open hole wall. The arrangement  10  includes a bottom sub  12  that is configured to be received in an anchor of the prior art (not shown). The bottom sub  12  includes at least one, and as shown, a series of ports  14  to prevent a swabbing effect of the tool as it is tripped into or out of the hole. A downhole end of the bottom sub  12  is, as noted above, configured for receipt by a conventional anchor (not shown) in the wellbore. This, then, is also the pivot point about which the arrangement  10  and a whipstock (not shown) attached thereto (at a top sub introduced later herein) pivot when the whipstock is urged laterally during a milling operation as discussed above. The bottom sub  12  is attached at an uphole end  16  thereof to each of a collet  18 , a mandrel  20  and a spring retainer  22 . The collet and the spring retainer are fixedly attached to the bottom sub  12  at affixation  24  and  26 , respectively, while the mandrel  20  is axially slidably received at the bottom sub  12 . A torque transmissive coupling  28  is provided between the mandrel and the bottom sub for two specific reasons. The first is to allow torque generated as a byproduct of the milling operation to be borne through the arrangement to the anchor (not shown) so that the whipstock (not shown) will remain in the orientation in which it is intended to exist. The second is to provide a stroke length that is designed into the tool and ensures that a fluid bypass closing operation (discussed more fully hereunder) takes place reliably. In one embodiment, the stroke length is about 1.5 inches although it is to be appreciated that other lengths can be designed in for particular applications. 
         [0011]    The collet  18  cooperates with the mandrel  20  through a resiliency of the collet occasioned by one or more slits  30  therein, a series of slits  30  being illustrated. The collet  18  includes a profile  32  thereon complementarily shaped to a recess  34  in the mandrel  20 . The profile  32  is disposed downhole of the recess  34  during run in and prior to actuation of the debris seal arrangement  10  and resides in the recess  34  after such actuation. It is to be appreciated that it is the mandrel that moves downhole rather than the collet moving uphole during actuation. The collet  18  is axially fixed. In one embodiment, the collet  18  is configured to provide a deflection force of about 20,000 pounds. This means that the collet can be snapped in for actuation and snapped out for deactivation of the arrangement  10  by using a set down weight of about 20,000 or a pull of about 20,000 pounds. Other amounts of force can be designed in. In the embodiment discussed, this rating is selected to be between the typical setting range of about 12,000 to about 15,000 pounds for the anchor (not shown) and about 40,000 pounds for the milling bit to whipstock release member (not shown but well known commercially available configuration). This will ensure that the arrangement  10  actuates at the appropriate time. In addition, it is to be appreciated that the collet as disclosed herein, in combination with the other components, disclosed results in an arrangement that does not utilize one time release members such as shear screws thereby enabling the arrangement to be snapped in/snapped out numerous times if necessary or desired for some reason. Debris excluding configurations of the prior art do not possess such capability. 
         [0012]    Consequent movement of the mandrel  20 , at least one opening  36  or a series of openings  36  as illustrated, are blocked during the actuation phase of the arrangement  10 . The openings  36  are necessary to allow fluid to flow from an annular area of the wellbore  40  through the arrangement  10  and through ports  14  back to the annular area when the arrangement is being run in or retrieved from the hole, a fluid bypass arrangement. After the arrangement  10  is landed in the anchor (not shown), blocking the openings  36  closes a potential debris path. In order to ensure that the bypass is closed, the stroke of the mandrel must be a substantially fixed dimension. As noted above, in one embodiment, the length is 1.5 inches. Were the arrangement  10  to stop stroking the mandrel  20  prior to achieving the full design stroke (of for example 1.5 inches), the blocking of the bypass might well be ineffective leading to potential migration of debris through the arrangement  10 . As this would be contrary to the point of the arrangement  10 , it is undesirable. Therefore, it is important to achieve a full stroke. Potentially impeding the gratification of full stroke, however, is the relative unknown of the casing or open hole inside dimension. If the debris excluding arrangement encounters resistance to the stroke due to contact with the casing or open hole wall, the full stroke can be in jeopardy. To alleviate this potential occurrence, resiliency in the arrangement is also provided (discussed further hereunder). 
         [0013]    Also, consequent movement of mandrel  20 , a debris catch system  42  of the arrangement  10 , is actuated. The debris catch system  10  comprises a cup thimble  44  (through which openings  36  extend) fixedly attached to the mandrel  20 . A cup  46  is nested within the cup thimble  44  and further anchored to the mandrel at shoulder  48 . Cup  46  may be constructed of a number of different materials providing they have a debris exclusionary effect. Materials include but are not limited to a resilient material such as rubber or plastic, a wire brush comprising metal or other material capable of withstanding the environment in which it is intended to be deployed, etc. The material is to act as a debris catch with the casing or open hole wall to exclude debris from falling downhole of the arrangement  10  when actuated. In one embodiment as illustrated, the cup  46  is a frustoconical structure that grows in diametrical dimension in a downhole direction. This provides an advantage for retrieval of the arrangement  10  because debris cannot collect in the concavity defined by the frustocone. Such debris would interfere with dimensional reduction of the cup  46  when retrieving the arrangement  10 , an undesirable occurrence. Prior to actuation (including during run in) the system  42  is a clearance fit within the borehole so that the cup  46  does not experience significant wear during the run in and so that the tool avoids “float” in the bore related to too small of an annular space around the cup  46  for fluid to easily pass during the run in. 
         [0014]    Once the arrangement  10  is in place in the borehole, it is actuated whereby the cup  46  is radially displaced, to effect a debris catch. Displacement in one embodiment is by a cone  50 . The cone  50  is fixedly mounted upon a support  52 , for example, a sleeve as illustrated, which is itself disposed about the mandrel  20  but not in contact therewith. The cone  50  acts as a wedge against the cup  46  to cause the cup  46  to grow in outside dimension. The sleeve  52  is axially moveably mounted about the mandrel  20  with a clearance annulus  54 . Clearance annulus  54  is disposed between an inside dimension surface  56  of the sleeve  52  and an outside dimension surface  58  of the mandrel  20 . This annulus, provided within the arrangement  10 , is important in that it allows the cone  50  to remain relatively centralized in the borehole even when the whipstock (not shown) is urged off center thereby causing the arrangement  10  to pivot about the anchor point at a downhole end of the bottom sub  12 . The centralized position of the cone causes the cup  46  to be pushed into contact with the wall of the casing or open hole even though the whipstock is out of center. Because of the arrangement  10 , debris exclusion is enhanced. In one embodiment, the cone  50  is mounted at one axial end of the sleeve while the other axial end of the sleeve is mounted to the mandrel  20  allowing the end of the sleeve supporting the cone to move laterally relative to the arrangement  10 . 
         [0015]    Further to the foregoing, the sleeve  52  includes at a downhole end thereof a radially thickened section  60  with a stop surface  62 . The stop surface  62  is cooperable with a stop flange  64 . Sleeve  52  further includes an end  66  that is limited in movement by a shoulder  68  of mandrel  20 . Total axial movement of the sleeve  52  and therefore cone  50  is limited to the illustrated distance between end  66  and shoulder  68 . Promoting articulation of the sleeve  52  about its thickened section  60  is a ridge  70  which spaces the thickened section  60  of the sleeve from the mandrel  20  providing an articulation point. 
         [0016]    The cone  50  is biased by a resilient member  70 , such as a spring, as illustrated. The resilient member  70  is protected by a cover  72 . The bias drives the cone into the cup  46  in order to expand the same when the sleeve  52  is driven in a downhole direction by the movement of the arrangement  10 . Further, the member  70  serves another purpose for the arrangement  10  and that is to allow resiliency in the system  42  when the cup  46  contacts the borehole wall prior to the mandrel fully stroking the designed in distance. For example then, assuming the cup  46  contacts the borehole wall early in the stroke of the mandrel, the mandrel will not be prevented from achieving a full stroke because the member  70  deflects to facilitate full stroke of the mandrel. In other words, because after the cup  46  contacts the borehole wall, the cone cannot significantly more move into cup  46 , something has to give or the mandrel will stop its stroke. What gives in the illustrated embodiment is the member  70  to allow the rest of the stroke to occur. It is to further be appreciated that while no seal is shown at the bypass, one could easily be created by providing seals such as o-rings on the collet straddling the openings  36 . Because the arrangement is primarily a debris catcher, sealing is unnecessary. It is well to note, however, the sealing potential of the arrangement  10  if needed for a particular application. 
         [0017]    Initial downhole movement of the arrangement comprises a downhole motion of a first sub assembly of the arrangement  10  comprising the mandrel  20 , cup  46 , cup thimble  44 , a top sub  62  (all of which are fixed relative to each other) and other components (not shown) attached uphole of the components illustrated relative to a second subassembly comprising the bottom sub  12 , the collet  18 , the spring retainer  22 , the sleeve  52 , the cone  50  and the resilient member  70 . When the mandrel moves downhole, the collet  18  deflects and moves the profile  32  into the recess  34 . Due to the retainer  22  being fixedly attached to bottom sub  12 , the resilient member  60  cannot move downhole but rather is compressed axially both facilitating stroke for the mandrel  20 , as noted above and resulting in a rebound force that is used to force the cup  46  to open. The rebound force facilitates the maintenance of the cup  46  in a position to effectively exclude debris even when the arrangement  10  is pivoted out of position due to the whipstock being urged off center into a wall of the borehole opposite the exit window being milled. 
         [0018]    While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.

Technology Classification (CPC): 4