Abstract:
A slip design has segments that move relatively axially before moving in tandem up a ramp for radial extension. Due to the fact of the relative movement the segments interlock due to their geometric configuration or their surface treatment such that at the conclusion of such relative movement the load carrying thickness is effectively increased. The extended position minimizes radial extension of the slips for a smaller tool drift dimension while still allowing the needed radial extension and actually extending the radial reach of the slip assembly. The segment can have triangular or trapezoidal tapered interfaces that provide bearing areas between slip segments and adjacent spacer segment. Alternatively, the slips segments can have opposing wickers so that after riding up an underlying support member can interact with that member for load transfer. The supporting members can also be secured to an underlying mandrel for further load transfer.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is anchoring slips to support subterranean tools at desired locations and more particularly slip designs that have a reduced thickness for minimizing drift dimension for running in and increased interacting components for enhanced load capacity when set. 
       BACKGROUND OF THE INVENTION 
       [0002]    As the temperatures and pressures of well completions continue to increase, the hanging performance ratings for liner hangers and hold down slips will have to be improved to meet customer requirements and stay competitive in the high pressure high temperature market. One area of improvement for these anchoring systems is to improve the hanging capacity of the slip. Current liner hanger and hold down slips are machined as a single component resulting in a constant slip thickness. The slip thickness dictates the amount of radial overlap (bearing area) between the slip and slip seat when the slips are set downhole. Thus, the slip thickness limits the hanging performance of the anchor system. The slip thickness is limited by the drift requirements of the wellbore and by the body outside diameter needed to meet the pressure and tensile ratings. This prevents the improvement of hanging performance by simply increasing slip thickness. To improve the hanging performance of the slips, the proposed invention comprises a novel slip design that allows the effective slip thickness to be increased down hole. The increased effective thickness will increase the available bearing area improving the hanging performance of the slip. The simplest embodiment is a segmented slip design. Here the slip is comprised of multiple segments whose thickness meets the drift requirements when retracted for running in the hole, and when the down hole position is reached the effective thickness is increased by compressing the segments together. In addition to improving the hanging capacity, the proposed invention will allow for greater radial expansion of the slips. 
         [0003]    In the past some of the slip designs have tried to extend the reach of a slip by using a combination of ramps as illustrated in U.S. Pat. Nos. 3,420,306 and 7,431,096. However, simply sliding a slip on a plurality of slopes to get enhanced radial extension does not increase the slip holding capacity as the ramps are not interlocking to function as a unitary structure so that the effective thickness of the slip itself is not effectively increased for additional carrying capacity. A traditional slip moving up a ramp is illustrated in U.S. Pat. No. 3,530,934. 
         [0004]    Those skilled in the art will appreciate that the slip design of the present invention allows the slip assembly to articulate in a manner where the segments overlap each other while interlocking in a manner to effectively increase the slip thickness for enhanced load capacity while keeping the drift dimension of the tool sufficiently small for running in so that the tool can be rapidly deployed at the desired location. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
       SUMMARY OF THE INVENTION 
       [0005]    A slip design has segments that move relatively axially before moving in tandem up a ramp for radial extension. Due to the fact of the relative movement the segments interlock due to their geometric configuration or their surface treatment such that at the conclusion of such relative movement the load carrying thickness is effectively increased. The extended position minimizes radial extension of the slips for a smaller tool drift dimension while still allowing the needed radial extension and actually extending the radial reach of the slip assembly. The segment can have triangular or trapezoidal tapered interfaces that provide bearing areas between slip segments and adjacent spacer segment. Alternatively, the slips segments can have opposing wickers so that after riding up an underlying support member can interact with that member for load transfer. The supporting members can also be secured to an underlying mandrel for further load transfer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a section view in the run in position of a first embodiment of the invention; 
           [0007]      FIG. 2  is the view of  FIG. 1  with the slip assembly compressed axially but still not radially extended into the surrounding tubular; 
           [0008]      FIG. 3  is the view of  FIG. 2  with the axially compressed assembly driven up a ramp to move out radially to engage a surrounding tubular; 
           [0009]      FIG. 4  is a section view of a run in position of a second embodiment of the present invention; 
           [0010]      FIG. 5  is the view of  FIG. 4  in the set position; 
           [0011]      FIG. 6  is a section view of a third embodiment showing a slip with wickers on opposed sides to ride up over an underlying member and functionally interact with the underlying member for enhanced load capacity; 
           [0012]      FIG. 7  is a variation of the embodiment in  FIG. 4  showing the underlying segments in the run in position; 
           [0013]      FIG. 8  is the view of  FIG. 7  with the abutting of the underlying segments showing the set position; 
           [0014]      FIG. 9  is the view of  FIG. 5  in closer detail; and 
           [0015]      FIG. 10  is a perspective view of  FIG. 5  in the set position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]      FIG. 1  illustrates an array of slip segments referred to generally as  1  that further comprises gripping segments  20  alternating with supporting segments  22 . Gripping segments  20  have exterior wickers  24  and opposed tapered sides  26  and  28 . Supporting segments  22  have opposed tapered surfaces  30  and  32  that respectively engage surfaces  26  and  28  for sliding engagement. End segment  34  has a ramp  36  that rides on ramp  38  of slip pocket  4 . A shear pin  40  shown in  FIG. 2  is still intact after relative axial movement of the driven segment  42  that is driven by mechanical or other force in a known manner and is schematically represented by arrow  44 . The desired motion sequence is that supporting segments  22  first move axially closer together to the  FIG. 2  position with no movement up the ramp  38  which means the shear pin or pins  40  stay intact. In going from the position of  FIG. 1  to the  FIG. 2  position, the wickers  24  move from within the drift dimension line  46  to across that line but without contacting the inner wall  48  of the casing  5 . However, in the  FIG. 2  position opposed surfaces  50  and  52  of adjacent segments  22  come into full contact to this limit the axial contraction of the assembly of segments  20  and  22 . In transitioning from the  FIG. 2  to the  FIG. 3  position, the wickers  24  engage inner wall  48  due to further axial force indicated by arrow  44  breaking the shear pin(s)  40  so that the fully compressed assembly moves in tandem as a unit up the ramp  38 . Those skilled in the art will appreciate that in the  FIG. 3  position there is a radial overlap among the segments to the extent of arrow  54  such that the effective thickness of the slip assembly is in effect dimension  56  as the segments  20  and  22  act as a unitary assembly for the purposes of supporting loads from the wall  48  of casing  5 . In climbing the ramp  38  the segments  20  and  22  can climb away from the body  2 . This design is to be contrasted with prior designs where the slip simply climbs on an intermediate member that in turn rides up the cone to simply gain further radial extension without any measurable gain in carrying capacity. It is the radial overlapping of segments in the  FIGS. 1-3  design that can not only enhance the radial extension of the gripping segments  20  by at least 30% but can also enhance the load capacity of the assembly by at least 39% compared to known slip up ramp designs described above. In the  FIGS. 1-3  design the segments  20  have v-shaped opposed tapered walls  26  and  28  with an apex  58  in between. The apex locates the axial travel limit of the supporting segments  22  as opposed surfaces  50  and  52  come into contact in alignment with apex  58 . Increasing the dimension of the slip pocket  4  can also help in enhancing the load capacity of the assembly as long as the outer dimension is within the drift diameter  46 . 
         [0017]    Referring now to  FIGS. 4 ,  5  and  9  there is a variation on the embodiment of  FIGS. 1-3 . The principle of operation is the same but the segment shapes are slightly different.  FIG. 9  shows in greater magnification the support or lower segments  11  that have opposed ramps  60  and  62  and a bottom set of wickers  66 . Grip or upper segments  7  have wickers  72  that bite into tubular  74  as shown in  FIG. 5 .  FIG. 10  illustrates the side guide rails that keep segments  7  and  11  aligned as they move relatively in the axial direction. In this embodiment the axial relative movement is facilitated by the climbing of the segments  7  up the ramps  60  and  62  while providing a reaction force that drives the segments  11  into the carrier slip  68  (alternatively to the body or mandrel) where wickers  66  can then penetrate for additional anchoring. In the  FIG. 9  position the ramps  60  and  62  can no longer be seen but the multifaceted contact surfaces can be better seen. These surfaces define the outward radial travel limit of the segments  7  with respect to the alternating segments  11 . Segments  7  have end surfaces  76 ,  78  and  80  that engage on opposed ends surfaces  82 ,  84  and  86  of segments  11  in effect making the assembly an integrally functioning unit of enhanced thickness for grater load carrying capability. The operation for setting involves advancing pusher segment  8  by known means toward front segment  9  that is supported in a stationary position by carrier slip  6 . In the preferred arrangement the surfaces  76  and  78  are perpendicular as are surfaces  78  and  80  to present a zig-zag pattern viewed in section in  FIG. 9 . Again the edge retention system  76  works with the various described embodiments in a known way to hold the segment assembly together while allowing the needed radial movement to take place to advance the components to the set position. Outward movement of the segments  7  stops in the position that is illustrated in  FIG. 9 . 
         [0018]    Further with regard to  FIG. 9  a carrier slip  6  is utilized as the primary interface between the segmented slip and the slip pocket. The slip segments are located on the carrier slip  6 . For running in the hole the slip segments are pulled apart which draws the upper segments  7  down onto the carrier slip  6  hiding the wicker profile in the carrier slip  6  and below drift. When the slip is in position downhole, the pusher segment  8  is compressed against the front segment  9  until the slip segments contact the mating shoulder  10 . This action cams the upper segments  7  out radially and moves the lower segments  11  to support the upper segments  7 . The amount of radial expansion acquired by compression of the segments is controlled by the location of the mating shoulder  10 . When compression of the segments is complete, the slip segment and the carrier slip  6  act together as a single conventional slip but with an increased effective thickness improving slip performance. The hanging performance of this embodiment may be limited by the bearing area between the pusher  8  and front segments  9  with the carrier slip  6 . To more evenly transfer the hanging load into the carrier slip  6  a wicker profile is machined on the bottom of the lower segments  11  allowing the lower segments to bite into the carrier slip  6  and transfer hanging load along the length of the carrier slip  6 . Similar to the segmented slip embodiment of  FIGS. 1-3 , this embodiment requires a mating mechanism between the slip segments that prevents disengagement during running in the hole and properly guides compression of the segments. This mechanism could be of machined rails and mating channels between the segments. Also, a mechanism such as a shear screw or shear ring is needed to ensure the slip segments  1  are fully compressed before setting the slip segments and carrier slip  6  up the slip pocket and into the casing. Calculation shows a 30% radial expansion increase and a 39% increase in hanging capacity over the current known designs. 
         [0019]      FIG. 6  illustrates another embodiment where the gripping slips  100  have exterior wickers  102  and interior wickers  104 . The interior wickers  104  can slide on support segments  106  that can be stationary or that can also be ramped out due to relative axial movement as between the segments  106  and adjoining segments  108  and  110  that define an underlying support ring. This type of axially relatively movable segments that change dimension is a known design of swages for tubular expansion. The gripping slips  100  can be dovetailed to the segments  106  in a manner that still allows some relative axial movement to let the segments  100  contact the surrounding tubular so that wickers  102  can dig into that tubular while at the same time the reaction force can force wickers  104  into penetrating contact with segments  106 . One such form of interlocking segments  100  and  106  is to use a T-shaped dovetail as illustrated in  FIG. 6 . As a result of the wickers  104  digging into the segments  106  the load carrying capacity of the segments  100  is enhanced along the lines discussed above for the other embodiments as the effective thickness is increased to the combined thicknesses of the overlapping segments  100  and  106  now held together with wickers  104 . Optionally the exterior surface of the segments  106  facing segments  100  can also have wickers. 
         [0020]      FIGS. 7 and 8  are a slight variation from the  FIGS. 1-3  embodiment where the support segments  200  have abutting surfaces  202  and  204  that push out the grip segments  206  to get wickers  208  to penetrate a surrounding tubular. Segments  200  have adjacent cylindrical surfaces  210  and  212  adjacent surfaces  202  and  204  respectively such that in the set position a bottom surface  214  straddles surfaces  210  and  212  as shown in  FIG. 8 . In essence the grip segments  206  have an interior trapezoidal shape when viewed in section from the side as in  FIGS. 7 and 8 . 
         [0021]    Those skilled in the art will now appreciate that the present invention that features a slip assembly with relatively movable components allows a low profile for running in where the initial position of the gripping slips is at or near the mandrel and the set position has the gripping slips moving out radially in response to an axial compressive force on the assembly that shortens the assembly and provides an enhanced load bearing capacity to the assembly. In essence the radial movement of the segments up edge ramps of support segments that flank them locks them together against axial shear forces from loading so that the segments are in effect interlocked when holding such loading by virtue of a series of opposed tapered surface pairs as between the gripping and the support segments. Alternatively, the gripping slips can have internal wickers that allow them to extend to grip the surrounding tubular and at the same time to penetrate the supporting segment that is between the slip segment and a mandrel to allow the combined structures of the gripping slip and its supporting segment to act as unit to enhance the holding capacity of the assembly in the set position by about 40 percent to slip designs that simply ride up a ramp to contact the surrounding tubular. The supporting segments in this latter embodiment can be stationary or radially movable. The grip segments can be dovetailed to the support segments when initially overlaid for the run in position. In this variation the segments can be simply circumferentially offset rather than an axial stack of interactive segments as in  FIGS. 1-5  and  7 - 9 . 
         [0022]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: