Abstract:
An expandable packer features a sealing element in an exterior recess that is straddled by projections or bumps. Upon expansion the bumps move out against the borehole wall as an anchor support. Optionally, the bumps may be covered with a sealing material and may be constructed to assist in their radial movement to the borehole wall as a result of expansion particularly if the mandrel is expanded in compression. The bumps are not necessarily expanded with the swage and their radial growth can be induced from longitudinal shrinkage resulting from radial expansion.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is packers that are set by expansion of the mandrel and more particularly with a recess feature for the element to give it protection for run in with the adjacent bumps also acting as grip locations. 
       BACKGROUND OF THE INVENTION 
       [0002]    Packers are isolation devices that are mounted to a tubular mandrel. Some are set with compression of a sealing element external to the mandrel to reduce the length of the sealing element and increase its radial dimension. Other designs expand the mandrel from within to bring the sealing element to the borehole wall. Some designs employ swelling elements to bridge the gap to the borehole wall after exposure to well fluids over a period of time. 
         [0003]    One recurring issue with packers is that they must be run into the well through a tubular with a drift dimension not much larger than the packer run in dimension and then the packer may have to be set in a much larger borehole. Packers with expandable mandrels have typically put the sealing element on the outside diameter of the mandrel leaving the sealing element exposed to damage during running in. US Publication 2010/0314130 puts the sealing elements on the mandrel outer diameter and uses a system of internal rings through which the swage has to pass to expand only at the seal locations with a resulting uniform internal diameter after expansion since the size of the swage is no larger than the drift diameter of the tubular being expanded. 
         [0004]    Other designs place gripping members adjacent a sealing element and expand the mandrel from its interior. In this design the assembly is placed on the mandrel outer diameter which limits the initial internal dimension of the mandrel for run in which makes it more difficult to expand to a sealing condition in a larger wellbore. Such a design is illustrated in U.S. Pat. No. 7,117,949. 
         [0005]    Other designs that are focused on using lighter wall pipe and giving it strength to resist collapse with a series of closely spaced corrugations make the claim that a sealing material can be deployed in the corrugations and a roller expander can be used to enlarge the corrugated segment with the sealing material for use as an isolation device. It claims protection for the sealing material during run in via the corrugations. The reality is that if the corrugations act as protection for a sealing material in a helical or circumferential groove then to try to get a seal with expansion will require elimination of the groove to even get the seal against the borehole wall. If that happens then the seal material will comprise of thin unsupported strips as the corrugations will be eliminated to even get sealing contact. The unsupported strips will roll on themselves and will not provide a reasonable annular seal. On the other hand if the corrugations are buried for run in then the sealing element is not protected for run in by the corrugations. Also a factor is that since the corrugations enable the use of thinner wall tubulars the expansion to the point of returning to parallel wall structure by flattening out all the corrugations will present a weaker mandrel that will have a fairly low differential pressure rating and may be too weak to retain the sealing element against the borehole wall in a sealing relationship. Such a design is illustrated in U.S. Pat. No. 7,350,584. 
         [0006]    What is needed and provided by the present invention is an expandable packer that can have the element protected for run in while still be configured to sealingly be expanded to the surrounding wellbore. These features are addressed by projections on opposed ends of long recesses that hold the sealing element. The projections can extend radially upon expansion to act as anchors or extrusion barriers. A swelling material can optionally be used. Those skilled in the art will better understand the invention 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 
       [0007]    An expandable packer features a sealing element in an exterior recess that is straddled by projections or bumps. Upon expansion the bumps move out against the borehole wall as an anchor support. Optionally, the bumps may be covered with a sealing material and may be constructed to assist in their radial movement to the borehole wall as a result of expansion particularly if the mandrel is expanded in compression. The bumps are not necessarily expanded with the swage and their radial growth can be induced from longitudinal shrinkage resulting from radial expansion. Shrinkage from expansion occurs from axial loading in compression from the swage to be advanced and it also occurs as a consequence of radial expansion resulting from advancing of the swage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a prior art arrangement of elements on a mandrel to be expanded; 
           [0009]      FIG. 2  is a section view of one embodiment with external recesses for the sealing elements and bumps between the elements that are uncovered with a seal material; 
           [0010]      FIG. 3  is a variation of the  FIG. 2  design with a sealing material mounted over the bumps that straddle the recess location where the sealing elements are disposed; 
           [0011]      FIG. 3   a  is a variation of the  FIG. 3  design where the bumps are configured for radial movement resulting from longitudinal shrinkage from radial mandrel expansion; 
           [0012]      FIG. 4  is a two segment bump in the extended position from axial compression of the mandrel that shrinks its length as well as shrinkage from radial expansion. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]      FIG. 1  illustrates multiple elements  10  on a mandrel  12  that is to be expanded. The mandrel  12  has a constant outer dimension and the elements  10  are exposed to damage for run in. The thickness of the seals  10  is limited by the drift dimension of the previously installed or existing tubular and the outside diameter of the mandrel. 
         [0014]      FIG. 2  has a mandrel  14  that has threaded connections  16  that are located preferably under seals  18 . While three are shown one or more seals  18  can be used. A series of humps  20  straddle at least some seals  18  and may bracket each seal  18 . The humps  20  can be formed of multiple segments  22 ,  24  and  26  with segments  22  and  26  tapered with respect to a longitudinal axis of mandrel  14  while segment  24  is substantially parallel to the longitudinal axis of mandrel  14 . Segments  22  on one side of a seal  18  and  26  on the other side of a seal  18  define a valley  28  which allows a greater thickness for the seal  18  while maintaining segment  24  as the largest dimension. Segment  24  preferable extends radially further than the outer surface  30  of the seal  18  but they can also extend co-extensively. Optionally, surface  24  can be eliminated in favor of two sloping surfaces  22  and  26  that join together to make a V shape and come to a point. The point can optionally penetrate the surrounding borehole wall for an anchoring grip. In either case it is preferred that the apex of tapers  22  and  26  or the radial position of a parallel to the axis surface  24  be the furthest extending location for protection of the seals  18  during run in. 
         [0015]    The swage  32  has an outer dimension  34  that in the preferred embodiment is no larger than internal diameter  36  of the bumps  20 , with an exception as pointed out below. In this manner as expansion occurs, with the mandrel  14  preferably in compression but can also occur with the mandrel  14  in tension, the valleys  28  disappear. The expansion in the radial direction reduces the axial length of the mandrel  14  so that the bumps are pushed radially outwardly against the borehole wall as shown in  FIG. 4 . Optionally the bumps  20  can have an external surface treatment such as a surface roughness or hard particles that will dig into the surrounding borehole wall to act as an anchor. 
         [0016]    Another option to the preferred embodiment is to size the swage outer dimension  34  to be larger than internal diameter  36  so that as a result of expansion the bumps  20  are radially expanded beyond their run in drift outer dimension. 
         [0017]    Another option for the bumps  20  is shown in  FIG. 3  where the sealing element  18 ′ is continuous and runs right over the bumps  20 ′. In this version the sealing material can sustain so wear in the region of the humps  20 ′ and on expansion of the mandrel  14 ′ that shrinks the mandrel  14 ′ longitudinally, the result of outward movement of the bumps  20 ′ is to extend a seal in that location with an added anchoring benefit that is less dramatic than the  FIG. 2  embodiment. 
         [0018]      FIG. 3   a  shows mandrel  14 ″ covered with sealing element  18 ″ with hump  20 ″ preferably extending radially about as far as the outer surface  36  of mandrel  14 ″. The hump  20 ″ is preferably a continuous arcuate surface  38  that defines opposed valleys  40  and  42  on opposed sides of peak surface  44 . In this embodiment the expansion that causes longitudinal shrinkage induces collapse of mandrel  14 ″ at valleys  40  and  42  that drives surface  44  into the seal  18 ″ to enhance the sealing against the borehole wall. 
         [0019]    Those skilled in the art will appreciate that in the  FIG. 2  embodiment the valleys  28  defined by the humps  20  allow for a thicker element  18  that is protected for run in by the humps  20 . The expansion with swage  32  does not have to expand the peak of the humps as for example segment  24 . The connections  16  being under seals  18  can even leak slightly from expansion but the presence of the seal  18  can close off that leak path. Optionally the seal elements can swell. All the seal elements need not be identical and some can swell while others do not. In some applications where damage during run in is a big concern, the seals  18  can extend radially further than the bumps  20 . The bumps  20  extend radially as a result of longitudinal shrinkage from expansion with the swage  32  and the shape of the bumps can be as shown in  FIG. 2  or varied to take out segment  24  so they are more pointed. The outer dimension of the bumps  20  can create an anchor for the packer and it can also bite into the surrounding tubular for a metallic seal as an option. The shape of the bumps  20  promotes their radial growth as a result of expansion. External surface roughening or hard particles can also enhance the ability of the bumps  20  to be packer anchors. Optionally, as shown in  FIG. 3  the bumps  20 ′ can be covered with a seal material so that the sealing ability is improved as the bumps  20 ′ drive segments of the seal  18 ′ that is a single long sleeve parts of which are nested in recesses for run in between the humps  20 ′ against the borehole wall for an enhanced seal. The continuous nature of the long seal in  FIG. 3  with the bumps that push it out further improves the performance of the assembly as compared to the  FIG. 2  design with a sacrifice of some protection of the seal  18 ′ during run in. 
         [0020]    In the  FIG. 3   a  embodiment the humps  20 ″ are fabricated in a manner using the arc to allow them to extend as a result of longitudinal shrinkage from expansion so as to push the seal that extends over them out to the borehole wall. Optionally the humps  20 ″ of  FIG. 3   a  can be exposed and used in replacement of the humps  20  in  FIG. 2 . The valleys  40  and  42  assist in the outward growth due to mandrel shrinkage from expansion. As a result of expansion of mandrel  14 ″ the bumps  20 ″ can extend further than the mandrel  14 ″. For run in it is preferred to have the bumps  20 ″ extend radially as far as the outer mandrel dimension but having the bumps extend slightly more as an aid to holing the element  18 ″ in place is also contemplated. 
         [0021]    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.