Abstract:
A downhole backup system includes, a tubular positionable within a downhole structure such that an annular space exists between the tubular and the downhole structure. The downhole backup system also includes, a plurality of wedges that are radially movably positioned within the annular space, and each of two opposing ends of the plurality of wedges are configured to completely cover the annular space at all possible radial positions of the plurality of wedges.

Description:
BACKGROUND OF THE INVENTION 
     In the downhole hydrocarbon recovery industry elastomeric seals are used to seal annular areas between concentric tubulars. To prevent axial extrusion of the elastomeric seals at high temperatures and high pressures, backups are employed. Backups are radially expanded to fill the annular area during deployment and are radially retracted during tripping thereof. Although a typical backup can adequately prevent a seal from extruding thereby, each backup can only backup one end of one seal, thereby requiring two backups per seal. With each backup having a separate actuation, two actuations are needed to back up the two ends of a single seal. The industry would be receptive of systems that permit a reduction in the number of actuations required to backup multiple seals. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed herein is a downhole backup system. The system includes, a tubular positionable within a downhole structure such that an annular space exists between the tubular and the downhole structure, and a plurality of wedges that are radially movably positioned within the annular space, each of two opposing ends of the plurality of wedges are configured to completely cover the annular space at all possible radial positions of the plurality of wedges. 
     Further disclosed herein is a method of backing up seals at a downhole tool. The method includes, moving a plurality of wedges radially, and covering perimetrical gaps between adjacent wedges on both longitudinal ends with wings disposed at the plurality of wedges. 
     Further disclosed herein is a method of occluding a downhole annular space. The method includes, radially moving a plurality of wedges positioned in the downhole annular space, and occluding the downhole annular space at both opposing ends of the plurality of wedges. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a perspective view of a downhole dual backup  10  disclosed herein; 
         FIG. 2  depicts a cross sectional view of the downhole dual backup of  FIG. 1 ; and 
         FIG. 3  depicts a perspective view of a wedge of the downhole dual backup of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring to  FIGS. 1-3 , the downhole dual backup  10  includes, a plurality of wedges  14 , positioned perimetrically adjacent to one another, between a pair of ramps  18 . One or more biasing member(s)  22 , disclosed herein as tension springs (three being illustrated), surround the wedges  14  and bias the wedges  14  radially inwardly. Each wedge  14  has one wing  26 ,  28  on each end that extends perimetrically beyond edges  30 ,  31  of the wedges  14 , respectively. The wing  26  on a first end  32  extends in a direction opposite to the direction of the wing  28  on a second end  36 , although designs having the wings  26 ,  28  extending in the same direction are possible. Each wedge  14  also has a surface  40  on the first end  32  and a surface  44  on the second end  36 . The wedges  14  are configured such that the wing  26  on the first end  32  of one wedge  14  slidably engages with the surface  40  on the first end  32  of an adjacent wedge  14 . Similarly, the wing  28  on the second end  36  of one wedge  14  slidably engages with the surface  44  on the second end  36  of an adjacent wedge  14 . 
     The foregoing allows the wedges  14  to provide two continuous perimetrical supports  50 ,  54  regardless of a specific radial position the wedges  14 . As such, elastomeric members  58 , shown herein as seals (not shown in  FIG. 2 ), are prevented from extruding through annular openings between an outer dimension  62  of the ramps  18  and an inner surface of a downhole structure, such as a liner, casing or open hole (not shown), for example, within which the backup  10  is positioned. These two continuous perimetrical supports  50 ,  54  are best seen in  FIG. 2  at radial dimensions greater than the outer dimension  62 . Since the dual backup  10  has the two continuous perimetrical supports  50 ,  54 , two ends  64 ,  65 , of two different seals  58 , can be backed up with just one of the dual backups  10 . A surface  66 , on the wing  26 , creates a portion of the first perimetrical support  50  and the surface  40  forms another portion of the first perimetrical support  50 . As such, the perimetrical support  50  is stepped by a thickness  70  of the wing  26  as viewed while proceeding around a perimeter thereof. The wing  26  provides a portion of the perimetrical support  50  that would be unsupported by perimetrical clearance between the edges  30  and  31  if the wing  26  were not present. Similarly, a surface  44  on the wing  28  creates a portion of the second perimetrical support  54  and the surface  44  forms another portion of the second perimetrical support  54 . The wings  26 ,  28  extend sufficiently to overlap with the surface  40 ,  44  at all radial positions of the wings  26 ,  28 , the radial movement of which will be described below. 
     Axial movement of the ramps  18  causes radial movement of the wedges  14 . As the ramps  18  move toward one another by a linear actuator (not shown), for example, angled surfaces  78  and  82 , of the ramps  18 , engage with angled surfaces  86 ,  88  of the wedges  14 , respectively. This engagement causes the wedges  14  to simultaneously move radially outwardly causing the springs  22  to lengthen in the process. The lengthening of the springs  22  increases the radial inward bias the springs  22  provide to the wedges  14 . Alternately, axial movement of the ramps  18  away from one another allows the wedges  14  to move radially inwardly under the biasing load of the springs  22 . 
     Alignment features  92  in the ramps  18 , shown herein as slots (although protrusions or other details could be employed), engage with complementary features  96  in the wedges  14 , shown herein as tabs, to maintain substantially equal angular spacing between the wedges  14  as the wedges  14  move radially. This assures that the perimetrical distance between adjacent wedges  14  remains uniform and the wings  26 ,  28  cover the clearances between edges  30  and  31  at all radial positions of the wedges  14 . 
     By assuring that the wings  26 ,  28  overlap with the surfaces  40 ,  44  the full perimetrical supports  50 ,  54  also form barriers that restrict the ingress of contamination to the backup  10  that could adversely affect the radial actuation of the wedges  14 . The elastomeric members  58 , by being on both axial ends of the dual backup  10 , further protect the backup  10  from contamination. This prevention of ingress of contamination coupled with the fact that there is no plastic deformation of the components during actuation of the dual backup  10  the dual backup  10  is capable of an indefinite number of cycles without degradation. Additionally, the dual back up is fully reusable. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.