Abstract:
A seal including a contact area; and two arms extending in opposite directions from the contact area, the seal when set exhibiting an asymmetric cross section.

Description:
BACKGROUND 
       [0001]    Annular seals for the drilling and completions industry have been known for many years and have benefitted over those years with improvements in material composition, setting strategies and systems, etc. Presently there are numerous types and kinds of seals available on the market. Notwithstanding ubiquitous solutions however, the number of possible situations is not finite and hence there is no end to the need and or desire for additional modifications to existing seal structure or design and indeed the development of entirely new concepts in sealing technology. 
         [0002]    One type of annular seal uses a relatively thin wall portion of a tubular form that is intended to bulge outwardly upon axial compression and/or fluid pressure. Such seals employ a central area, sometimes including one or more pips, that is radially forced into contact with a casing. The portions of the seal sometimes referred to as arms, on either side of the central area create roughly symmetrical frustocones upon setting of the seal. Such seals can be constructed of metal, plastic, rubber, etc. and generally include an o-ring at a mandrel thereof to prevent fluid movement past the seal once it is set. Typically the O-ring is disposed at one end of the seal. O-rings are generally not placed at both ends of the seal as in the event that a liquid fluid filled the open space defined by the seal, it might well be impossible to set due to the relative incompressibility of liquid fluids. These seals have performed well for their intended purposes but do improvement as noted above is always desired. Accordingly the art will well receive seals having greater function. 
       SUMMARY 
       [0003]    A seal including a contact area; and two arms extending in opposite directions from the contact area, the seal when set exhibiting an asymmetric cross section. 
         [0004]    A method for sealing an annulus including running a seal as claimed in claim  1  to a target location; and setting the seal at the target location in a cross sectionally asymmetric configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0006]      FIG. 1  is a schematic view of a prior art seal cross section in a set position; 
           [0007]      FIG. 2  is a schematic view of an embodiment of an asymmetric seal as disclosed herein that shows pressure acting on the seal from an end thereof that includes an o-ring seal; 
           [0008]      FIG. 3  is a schematic view of the same embodiment of an asymmetric seal as in  FIG. 2  but showing pressure acting on the seal from an end thereof that does not include the o-ring seal; 
           [0009]      FIG. 4  is a schematic section view of another embodiment of an asymmetric seal as disclosed herein in a run in position; 
           [0010]      FIG. 5  is the embodiment of  FIG. 4  in a set position. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring to  FIG. 1 , one of ordinary skill in the art will recognize a type of seal  10  known to the art. The seal  10  includes a contact area  12  that is positioned between two frustoconical (when in the set position as illustrated) arms  14  and  16  and two end rings  18  and  20 . Each end ring also includes a groove, illustrated as  22  and  24  in  FIG. 1  to promote radial movement of a central portion of the seal  10 , i.e. the contact area  12  and the arms  14  and  16 . Finally the seal  10  includes a mandrel seal such as an o-ring  26  positioned at one end of the seal  10 . The O-ring seal  26  prevents pressure leakage between the seal  10  and a mandrel  28  but note that the o-ring  26  is positioned at only one end of the seal  10  to avoid potential hydraulic locking of the seal  10 . This means to that pressure acting from one end of the seal is borne differently than from the other end of the seal. This is further discussed hereunder. With respect to  FIG. 1 , it is important to note in the illustration is that the two frustoconical arms  14  and  16  are generally symmetrical. The invention is distinct in this regard. 
         [0012]    In accordance with the disclosure hereof, and referring to  FIGS. 2 and 3 , the inventor has discovered that an asymmetrical seal  110  performs better than the configuration of  FIG. 1 . The seal  110 , it will be appreciated, has one arm  114  that is shorter than the other arm  116 . The arm that is shorter should be the one that is on the same end of the seal  110  that the o-ring  126  is on. In this illustration, the one that is shorter is  114 . It is important to have the shorter arm on the end with the o-ring  126  because of the way that pressure sources from one end of the seal  110  are borne versus pressures from the other end of the seal are borne. It is not relevant whether the pressure is from uphole, downhole, or any other direction indicator but rather only whether the pressure from a particular end of the seal will have access to an inside surface  130  of the seal  110  or not. Pressure that comes from an end of the seal  110  that does not have the o-ring will have access to the inside surface of the seal whereas pressure from an end of the seal  110  that does have the o-ring  126  will not have access to the inside surface  130  of the seal. 
         [0013]    As can be seen in  FIGS. 2 and 3 , the result of the longer arm  116  upon setting is that it achieves a shallower angle relative to the mandrel  128  or axis of the seal  110  than the angle achieved by the shorter arm  114 . Angle ranges for the arms  114  and  116  is about 45 degrees to about 50 degrees and about 40 degrees to about 45 degrees, respectively relative to a longitudinal axis of the seal  110 . Such a configuration has been shown via Finite Element Analysis to improve pressure rating for the seal  110  over similar symmetrical seals  10 . It is believed that the shorter arm  114  at a higher angle has greater rigidity against the pressure on an outside surface  132  of the seal, see arrow P o , which stands for pressure o-ring end. This is helpful since pressure from that end of the seal, due to the location of o-ring  126 , is borne only at surface  132  and the seal  110  is not assisted from the inside surface  130 . The longer arm  116 , although it is necessarily less rigid due to length, benefits from the pressure from its end of the seal on surface  130  thereby reducing the ultimate load on the seal from the outside surface  134 , see arrows P no , which stands for pressure non o-ring end. In other words, because the pressure affects both inside  130  and outside  134  of the seal  110  from this direction, the pressure differential directly across the arm  116  is insignificant and therefore the reduced rigidity of the longer arm  116  is of no consequence. The length of the shorter arm  114  relative to the longer arm  116  is in one embodiment in the range of about 90% to about 97% of the length of the longer arm  116 . 
         [0014]    Referring to  FIGS. 4 and 5 , an alternate embodiment asymmetrical seal  210  is illustrated. The ultimate set position of this embodiment is similar to the foregoing described embodiment in that one arm achieves an angle relative to the mandrel  228  or longitudinal axis of the seal  210  that is greater than an angle achieved by the other arm but it does not require that the length of the arms differ. Rather, in this embodiment it is grooves  222  and  224  that are distinct. Configuring a groove  222  or  224 , (depending upon which groove is proximate the o-ring  226 , which is groove  222  in the illustration) with a limited amount of space used for accommodation of the arm associated therewith. Stated alternatively, the amount of space available within a groove can be a limiting factor in how much radial movement the arm can experience. By carefully sizing the grooves  222  and  224 , one can ensure that one arm will deflect radially outwardly less than the other arm thereby ensuring that the arm that is allowed to deflect farther will achieve a greater angle relative to the mandrel  228  or an axis of the seal  210  resulting in an asymmetric seal cross section. This configuration has been noted above to exhibit improved results over the seal  10  of  FIG. 1 . The Seal configuration of  FIG. 3  thus is also beneficial to the art. The groove size limitation that is contemplated is that the smaller groove is in a range of from about 70% to about 80% of the size of the larger groove, the larger groove being the one that is proximate the O-ring  226 . 
         [0015]    While each of the configurations discussed above are capable of achieving the favorable results of better pressure ratings over the seal  10  of  FIG. 1 , this is not to say that the two configurations cannot be combined. To the contrary, the above-disclosed concepts can indeed be combined if desired. 
         [0016]    While one or more 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.