Abstract:
A downhole seal includes a seal body; a prominent pip having extending from the seal body; and one or more reduced prominence pips adjacent the prominent pip.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application contains subject matter related to the subject matter of co-pending application, which is assigned to the same assignee as this application, Baker Hughes Incorporated of Houston, Tex. and is being filed on Dec. 23, 2009. The below application is hereby incorporated by reference in its entirety: 
         [0002]    U.S. Patent Application Attorney Docket No. TTI4-48541-US-01 (BA000387US), entitled HIGH EXPANSION METALLIC SEAL. 
       BACKGROUND 
       [0003]    In the downhole drilling and completion arts, sealing of various things such as an annulus between a mandrel or basepipe and a casing, for example is a common requirement. Many different types of seals have been developed and have used many different types of material and/or combinations of material. More recently, high expansion metal seals have become of interest to the industry yet while they suffer little from the deleterious effects of the downhole environment and relatively easily resist mechanical insults such as pressure inversions, extrusion, and the ravages of time, they present greater difficulty with regard to establishing a competent seal to begin with. Various means have been used to assist in the creating of the seal each having effective success to some degree. 
         [0004]    None of the known solutions has proven a panacea in all situations and consequently, the art still seeks alternative solutions and well receives those proposed. 
       SUMMARY 
       [0005]    A downhole seal including a seal body; a prominent pip extending from the seal body; and one or more reduced prominence pips adjacent the prominent pip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0007]      FIG. 1  is a schematic cross sectional representation of a prior art seal in a run in position; 
           [0008]      FIG. 2  is a schematic cross sectional representation of the same seal shown in  FIG. 1  but in a set position; 
           [0009]      FIG. 3  is a schematic cross sectional representation of a seal configuration as disclosed herein in a run in position; 
           [0010]      FIG. 4  is a schematic cross sectional representation of the same seal shown in  FIG. 3  but in a set position; 
           [0011]      FIG. 5  is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position; 
           [0012]      FIG. 6  is a schematic cross sectional representation of the same seal shown in  FIG. 5  but in a set position; 
           [0013]      FIG. 7  is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position; 
           [0014]      FIG. 8  is a schematic cross sectional representation of the same seal shown in  FIG. 7  but in a set position; 
           [0015]      FIG. 9  is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position; 
           [0016]      FIG. 10  is a schematic cross sectional representation of the same seal shown in  FIG. 9  but in a set position; 
           [0017]      FIG. 11  is a schematic cross sectional representation of the seal configuration shown in  FIG. 3  with an optional sleeve, as disclosed herein in a run in position; 
           [0018]      FIG. 12  is a schematic cross sectional representation of the same seal shown in  FIG. 11  but in a set position; and 
           [0019]      FIGS. 13-20  are schematic cross sectional representations of alternate elastomer configurations for the seal embodiments of  FIGS. 3-12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    In order to enhance understanding of the invention disclosed herein initial reference will be made to the prior art, represented in  FIGS. 1 and 2 . A prior art seal  10  includes pips  12  and  14 . The pips together define parallel facing surfaces  16  and  18 . Once the seal  10  is set, the pips  12  and  14  are moved to a position illustrated in  FIG. 2 , with the surfaces  16  and  18  moving to a splayed open position as shown. In the prior art this was considered a positive occurrence and hence is the state of the art. 
         [0021]    Referring now to  FIGS. 3 and 4 , a first embodiment of the seal concept disclosed herein is illustrated. A seal body  110  comprises a relatively rigid material such as a metal material. In one embodiment the material is a steel alloy such as stainless steel or inconel. The seal body  110  includes a set of depending pips  112  and  114  that extend radially relative to an axis of the seal body  110  and in one embodiment, as illustrated, extend radially outwardly. Significantly, the pips  112  and  114  each define nonparallel facing surfaces  116  and  118 , respectively. These surfaces are oriented to generally oppose each other but they are not parallel to each other in the run in condition. Moreover, as can be appreciated from the Figures, the surfaces grow closer to one another as distance from the seal body  110  increases. The surfaces  116  to  118  form an acute angle with respect to a centerline  119  of the seal body as displayed in the Figures. Pips having angled surfaces, as illustrated, more reliably achieve metal-to-metal contact with a casing inside surface (casing ID)  120 . Further the angled surfaces  116  and  118  help to minimize a radial extrusion gap between the pip  112  or  114  contact surface  122  or  124 , respectively, and casing ID  120  than does the prior art seal shown in  FIGS. 1 and 2 . The acute angle of the pips also helps to self-energize the seal, in an embodiment where soft material filler  130  is included, with the application of differential pressure. The acute angle of the pips allows for a larger cross sectional area between the two pips for a given dimension between distal ends  121  and  123  of the pips, which will provide larger volume of soft material than the geometry of the prior art such as illustrated in  FIG. 1 . The performance increase is due to the pips  112  and  114  having higher contact pressure against a casing ID  120  or to the pips  112  and  114  attaining a final set position in closer proximity to the casing. As can be appreciated in  FIG. 4 , the orientation of the pips  112  and  114  creates an acute angle between surface  116  and  120  when measuring the angle toward the left side of the drawing and an acute angle between surface  118  and  120  when measuring the angle toward the right side of the drawing. 
         [0022]    In another embodiment, referring to  FIGS. 5 and 6 , the configuration of  FIGS. 3 and 4  is repeated except for the addition of an additional pip  126 . The additional pip  126  is configured to contact the casing  120  as shown in  FIG. 6 . The advantages to adding a center pip is that it offers the potential of a third metal-to-metal contact point or reduced extrusion gap and it controls the set volume of soft material  130 , which prevents excessive squeeze. 
         [0023]    In another embodiment, referring to  FIGS. 7 and 8 , the configuration of  FIGS. 5 and 6  are repeated except the pips  128  and  131  have a reduced diameter (reduced prominence) that is less than the diameter of the center pip  126  (prominent pip). The advantage to reducing the diameter of the outer pips  128  and  131  is that metal-to-metal contact between the center pip  126  and the casing ID  120  is even more reliably achieved. The pips  128  and  131  still provide for soft material filler anchoring to help prevent washing away of the soft material. In this embodiment however, the shorter pips encourage the soft material to flow between the pips and the casing ID  120 . This helps with sealing small irregularities in the surface  120 . Further, it is to be appreciated that in this embodiment the angled inner surfaces of the pips of the foregoing embodiments may be used but are permissive rather than required. Stated alternatively, in embodiments with reduced prominence pips, the pips need not have the angled surfaces  116  and  118  as in the foregoing embodiments but could be configured with surfaced  16  and  18  as in the prior art. 
         [0024]    In another embodiment, referring to  FIGS. 9 and 10 , the configuration of  FIGS. 3 and 4  is repeated except a span surface  134  between pips  112  and  114  is not perpendicular to the centerline  119  of the seal but rather has a concave shape with respect to the centerline of the seal as illustrated. The concavity of span surface  134  alters the set volume of the seal  110  and allows for greater selection in soft material volume. It is to be understood however, that the volume of the area defined by the pips, surface  134  and casing surface  120  will change during setting of the seal  110  and therefore consideration of the amount of soft material is important to ensure that it does not prevent metal to metal contact of the seal with the casing  120 , something that can occur as a result of excessive squeezing of the soft material. 
         [0025]    In all embodiments  FIGS. 3-10 , an additional optional sleeve  136  is contemplated. Referring to  FIGS. 11 and 12 , an illustration of a seal configuration like that of  FIGS. 3 and 4  is used to illustrate the sleeve  136 . The illustration is certainly by way of illustration rather than limitation since the sleeve may be used on any of the embodiments disclosed herein or others. In one embodiment the sleeve  136  comprises non-metallic material although metallic material having appropriate structural characteristics could be substituted. Structural characteristics that are desired include toughness to resist borehole impacts during running and softness to promote sealing at pip contact surfaces  122  and  124 . The sealing function of the sleeve  136  occurs similarly to that of the soft material  130  in that it flows into small irregularities at casing surface  120  but is located at the pips as opposed to between the pips. 
         [0026]    As has been alluded to hereinabove, each of the embodiments disclosed may be used with or without a soft material  130 . Each of the foregoing seal configurations used alone will create a reliable seal. These configurations when endowed with a softer material  130  (see  FIGS. 13-20 ) than the material from which the seal itself is constructed, that softer material being positioned between pip  112  and pip  114  or  128  and  130  exhibit different sealing properties that may be helpful in tubular structures having a pitted surface, for example. Softer materials contemplated include but are not limited to nonmetallic materials such as polytetrafluoroethylene, rubber, plastic, and soft metallic materials such as lead, gold, silver, etc. Each of these materials tends to flow relatively easily under stress. They are therefore helpful in ensuring sealing in smaller discontinuities of the sealing surface. The configurations of the pips as described above enhance the utility and reliability of these softer materials by helping to keep them contained between the pips rather than to allow the material to flow to a position where it is between the pips and the casing  120 , where it can have a detrimental affect on sealing. Reference is made to a number of embodiments of soft material  130 . The embodiments are self explanatory, each of which being configured to provide for good sealing characteristics while exhibiting an unstressed shape that allows space into which the stressed material  120  may flow to avoid flow of that material between the pips  112  and  114  and the casing  120 . It is to be appreciated that in some illustrated embodiments the material is a single piece of material ( FIGS. 13 ,  17 ,  18  and  19 ) while in other embodiments the material  130  is configured as more than one piece of material ( FIGS. 14 ,  15 ,  16 , and  20 ). It is further to be appreciated that in  FIG. 20 , O-rings are illustrated having different cross sectional diameters. O-rings with the same cross sectional diameters can also be used as well as different numbers of O-rings. All of the configurations shown  FIGS. 13-20  may have soft material that is molded into a separate ring and placed onto the seal body or molded and bonded directly onto the seal body. 
         [0027]    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.