Abstract:
A seal for use in temperature and pressure extremes is disclosed. It features springs internal to the sealing members and the ability to seal against pressure differentials from opposed directions. A spacer ring prevents contact from oppositely oriented seal components and at the same time prevents spring and seal collapse under extreme loading conditions. The seal assembly is self-centering in a downhole seal bore and can be used on tools delivered on wireline, where the insertion forces available are at a minimum. The seal can withstand pressure differentials in excess of 13,500 PSI and temperatures above 350 degrees Fahrenheit.

Description:
PRIORITY INFORMATION  
       [0001]     This application is a continuation application claiming priority from U.S. patent application Ser. No. 10/443,489, filed on May 22, 2003, which claims the benefit of U.S. Provisional Application No. 60/384,601, filed on May 30, 2002. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of this invention is a seal for use in temperatures of over 300 degrees Fahrenheit and over 10,000 pounds per square inch (PSI) and more particularly a seal adapted for wireline use where insertion forces are limited.  
       BACKGROUND OF THE INVENTION  
       [0003]     Currently, in downhole applications, there are different types of seals to handle high temperature and pressure applications. The present limits of service of these designs are roughly about 350 degrees Fahrenheit and about 13,500 PSI. Under more severe temperature or/and pressure conditions, the presently known designs have been tested and have failed to perform reliably.  
         [0004]     Depending on the application, there are different types of seals for high temperatures or/and pressures. In the case of packers set in high temperature applications, U.S. Pat. No. 4,441,721 asbestos fibers impregnated with Inconel wire are used in conjunction with a stack of Belleville washers to hold the set under temperature extremes. Apart from packers or bridge plugs which require seal activation after placement in the proper position, there are other applications involving seals on tools that have to engage a seal bore receptacle downhole and still need to withstand these extremes of temperature and pressure. In many cases, the tool with the seal to land in a seal bore is delivered on wireline. This means that insertion forces are limited because minimal force can be transmitted from the surface through wireline. In these applications, the limited insertion force is a design parameter that has to be counterbalanced with the frictional resistance to insertion created by the interference of the seal in the seal bore. This interference is built into the design of the seal to allow sufficient contact with the seal bore after insertion for proper seal operation. Clearly if the interference is too great the insertion, particularly with a wireline, will become problematic. On the other hand, reducing the interference can result in seal failure under the proposed extreme conditions of pressure and temperature.  
         [0005]     There are other design considerations for seals that engage a seal bore downhole. Clearly, on the trip downhole, the seal is exposed to mechanical contact with well tubulars or other equipment. The materials for the seal must be rugged enough to withstand such mechanical impacts as well as to withstand the temperatures and pressures anticipated in the downhole location.  
         [0006]     These seals also need to control extreme pressure differentials in an uphole and a downhole direction. Such seals may be inserted and removed from several seal bores during their service life. The design has to be flexible enough to allow long service periods under such extreme conditions as well as the resiliency to allow removal and reinsertion without damage to the seal or the surrounding seal bore.  
         [0007]      FIG. 1  illustrates the current commercially available seal that is promoted for severe duty applications. It illustrates a mirror image arrangement around a central adapter  16 . A pair of chevron packing rings  14  are disposed about the adapter  16  and outside of the rings  14  is a back-up v-ring  12  and outside of v-ring  12  is an end ring  10  to complete one half of the mirror image arrangement shown in  FIG. 1 . The open portions of the v-shaped rings open toward the central adapter in an effort to position the rings to withstand pressure differentials from opposite directions. The rings are made of materials suitable for the anticipated temperatures. Tests at pressure extremes of over 13,500 PSI and temperatures above 350 degrees Fahrenheit revealed that this design was unsuitable for reliable service.  
         [0008]     In an effort to improve on the performance of the seal shown in  FIG. 1 , the design of  FIG. 2  was tried. It featured a central o-ring  18  surrounded by a pair of center adapters  20 . On either side of the center adapters  20  the arrangement was similar to  FIG. 1  except that the orientation of the v-shaped opening were now all away from the central o-ring  18  rather than towards each other as had been the case in the design of  FIG. 1 . Additionally, there was an alternating pattern of material in the rings  22  and  24  of  FIG. 2  as compared to the stacking of rings  14  of a like material as shown in  FIG. 1 . This design of  FIG. 2  showed improved performance in high temperature and pressure conditions but was not to be the final solution. The present invention, an illustrative example of which is discussed in the preferred embodiment below, addresses the temperature and pressure extremes while allowing for insertion using a wireline. It features an internal spring mechanism and a feature that prevents collapse of the spring and the sealing elements under extreme conditions. The opposing members in the assembly are also prevented from engaging each other under extreme conditions. The collapse-preventing feature also has a beneficial aspect of seal centralization as the seal is inserted into the seal bore. Those skilled in the art from a review of the description of the preferred embodiment below and the claims that appear thereafter will readily understand these and other beneficial features of the present invention.  
       SUMMARY OF THE INVENTION  
       [0009]     A seal for use in temperature and pressure extremes is disclosed. It features springs internal to the sealing members and the ability to seal against pressure differentials from opposed directions. A spacer ring prevents contact from oppositely oriented seal components and at the same time prevents spring and seal collapse under extreme loading conditions. The seal assembly is self-centering in a downhole seal bore and can be used on tools delivered on wireline, where the insertion forces available are at a minimum. The seal can withstand pressure differentials in excess of 13,500 PSI and temperatures above 350 degrees Fahrenheit.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a section view of a prior art seal for extreme temperature and pressure conditions;  
         [0011]      FIG. 2  is an early version of the present invention developed by the inventors;  
         [0012]      FIG. 3  is a section view of the seal of the present invention in a position before extreme temperature and pressure conditions are applied;  
         [0013]      FIG. 4  is the view of  FIG. 3  shown under fully loaded conditions; and  
         [0014]      FIG. 5  is a view showing how the seal of the present invention would collapse if the central ring were to be omitted. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]     Referring to  FIG. 3 , the seal S of the present invention is shown without the tool that it would be secured to. The seal bore into which the seal S is to be inserted is also omitted on the basis that those skilled in the art are readily familiar with downhole tools and seal bores into which seals such as seal S are inserted. For similar reasons, the surface wireline equipment and the wireline are omitted due to their familiarity to the person skilled in this art. It should be noted that seal S can be used on a subsurface safety valve that can be delivered on wireline. This is only the preferred use and those skilled in the art will recognize that the seal S can be used with a broad variety of tools and delivered downhole in a variety of ways other than a wireline. Seal S is preferably used in applications of sealing in a seal bore downhole under conditions of high pressure and temperature differentials. Seal S can withstand differentials in pressure in either direction in excess of 13,500 PSI and temperatures well in excess of 350 degrees Fahrenheit.  
         [0016]     The components will be described from the downhole end  26  to the uphole end  28 . A female adapter  30  has an uphole oriented notch  32 , which is preferably v-shaped. Located in notch  32  is a chevron shaped ring  34  with a notch  36  oriented in an uphole direction. Mounted in notch  36  is chevron shaped ring  38  with a notch  40  oriented in an uphole direction. Lower seal  42  sits in notch  40  and has an uphole oriented opening  44  in which is disposed one or more generally u-shaped spring rings such as  46  and  48  that are shown stacked on each other with their respective openings oriented uphole. Spring rings  46  and  48  are preferably mounted within opening  44  and in an abutting relation. Inserted into opening  44  and opening  52  of upper seal  54  is ring  50 . Ring  50  has a radial component  56  extending toward the downhole tool (not shown). Located preferably within opening  52  are stacked and abutting spring rings  58  and  60 , which are preferably identical to spring rings  46  and  48  except that they are disposed in a mirror image relation to them. In fact, the upper portion of the seal S above the ring  50  is the mirror image of the previously described components that are located below ring  50 . In the preferred embodiment going uphole or downhole from ring  50  the hardness of the rings going from seal  42  to ring  38  to ring  34  is progressively harder. The same goes for their mirror image counterparts, seal  54 , ring  62 , ring  64 , and female adapter  66 . The preferred material for the female adapters  30  and  66  is Inconel  718 . For ring  64  and its counterpart ring  34  the preferred material is virgin polyetheretherketone. For ring  62  and its counterpart ring  38  the preferred material is a PTFE (Teflon) with 20% polyphenylenesulfide and some carbon. The preferred material for the seals  42  and  54  is a PTFE (Teflon) flourocarbon base with 15% graphite.  
         [0017]     Seals  42  and  54  could have one ore more interior  68  or exterior  70  notches to promote sealing contact with the tool (not shown) and the seal bore (not shown) respectively. These notches promote some flexibility in response to pressure or thermal loads.  
         [0018]     The operation of the seal S under a pressure differential from uphole is illustrated in  FIG. 4 . Arrow  72  represents such pressure from uphole going around seal  52  because its opening  52  is oriented downhole. The wings  74  and  76  flex toward each other responsive to the pressure differential. The seal  54  is moved with respect to ring  50 . This movement allows the spring rings  58  and  60  to become more nested and to apply a greater spread force against wings  74  and  76 . However, ring  50  also prevents collapse of spring rings  58  and  60  because the described movement has resulted in positioning ring  50  in the openings defines by generally u-shaped spring rings  58  and  60 . For that same reason, wings  74  and  76  are prevented from collapse toward each other. Meanwhile, the pressure represented by arrow  72  enters opening  44  with the result that ring  50  is pushed into spring rings  46  and  48  to not only splay apart the wings  78  and  80  but also to keep such wings from collapsing and permanently deforming due to movement of ring  50  into the openings defined by nested spring rings  46  and  48 . Ring  50  pushes the spring rings  46  and  48  into a more nested relation but at the same time, its presence in their openings prevents collapse of not only spring rings  46  and  48  but also of wings  78  and  80  to their immediate exterior. Another benefit of ring  50  is that it is of the appropriate length to prevent wings  74  and  76  from contacting wings  78  and  80  under maximum loading conditions. Contact at such high temperatures and pressures could fuse the wings together with a seal failure being a possibility. This is illustrated in  FIG. 5  where the ring  50  has been eliminated and wings  74  and  76  have contacted wings  78  and  80 . The spring rings in  FIG. 5  have all buckled and are permanently deformed. This seal is likely to be in failure mode.  
         [0019]     Another advantage of having the ring  50  is that upon insertion of the downhole end of seal S into a seal bore, ring  50  adds some rigidity to that portion of seal S already inserted into the seal bore to act as a centralizer for the remaining portions of seal S to facilitate its insertion without damage. Radial component  56  also helps in the centralizing function for insertion of seal S into a seal bore (not shown).  
         [0020]     Those skilled in the art will appreciate that while  FIG. 4  illustrates a pressure differential from uphole that the response of seal S to a differential pressure from downhole is essentially the mirror image of what was described as the situation in  FIG. 4 . The design of seal S is unique in high temperature and pressure service and one such feature is the internal spring component. While spring rings having a generally u-shaped cross-section have been illustrated other cross-sectional shapes for the spring rings are contemplated as long as the response is to splay out the wings while exhibiting resiliency to return to a neutral position when the extreme pressure or temperature conditions are removed. The use of a separation ring to keep the wings apart and to prevent their collapse and the collapse of the spring rings inside them allows the seal S to withstand cycles of temperature and pressure extremes and continue to be serviceable. The placement of the components in a nesting relation in conjunction with ring  50  and radial component  56  helps to centralize seal S with respect to the downhole tool to which it is mounted as well as to facilitate its insertion into a seal bore. This is because the downhole end  26 , upon entering the seal bore centralizes the seal S so that the rest of it is simply advanced into the seal bore without damage.  
         [0021]     While the seal S is ideal for high pressure and temperature applications, it can also be serviceable in less severe environments and can be delivered into a seal bore by a variety of conveyances such as coiled tubing, rigid pipe as well as wireline, among others. Its construction makes it easily insertable in a wireline application, when minimal force is available get the seal S into the seal bore.  
         [0022]     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.