A preload is applied to a thermoplastic seal to induce deformation of the seal. As the seal undergoes deformation (e.g., cold flow), it completes the seal. Thermoplastics such as PEEK, PEK, PPS, PEKEKK, and PET are examples of materials that may be used in the seal. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates to the field of seals. More specifically, the invention relates to a device and method for creating a seal using a thermoplastic component that is made to deform or cold flow.  
         [0003]     2. Related Art  
         [0004]     Many downhole applications require a reliable seal. For example, downhole control lines or cables (e.g., hydraulic, fiber optic, electric and combinations thereof) must frequently pass through or connect to downhole tools. Studies have proven that these connections often serve as the weak point in the system in terms of reliability. A failure of a seal in a control line connection may cause the complete system to fail.  
         [0005]     Prior downhole seals include rubber or elastomeric seals, metal-to-metal seals, and seals that rely upon well fluid pressure to create the seal. Experience has shown that rubber or elastomeric seals are often unreliable, particularly at elevated temperatures. Metal-to-metal seals use a ferrule around a tube that is pushed into a housing to create the seal. While these seals are generally reliable, they rely upon carefully controlled metal surface finish. The metal surfaces may become easily scratched during installation (e.g., as the tubing and ferrule slides into the housing) or handling on a rig floor, which may result in a failure of the connection downhole. Additionally, the close tolerances required for a metal-to-metal seal are often difficult to achieve in relatively large parts.  
         [0006]     Another type of downhole seals relies on fluid pressure to create the seal (e.g., chevron seals; see U.S. Pat. No. 6,406,028 as an example). These types of seals are commonly formed of elastomers or thermoplastics. While these seals are effective in certain applications, they are not suitable for all applications.  
         [0007]     Thus, there is a continuing need for improvements in the area of downhole seals.  
       SUMMARY  
       [0008]     One aspect of the present invention provides a seal comprised of a thermoplastic material, such as PEEK, PEK, PPS, and the like. A preload applied to the seal causes the seal to deform or cold flow and form a seal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:  
         [0010]      FIG. 1  illustrates a well tool having a control line extending therethrough and a seal of the present invention.  
         [0011]      FIGS. 2-10  also illustrate seals of the present invention.  
         [0012]      FIG. 8  further illustrates a system for testing such a seal.  
         [0013]     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.  
         [0015]      FIG. 1  illustrates a well tool  2  having a control line (or cable)  4  extending therethrough and a seal  10  of the present invention providing a fluidic seal therebetween. Although the seal  10  of the present invention is described herein as sealing between a well tool  2  (or housing) and a control line  4 , the seal  10  may be used in other applications and other downhole applications that require a reliable seal.  
         [0016]     The seal  10  is formed of an assembly of cooperating components. The seal  10  comprises a seal member  12  that is formed of a thermoplastic material. Ferrules  14   a - b  are provided on each side of the seal member  12 . Ferrule  14   b  abuts a shoulder  16  provided in the well tool  2 . A mandrel  18  (e.g., a screw) threadably mates with the well tool  2  and abuts ferrule  14   a.  As the mandrel  18  is screwed into the well tool, the mandrel  18  applies a force to ferrule  14   a  and squeezes ferrule  14   a,  seal member  12 , and ferrule  14   b  between the mandrel  18  and the shoulder  16 . Although primarily described herein as a stand-alone piece, the ferrule  14  may be integrated into a piece to be sealed.  
         [0017]      FIG. 2  illustrates a seal  10  of the present invention. In this embodiment of the seal  10 , the thermoplastic seal member  12  forms slots  13   a - b  (e.g., a v-slot) in each end. Each of the ferrules  14   a - b  have a protruding, tapered end  15   a - b  that abut the seal member  12  and extend into its respective slotted end  13   a - b.    
         [0018]      FIG. 3  illustrates another seal  10  of the present invention. This embodiment of the seal  10  has a thermoplastic seal member ( 12   a - b ) positioned on each side of an intermediate ferrule  22 . The ferrule  22  has protruding, tapered ends  15   a - b  that abut and extend into slotted ends  13   a - b  of each of the seal members  12   a - b.  Washers  20   a - b  are placed on the respective opposite ends of the seal members  12   a - b  from the ferrule  22 . The assembly shown in  FIG. 3  has a spring  24 , such as a Bellville washer, placed between the seal  10  and the mandrel  18 .  
         [0019]     With the seal  10  in place, a preload is applied thereto by, for example, tightening the mandrel  18  to squeeze the seal  10  as discussed above. The mandrel  18  is referred to generally herein along with other ways of applying a preload to the seal  10  as a “preload member.” When the thermoplastic seal member  12  is subjected to the preload, the end  13  of the seal member  12  will spread over the protruding, tapered end  15  of the ferrule  14  and fill the gap or annulus  6  between the parts to be sealed. The seal  10  of the present invention is subjected to a sufficient preload to induce a cold flow of the thermoplastic material into the gap between the ferrule  14  and the parts to create the seal.  FIG. 4  illustrates the seal  10  after it has been subjected to a sufficient preload. As shown in  FIG. 4 , the seal member  12  deforms to fill the gap  6  and create the seal. If desired, the assembly may incorporate a spring  24  ( FIG. 3 ) to maintain a force on the seal  10 . However, once the preload is applied and the seal member  12  has undergone cold flow, the preload may relax or be removed in some applications without affecting the sealing capability of the seal  10 .  
         [0020]     The ferrule(s)  14  and washers  20  is formed of a relatively hard material suitable for the environment, such as a metal material. The seal member  12  is formed of a thermoplastic material that is capable of cold flow. Thermoplastic materials having a tensile modulus equal to or greater than 500,000 psi at room temperature are suitable for many downhole applications. Similarly, Thermoplastic materials having a flexural modulus that is equal to or greater than 500,000 psi at room temperature are suitable for many downhole applications. Particular thermoplastic materials that exhibit the desired cold flow characteristics for the seal  10  of the present invention are polyetheretherketone (PEEK), polypheneline sulfide (PPS), polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK), polyethylene terephthalate (PET), and similar materials.  
         [0021]      FIG. 5  shows a seal  10  for sealing around a control line (or cable)  4 . The control line  4  extends through a housing  8 . The seal has a thermoplastic seal member  12  inside the housing  8 . The seal and seal member have tapered mating surfaces. Mandrel  18  threadably mates with the housing  8 . When the mandrel  18  is screwed into the housing  8 , the mandrel  18  applies a force to the seal member  12  causing it to deform (and cold flow) into the gap between the control line  4  and the housing  8 . The deformed seal member  12  creates the seal between the control line  4  and the housing  8 .  
         [0022]      FIG. 6  illustrates a seal  10  having two seal members  12  and mandrels  18 , one on each side of housing  8 . Each of the seal members operates as described in connection with  FIG. 5 . The housing  8  defines a void within which two cables  4  are connected (connection  30 ) and, therefore, defines a connector housing.  
         [0023]      FIG. 7  illustrates another type of seal  10  of the present invention. In the seal of  FIG. 7 , the seal member  12  is placed around the control line  4  within the housing  8 . The housing  8  is then crimped to deform the housing  8  as well as the thermoplastic seal member  12 . The deformation of the seal member  12  creates the seal between the housing  8  and the control line  4 . Note the connection  30  of cables  4  formed between seals  10  of the assembly. Also note that the housing  8  and seal member  12  may be deformed at multiple spaced locations to create multiple seals.  
         [0024]      FIG. 8  illustrates a system for testing a seal  10  of the present invention. The testing system  40  comprises pump(s)  42  communicating with ports  44  in the housing  8  between adjacent seals. By applying a pressurized fluid between the seals  10  and monitoring the pressure, leaks are detected as pressure drops. Also the testing system  40  may comprise a power source  46  used to apply a voltage to the control line  4  and the housing  8  to detect current leakage.  
         [0025]      FIGS. 9 and 10  illustrate another embodiment for the seal  10  of the present invention. In this embodiment the seal member  12  is placed over the control line  4  in housing  8 . Then, a squeezing force is applied to the thermoplastic seal member  12  by tightening screws  50  in the housing  8  to clamp on the seal member  12 . The clamp force applied by the housing  8  causes the seal member  12  to deform and create the desired seal around the cable(s)  4 . Note the connection  30  in the housing  8 .  
         [0026]     In each of the above seals  10 , the seal member  12  is subjected to a preload force (e.g., by squeezing, crimping, clamping, etc.) that causes the seal member  12  to deform and create a seal.  
         [0027]     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. For example, although discussed primarily in connection with a control line and a well tool, the seal  10  may be used with other downhole tools and in other applications. Similarly, the shapes of the seal member  12  and the ferrules  14  (e.g., the slots  13  and protruding, tapered ends  15 ) may be replaced with other features, or omitted depending upon the application. For example, the ends of one or both pieces may be flat or have a small chamfer, etc. depending upon the particular application, materials, preload, and other factors. Additionally, the seal member  12  and other components may have other shapes and features. Further, the seal member  12  may formed integrally with other components or applied to components in various manners. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.