Abstract:
A sealing device of enhanced configuration for use in downhole in a well. The device may include an element of elastomeric and unitary construction. At the same time, however, the element may include a substantially cured outer shell disposed about a substantially under-cured inner core. Thus, enhanced robustness and durability may be provided to the device in light of downhole conditions without sacrifice to sealable function of the device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61,696,950 filed Sep. 5, 2013 entitled “Functionally Gradient Elastomer material for Downhole Sealing Element” which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming, and ultimately very expensive endeavors. As a result, over the years, a significant amount of added emphasis has been placed on maximizing hydrocarbon recovery for every well drilled. Along these lines, well monitoring and maintenance have become critical to effective well management throughout the life of the well. Additionally, overall well completions and architecture design are directed at enhancing overall recovery. 
         [0003]    Well completions as well as management of the well throughout the life thereof, often involve the utilization of downhole sealing elements. For example, the well may be partitioned off into different productive and non-productive zones through the use of zonal isolation packers. Such isolation may be undertaken at the outset of well completions, over the course of the life of the well, or for sake of temporary interventional applications. Regardless, effective sealing in the often extreme conditions of a downhole environment may be sought for some substantial duration. 
         [0004]    Unfortunately, sealing devices and device features such as swell packers, mechanical packer elements, and others, are often prone to extrude, degrade and otherwise fail. That is, whether due to the downhole conditions themselves, or added stress imparted due to the nature of the deployment, such isolating devices are unlikely to maintain an effective seal for extended periods of time such as the life of the well. 
       SUMMARY 
       [0005]    A sealing device is disclosed for downhole use in a well. The device includes a structurally supportive mandrel platform. Thus, a seal element may be disposed thereabout. Further, the seal element includes a substantially cured outer shell about a substantially under-cured inner core. 
         [0006]    In some embodiments, the present invention is directed to a sealing device for downhole deployment in a well. The device includes a mandrel, a first sealing element coupled to the mandrel and being cured to a first curing level, and a second sealing element coupled to the mandrel and being cured to a second curing level different from the first curing level. The first and second sealing elements are operatively coupled together. 
         [0007]    In other embodiments the first and second sealing elements each have a radial cross-sectional shape. The radial cross-sectional shape of the first and second sealing elements is generally similar but the radial cross-sectional shape of the first sealing element is smaller than the radial cross-sectional shape of the second sealing element such that the second sealing element surrounds the first sealing element with a uniform thickness. 
         [0008]    In still further embodiments, the present invention is directed to a functionally gradient elastomer material for use with a packer including a first element having a first characteristic configured to resiliently seal against an exterior surface and a second element having a second characteristic configured to resist extrusion. The second element resiliently seals against an exterior surface to a lesser degree than the first element, and the first element resists extrusion to a lesser degree than the second element. The first and second elements are coupled together such that, when actuated, pressure causes the first and second elements to deform together to form a seal. The device also includes a mandrel coupled to at least one of the first or second elements and configured to support the first and second elements as the functionally gradient elastomer material forms the seal. 
         [0009]    In still further embodiments the present invention is directed to a method of forming a sealing device for use with a downhole tool, including forming a first elastomeric sealing element having a first physical property, forming a second elastomeric sealing element having a second physical property, wherein the first physical property causes the first elastomeric sealing element to be comparatively more resilient than the second elastomeric sealing element and the second physical characteristic causes the second elastomeric sealing element to be comparatively better at resisting extrusion stresses than the first elastomeric sealing element. The method also includes coupling the first and second elastomeric sealing elements together, and coupling the first and second elastomeric sealing elements to a mandrel configured to support the elastomeric sealing elements as pressure is exerted upon the elastomeric sealing elements to form a seal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  includes side and enlarged sectional views of an embodiment of a functionally gradient material sealing element. 
           [0011]      FIG. 2  is a chart summarizing modulus data for the material of  FIG. 1  upon exposure to varying temperatures. 
           [0012]      FIG. 3  is a side view of an alternate embodiment of the material employed in an O-ring seal configuration. 
           [0013]      FIG. 4  is an alternate embodiment of the material employed in a T-seal configuration. 
           [0014]      FIG. 5  is an alternate embodiment of the material employed in a V-seal configuration. 
           [0015]      FIG. 6  is an alternate embodiment of the material employed as cased hole hydraulic packer elements. 
           [0016]      FIG. 7  is an alternate embodiment of the material employed as open hole hydraulic packer elements. 
           [0017]      FIG. 8  an alternate embodiment of the material employed as open hole hydraulic packer elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Embodiments herein are described with reference to certain types of downhole sealing devices. For example, conventional packers are shown for zonal isolation in a well. However, more unique types of packers and a host of other sealing devices may take advantage of embodiments of functionally gradient elastomer materials as detailed herein. Regardless, the sealing device may include an element utilizing an elastomer with a substantially cured outer shell about a substantially under-cured inner core. 
         [0019]    Referring now to  FIG. 1 , side and enlarged sectional views of an embodiment of a functionally gradient material sealing element are shown. In this embodiment, the sealing element is incorporated into a downhole isolation packer disposed about a tubular. The downhole sealing element in a borehole annulus includes an elastomeric material (e.g. a rubber) molded in ring shape and installed into the metal mandrel. The element can energize and/or swell when an activating system (mechanical loads or fluids) is in place. Conventional sealing element is made from homogeneously mixed polymer compounds and then cured to a uniform part. The present invention relates, in general, to a seal element that were intentionally made with non-uniformly distributed property to achieve better sealing performance by minimizing seal failures associated with extrusion, temperature cycles, and degradation. 
         [0020]    The Packer sealing element consists of 1 to 3 pieces of elastomeric rings installed in a metal mandrel. When activated, the elements provide a seal in annulus space between the mandrel and casing. Once sealed, the elements undergo pressure differential from both above and below the seal, as well as temperature cycles due to downhole temperature and fluid injection from surface. 
         [0021]    In the case when packer element is energized by mechanical force pushing the gage ring, hyper-elastic strain energy is stored in the packing elements due to large compressive deformation within the elements. This stored strain energy results in contact pressure at the sealing surfaces (casing ID and mandrel OD) thus provides seals. In a defined setting load case, the lower modulus (softer) element generates more stored elastic energy. When temperature decrease occurs due to fluid injection, the decrease of contact force is proportional to the modulus of element (G), the coefficient of thermal expansion (α), and the temperature drop (ΔT) as was stated in the following expression: 
         [0000]    
       
      
       P∝G·α·ΔT  
      
     
         [0022]    Therefore, a softer elastomer compound is favored by maintaining a better seal with less loss in sealing force when cooling down. However, most of the downhole seal failure attributes to extrusion of the sealing elements under differential pressure. Higher modulus material generally provides better extrusion resistance. So to combine those two requirements, a functionally gradient elastomer material (FGEM) is presented in this invention where a softer inner core is embedded in the harder outer shell. The modulus differential can be achieved by adjusting curing characteristic of the part during molding process. 
         [0023]      FIG. 1  illustrates the design of the FGEM material in a downhole packer element. The harder shell is mainly for extrusion resistant purpose and the overall softer material will help with sealing capability. Tests were performed using side-by-side comparison between homogeneous material and FGEM in system level. 
         [0024]    With added reference to  FIG. 2  a chart summarizing modulus data for the material of  FIG. 1  upon exposure to varying temperatures is depicted. More specifically,  FIG. 2  shows the FGEM element being used for the test. Test follows ISO 14310 V3 standard and the pressure holding results for the two element systems are summarized in the following two tables. The FGEM elements exhibit better differential pressure capability, especially when a larger ΔT is present. Due to the nature of this particular FGEM element design with soft inner core extends to element ID, excessive amount of rubber was extruded from the OD of mandrel. 
       Homogeneously Cured Material: ET201104959 50,000 lbf Setting Force; 2.590″ Stroke 
       [0025]      
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Pressure holds summary 
               
             
          
           
               
                   
                 Above 
                 Below 
               
             
          
           
               
                 Temperature 
                 5 ksi 
                 10 ksi 
                 15 ksi 
                 20 ksi 
                 5 ksi 
                 10 ksi 
                 15 ksi 
                 20 ksi 
               
               
                   
               
               
                 450 F. (1, 2, 3) 
                   
                   
                 ✓ 
                 ✓ 
                   
                   
                 ✓ 
                 ✓ 
               
               
                 200 F. 
                   
                   
                   
                 ✓ 
                   
                 ✓ 
                 ✓ 
                 ✓ 
               
               
                 175 F. 
                   
                   
                 ✓ 
                 ✓ 
                 X 
                 X 
                 X 
               
               
                 150 F. 
                   
                 ✓ 
                 X 
                   
                   
                 X 
                 X 
               
               
                   
               
             
          
         
       
     
       Functionally Gradient Material (FGEM): ET201111659 50,000 lbf Setting Force; 2.553″ Stroke 
       [0026]      
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                 Pressure holds summary 
               
             
          
           
               
                   
                 Above 
                   
                 Below 
                   
               
             
          
           
               
                   
                 Temperature 
                 15 ksi 
                 20 ksi 
                 15 ksi 
                 20 ksi 
               
               
                   
                   
               
               
                   
                 450 F. (1, 2) 
                 ✓ 
                   
                 ✓ 
                   
               
               
                   
                 150 F. 
                 ✓ 
                 ✓ 
                 ✓ 
                 ✓ 
               
               
                   
                 450 F. (3, 4) 
                   
                 ✓ 
                   
                 ✓ 
               
               
                   
                   
               
             
          
         
       
     
         [0027]    In addition to the uses noted hereinabove, the embodiments of the seal element material construction detailed hereinabove may be utilized in any bottom hole assembly where packers and/or seals may be employed. The sealing element of the present invention maybe O-ring seals, T-seals, V-seals, and packing elements for cased hole packers, open hole packers, and swell packers. The polymer material may comprise elastomer such as NBR, HNBR, EPDM, FEPM, FKM, FFKM. The seal element may further include a reinforcement material such as a powder material, a fiber material, or nanoparticles with scale range from 1 nanometer to approximately 500 nanometers. Depend on application, the property/functionality in the FGEM that varies spatially may include modulus, hardness, strength, elongation, volume swell, degradation temperature. The gradient of those properties can also be in all directions (radial, angular, and axial). 
         [0028]    With specific reference to the alternate embodiments of  FIGS. 3-8 ,  FIG. 3  depicts a side view of an alternate embodiment of the material employed in an O-ring seal configuration. Meanwhile,  FIG. 4  depicts an alternate embodiment of the material employed in a T-seal configuration. Similarly,  FIG. 5  is an alternate embodiment of the material employed in a V-seal configuration. 
         [0029]    Continuing with added reference to  FIGS. 6-8 , packer embodiments are depicted. Specifically,  FIG. 6  depicts an alternate embodiment of the material employed as cased hole hydraulic packer elements. Alternatively,  FIG. 7  is an embodiment of the material employed as open hole hydraulic packer elements whereas  FIG. 8  is an embodiment of the material employed as open hole hydraulic packer elements. 
         [0030]    Embodiments detailed hereinabove provide elastomeric material seals and construction configured for enhanced sealing capability in conjunction with extended life even upon exposure to extreme and/or harsh downhole environmental conditions. The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.