Abstract:
A variable ram assembly for use in a blowout preventer (BOP) stack includes a packer element. The packer element includes an elastomeric body having a contact surface configured with a curved recess for sealing engaging a tubular. At least a portion of the body adjacent the contact surface is reinforced to define a reinforced area. The reinforced area exerts a restraining force to prevent extrusion of the elastomeric body when it is forced against the tubular. The reinforced area is integrally formed with the body using a molding process.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/747,589 filed on Dec. 31, 2012, the full disclosure of which is hereby incorporated by reference herein for all purposes. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present disclosure relates in general to a variable ram packer for use with a blowout preventer (BOP) mounted on a wellhead. More specifically, the present disclosure relates to a variable ram packer with a packer element whose contact surface is reinforced. 
         [0004]    2. Description of Prior Art 
         [0005]    Wellbores in hydrocarbon bearing subterranean formations are formed by rotating a drill bit mounted on a lower end of a drill string. Typically, a wellhead housing is installed at the earth&#39;s surface and through which bit and string are inserted. A blow out preventer (BOP) stack usually mounts on top of the wellhead housing that provides pressure control of the wellbore, and often includes rams to shut in the wellbore should pressure in the wellbore become uncontrollable. Additional rams are often included with BOP stacks that are for shearing the string within the BOP stack, and also for pressure testing within the BOP. Further typically included with BOP stacks are flow lines and valves to allow fluid flow through the BOP stack for remediating overpressure in the wellbore. 
         [0006]    One type of BOP ram for pressure testing within a BOP stack is a variable ram packer. Variable ram packers usually include a pair of hydraulically powered rams on opposing lateral sides of the BOP stack, which are selectively forced radially inward into compressive engagement with the tubular. An elastomer packer element is typically provided with the variable ram packers for engaging the tubular, and has a curved recess on its engaging surface for receiving the tubular. The curved recesses on the pair of packers form a seal in the bore and around the tubular so pressure in the wellbore can be verified. Adjacent the curved recess, each packer element often has a planar surface that defines an edge at the interface between the recess and planar surface. During operation of the variable ram packers, compressive stresses in the recess transfer to the unsupported edge portion and extrude it outward. Over time, the edge portion is susceptible to damage from these multiple extrusion cycles, especially during exposure to varying low and high temperatures. 
       SUMMARY OF THE INVENTION 
       [0007]    Disclosed herein is an example of a variable ram, that in an embodiment includes a ram block selectively moveable within a blowout preventer (BOP) and a ram packer disposed in the ram block. In this example, the ram packer is made up of an elastomer body, a contact surface along a lateral side of the elastomer body, a recess portion on a mid-portion of the contact surface that projects radially into the elastomer body and that is in selective sealing engagement with a tubular in the BOP, and a reinforced area in the elastomer body adjacent the contact surface. Further in this example, the reinforced area has a stiffness greater than a stiffness of the elastomer body, so that when the ram block is moved radially inward into sealing contact with the tubular, the reinforced area exerts a restraining force on the elastomer body. The reinforced area can be made from a material such as neoprene, nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, or combinations thereof. In an embodiment, the contact surface adjacent an end of the recess portion is at an angle with respect to the recessed portion to define an edge on the contact surface, and wherein the reinforced area extends adjacent the edge. The elastomer body can be substantially solid, and the reinforced area can extend substantially along a length of the contact surface. In one example, the restraining force on the elastomer body retains the elastomer body in a non-extruded configuration when the ram block is moved radially inward into sealing contact with the tubular. 
         [0008]    Also provided herein is a ram packer assembly for use in a blowout preventer (BOP), that in one example is made from an elastomeric body selectively disposed in a ram block. A contact surface is on the body, which has a curved recess that selectively seals against a tubular in the BOP. A reinforced area is integrally formed in the body adjacent the contact surface, so that when the body is forced against the tubular, the reinforced area exerts a force on that opposes extrusion of the body. A series of interlocking inserts may be included that selectively slide with respect to one another on a radial surface of the body when the body is radially compressed. The reinforced area can include neoprene, nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, or combinations thereof. The reinforced area can be provided along an interface between an end of the curved recess and an adjacent planar portion of the contact surface. In one optional embodiment, a portion of the body adjacent the reinforced area is stiffer than a portion of the body distal from the reinforced area. 
         [0009]    A method is also disclosed that involves forming a ram packer assembly having a contact surface and that is for use in a blowout preventer (BOP). One embodiment of the method includes providing an uncured elastomer, disposing the uncured elastomer into a ram packer assembly mold, inserting the uncured elastomer into the mold, providing a substance for forming a reinforcing material, strategically disposing the substance for forming the reinforcing material in the mold to be adjacent the contact surface, and curing the uncured elastomer to form a body with the reinforced material integrally set in the body to define a reinforced area adjacent the contact surface that has a stiffness greater than a stiffness of the body. The method may further include providing sliding inserts in the mold that mount on opposing surfaces of the body. Optionally, the substance for forming a reinforcing material is a material from the group of neoprene, nitrile rubber, hydrogenated nitrile rubber, and combinations thereof. The body can be included into a ram packer assembly and sealed against a tubular, so that the reinforcing material restrains the body in an unextruded configuration. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a perspective view of an example of a variable ram having an embodiment of a packer element in accordance with an embodiment of the present invention. 
           [0012]      FIG. 2  is a side partial sectional view of an example of the variable ram of  FIG. 1  included in a blowout preventer stack in accordance with an embodiment of the present invention. 
           [0013]      FIG. 3  is a perspective view of an example of a packer element of  FIG. 1  in accordance with an embodiment of the present invention. 
           [0014]      FIG. 4  is a plan view of an alternate embodiment of the packer element of  FIG. 1  in accordance with an embodiment of the present invention. 
           [0015]      FIG. 5  is a plan view of an example of molding an embodiment of the packer element of  FIG. 1  in accordance with an embodiment of the present invention. 
       
    
    
       [0016]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0017]    The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. 
         [0018]    It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
         [0019]      FIG. 1  provides a perspective view of an example embodiment of a variable ram  10 , which includes a ram block  12  which houses a ram packer assembly  14 . A recess  15  in the ram block  12  is configured to receive the ram packer assembly  14 . The recess  15  intersects with a forward facing end of the ram block  12 , and extends partially across the width and length of the ram block  12 . In the example of  FIG. 1 , the ram block  12  is a substantially metallic member that is generally rectangular shaped, and where its length and width exceed its height. A packer element  16  makes up part of the packer assembly  14 , which in an example is made at least in part from an elastomeric material. Inserts  18  shown set on an upper radial surface of the packer element  16  and arranged in a semi-circle with its outer radius projecting into the recess  15 . Brackets at opposing terminal ends of the semi-circle are coupled to the forward facing end of the packer element  16 , but the individual inserts  18  are laterally moveable on the radial surface of the packer element  16 . Inserts  18  are interlocked on their respective adjoining edges, but slideable towards one another so the semi-circle compresses when the packer element  16  is laterally compressed. 
         [0020]    An example of a blowout preventer (BOP)  20  is shown in a side sectional view in  FIG. 2  and which includes an embodiment of the variable ram  10 . The BOP  20  includes a body  21  for housing a pair of variable rams  10 ; the variable rams  10  can be selectively actuated laterally in and out of body  21 . BOP  20  is shown mounted on an upper end of a wellhead housing  22  that anchors on a surface  24 , where surface  24  may be subsea or on land. A main bore  26  through wellhead assembly  22  and BOP  20  is shown registering with a wellbore  28  that is being formed through the surface  24  by a drill string  30 . In the example, the drill string  30  extends through the main bore  26  and the wellbore  28 , and includes a drill bit (not shown) on its lower end, that when rotated by drill string  30  excavates wellbore  28 . As illustrated in the example of  FIG. 2 , variable rams  10  project radially inward from opposing bodies  21  into sealing engagement with an outer surface of tubular  30 . In one example, sealingly engaging the tubular  30  with variable ram allows a pressure test to be performed in wellbore  28 . 
         [0021]    A perspective view of an example of packer assembly  14  is provided in  FIG. 3  wherein opposing lateral ends of packer assembly  14  are shown angled upward away from an upper radial surface. A contact surface  32  is defined on the side of the packer element  16  that projects outward from the ram block  12  ( FIG. 1 ) and which includes curved recess  34 , which can have a semi-circular or semi-elliptical shape. The curved recess  34  is shown formed along a mid-portion of the contact surface  32  and projects radially inward and follows a generally curved path with its outer radius set adjacent inner radius of the inserts  18 . In an example, when the variable ram  10  is urged radially inward as illustrated in  FIG. 2 , the contact surface  32  is compressed against outer surface of drill string  30 . Strategically profiling the curved recess  34  in combination with compressing the contact surface  32  against the drill string  30 , forms a sealing surface between packer element  16  and tubular  30  to define an axial pressure barrier in the main bore  26 . Adjacent opposing ends of the curved recess  34 , the contact surface  32  is disposed in a plane generally parallel with an axis A X  of drill string  30  ( FIG. 2 ) thereby defining flats  36  on lateral ends of the curved recess  34 . 
         [0022]    Further illustrated in the example of  FIG. 3  is that the packer element  16  is stiffened and/or strengthened along at least a portion of the contact surface  32  to define a reinforced area  38 . In an example, the reinforced area  38  has greater strength and/or stiffness than a remaining portion of the packer element  16 . Example properties for quantifying strength and/or stiffness include tensile strength, hardness, modulus of elasticity, yield strength, and percent elongation at breakage. The reinforced area  38  can be formed by treating the packer element  16  proximate the contact surface  32 , or disposing a stronger and/or stiffer material  39  to the contact surface  32 . In  FIG. 3 , the reinforced area  38  is shown extending over an interface  40  on the contact surface  32  where curved recess  34  transitions into flat  36 . In an example, interface  40  is defined as an edge where the contact surface  32  angles in a radial direction at the boundary between flat  36  and curved recess  34 . The reinforced area  38  supports the contact surface  32  and resists extrusion of the interface  40  when the packer element  16  is set in sealing contact with drill string  30  ( FIG. 2 ). Moreover, although the stiffer and/or stronger reinforced area  38  is more resistive to deformation than the packer element  16 , the packer assembly  14  can still seal around the drill string  30  ( FIG. 2 ) due to compliant deformation of the more elastic packer element  16 . 
         [0023]    In an embodiment, the reinforced area  38  includes one or more of neoprene, nitrile rubber, hydronated nitrile rubber, and carboxylated nitrile rubber. Tables 1 and 2 below include example values for properties of the reinforced area  38 , or materials making up or included within the reinforced area  38 . Examples exist wherein the materials having the properties of Tables 1 and 2 include one or more of hydronated nitrile rubber and carboxylated nitrile rubber. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Value 
                 Range 1 
                 Range 2 
                 Range 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 % Elongation at failure 
                 731 
                 681-781 
                 656-806 
                 631-831 
               
               
                 100% Modulus (psi) 
                 323 
                 273-373 
                 248-398 
                 223-423 
               
               
                 Tensile Strength (psi) 
                 3132 
                 3032-3232 
                 2982-3282 
                 2932-3332 
               
               
                 Hardness 
                 75 
                 70-80 
                 65-85 
                 60-90 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Value 
                 Range 1 
                 Range 2 
                 Range 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 % Elongation at failure 
                 369 
                 319-419 
                 294-444 
                 269-469 
               
               
                 100% Modulus (psi) 
                 1251 
                 1201-1301 
                 1151-1351 
                 1101-1401 
               
               
                 Tensile Strength (psi) 
                 3630 
                 3530-3730 
                 3480-3780 
                 3430-3830 
               
               
                 Hardness 
                 85 
                 80-90 
                 75-95 
                  70-100 
               
               
                   
               
             
          
         
       
     
         [0024]      FIG. 4  illustrates an alternate embodiment of the packer assembly  14  shown in a plan view, wherein the reinforced area  38  extends onto the upper radial surface  42 . More specifically, in the example of  FIG. 4 , the reinforced area  38  extends a distance D from a contact surface  32  of packer assembly  14  on the upper radial surface  42 . Further, the reinforced area  38  is provided along substantially all of the curved recess  34  and approximately to a midpoint between terminal ends of the packer assembly  14  along the flat portion  36 . Optionally however, embodiments exist wherein the reinforced area  38  is concentrated at or adjacent to the interface  40  between the curved recess  34  and flat  36 . In another optional embodiment, the reinforced area  38  extends along the entire or substantially entire surface of contact surface  32 . Further illustrated in  FIG. 4  is a rearward surface  44  of the packer assembly  14  that is curved and projects radially outward from the contact surface  32 . 
         [0025]    One example of forming a packer element  16  is shown in  FIG. 5 . In this example, a mold  46  is provided having sidewalls  48  that approximate the outer periphery of the packer element  16  ( FIG. 3 ). In this example, an amount of uncured elastomer  50  is provided within the mold  46 , and in an amount to substantially fill the mold  46  when cured in the mold. Included with the uncured elastomer  50  is an example of material making up the reinforced area  38  shown set along an inside of sidewall  48  adjacent where the contact surface  32  ( FIG. 3 ) will be located on completion of the formation process. As is known, the mold  46  is enclosed and subjected to increased temperature and/or pressure for a period of time until the uncured elastomer  50  cures and transforms into the packer element  16 . In one optional example, a precursor or uncured material is set in the mold  46  that is transformed into the reinforced area  38  during the formation/curing process. Thus in one example, disposing the material that forms the reinforced area  38  along with the uncured elastomer  50  integrates the finally formed reinforced area  38  with the packer element  16  during the curing process to produce a uni-body element. Furthermore, the process illustrated in  FIG. 5  can in one example create a substantially solid packer element  16 . 
         [0026]    The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.