Annular seal for spherical blowout preventer

Abstract

A method for closing an annular BOP and restricting flow from the wellbore through the BOP using hardened segments of the packing element is provided. The method relies on a translation motion (e.g., at least partially in a tangential direction) of the hardened segments, rather than a purely radial motion of the segments. The translation motion is a spiral motion of the hardened segments with respect to a longitudinal axis of the packing element. An elastomer is bonded to the hardened segments, and the translation action of the hardened segments supports the elastomer to close to a zero position and affect a fluid tight seal of the bore.

What is claimed is: 
     
         1 . A method, comprising:
 pressing on a packing element of an annular blowout preventer (BOP) via a piston of the annular BOP, wherein the packing element comprises:
 an array of hardened segments arranged circumferentially about a longitudinal axis of the packing element; 
 an actuator plate; and 
 an elastomer disposed between and bonded to the actuator plate and the array of hardened segments; and 
   moving the array of hardened segments in a spiral configuration relative to the longitudinal axis of the packing element to reduce a size of or fully close a bore through the packing element.   
     
     
         2 . The method of  claim 1 , wherein each hardened segment of the array of hardened segments comprises a leading edge oriented substantially tangential to the bore through the packing element, and wherein moving the array of hardened segments in a spiral configuration comprises moving each hardened segment in a tangential direction relative to the bore and in a radially inward direction with respect to the axis of the packing element. 
     
     
         3 . The method of  claim 1 , wherein the annular BOP comprises a BOP head with a concave semi-spherical internal surface formed therein, wherein each of the hardened segments comprise a convex external surface, and wherein pressing on the packing element engages the convex external surfaces of the array of hardened segments with the concave semi-spherical internal surface. 
     
     
         4 . The method of  claim 3 , wherein the concave semi-spherical internal surface of the BOP head guides the array of hardened segments to move in the spiral configuration. 
     
     
         5 . The method of  claim 1 , further comprising guiding the movement of the array of hardened segments in the spiral configuration via the actuator plate, wherein the actuator plate comprises slots formed therein, and wherein each hardened segment comprises a support arm extending therefrom and seated in a corresponding one of the slots in the actuator plate. 
     
     
         6 . The method of  claim 1 , comprising moving the array of hardened segments in the spiral configuration to fully close the bore through the packing element. 
     
     
         7 . The method of  claim 6 , further comprising sealing the bore through the packing element via the elastomer. 
     
     
         8 . The method of  claim 7 , wherein the elastomer seals the bore through the packing element before the array of hardened segments fully close the bore through the packing element. 
     
     
         9 . The method of  claim 1 , wherein each hardened segment comprises a wedge shape with a leading edge facing the axis of the packing element, a trailing edge facing away from the axis of the packing element, and complementary stepped profiles formed along the leading edge and the trailing edge, wherein the trailing edge of each hardened segment receives and guides the leading edge of an adjacent hardened segment. 
     
     
         10 . The method of  claim 1 , comprising providing variable bore sealing of the annular BOP via the packing element. 
     
     
         11 . A packing element for an annular BOP, the packing element comprising:
 an array of hardened segments arranged circumferentially about a longitudinal axis of the packing element;   an actuator plate; and   an elastomer disposed between and bonded to the actuator plate and the array of hardened segments;   wherein the array of hardened segments is movable in a spiral configuration relative to a longitudinal axis of the packing element to reduce a size of or fully close a bore through the packing element.   
     
     
         12 . The packing element of  claim 11 , wherein each of the hardened segments comprises a leading edge oriented substantially tangential to the bore through the packing element. 
     
     
         13 . The packing element of  claim 12 , wherein the array of hardened segments is movable in a spiral configuration whereby each hardened segment moves in a tangential direction relative to the bore and in a radially inward direction with respect to the axis of the packing element. 
     
     
         14 . The packing element of  claim 11 , wherein each of the hardened segments comprise a convex external surface configured to engage with a complementary concave semi-spherical internal surface formed in a BOP head of the annular BOP. 
     
     
         15 . The packing element of  claim 11 , wherein each hardened segment comprises a rounded wedge shape with a leading edge facing the axis of the packing element, a trailing edge facing away from the axis of the packing element, and a convex external surface extending between the leading and trailing edges. 
     
     
         16 . The packing element of  claim 15 , wherein each hardened segment comprises a stepped profile formed along the leading edge and a complementary stepped profile formed along the trailing edge, wherein the trailing edge of each hardened segment receives and guides the leading edge of an adjacent hardened segment. 
     
     
         17 . The packing element of  claim 11 , wherein the actuator plate comprises slots formed therein, and wherein each hardened segment comprises a support arm extending therefrom and seated in a corresponding one of the slots in the actuator plate. 
     
     
         18 . The packing element of  claim 17 , wherein each of the slots is aligned in a tangential orientation with respect to the bore through the packing element. 
     
     
         19 . The packing element of  claim 11 , wherein each hardened segment comprises a downward facing surface with an extension extending therefrom, wherein the elastomer is bonded to the concave surface and to the extension. 
     
     
         20 . The packing element of  claim 11 , wherein movement of the array of hardened segments in the spiral configuration forces the elastomer to deform radially inward.