Wellhead Component with Seal Surface and Method of Forming the Seal

Abstract

A subset wellhead component has a metal seal surface having voids. The voids are initially filled with an elastomeric substrate having hollow beads. When lowered into the subsea assembly, the beads have sufficient strength to resist collapsing under a hydrostatic pressure of liquid within the subsea wellhead assembly to prevent shrinking of a volume of the substrate. Exerting a setting force on the metal seal surface to form the sealing engagement causes the beads to collapse and reduce the volume of the substrate within the voids. The seal surface may be folds of a bellows-type nose ring of a seal assembly. The seal surface may alternately be wickers formed in the bore of the wellhead housing.

1  A method of forming a sealing engagement in a subsea wellhead assembly having an axis, comprising:
 providing a subsea wellhead component with a metal seal surface having voids; 
 filling the voids with an elastomeric substrate having hollow beads embedded therein; 
 then, lowering the wellhead component into the sea and installing the wellhead component in the subsea wellhead assembly, the beads having sufficient strength to resist collapsing under a hydrostatic pressure of liquid within the subsea wellhead assembly to prevent shrinking of a volume of the substrate; and 
 then, exerting a setting force on the metal seal surface to form the sealing engagement, the setting force being at a level sufficient to collapse the beads and reduce the volume of the substrate within the voids. 
 
     
     
         2 . The method according to  claim 1 , wherein the beads are filled with a compressible fluid. 
     
     
         3 . The method according to  claim 1 , wherein the beads encapsulate a gas. 
     
     
         4 . The method according to  claim 1 , wherein the beads comprise glass microspheres. 
     
     
         5 . The method according to  claim 1 , wherein the elastomeric substrate is substantially incompressible. 
     
     
         6 . The method according to  claim 1 , wherein:
 the seal surface comprises a set of wickers formed on a side wall of a bore of a wellhead housing, the wickers comprising parallel grooves having valleys and crests;   the voids comprise the valleys of the wickers;   the method further comprises lowering a metal seal member into the bore of the wellhead housing; and   the setting force is exerted by radially moving the seal member against the wickers to embed the crests into the seal member and form the sealing engagement.   
     
     
         7 . The method according to  claim 1 , wherein:
 the seal surface comprises a seal body with folds defining crests and valleys, the voids comprising the valleys; and   the setting force is exerted axially on the seal body, causing the folds to move toward each other, and the crests to sealingly engage a portion of the wellhead assembly to form the sealing engagement.   
     
     
         8 . The method according to  claim 1 , wherein the beads are capable of withstanding collapsing to a pressure in a selected range from 10,000 to 20,000 psi. 
     
     
         9 . A method of forming a sealing engagement in a subsea wellhead assembly, comprising:
 providing a wellhead housing with a bore having an axis and a side wall containing a set of wickers comprising crests separated by valleys;   filling the valleys with an elastomeric substrate having hollow glass microspheres embedded therein;   then lowering the wellhead housing into the sea and installing the wellhead housing in the subsea wellhead assembly, the microspheres having sufficient strength to resist collapsing due to a hydrostatic pressure of liquid within the wellhead housing, so as to prevent a volume of the substrate horn decreasing;   then, lowering a metal seal member having a metal seal surface into the wellhead housing; then   energizing the seal member to cause the seal surface to radially move into engagement with the crests of the wickers with sufficient force for the crests to embed into the seal surface and the microspheres to collapse to allow the volume of the substrate in the valleys to decrease.   
     
     
         10 . The method according to  claim 9 , wherein the microspheres are filled with a compressible fluid. 
     
     
         11 . The method according to  claim 9 , wherein the microspheres encapsulate a gas. 
     
     
         12 . The method according to  claim 9 , wherein the elastomeric substrate is substantially incompressible. 
     
     
         13 . The method according to  claim 9 , wherein the microspheres are configured to collapse only after reaching a pressure in a selected range from 25,000 to 30,000 psi. 
     
     
         14 . A subsea wellhead assembly having an axis and comprising:
 a subsea wellhead component having a metal seal surface with voids;   the voids being filled with an elastomeric substrate having hollow beads embedded therein, the beads having sufficient strength to resist collapsing under a hydrostatic pressure of the sea to prevent shrinking of a volume of the substrate; and   energizing means for exerting a setting force on the metal seal surface to form a sealing engagement, the setting force being at a level sufficient to collapse the beads and reduce the volume of the substrate within the voids.   
     
     
         15 . The assembly according to  claim 14 , wherein the beads are filled with a compressible fluid. 
     
     
         16 . The assembly according to  claim 14 , wherein the beads comprise glass microspheres. 
     
     
         17 . The assembly according to  claim 14 , wherein the elastomeric substrate is substantially incompressible. 
     
     
         18 . The assembly according to  claim 14 , wherein:
 the wellhead component comprises a subsea wellhead housing having a bore with an axis;   the seal surface comprises a set of wickers formed on a side wall of the bore, the wickers comprising annular parallel grooves having valleys and crests;   the voids comprise the valleys of the wickers;   the assembly further comprises a metal seal member; and   the energizing means comprises an energizing ring that when moved axially, radially moves the seal member against the wickers at a sufficient setting force to embed the crests into the seal member and form the sealing engagement.   
     
     
         19 . The apparatus according to  claim 14 , further comprising:
 a subsea wellhead housing having a bore with an axis and a metal seal member deployed in the bore; wherein:   the seal surface comprises folds formed on the seal member that define crests and valleys, the voids comprising the valleys; and   the energizing means comprises an energizing ring that when moved axially, exerts the setting force axially on the seal member, causing the folds to move toward each other, and the crests to sealingly engage a side wall of the bore of the wellhead housing.   
     
     
         20 . The assembly according to  claim 14 , wherein:
 the beads are capable of withstanding collapsing up to a pressure in a selected range from 10,000 to 20,000 psi, and are configured to collapse when subjected to a pressure of 25,000 to 30,000 psi.