Seal with flexible nose for use with a lock-down ring on a hanger in a wellbore

Abstract

A seal system selectively set between coaxial downhole tubulars seals between the tubulars; the system also locks the tubulars together to resist relative axial movement from thermal expansion. The seal system includes a seal element with a nose ring that couples a lock-down ring to both the inner and outer tubulars. Before inserting the seal system between the tubulars, the lock-down ring is disposed in a groove on the inner tubular. Setting the seal system drives a lower tip of the nose ring between the lock-down ring and inner tubular, thereby urging the lock-down ring radially outward. A portion of the lock-down ring remains in the groove, while an outer radial portion of the lock-down ring inserts into a profile on the outer tubular. Axial movement of a tubular transfers force to the other tubular through the lock-down ring, while a minimal amount of force transfers through the seal system.

What is claimed is: 
     
         1 . A seal system for use between downhole inner and outer tubulars comprising:
 a seal element having a body and inner and outer annular legs projecting from the body that are spaced radially apart to define a gap between the legs;   a lock-down ring between the tubulars; and   a nose ring on an end of the body of the seal element distal from the legs that has an elongate side having an inserting configuration that is generally parallel with an axis of the tubulars, and selectively changeable to a set configuration that is generally oblique with the axis when inserted between the lock-down ring and inner tubular.   
     
     
         2 . The seal system of  claim 1 , wherein when the nose ring is inserted between the lock-down ring and inner tubular, the nose ring substantially occupies the space between the lock-down ring and inner tubular. 
     
     
         3 . The seal system of  claim 1 , wherein when the nose ring is inserted between the lock-down ring and inner tubular, an outer radial portion of the lock-down ring projects into a profile in the outer tubular and an inner radial portion is disposed in a lock-down groove on the inner tubular thereby axially affixing together the inner and outer tubulars. 
     
     
         4 . The seal system of  claim 1 , further comprising slots that extend through sidewalls of the nose ring from an end of the nose ring distal from the seal element. 
     
     
         5 . The seal system of  claim 4 , wherein fingers are defined between adjacent slots. 
     
     
         6 . The seal system of  claim 1 , wherein the inner radius of the lock-down ring projects radially inward proximate a side of the lock-down ring distal from the seal element. 
     
     
         7 . The seal system of  claim 1 , wherein the outer tubular comprises a wellhead housing that is part of a wellhead assembly, and wherein the inner tubular comprises a casing hanger. 
     
     
         8 . The seal system of  claim 1 , wherein directing the energizing ring against the seal element with a nose ring energizing force urges the nose ring between the lock-ring and the inner tubular, wherein inserting the energizing ring into the gap between the inner and outer legs with a seal energizing force on the energizing ring, drives the energizing ring into the gap and urges the legs radially outward into sealing contact with the tubulars, and wherein the seal energizing force is greater than the nose ring energizing force. 
     
     
         9 . A seal system for sealing between coaxial tubulars that are part of a wellhead assembly comprising:
 an annular seal element having radially spaced apart inner and outer legs that define a gap therebetween, and that are in sealing contact with opposing surfaces of the tubulars;   a lock-down ring having opposing radial portions in interfering contact with oppositely facing profiles in the tubulars, so that portions of the tubulars adjacent the seal element are axially static; and   a nose ring having an end coupled with an end of the seal element and a portion spaced from the seal element that is wedged between the lock-down ring and one of the tubulars and projects along a path generally oblique to the seal element, and thereby retaining the lock-down ring in interfering contact with the tubulars.   
     
     
         10 . The seal system of  claim 9 , wherein the one of the tubulars comprises a casing hanger, and wherein the portion of the nose ring projects radially inward. 
     
     
         11 . The seal system of  claim 9 , wherein a notch is scored on a radial surface of the nose ring so the nose ring can be changed from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars. 
     
     
         12 . The seal system of  claim 9 , wherein the nose ring changes from an elongate shape to the oblique shape when inserted between the lock-ring and the one of the tubulars, and wherein a force for inserting the nose ring between the lock-ring and the one of the tubulars is less than a force for energizing the seal element. 
     
     
         13 . The seal system of  claim 9 , wherein the tubulars comprise an inner tubular and an outer tubular, and oppositely facing profiles in the tubulars comprise an upward facing pedestal defined by a lower surface of a lock-down groove formed along an outer circumference of the inner tubular and a downward facing shoulder defined by a profile formed along an inner circumference of the outer tubular. 
     
     
         14 . A system for sealing between tubulars in a wellhead assembly comprising:
 a seal element selectively inserted between the tubulars;   a lock-down ring selectively disposed on an profile on an outer surface of a one of the tubulars, and selectively urged to a position towards another one of the tubulars and into interfering contact with an oppositely facing profile on the another one of the tubulars; and   a nose ring on an end of the seal element that selectively inserts between the lock-down ring and the one of the tubulars into a setting position to urge the lock-down ring into the interfering contact, so that forces resulting from relative axial movement of the tubulars are applied to the lock-down ring and bypass the seal element.   
     
     
         15 . The system of  claim 14 , wherein the interfering contact of the lock-down ring maintains the portions of the tubulars adjacent the seal in relative static positions. 
     
     
         16 . The system of  claim 14 , wherein when the nose ring is in the setting position the nose ring substantially occupies the space between the lock-ring and the one of the tubulars. 
     
     
         17 . The system of  claim 14 , wherein the one of the tubulars comprises a casing hanger and the another one of the tubulars comprises a wellhead housing.