Patent ID: 8631878

Claim:
A wellhead assembly comprising: a wellhead housing; a tubular inner wellhead member coaxial within the wellhead housing relative to an axis of the wellhead housing and stationarily landed within the wellhead housing; an external upward facing shoulder on the inner wellhead member, defining is seal pocket between the inner wellhead member and the wellhead housing, the shoulder being in a plane perpendicular to the axis, an outer surface of the inner wellhead member within the seal pocket being cylindrical, and inner surface of the outer wellhead member within the seal pocket being cylindrical; an annular seal assembly in the seal pocket and comprising, an annular elastomeric sealing ring, an annular metallic upper ring on an upper end of the sealing ring, an annular metallic base ring attached to a lower end of the sealing ring, the base ring having a lower portion that abuts the upward facing shoulder and is integrally formed with the base ring and configured into a resilient member; a lockdown member in engagement with the inner wellhead member and the wellhead housing and having a lower end in abutment with the upper ring to deform the sealing ring into static sealing engagement with the inner wellhead member and the wellhead housing when an axial force is applied to the lockdown member, and wherein the axial force on the lockdown member exerts a compressive force to axially deform the lower portion of the base ring; and wherein the axially deformed lower portion of the base ring exerts an upward force on the sealing ring to maintain the static scaling engagement in the event that cooling causes the sealing ring to shrink.