Patent ID: 8387708

Claim:
A surface wellhead apparatus, comprising: an outer wellhead member having a bore coupled to an upper end of a string of conduit extending into a well; an inner wellhead member within the bore of the outer wellhead member, the inner wellhead member having a first toothed profile on an outer surface; an annular packoff configured to be located in an annulus between the inner and outer wellhead members to form a seal therebetween, the annular packoff having a tubular body; an inner seal on a inner surface of the body that seals against the inner wellhead member; an outer seal on an outer surface of the body that seals against the outer wellhead member; and an expandable inner retaining ring carried within a groove on the inner surface of the body below the inner seal, the inner retaining ring having a second toothed profile on an inner surface that engages the first toothed profile to lock the body of the packoff to the inner wellhead member, wherein the inner retaining ring ratchets inward and outward as the second toothed profile engages the first toothed profile during the insertion of the body of the packoff into the annulus.