Patent ID: 7644757

Claim:
A fixed-point packoff element of a full-bore wellhead isolation tool, comprising: a hollow body with a continuous sidewall and a central passage that is at least as large as a diameter of a production tubing supported by a tubing head spool of a wellhead isolated by the full-bore wellhead isolation tool, the hollow body having a cylindrical top end and a cylindrical bottom end, the cylindrical top end of the hollow body being adapted to be received in a seal bore above a side port of the tubing head spool and the cylindrical bottom end is adapted to be received in another seal bore below the side port of the tubing head spool; at least one O-ring groove adapted to receive an O-ring that provides a primary seal between the cylindrical bottom end and the other seal bore below the side port of the tubing head spool; at least one O-ring groove adapted to receive an O-ring that provides a test seal between the cylindrical top end and the seal bore above the side port of the tubing head spool; and an O-ring groove in a bevel on the cylindrical bottom end that mates with a bit guide of the tubing head spool, the O-ring groove receiving an O-ring that inhibits well stimulation fluid from migrating between the bevel and the bit guide.