Patent ID: 7604058

Claim:
A casing mandrel for wells completed using an independent screwed wellhead, comprising: a casing mandrel body having an annular shoulder adapted for mating engagement with a top flange of a casing bowl nut of the independent screwed wellhead, an outer contour below the annular shoulder that mates with a casing bowl of the independent screwed wellhead, an axial passage that extends from a casing mandrel bottom end to a casing mandrel top end of the casing mandrel body, the axial passage having a diameter at least as large as an internal diameter of a casing that the casing mandrel suspends in the well, and a seal bore at a top of the axial passage, the seal bore having a larger diameter than the axial passage and adapted to receive a fixed-point packoff connected to a high pressure mandrel of a pressure isolation tool; and the casing mandrel top end extends above the annular shoulder and includes a pin thread located above a top of the casing bowl nut when the casing bowl nut secures the casing mandrel to the independent screwed wellhead, the pin thread adapted to be engaged by a box thread of a tubing head supported by the casing mandrel.