Wellhead isolation tool and methods

Abstract

An isolation tool and related methods for protecting a wellhead to which a casing string is operably coupled. In an exemplary embodiment, the isolation tool includes an anchor assembly adapted to be connected to the wellhead; a mandrel adapted to sealingly engage an interior portion of at least one of the wellhead and the casing string; and a lock assembly including a mandrel head connected to the mandrel and adapted to be displaced, relative to the anchor assembly and the wellhead, to sealingly engage the mandrel with the interior portion; a landing sleeve connected to the mandrel head and adapted to be displaced, relative to the mandrel head, the mandrel, the anchor assembly, and the wellhead, to engage the anchor assembly; and a connector adapted to secure the landing sleeve to the anchor assembly when the mandrel sealingly engages the interior portion and the landing sleeve engages the anchor assembly. In an alternative embodiment, the landing sleeve may be unnecessary, as the range of adjustment for the mandrel may be provided by the combination of a lockdown wing which threadably engages the anchor assembly and a weight holding lug which threadably engages the mandrel head.

1 . An isolation tool for protecting a wellhead to which a casing string is operably coupled, the isolation tool comprising:
 an anchor assembly comprising a support member, at least a portion of said support member being externally threaded;   a mandrel comprising a packoff assembly; and   a lock assembly comprising:
 a mandrel head operably connected to said mandrel, said mandrel comprising an exterior annular shoulder, and at least a portion of said mandrel head being externally threaded; 
 a lockdown wing comprising an interior annular shoulder and an upper annular surface, at least a portion of said lockdown wing being internally threaded and configured to threadably engage with the externally threaded portion of said support member; and 
 a weight holding lug comprising a lower annular surface configured to abut the upper annular surface of said lockdown wing, at least a portion of said weight holding lug being internally threaded and configured to threadably engage with the externally threaded portion of said mandrel head. 
   
     
     
         2 . The isolation tool of  claim 1 , further configured such that said mandrel and mandrel head are locked in position when said lockdown wing has threadably engaged said support member. 
     
     
         3 . The isolation tool of  claim 1 , wherein the anchor assembly further comprises:
 a first member adapted to be connected to a wellhead;   a base plate connected to the first member and adapted to be secured to said support member via a weld-less connection.   
     
     
         4 . A method of protecting a wellhead to which a casing string is operably coupled, the method comprising:
 connecting to a wellhead an anchor assembly comprising a support member;   positioning within the wellhead a mandrel comprising a packoff assembly, wherein the mandrel is connected to, and adapted to move axially together with, a mandrel head;   threadably engaging a weight holding lug with an externally threaded portion of said mandrel head;   axially displacing the mandrel and mandrel head relative to the anchor assembly and wellhead, such that the packoff assembly is positioned at a desired location within at least one of the wellhead and the casing string;   threadably engaging a lockdown sleeve with an externally threaded portion of said support member, such that said mandrel and mandrel head are locked in the desired position;   rotating said weight holding lug such that the lug advances axially in a downward direction until a lower annular surface of the weight holding lug abuts an upper annular surface of said lockdown wing.   
     
     
         5 . The method of  claim 4 , wherein the desired location of the packoff assembly creates a sealing engagement with at least one of the wellhead and the casing string. 
     
     
         6 . The method of  claim 4 , wherein the anchor assembly further comprises:
 a first member adapted to be connected to a wellhead;   a base plate connected to the first member and adapted to be secured to said support member via a weld-less connection.