Running Tool with Retractable Collet for Liner String Installation in a Wellbore

Abstract

A running tool for installing a liner string having a profile in a wellbore. The running tool includes a mandrel, a prop assembly positioned about the mandrel and a collet assembly slidably positioned on the mandrel. The collet assembly has a generally cylindrical collet collar with a plurality of collet fingers extending therefrom each having a collet head on a distal end thereof. In a first position, the prop assembly radially outwardly flexes the collet fingers such that the collet heads engage the profile of the liner string and are operable to apply a force in the downhole direction to the liner string. In a second position, the collet assembly is remote from the prop assembly such that the collet fingers radially inwardly contract disengaging the collet heads from the profile of the liner string, thereby enabling removal of the running tool from the liner string.

What is claimed is: 
     
         1 . A running tool for installing a liner string having a profile in a wellbore, the running tool comprising:
 a mandrel;   a collet assembly slidably positioned on the mandrel, the collet assembly having a generally cylindrical collet collar with a plurality of collet fingers extending therefrom each having a collet head on a distal end thereof; and   a prop assembly positioned about the mandrel,   wherein, in a first position of the collet assembly relative to the mandrel, the prop assembly radially outwardly flexes the collet fingers such that the collet heads engage the profile of the liner string and are operable to apply a force in the downhole direction to the liner string; and   wherein, in a second position of the collet assembly relative to the mandrel, the collet assembly is remote from the prop assembly such that the collet fingers radially inwardly contract disengaging the collet heads from the profile of the liner string, thereby enabling removal of the running tool from the liner string.   
     
     
         2 . The running tool as recited in  claim 1  wherein, in the second position of the collet assembly relative to the mandrel, an inner surface of the collet heads is proximate the mandrel forming clearance gaps therebetween. 
     
     
         3 . The running tool as recited in  claim 1  wherein, in the second position of the collet assembly relative to the mandrel, an inner surface of the collet heads contacts the mandrel. 
     
     
         4 . The running tool as recited in  claim 1  wherein, in the second position of the collet assembly relative to the mandrel, the collet fingers are angled toward the mandrel from the collet collar to the collet heads. 
     
     
         5 . The running tool as recited in  claim 4  wherein the collet fingers are angled between about 2 degrees and about 6 degrees. 
     
     
         6 . The running tool as recited in  claim 1  wherein, in the first position of the collet assembly relative to the mandrel, the collet fingers are in a first radially outwardly flexed state and wherein, in the second position of the collet assembly relative to the mandrel, the collet fingers are in a second radially outwardly flexed state that is less than the first radially outwardly flexed state. 
     
     
         7 . The running tool as recited in  claim 1  wherein, in the first position of the collet assembly relative to the mandrel, the collet fingers are in the radially outwardly flexed state and wherein, in the second position of the collet assembly relative to the mandrel, the collet fingers are in a radially relaxed state. 
     
     
         8 . The running tool as recited in  claim 7  wherein, in the second position of the collet assembly relative to the mandrel, the collet fingers are operable to be radially inwardly flexed to contact an inner surface of the collet heads with the mandrel. 
     
     
         9 . A method for installing a liner string with a profile in a wellbore, the method comprising:
 lowering the liner string into the wellbore on a running tool, the running tool including a mandrel, a prop assembly positioned about the mandrel and a collet assembly slidably positioned on the mandrel, the collet assembly having a generally cylindrical collet collar with a plurality of collet fingers extending therefrom each having a collet head on a distal end thereof;   engaging the collet heads in the profile of the liner string by radially outwardly flexing the collet fingers with the prop assembly;   applying a force in the downhole direction to the liner string with the collet assembly;   positioning the liner string at a desired location in the wellbore;   disengaging the collet heads from the profile of the liner string by unpropping the collet assembly such that the collet fingers radially inwardly contract; and   removing the running tool from the liner string.   
     
     
         10 . The method as recited in  claim 9  further comprising lowering the running tool downhole into the liner string after disengaging the collet heads from the profile of the liner string. 
     
     
         11 . The method as recited in  claim 9  wherein disengaging the collet heads from the profile of the liner string further comprises locating an inner surface of the collet heads proximate to the mandrel forming clearance gaps therebetween. 
     
     
         12 . The method as recited in  claim 9  wherein disengaging the collet heads from the profile of the liner string further comprises contacting an inner surface of the collet heads with the mandrel. 
     
     
         13 . The method as recited in  claim 9  wherein disengaging the collet heads from the profile of the liner string further comprises positioning the collet fingers at an angle toward the mandrel from the collet collar to the collet heads. 
     
     
         14 . The method as recited in  claim 9  wherein disengaging the collet heads from the profile of the liner string further comprises placing the collet fingers in a reduced radially outwardly flexed state. 
     
     
         15 . The method as recited in  claim 9  wherein disengaging the collet heads from the profile of the liner string further comprises placing the collet fingers in a radially relaxed state. 
     
     
         16 . The method as recited in  claim 15  further comprising radially inwardly flexing the collet fingers to contact an inner surface of the collet heads with the mandrel.