Axially actuated external wellhead latch

Abstract

A wellhead latch assembly may include one or more latches for attaching to a wellhead and allowing removal of the wellhead during a well abandonment process. The wellhead latch assembly may include an inner core coupled to the latches, and an outer sleeve for selectively latching and unlatching the latches to the wellhead. The inner core may abut the wellhead and can include a groove having circumferential and/or longitudinal features. The outer sleeve may include a pin which travels within the groove and a set of cut-outs for alignment with the latches. When the cut-outs align with the latches, the latches may expand radially outward and disengage the wellhead. As the outer sleeve moves axially or rotationally relative to the inner core, the latches may fall out of alignment with the cut-outs and move radially inwardly to engage or capture the wellhead.

What is claimed is: 
     
         1 . A method for removing a wellhead, comprising:
 deploying a well abandonment tool to a subsea wellhead, the well abandonment tool including a cutting tool and a wellhead latch assembly;   applying an axial force to the wellhead latch assembly using a conveyance system, the axial force causing the wellhead latch assembly to latch to an external surface of the subsea wellhead without rotation of the conveyance system;   separating the subsea wellhead from at least a portion of the borehole casing using the cutting tool; and   removing the subsea wellhead using the wellhead latch assembly and the conveyance system.   
     
     
         2 . The method of  claim 1 , further comprising:
 releasing the axial force, wherein the wellhead latch assembly remains latched to the subsea wellhead following release of the axial force.   
     
     
         3 . The method of  claim 1 , wherein applying the axial force to the wellhead latch assembly includes moving an outer sleeve relative to an inner core. 
     
     
         4 . The method of  claim 3 , wherein applying the axial force to the wellhead latch assembly includes moving the outer sleeve axially relative to the inner core. 
     
     
         5 . The method of  claim 3 , wherein applying the axial force to the wellhead latch assembly includes rotating the outer sleeve axially relative to the inner core. 
     
     
         6 . The method of  claim 3 , wherein causing the wellhead latch assembly to latch to the external surface of the subsea wellhead includes misaligning one or more latches coupled to the inner core with one or more cut-outs of the outer sleeve. 
     
     
         7 . The method of  claim 3 , wherein moving the outer sleeve relative to the inner core includes moving the outer sleeve along a path defined by a circumferential groove having rotational and axial components. 
     
     
         8 . A wellhead latch assembly, comprising:
 an inner core;   an outer sleeve movably coupled to the inner core; and   one or more latches configured to selectively engage an external surface of a wellhead in response to a purely axial force applied to the outer sleeve.   
     
     
         9 . The wellhead latch assembly of  claim 8 , the one or more latches being configured to selectively move between a released position in which the one or more latches align with one or more cut-outs of the outer sleeve, and a latched position when the one or more latches are out of alignment with the one or more cut-outs of the outer sleeve. 
     
     
         10 . The wellhead latch assembly of  claim 8 , the outer sleeve being configured to rotate relative to the inner core in response to the purely axially force. 
     
     
         11 . The wellhead latch assembly of  claim 8 , the inner core and the one or more latches being configured not to rotate in response to the purely axial force. 
     
     
         12 . The wellhead latch assembly of  claim 8 , the one or more latches being configured to move in purely radial directions to selectively engage and disengage the external surface of the wellhead. 
     
     
         13 . The wellhead latch assembly of  claim 8 , the outer core being coupled to the inner core using at least one circumferential feature configured to cause the purely axial force applied to the outer sleeve to move the outer sleeve axially and rotationally relative to the inner core. 
     
     
         14 . The wellhead latch assembly of  claim 8 , the inner core being configured to engage the wellhead and remain axially stationary in response to the purely axial force applied to the outer sleeve. 
     
     
         15 . The wellhead latch assembly of  claim 8 , further comprising:
 a downhole motor coupled to the inner core; and   a pipe cutter coupled to the downhole motor.   
     
     
         16 . The wellhead latch assembly of  claim 8 , further comprising:
 a biasing member resisting movement of the outer sleeve in at least one axial direction relative to the inner core.   
     
     
         17 . The wellhead latch assembly of  claim 8 , further comprising:
 a locking system for restricting the outer sleeve from moving axially relative to the inner core.