Slip release mechanism

An apparatus for activating a slip for downhole use, comprising:

• at least one slip;
• a slip support member having a longitudinal axis, said slip movably mounted to said slip support member for selective movement toward and away from said longitudinal axis of said slip support member;
• a weakening assembly on said slip support member selectively operable to facilitate retraction of said slip toward said longitudinal axis of said slip support member;
• said slip support member has a wall in which said weakening assembly is mounted;
• and
• said weakening assembly selectively allowing portions of said wall to move with respect to each other thereby undermining support for said slip when it is in contact with an object and in a position away from the longitudinal axis of said slip support member.

A method of releasing a slip from a set position where it is wedged between a support member and a casing or liner, comprising:

• providing a weakening assembly retained by the support member;
• moving the weakening assembly with respect to the support member while continuing to retain said weakening assembly thereto;
• weakening a wall in said support member by said moving;
• and
• retracting the slip from the casing or wellbore.

A method of releasing a slip from a set position where it is wedged between a support member and a casing or liner, comprising:

• providing a weakening assembly in the support member;
• providing as a part of said weakening assembly at least one notch in the wall of said support member;
• providing a movable element in said notch;
• actuating the weakening assembly to weaken a wall in said support member;
• selectively positioning said element to allow opposed forces of said notch to move with respect to each other as a result of said actuating step;
• retracting the slip from the casing or wellbore.

A release mechanism for an uppermost slip assembly used to selectively retain a removable downhole tool against a liner or casing comprising:

• a cone having a wall and movably supporting a plurality of slips;
• a movable wall member movably retained in said cone wall between a first and second position and selectively operable to provide wall support in said first position and no wall support in said second position;
• and
• whereupon actuation of said wall member, circumferential flexing of portions of said cone wall with respect to said wall member relieves a wedging force on said slips, facilitating their retraction from the casing or liner.

A release mechanism for an uppermost slip assembly used to selectively retain a removeable downhole tool against a liner or casing, comprising:

• a cone having a wall and movably supporting a plurality of slips;
• a movable wall member in said cone wall selectively operable to provide wall support in a first position and no wall support in a second position;
• and
• whereupon actuation of said wall member, flexing of portions of said cone wall with respect to said wall member relieves a wedging force on said slips, facilitating their retraction from the casing or liner;
• a mandrel, said mandrel acting on said slips to set them against the casing or liner and to retract said slips after it moves said movable wall member to its second said position;
• said movable wall member is a tapered element disposed in a notch in said cone wall;
• said tapered element having a thick portion which spans said notch and is releasably secured for structural support of said wall of said cone, with said thick segment spanning said notch;
• and
• said mandrel selectively overcoming the securing forces on said tapered element and shifting it so a thinner portion is disposed in said notch.