Hydrostatic module interlock, method and system

Abstract

A hydrostatic module interlock for a downhole tool including a piston having fingers extending from a body thereof, a piston mandrel telescopically arranged with the piston, and a retaining piston disposed to prevent finger deflection in the first position and allow finger deflection in the second position. A method for actuating an interlocked tool including loading a release configuration to a threshold force, releasing the release configuration, moving a retaining piston out of a first position wherein the retaining piston physically impedes deflection of a finger of a piston, deflecting the finger out of engagement with a piston mandrel telescopically arranged relative to the piston, and moving the piston relative to the piston mandrel. A borehole system including a borehole in a subsurface formation, a string disposed in the borehole, and a hydrostatic module interlock disposed within or as a part of the string.

What is claimed is: 
     
         1 . A hydrostatic module interlock for a downhole tool comprising:
 a piston having fingers extending from a body thereof;   a piston mandrel telescopically arranged with the piston; and   a retaining piston disposed to prevent finger deflection in the first position and allow finger deflection in the second position.   
     
     
         2 . The interlock as claimed in  claim 1  wherein the piston fingers include gripping ends. 
     
     
         3 . The interlock as claimed in  claim 2  wherein the gripping ends are teeth. 
     
     
         4 . The interlock as claimed in  claim 1  wherein the fingers are collet fingers. 
     
     
         5 . The interlock as claimed in  claim 2  wherein the mandrel includes a feature to engage the gripping ends. 
     
     
         6 . The interlock as claimed in  claim 1  wherein the retaining piston includes a ring adjacent perimetrical surfaces of the fingers. 
     
     
         7 . The interlock as claimed in  claim 1  wherein the retaining piston includes retaining appendages engaged with the fingers when in the first position. 
     
     
         8 . The interlock as claimed in  claim 7  wherein the appendages are interspersed with the fingers. 
     
     
         9 . The interlock as claimed in  claim 7  wherein the appendages include non radial angled side surfaces that engage finger side surfaces thereby preventing radial deflection of the fingers while the retaining piston is in the first position. 
     
     
         10 . The interlock as claimed in  claim 1 , further comprising a release configuration preventing movement of the retaining piston from the first position to the second position. 
     
     
         11 . The interlock as claimed in  claim 10 , wherein the release configuration releases at a threshold force on the retaining piston. 
     
     
         12 . The interlock as claimed in  claim 11 , wherein the release configuration is a shear member. 
     
     
         13 . A method for actuating an interlocked tool comprising:
 loading a release configuration to a threshold force;   releasing the release configuration;   moving a retaining piston out of a first position wherein the retaining piston physically impedes deflection of a finger of a piston;   deflecting the finger out of engagement with a piston mandrel telescopically arranged relative to the piston; and   moving the piston relative to the piston mandrel.   
     
     
         14 . The method as claimed in  claim 13  wherein the moving of the retaining piston is moving a ring out of contact with a perimetrical surface of the finger. 
     
     
         15 . The method as claimed in  claim 13  wherein the moving of the retaining piston is moving a retaining appendage out of contact with a side surface of the finger. 
     
     
         16 . A borehole system comprising:
 a borehole in a subsurface formation;   a string disposed in the borehole; and   a hydrostatic module interlock as claimed in  claim 1  disposed within or as a part of the string.