Annulus activated drain valve, method and system

Abstract

An annulus activated drain valve comprising a mandrel, a port extending laterally through the mandrel, a first piston disposed initially to block the port and responsive to pressure in a volume that radially outwardly surrounds the first piston, a second piston interactive with the first piston, and a biaser associated with the second piston that biases the second piston to a predetermined position. A method for managing a borehole system including reaching a threshold pressure in an annular space around an annulus activated drain valve, shifting a first and a second piston from initial positions to second positions, and locking the first piston in the second position, and returning the second piston to the second piston initial position. A borehole system including a borehole in a subsurface formation, a string in the borehole, an annulus activated drain valve disposed within or as a part of the string.

What is claimed is: 
     
         1 . An annulus activated drain valve comprising:
 a mandrel;   a port extending laterally through the mandrel;   a first piston disposed initially to block the port and responsive to pressure in a volume that radially outwardly surrounds the first piston;   a second piston interactive with the first piston; and   a biaser associated with the second piston that biases the second piston to a predetermined position.   
     
     
         2 . The valve as claimed in  claim 1 , wherein the first piston includes an interlock feature that automatically locks the first piston in a second position. 
     
     
         3 . The valve as claimed in  claim 2 , wherein the interlock is a C-ring. 
     
     
         4 . The valve as claimed in  claim 1 , wherein the first piston is initially fixed in a first position by a release. 
     
     
         5 . The valve as claimed in  claim 4 , wherein the release is a shear release. 
     
     
         6 . The valve as claimed in  claim 1 , wherein the first piston is configured to experience a load from the second piston. 
     
     
         7 . The valve as claimed in  claim 1 , wherein the second piston is drivable by annulus pressure. 
     
     
         8 . The valve as claimed in  claim 1 , wherein the biaser is at rest with the second piston in an initial position and in a potential energy storage condition when the second piston is in a second position. 
     
     
         9 . The valve as claimed in  claim 1 , wherein the second piston departs from an initial position upon the valve experiencing a threshold pressure in the volume and is moved by the biaser from a second position back to the initial position when pressure in the volume subsides below the threshold pressure. 
     
     
         10 . A method for managing a borehole system comprising:
 reaching a threshold pressure in an annular space around an annulus activated drain valve;   shifting a first and a second piston from initial positions to second positions; and   locking the first piston in the second position; and   returning the second piston to the second piston initial position.   
     
     
         11 . The method as claimed in  claim 10 , wherein the valve includes a port. 
     
     
         12 . The method as claimed in  claim 11 , further including opening the port upon returning the second piston to the initial position. 
     
     
         13 . The method as claimed in  claim 10 , wherein the reaching the threshold causes shifting of a plurality of annulus activated drain valves simultaneously. 
     
     
         14 . A borehole system comprising:
 a borehole in a subsurface formation;   a string in the borehole;   an annulus activated drain valve as claimed in  claim 1  disposed within or as a part of the string.   
     
     
         15 . The system as claimed in  claim 14  including a plurality of simultaneously actuable annulus activated drain valves.