Energy Retaining Toe Valve

Abstract

A downhole tool comprises a mechanical energy storage component that retains energy supplied by a first pressure increase and transfers such energy to actuate another component of the tool. In one aspect, the tool is a toe valve that is activated for opening ports thereon upon application of a first pressure and actuated to open the ports upon application of a second pressure lower than the first pressure.

We claim: 
     
         1 . A tool for deployment in a wellbore for performing a perforation step, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, wherein the tool comprises:
 a top sub, adapted to be connected to an uphole tubular component, and a bottom sub, adapted to be connected to a downhole tubular component;   a tubular housing extending between the top sub and the bottom sub, the tubular housing having a first end connected to the top sub and a second end connected to the bottom sub, and a wall with at least one perforation port for fluid communication through the wall;   a slidable sleeve provided within the tubular housing, the sliding sleeve being axially moveable with respect to the housing between a closed position, wherein the sleeve covers the at least one perforation port, and an open position, wherein the at least one perforation port is exposed allowing fluid communication through the wall of the tubular housing;   the top sub including a plurality of pistons, wherein each piston comprises a respective first end and second end;   the top sub including a biasing means for applying an axial force against the first ends of the pistons;   at least one first valve adapted to permit pressurized fluid within the lumen of the tool to impinge on the second ends of the pistons and energize the biasing means; and,   at least one second valve adapted to be actuated by the energized biasing means, whereby, upon actuation, the second valve provides a fluid channel between the lumen of the tool and the slidable sleeve.   
     
     
         2 . The tool of  claim 1 , wherein the sliding sleeve comprises a cylindrical body coaxially provided within the tubular body. 
     
     
         3 . The tool of  claim 1  further comprising a means of retaining the sliding sleeve in the closed position. 
     
     
         4 . The tool of  claim 1 , wherein the sliding sleeve includes a plurality of seals to prevent flow of fluid there-around when in the closed position. 
     
     
         5 . The tool of  claim 1 , wherein the pistons are circumferentially spaced apart. 
     
     
         6 . The tool of  claim 5 , wherein the pistons are provided within a piston housing connected to the top sub. 
     
     
         7 . The tool of  claim 6 , wherein the piston housing comprises a generally cylindrical body having a plurality of barrels for housing the pistons, wherein the second ends of the pistons are contained within respective apertures. 
     
     
         8 . The tool of  claim 1 , wherein the top sub includes at least one actuation port for transferring pressurized fluid from the lumen of the tool to the second ends of the pistons. 
     
     
         9 . The tool of  claim 8 , wherein the at least one actuation port is provided with a burst plug. 
     
     
         10 . The tool of  claim 1 , wherein the at least one first valve is a check valve. 
     
     
         11 . The tool of  claim 1 , wherein the at least one second valve is a spool valve. 
     
     
         12 . The tool of  claim 1 , wherein the biasing means comprises a spring. 
     
     
         13 . The tool of  claim 12 , wherein the spring comprises a wave spring or a labyrinth spring. 
     
     
         14 . A method of operating a tool deployed in a wellbore, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, the tool comprising:
 a top sub, adapted to be connected to an uphole tubular component, and a bottom sub, adapted to be connected to a downhole tubular component;   a tubular housing extending between the top sub and the bottom sub, the tubular housing having a wall with at least one port for fluid communication through the wall;   the housing including a slidable sleeve, wherein the sleeve is axially moveable between a closed position covering the at least one port, and an open position, wherein the at least one port is exposed allowing fluid communication through the wall of the tubular housing;   the top sub including a biasing means;   the method comprising:
 pressurizing the lumen of the tool with a fluid under a first pressure and actuating a first valve to permit the fluid to energize the biasing means; 
 reducing the pressure within the lumen of the tool and actuating a second valve to permit fluid within the lumen to impinge on the sliding sleeve; 
 pressurizing the lumen of the tool with a fluid under a second pressure to axially shift the sliding sleeve from the closed position to the open position; and, 
 pressurizing the lumen of the tool with a pressurized fluid to force the pressurized fluid through the at least one port provided on the housing. 
   
     
     
         15 . The method of  claim 14 , wherein energizing the biasing means comprises compressing a spring. 
     
     
         16 . The method of  claim 14 , further comprising conducting a perforation operation by ejecting a pressurized fluid through the ports.