Downhole Cross Flow Prevention During Well and Power Shutdown

Abstract

A system and method for automatically preventing cross flow in a subterranean well during a shutdown event includes a plurality of downhole control valves located within the subterranean well. An energy storage device releases a stored energy during a shutdown event. A primary fail device is a normally close, fail open device that moves to a primary open position during a shutdown event, providing a portion of the stored energy to each of the plurality of downhole control valves during a shutdown event. The portion of the stored energy delivered to each of the plurality of downhole control valves is sufficient to move each of the plurality of downhole control valves to a valve closed position.

What is claimed is: 
     
         1 . A system for automatically preventing cross flow in a subterranean well during a shutdown event, the system comprising:
 a plurality of downhole control valves located within the subterranean well;   an energy storage device, the energy storage device releasing a stored energy during the shutdown event; and   a primary fail device, the primary fail device being a normally close, fail open device that moves to a primary open position during the shutdown event, providing a portion of the stored energy to each of the plurality of downhole control valves during the shutdown event, the portion of the stored energy delivered to each of the plurality of downhole control valves being sufficient to move each of the plurality of downhole control valves to a valve closed position.   
     
     
         2 . A system in accordance with  claim 1 , further comprising a secondary fail device, the secondary fail device being a normally open, fail close device that moves to a secondary closed position during the shutdown event, the secondary fail device being associated with a one of the downhole control valves and preventing such one of the downhole control valves from moving to the valve closed position when the portion of the stored energy is provided to each of the plurality of downhole control valves and each of the other of the plurality of downhole control valves is moved to the valve closed position. 
     
     
         3 . A system in accordance with  claim 2 , wherein the energy storage device is an accumulator and the plurality of downhole control valves are hydraulic valves. 
     
     
         4 . A system in accordance with  claim 2 , wherein the energy storage device is an electric storage device and the plurality of downhole control valves are electrically activated devices. 
     
     
         5 . A system in accordance with  claim 2 , wherein the energy storage device, primary fail device, and secondary fail device are located at an earth's surface outside of the subterranean well. 
     
     
         6 . A system in accordance with  claim 2 , wherein each downhole control valve is a hydraulically operated valve and the secondary fail device is a valve that is positioned to prevent a pressure media from traveling from the one of the downhole control valves when the secondary fail device is in the secondary closed position. 
     
     
         7 . A system in accordance with  claim 1 , wherein each downhole control valve is associated with a separate zone of the subterranean well and in the valve closed position, each downhole control valve restricts a flow of fluids into and out of the separate zone associated with such downhole control valve. 
     
     
         8 . A system for automatically preventing cross flow in a subterranean well during a shutdown event, the system comprising:
 a plurality of downhole control valves located within the subterranean well;   an accumulator associated with each of the plurality of downhole control valves, the accumulator storing a pressure media;   a primary fail device, the primary fail device being a valve that moves to a primary open position during the shutdown event, releasing a portion of the pressure media to the close side of each of the plurality of downhole control valves during the shutdown event; and   a secondary fail device, the secondary fail device being a valve that moves to a secondary closed position during the shutdown event, the secondary fail device being associated with one of the downhole control valves and preventing such one of the downhole control valves from moving to a valve closed position when the portion of the pressure media is provided to each of the plurality of downhole control valves and each of the other of the plurality of downhole control valves is moved to the valve closed position.   
     
     
         9 . A system in accordance with  claim 8 , wherein the accumulator, primary fail device, and secondary fail device are located at an earth's surface outside of the subterranean well. 
     
     
         10 . A system in accordance with  claim 8 , wherein each downhole control valve is associated with a separate zone of the subterranean well and in the valve closed position, each downhole control valve restricts a flow of fluids into and out of the separate zone associated with such downhole control valve. 
     
     
         11 . A system in accordance with  claim 8 , further comprising a fluid return line associated with an open side of each of the plurality of downhole control valves and providing a fluid flow path for a trapped pressure media to exit the open side of the downhole control valve as the downhole control valve moves to the valve closed position. 
     
     
         12 . A system in accordance with  claim 11 , wherein the secondary fail device is positioned between the open side of the one of the downhole control valves and the fluid return line so that in the secondary closed position, the secondary fail device prevents the trapped pressure media from exiting the open side of the one of the downhole control valves. 
     
     
         13 . A method for automatically preventing cross flow in a subterranean well during a shutdown event, the method comprising:
 locating a plurality of downhole control valves located within the subterranean well; and   during the shutdown event, providing a portion of a stored energy to each of the plurality of downhole control valves, the portion of the stored energy being sufficient to move each of the plurality of downhole control valves to a valve closed position, the stored energy being released from an energy storage device with a primary fail device, the primary fail device being a normally close, fail open device that moves to a primary open position during the shutdown event.   
     
     
         14 . A method in accordance with  claim 13 , further comprising preventing one of the plurality of downhole control valves from moving to the valve closed position during the shutdown event with a secondary fail device, the secondary fail device being a normally open, fail close device associated with a one of the downhole control valves that moves to a secondary closed position during the shutdown event, so that the one of the downhole control valves remains in a valve open position and each of the other of the plurality of downhole control valves is moved to the valve closed position. 
     
     
         15 . A method in accordance with  claim 14 , wherein the energy storage device is an electric storage device and the plurality of downhole control valves are electrically activated devices, and wherein the step of releasing the stored energy from the energy storage device includes releasing a portion of stored electric energy to each of the plurality of downhole control valves during the shutdown event. 
     
     
         16 . A method in accordance with  claim 14 , wherein the energy storage device is an accumulator and the primary fail device and the secondary fail device are hydraulic valves, and wherein the step of releasing the stored energy from the energy storage device includes releasing the portion of a pressure media to a close side of each of the plurality of downhole control valves during the shutdown event. 
     
     
         17 . A method in accordance with  claim 14 , further comprising providing a fluid flow path for a trapped pressure media to exit an open side of the downhole control valve as the downhole control valve moves to the valve closed position with a fluid return line associated with the open side of each of the plurality of downhole control valves. 
     
     
         18 . A method in accordance with  claim 17 , wherein the secondary fail device is positioned between the open side of the one of the downhole control valves and the fluid return line, the method further comprising preventing the trapped pressure media from exiting the open side of the one of the downhole control valves with the secondary fail device when the secondary fail device is in the secondary closed position. 
     
     
         19 . A method in accordance with  claim 14 , further comprising locating the energy storage device, primary fail device, and secondary fail device at an earth's surface outside of the subterranean well. 
     
     
         20 . A method in accordance with  claim 14 , further comprising after the shutdown event:
 moving the primary fail device to a primary closed position;   moving the secondary fail device to a secondary open position;   moving at least one of the other of the plurality of downhole control valves to the valve open position; and   recharging the energy storage device.   
     
     
         21 . A method in accordance with  claim 13 , further comprising associating each downhole control valve with a separate zone of the subterranean well so that in the valve closed position, each downhole control valve restricts a flow of fluids into and out of the separate zone associated with such downhole control valve.