Pressure cycle downhole tool actuation

Abstract

A pressure isolation assembly can include multiple pressure isolation modules arranged in series and isolating a pressure actuated downhole tool from a downhole fluid pressure. Each of the modules may be configured to open in response to a single pressure cycle comprising an increase in the downhole fluid pressure followed by a decrease in the downhole fluid pressure. A method can include determining a number of fluid pressure cycles to apply to enable actuation of a downhole tool; installing a number of pressure isolation modules in a pressure isolation assembly, the number corresponding to the number of pressure cycles; deploying the downhole tool and the pressure isolation assembly while the pressure isolation assembly isolates a fluid passage of the downhole tool from downhole fluid pressure; and applying the number of pressure cycles, thereby permitting communication of at least a fraction of the downhole fluid pressure to the fluid passage.

What is claimed is: 
     
         1 . A pressure isolation assembly for use with a pressure actuated downhole tool in a subterranean well, the pressure isolation assembly comprising:
 multiple pressure isolation modules arranged in series and configured to isolate the pressure actuated downhole tool from a downhole fluid pressure,   each of the pressure isolation modules being configured to open in response to single pressure cycle comprising an increase in the downhole fluid pressure followed by a decrease in the downhole fluid pressure.   
     
     
         2 . The pressure isolation assembly of  claim 1 , in which each of the pressure isolation modules has a first configuration in which pressure communication through the pressure isolation module is prevented and the downhole fluid pressure is less than a first predetermined level, a second configuration in which pressure communication through the pressure isolation module is prevented and the downhole fluid pressure is greater than the first predetermined level, and a third configuration in which pressure communication through the pressure isolation module is permitted and the downhole fluid pressure is less than a second predetermined level. 
     
     
         3 . The pressure isolation assembly of  claim 1 , in which each of the pressure isolation modules comprises a piston sealingly received in a bore, and a release member configured to release the piston for displacement relative to the bore in response to a predetermined pressure applied to the piston. 
     
     
         4 . The pressure isolation assembly of  claim 3 , in which each of the pressure isolation modules further comprises a biasing device configured to displace the piston to a position in which pressure communication through the bore is permitted. 
     
     
         5 . The pressure isolation assembly of  claim 1 , further comprising a pressure reduction device configured to apply a fraction of the downhole fluid pressure to the pressure isolation modules, the fraction being less than one. 
     
     
         6 . The pressure isolation assembly of  claim 5 , in which the pressure reduction device comprises first and second piston areas, and the fraction is a ratio of the first and second piston areas. 
     
     
         7 . The pressure isolation assembly of  claim 1 , in which a number of the pressure isolation modules in the pressure isolation assembly equals a number of the pressure cycles necessary to enable actuation of the downhole tool with the downhole fluid pressure. 
     
     
         8 . A downhole tool assembly, comprising:
 a pressure actuated downhole tool configured to actuate in response to application of a downhole fluid pressure to the downhole tool assembly; and   a pressure isolation assembly that isolates a fluid passage of the downhole tool from the downhole fluid pressure, the pressure isolation assembly being configured to permit communication of at least a fraction of the downhole fluid pressure to the fluid passage in response to application of a predetermined number of pressure cycles to the pressure isolation assembly, each of the pressure cycles comprising a single increase in the downhole fluid pressure followed by a single decrease in the downhole fluid pressure.   
     
     
         9 . The downhole tool assembly of  claim 8 , in which the pressure isolation assembly comprises multiple pressure isolation modules arranged in series. 
     
     
         10 . The downhole tool assembly of  claim 9 , in which the multiple pressure isolation modules comprise at least first and second pressure isolation modules, the first pressure isolation module being configured to isolate the second pressure isolation module from the downhole fluid pressure until a first one of the pressure cycles is applied. 
     
     
         11 . The downhole tool assembly of  claim 9 , in which a number of the pressure cycles is equal to a number of the pressure isolation modules. 
     
     
         12 . The downhole tool assembly of  claim 9 , in which each of the pressure isolation modules is configured to open in response to application of a respective one of the pressure cycles. 
     
     
         13 . The downhole tool assembly of  claim 9 , in which each of the pressure isolation modules is configured to open in response to the decrease in the downhole fluid pressure of the respective one of the pressure cycles. 
     
     
         14 . The downhole tool assembly of  claim 8 , in which the pressure isolation assembly further comprises a pressure reduction device configured to apply the fraction of the downhole fluid pressure to the downhole tool, the fraction being less than one. 
     
     
         15 . A method of actuating a downhole tool, the method comprising:
 determining a number of downhole fluid pressure cycles to apply in a subterranean well to enable actuation of a downhole tool;   installing a number of pressure isolation modules in a pressure isolation assembly, the number of pressure isolation modules corresponding to the number of pressure cycles;   deploying the downhole tool and the pressure isolation assembly into the well while the pressure isolation assembly isolates a fluid passage of the downhole tool from downhole fluid pressure; and   applying the number of pressure cycles in the well, the pressure isolation assembly thereby permitting communication of at least a fraction of the downhole fluid pressure to the fluid passage.   
     
     
         16 . The method of  claim 15 , in which the installing comprises connecting the pressure isolation modules in series in the pressure isolation assembly. 
     
     
         17 . The method of  claim 15 , in which the applying comprises opening each of the pressure isolation modules in response to application of a respective one of the pressure cycles. 
     
     
         18 . The method of  claim 17 , in which the applying comprises opening each of the pressure isolation modules in response to a downhole fluid pressure decrease of the respective one of the pressure cycles. 
     
     
         19 . The method of  claim 15 , in which each of the pressure cycles is a single downhole fluid pressure increase followed by a single downhole fluid pressure decrease. 
     
     
         20 . The method of  claim 15 , in which the applying comprises applying the fraction of the downhole fluid pressure to the pressure isolation modules, the fraction being less than one.