Multistage well system and technique

Abstract

A technique that is usable with a well includes using untethered objects to operate a first plurality of tool of the string and using a string-conveyed tool to operate a second plurality of tools of the string.

What is claimed is: 
     
         1 . A method usable with a well, comprising:
 using untethered objects to operate a first plurality of tool of the string; and   using a string-conveyed tool to operate a second plurality of tools of the string.   
     
     
         2 . The method of  claim 1 , wherein the first plurality of tools are disposed closer to a distal end of the string than to another end of the string. 
     
     
         3 . The method of  claim 2 , wherein the first plurality of tools are disposed at a length greater than approximately 5000 feet from a heel of the well. 
     
     
         4 . The method of  claim 1 , wherein using the untethered objects to operate the first plurality of tools comprises using the untethered objects to selectively shift valve assemblies of the string open. 
     
     
         5 . The method of  claim 1 , wherein using the string-conveyed tool comprises using a shifting tool to operate the valve assemblies of the string. 
     
     
         6 . The method of  claim 1 , wherein using the untethered objects comprises:
 sensing a property of an environment of the string as at least one of the objects is being communicated through the passageway; and   selectively autonomously operating the at least one object in response to the sensing.   
     
     
         7 . The method of  claim 6 , wherein the property comprises a physical property. 
     
     
         8 . The method of  claim 7 , wherein the physical property comprises a magnetic field produced by a magnetic marker, a geometric discontinuity of the string, an acoustic wave, a pressure or a conductivity. 
     
     
         9 . The method of  claim 7 , wherein the physical property comprises an element selected from the group consisting essentially of a dedicated marker, a radioactive source, a magnet, a microelectromechanical system (MEMS)-based marker and a pressure. 
     
     
         10 . The method of  claim 1 , wherein using the untethered objects comprises pushing at least one of the objects with fluid into the well. 
     
     
         11 . The method of  claim 1 , further comprising:
 using the untethered objects and the string-conveyed object to perform a plurality of multiple stage stimulation operations.   
     
     
         12 . The method of  claim 1 , wherein using the string-conveyed object comprises deploying a shifting tool downhole on a coiled tubing string and manipulating the tool to shift open at least one downhole valve assembly. 
     
     
         13 . A method usable with a well, comprising:
 deploying untethered objects to selectively shift open valve assemblies of a string;   performing stimulation operations in zones associated with the valve assemblies after the valve assemblies are opened by the shifting by the untethered objects;   running a string-conveyed shifting tool into the string;   using the string-conveyed shifting tool to selectively shift other valve assemblies of the string; and   performing stimulation operations in additional zones associated with the other valve assemblies.   
     
     
         14 . The method of  claim 13 , wherein the first plurality of tools are disposed closer to a distal end of the string than to another end of the string. 
     
     
         15 . The method of  claim 14 , wherein the first plurality of tools are disposed at a length greater than approximately 5000 feet from a heel of the well. 
     
     
         16 . The method of  claim 13 , wherein using the untethered objects to operate the first plurality of tools comprises using the untethered objects to selectively shift valve assemblies of the string open. 
     
     
         17 . The method of  claim 13 , wherein using the string-conveyed tool comprises using a shifting tool to operate the valve assemblies of the string.