Downhole fracturing system and technique

Abstract

A system that is usable with a well includes a first tubing string and a plurality of tubing segments. The first tubing string is deployed in the well and includes a plurality of valve assemblies, which span a segment of the first tubing string. The tubing segments are adapted to be deployed in the well inside the first tubing string and attach together in the segment of the first tubing string in a sequence to form a second tubing string in a manner that allows sequential operation of the valve assemblies of the first tubing string.

What is claimed is: 
     
         1 . A method comprising:
 deploying a first tubing string comprising a plurality of valve assemblies in a well;   deploying tubing segments inside the first tubing string;   stacking the deployed tubing segments together downhole in the well to construct a second tubing string inside the first tubing string; and   using the stacking to sequence operations of the valve assemblies.   
     
     
         2 . The method of  claim 1 , wherein the using comprises opening the valve assemblies one at a time and in response to opening each valve assembly communicating fluid through the assembly to fracture a region of the well. 
     
     
         3 . The method of  claim 1 , wherein the first tubing string further comprises a bottom valve assembly disposed below the plurality of valve assemblies, the method further comprising:
 before the deploying of the tubing segments begins, opening the bottom valve assembly and communicating fluid through the bottom valve assembly to fracture a region of the well.   
     
     
         4 . The method of  claim 3 , wherein deploying the tubing segments comprises deploying a set of at least one segment of the tubing segments to anchor the set to the bottom valve assembly, form an annular seal between the set and the first tubing string and restrict flow through the set to a single flow direction. 
     
     
         5 . The method of  claim 4 , further comprising:
 using the annular seal and the flow restriction to open one of the valve assemblies of the plurality of valve assemblies.   
     
     
         6 . The method of  claim 1 , wherein deploying the tubing segments comprises deploying a set of at least one segment of the tubing segments to restrict flow between two of the valve assemblies to a single direction and form an annular seal between the set and the first tubing string. 
     
     
         7 . The method of  claim 6 , further comprising:
 using the annular seal and the flow restriction to open one of the valve assemblies of the two valve assemblies.   
     
     
         8 . The method of  claim 1 , further comprising:
 using the second tubing string as a production tubing string.   
     
     
         9 . The method of  claim 8 , wherein deploying the tubing segments comprises deploying at least one tubing segment comprising a ported valve assembly to selectively isolate a region of the well from hydraulic communication with the production tubing string. 
     
     
         10 . The method of  claim 1 , wherein:
 the first tubing string further comprises a bottom valve assembly disposed below the plurality of valve assemblies,   the deployed tubing segments comprise a first bottom hole assembly, second bottom hole assemblies and a third bottom hole assembly; and   the deploying and stacking comprises:
 deploying the first bottom hole assembly and anchoring the first bottom hole assembly to the bottom valve assembly; 
 deploying at least one of the second bottom hole assemblies based on a spacing between the bottom valve assembly and a lowermost valve assembly of the plurality of valve assemblies; 
 deploying the third bottom hole assembly to restrict flow between the lowermost valve assembly of the plurality of valve assemblies and the third bottom hole assembly to a single direction and form an annular seal between the third bottom hole assembly and the first tubing string. 
   
     
     
         11 . The method of  claim 10 , wherein:
 using the flow restriction and the annular seal to open the lowermost valve assembly of the plurality of valve assemblies.   
     
     
         12 . The method of  claim 11 , wherein:
 the deploying and stacking further comprises:
 deploying at least one additional second bottom hole assembly of the second bottom hole assemblies based on a spacing between the lowermost valve assembly and the adjacent valve assembly of the plurality of valve assemblies uphole from the lowermost valve assembly; 
 deploying a fourth bottom hole assembly to restrict flow between the adjacent valve assembly of the plurality of valve assemblies and the fourth bottom hole assembly to a single direction, form an annular seal between the fourth bottom hole assembly and the first tubing string, and allow selective fluid communication between a region outside the second tubing string and an interior flow path of the second tubing string. 
   
     
     
         13 . A system usable with a well, comprising:
 a first tubing string to be deployed in the well and comprising a plurality of valve assemblies spanning a segment of the first tubing string; and   a plurality of tubing segments, wherein the tubing segments are adapted to:
 be deployed in the well inside the first tubing string; and 
 attach together in the segment of the first tubing string in a sequence to form a second tubing string in a manner that allows sequential operation of the valve assemblies of the first tubing string. 
   
     
     
         14 . The system of  claim 13 , wherein the second tubing string comprises a production tubing string. 
     
     
         15 . The system of  claim 13 , wherein the plurality of valve assemblies comprises ports to communicate a fracturing fluid. 
     
     
         16 . The system of  claim 13 , wherein the first tubing string comprises a liner string or a casing string. 
     
     
         17 . An apparatus usable with a well, comprising:
 a tubular housing adapted to deployed through a lubricator inside a first tubing string and descend untethered to a downhole location of the well to form a segment of a second tubing string;   at least one connector to attach the tubular housing to another segment of the second tubing string downhole in the well;   a check valve to restrict fluid communication within a central flow path of the tubular housing; and   at least one wiper cup to form an annular seal between the tubular housing and the first tubing string.   
     
     
         18 . The apparatus of  claim 17 , further comprising a ported valve assembly to be selectively operated to regulate fluid communication between the central flow path of the tubular housing and a region outside of the housing. 
     
     
         19 . The apparatus of  claim 17 , further comprising a seal nose to form a seal between the central flow path and the central flow path of the another segment of the second tubing string. 
     
     
         20 . The apparatus of  claim 17 , further comprising a ratchet teeth to engage a ratchet sleeve of the another segment of the second tubing string.