Drillable Debris Barrier Tool

Abstract

A drillable debris barrier tool is positioned under a stage tool to protect tools therebelow from contamination with debris from the stage tool, as it is drilled out. The debris barrier tool includes features that facilitate drill up of stage tool debris and reduce the size of debris generated from removal of the barrier tool.

1 . A debris barrier tool comprising:
 a liner forming a seat in a bore through the tool; and   a ball formed to land in the seat,   wherein the liner is formed of a cast iron.   
     
     
         2 . The debris barrier tool of  claim 1  wherein the liner is formed of class 30 to class 50 gray iron. 
     
     
         3 . The debris barrier tool of  claim 1  further comprising an outer housing including an inner wall defining a bore and an annular recess in the inner wall and the liner being mounted in the annular recess and a contact shoulder formed between the outer housing and the liner at a lower end of the liner. 
     
     
         4 . The debris barrier tool of  claim 3  wherein a lower end wall of the annular recess and a lower end of the liner are corresponding shaped. 
     
     
         5 . The debris barrier tool of  claim 3  wherein the tool has a drift diameter and the liner has an outer diameter greater than the drift diameter. 
     
     
         6 . The debris barrier tool of  claim 2  wherein the outer housing is formed of a material harder than cast iron. 
     
     
         7 . The debris barrier tool of  claim 1  further comprising a full bore diameter portion between an upper end of the liner and the seat. 
     
     
         8 . The debris barrier tool of  claim 7  further comprising a frustoconical surface between the upper end and the seat. 
     
     
         9 . The debris barrier tool of  claim 1  further comprising a full bore diameter interval at a lower end of the liner. 
     
     
         10 . The debris barrier tool of  claim 9  further comprising an outer housing and the liner is mounted within the outer housing and threadedly engaged to the outer housing opposite the full bore diameter interval. 
     
     
         11 . The debris barrier tool of  claim 1  further comprising a right hand thread between the seat and the outer housing preventing rotation of the seat during drill out. 
     
     
         12 . A method for drilling out a wellbore string comprising:
 landing a ball in a seat of a debris barrier tool;   operating a drilling assembly to drill through the wellbore string uphole of the debris barrier tool; and   drilling through the seat of the debris barrier tool while debris from uphole drilling is crushed between the drilling assembly and the debris barrier tool.   
     
     
         13 . The method of  claim 12  wherein drilling through the seat includes passing the drilling assembly through a full bore portion at an upper end of a drillable liner on which the seat is formed without drilling into the full bore portion. 
     
     
         14 . The method of  claim 12  wherein drilling the debris barrier tool includes passing the drilling assembly through a full bore interval at a lower end of the drillable liner without drilling into the full bore interval. 
     
     
         15 . The method of  claim 12  wherein drilling through the seat leaves a cylindrical portion of the seat remaining in debris barrier tool. 
     
     
         16 . The method of  claim 12  wherein during drilling, stopping rotation of the seat by providing a thread engaging the seat to an outer housing of the debris barrier tool. 
     
     
         17 . The method of  claim 12  further comprising circulating fluid through the drilling assembly. 
     
     
         18 . The method of  claim 12  further comprising stage cementing through a stage tool uphole of the debris barrier tool and operating a drilling assembly drills out portions of the stage tool.