Pressure perforated well casing systems

Abstract

Pressure perforated casing system has a plurality of grooves cut to an equal depth in an outer surface of a casing joint or a casing collar. Each groove has a bottom spaced from and internal surface of the casing joint or the casing collar. Sidewall bottom material in the groove ruptures at a predetermined fluid pressure below the burst pressure rating of the casing joint or casing collar.

1 . (canceled) 
     
     
         2 . The pressure perforated well casing joint as claimed in  claim 4 , wherein the grooves are arranged in at least one cluster, a total area of the at least one cluster being less than a total area of the outer surface between the external threads on the first and second ends of the pipe. 
     
     
         3 . (canceled) 
     
     
         4 . A pressure perforated well casing joint, comprising:
 a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating;   an external thread on each of the first and second ends adapted to threadedly engage a casing collar; and   a plurality of spaced apart grooves cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove and the grooves are cuts having ends that overlap;   whereby fluid pressure applied within the pressure perforated well casing will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the pipe is reached, thereby opening a slot through the sidewall at each of the plurality of grooves subjected to the fluid pressure.   
     
     
         5 . The pressure perforated well casing joint as claimed in  claim 4 , wherein the grooves surround a narrow column of sidewall material designed to facilitate cement penetration when the sidewall bottom material in the grooves rupture. 
     
     
         6 . The pressure perforated well casing joint as claimed in  claim 4 , wherein the grooves are filled with a coating material to protect machined surfaces while the casing joint is in storage and while the casing joint is being run into a recently drilled well bore. 
     
     
         7 . The pressure perforated well casing joint as claimed in  claim 4 , wherein the grooves are grouped in at least two spaced apart clusters between the external thread on the respective first and second ends. 
     
     
         8 . The pressure perforated well casing joint as claimed in  claim 4 , wherein the grooves are grouped in three equally spaced apart clusters between the external thread on the respective first and second ends. 
     
     
         9 . The pressure perforated well casing joint as claimed in  claim 4 , further comprising a groove cut on the inside surface of each of the respective first and second ends to positively identify the perforated well casing joint in a well casing string comprising perforated well casing joints and plain casing joints connected together. 
     
     
         10 . A pressure perforated well casing collar, comprising:
 a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating;   an internal thread on each of the first and second ends adapted to threadedly engage an external thread on a casing joint;   a plurality of spaced apart grooves respectively having overlapping ends cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove;   whereby fluid pressure applied within the pressure perforated well casing collar will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the casing collar is reached, thereby opening a slot through the sidewall at each of the plurality of grooves.   
     
     
         11 . The pressure perforated well casing collar as claimed in  claim 10 , wherein the plurality of grooves are filled with a coating material to protect machined surfaces while the casing collar is in storage and while a casing string including the casing collar is being run into a recently drilled well bore. 
     
     
         12 . (canceled) 
     
     
         13 . The pressure perforated well casing system as claimed in  claim 16  further comprising an interval on an outer surface of the well casing joint or the well casing collar without grooves. 
     
     
         14 . The pressure perforated well casing system as claimed in  claim 16  wherein the well casing joint comprises at least two clusters of grooves, each cluster of grooves being separated from the ends of the well casing joint and any other cluster of grooves by an outer surface of the well casing joint without grooves. 
     
     
         15 . (canceled) 
     
     
         16 . A pressure perforated well casing system, comprising:
 a well casing joint and a well casing collar respectively having a plurality of spaced apart if grooves cut in an outer surface thereof, the grooves being cut to an equal depth in the outer surface, each groove having sidewall bottom material remaining in a bottom of the groove the respective grooves having ends that overlap;   whereby sufficient fluid pressure applied to the grooves cause the sidewall bottom material in the respective grooves to rupture before a burst pressure rating of the well casing joint or the well casing collar is reached, thereby opening slots through the sidewalls at each of the respective grooves under sufficient fluid pressure.   
     
     
         17 . The pressure perforated well casing system as claimed in  claim 16  wherein the grooves respectively surround a sidewall material designed to facilitate cement penetration when the sidewall bottom material in the grooves rupture. 
     
     
         18 . The pressure perforated well casing system as claimed in  claim 16 , wherein the grooves are filled with a coating material to protect machined surfaces while the casing joint or the casing collar is in storage and while the casing joint or the casing collar is in a casing string being run into a recently drilled well bore. 
     
     
         19 . A well casing string comprising the pressure perforated well casing joints claimed in  claim 16 . 
     
     
         20 . A well casing string comprising the pressure perforated well casing collars claimed in  claim 16 .