DEVICE FOR EXTENSION OF WELL CASING STRING Russian patent published in 2012 - IPC E21B7/20 

FIELD: mining.

SUBSTANCE: device for extension of well casing string contains connection pipe installed on lower end of string and easily drilled out shoe on the end. From below connection pipe is equipped with inner technologic recess, cylindrical sleeve made from easily drilled out material and with a seat for cementing plug from above. From above, under join to casing string, inside connection pipe there is an annular groove in which a seat is tightly installed equipped with cylindrical pit from lower end. Cylindrical sleeve is made from flexible material, from below it is rigidly and tightly connected to the shoe and from above it is tightly inserted in cylindrical seat pit with possibility of lengthwise displacement. It guarantees performance of procedure for extension of casing string from below by profiled shutter without additional round-trip operations related to cleaning (shaping) of technologic recess in coupling sleeve.

EFFECT: cylindrical sleeve made from flexible material and sealing elements installed outside and inside the seat allow safety of technologic recess during casing string cementing.

2 dwg