CASING STRING DRILLING DEVICE Russian patent published in 2023 - IPC E21B7/20 E21B33/10 

FIELD: oil and gas industry; drilling of oil and gas wells.

SUBSTANCE: casing drilling device includes a casing string, a drilling bit and a sub. The sub is installed in the upper part of the casing and is provided with threads on top for connection with the drill pipe. The casing string is made of casing pipes interconnected by couplings. The drillable bit is screwed to the downhole motor and is designed as a drillable drilling head with a multifaceted hole with a non-drillable sub inserted into the multifaceted hole of the drilling head. The non-drillable sub is fixed with the drill head by a shear element, which is destroyed during the extraction of the sub when the drill head rests against the end of the connecting device. The top sub is designed with a diameter equal to the diameter of the casing collar, and is equipped with a centralizer with a diameter 1.5-2% less than the inner diameter of the casing. The centralizer is made of polymeric material.

EFFECT: increased reliability of drilling and reduced time for drilling with casing string.

1 cl, 3 dwg