CASING STRING CENTRALIZER Russian patent published in 1995 - IPC

FIELD: well drilling. SUBSTANCE: centralizer has working cylinder with piston installed on casing with connecting sleeves at ends and centering members. Centering members are made in form of levers with hinge shoes articulated to casing string. Lever ends interact with wedge-shaped members rigidly connected to working piston. Located opposite to working piston is locking piston whose opposite end is tapered for sliding over inner surface of lock ring located between cylinders and other connecting sleeve. In operating position, centering members are rigidly connected relative to casing string ensuring its reliable centering in well. EFFECT: higher efficiency. 2 cl, 5 dwg