CASING STRING FOR DEEP WELLS Russian patent published in 1994 - IPC

FIELD: well drilling. SUBSTANCE: installed in hollow of casing string are long members of material having density lower than density of well fluid. Long members are joined in assembly on thread made on metal reinforcing end fittings attached to long members. Long member is locked relative to internal surface of casing with aid of joint unit containing drive shaft with nipple on upper end. Turning shaft clockwise results in moving of slips of long member out of ribs with their simultaneous locking. EFFECT: higher efficiency. 2 cl, 2 dwg