ARRANGEMENT OF LOWER PART OF DRILL PIPE STRING FOR EXPANSION OF SHAFT OF HOLE Russian patent published in 2001 - IPC

FIELD: mining industry. SUBSTANCE: invention can be used as technical facility for expansion of shafts of oil and gas wells. Arrangement includes milling cutter with body in the form of hollow shaft and rolling cutter bit coming in the form of truncated ellipsoid. Body of milling cutter is linked to lower heavy drill pipe which is coupled with the use curvilinear adapter to next heavy pipe. Upper pipe carries two blade stabilizers as minimum which center heavy pipe in casing string. Rolling cutter bit is anchored on shaft by means of roller and ball bearings. Protector-slipper with grippers which makes lowering of arrangement easier thanks to slip of milling cutter in face interval of coupling connection of casing string is mounted on milling cutter before its lowering into hole. Milling cutter is anchored on end of lower heavy pipe which longitudinal axis crosses longitudinal axis of next heavy pipe at angle of 2.5-7.0 degrees. EFFECT: increased operational efficiency of arrangement of lower part of drill pipe string for expansion of drilled shaft of hole. 1 cl, 4 dwg