TOOL FOR DRILLING OF WELL BORES Russian patent published in 1998 - IPC

FIELD: equipment for well drilling. SUBSTANCE: tool includes string of drill pipes and collars, stabilizers, spindle turbodrill whose upper turbine section body is threaded with lower collar of drill string. Threaded to nipple of spindle body of turbodrill is reamer. Drill string, collars, stabilizers, turbine section body and spindle body with reamer secured to nipple are rotated by rotary table of drilling rig at relatively low speed. Turbodrill spindle shaft protrudes beyond lower rock-breaking member of reamer through 4-6 m. Secured to spindle shaft by means of thread is pilot diamond or drag drilling bit whose diameter equals 0.45-0.6 of reamer diameter and smaller than diameter of turbodrill spindle body. Turbodrill spindle shaft is centered in turbodrill body with the help of rotor and stator members of radial bearings ensuring radial play of spindle shaft within 2-5 mm. Pilot bit is rotated by turbodrill at speed exceeding that of reamer by one order of magnitude. EFFECT: high rate of penetration and increased total footage per run with preservation of strict vertical position of well bore. 4 cl, 5 dwg