Helical bottomhole motor
HELICAL BOTTOMHOLE MOTOR (EN: downhole drilling motors; DE: Bohrlochschraubenmotor, Strebschraubenmaschine; FR: moteur d'attaque helicoidal; ES: motor de atague helicoidal; RU: винтовой забойный двигатель) is the hydraulic bottomhole motor of the volumetric type, the working tools of which are made according to the scheme of the planetary gear mechanism, which is brought into action on the account of the energy of the flushing liquid. The first helical bottomhole motors with the high speed of the rotation have been developed within the USA during the 1962 by Harrison on the basis of the inverted single-start gerotor helical Moineau pump. The multi-start helical bottomhole motor with the low speed of the rotation has been created within the USSR during the 1966-70 by S. S. Nikomarov, M. T. Gusman, and others.
The multi-start helical bottomhole motor (see the Figure) is the gerotor planetary gear mechanism, the stator of which is made in the form of the steel cylinder with the multi-start rubber helix, which is bonded to the inner surface of the stator using the vulcanization.
The rotor (the single-start or multi-start helix with the quantity of the starts, which is one less, than such quantity of the helix of the stator) is positioned inside the stator. Under the pressure of the flushing liquid, the rotor, while rolling on the inner surface of the stator, performs the planetary motion, which is transmitted through the universal joints to the shaft of the spindle, which is rotating the tool for the destruction of the rock. The diameter of the helical bottomhole motor is 54-195 millimetres, the frequency of the rotation is approximately 2-6 revolutions per second, the torque is 80-5000 newton-metres, the differential pressure is 4-6 megapascals, the consumption of the flushing liquid is 0.0015-0.036 cubic metres per second and more. The helical bottomhole motors are most effective during the penetration of the deep intervals.
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