دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a drilling tool made up in the drill string directly above the bit. It causes the bit to turn while the drill string remains fixed. It is used most often as a deflection tool in directional drilling, where it is made up between the bit and a bent sub (or, sometimes, the housing of the motor itself is bent). Two principal types of down-hole motor are the positive-displacement motor and the downhole turbine motor. Also called mud motor.

n: A special tool mounted in the BHA (q.v.) to drive the bit without rotating the drill string from surface (see positive displacement motor).