دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a device used to rotate the bit without rotating the drill stem. Basically, the motor comprises a spiral rod that is housed inside a helical-shaped chamber-the rod and chamber are a pump. Circulating mud down the drill stem and to the motor causes the rod to rotate. Since the bit is mechanically connected to the motor, as the motor rotates, so does the bit. This method of bit rotation eliminates the need to rotate the entire drill stem and thus is especially useful in directional drilling.