SYSTEM AND METHOD FOR CONTROLLING DRILL MOTOR ROTATIONAL SPEED

摘要

In one embodiment, a system (10) for controlling drill motor rotational speed includes a downhole motor (70) disposed in a drill string (40) and having a rotor (72) operable to be rotated by a flow of drilling fluid (100) through the motor (70). The system (10) also includes one or more bypass ports (52) operable to allow a portion of the drilling fluid (100) to exit the drill string (40) into a well bore (20) and a governor (50) coupled to the rotor (72) and comprising a valve (51) operable to move in response to the rotational speed of the rotor (72). The valve (51) movement controls the amount of drilling fluid (100) allowed to flow through the bypass ports (52) and exit the drill string (40) into the well bore (20). The valve (51) also directly controls the flow of the drilling fluid (100) into the motor (70) based on the amount of drilling fluid (100) allowed to flow through the bypass ports (52), thereby controlling the rotational speed of the rotor (72).