Abstract: A downhole motor operated by circulating mud fluid in the wellbore is revealed. The motor has nested rotors and is geared to a bit drive. The motor is a dual-rotor pump that is operated as a motor with mud flow through the rotor housing on end connections. The structures of the rotor housing and the rotors can be made of the same material. An angular offset can be incorporated between the centerline of the output of the motor and the bit drive. In the preferred embodiment, the motor output is through a gear located within a bigger gear connected to the bit so as to provide a speed reducer. The gear on the bit shaft is preferably made of spaced rods to mesh with the gear on the motor output shaft. The drive between the rotors and the bit can accommodate angular offsets of a predetermined amount for directional drilling. The design is compact and can be used to drill wellbores as small as about 2½″ in diameter, or even smaller.
Abstract: A simple torque-testing tool, particularly for downhole progressing-cavity motors, easily bolts on to the bearing housing on one end and the bit box on the other end. The assembly is first screwed together where a predetermined amount of preload is applied to opposing clutch surfaces. Opposite ends of the housing are affixed to the bearing housing uphole and the bit box downhole and a predetermined amount of flow is run through the stator housing. If the downhole motor is close to its design operating parameters for a given flow rate, it should be able to drive the bit box despite the drag applied by the opposing clutch surfaces. Failure of the downhole motor to be able to overcome the resistance from the device at the predetermined flow rate indicates that the motor is worn. Torque resistance is applied preferably by stacked Belleville washers which can be stacked in a number of arrangements to alter the amount of force.