Mud motor

The mud motor uses different rotor and stator configurations to provide optimum performance for the desired drilling operation, typically increasing the number of lobes and length of power assembly for greater horsepower.

[1] Normal mud motor construction consists of a top sub, which connects the mud motor to the drill string; the power section, which consists of the rotor and stator; the transmission section, where the eccentric power from the rotor is transmitted as concentric power to the bit using a constant-velocity joint; the bearing assembly which protects the tool from off bottom and on bottom pressures; and the bottom sub which connects the mud motor to the bit.

When the bit is bottomed and the motor is effectively working, there is a notable increase in the pressure in the fluid system.

If this differential pressure is too high then the motor can stall which means the bit has stopped turning and this can cause severe damage to the internal surface of the stator.

A mud motor is described in terms of its number of stages, lobe ratio and external diameter.

By using a measurement while drilling (MWD) tool, a directional driller can steer the bit to the desired target zone.

In hard abrasive formations the high-side forces at kick off can cause severe bit shank wear.

However, the operating conditions[3] and environment should not degrade or induce mechanical failure of the elastomer part for the life of the equipment.

Unfortunately, the industry does not have elastomers that can last longer, resisting abrasive fluids and solids, and withstand deflections in operating temperatures.