Mud Motor - Major Disadvantage in Oilfield Applications

Major Disadvantage in Oilfield Applications

The PCPD stator, which is a major component of the pump, is usually lined with an elastomer. Most of PCPD pump failures are due to this elastomer part. Having said that, the operating conditions 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. The most common elastomer grades used for this application are the NBR (Nitrile or Acrylonitrile Butadiene Rubber) grades, which perform moderately well. There is definitely a need for better elastomer compounds to reach areas which are not currently accessible by PCPs and also improve the life of current products.

1. Bit speeds can be very high as such bit selection is important. The high speeds may limit the use of certain types of bits.

2. Special pump requirements may be needed as particular pressures and flow rates may be needed to maintain proper and efficient motor operation.

3. If used for directional control the down-hole assembly may be long and this may take time to assemble on the rig floor.

4. The mud motor may be sensitive to fouling agents. This means that certain types of drilling fluids or additives may ruin the motor or lower its performance. One particular example, as mentioned above, would be the use of oil based mud with the mud motor. Over time the oil degrades the elastomers and the seals in the motor.