Mud Motors: What You Need to Know

Horizontal directional drilling (HDD), also known as directional boring, is a method used to install underground cables and pipelines without digging expansive trenches.

This technology has applications in various sectors such as the oil and gas industries. Directional drilling allows pipes and conduits to be installed under roads, rivers, and other structures with minimum disturbance.

When drilling in rock, mud motors are critical additions to HDD reamers that make an otherwise impossible job doable. Also known as progressive cavity positive displacement pumps (PCPD), mud motors started gaining popularity in the 1970s. They are placed in the drill string to increase the power of HDD bits, enabling HDD reamers to penetrate hard terrain efficiently.

Choosing a Mud Motor

Each drilling job is different. Therefore, contractors must use the appropriate mud motors for HDD reamers to get the job done in a timely and effective manner. To simplify the process, ask yourself the following questions:

  • – What type of rock will you be drilling?
  • – How hard is the rock?
  • – Which rig do you plan to use?
  • – The maximum pump volume (GPM) of your pump?
  • – How long is the bore?

By knowing the type of rock and how hard it is, you will be able to estimate the potential wear and tear on the motor. For instance, there will be more wear and tear when drilling through sandstone than when boring through shale.

Each mud motor operates in a specific flow range. Always try to maximize the flow rate to the motor as it will optimize torque output and rotation at the bit box. As a result, you will have maximum steerability in the rock and the best penetration; two things you should always maximize without exceeding the limits of hole cleaning ability.

It is also essential to consider the outer diameter (OD) of the drill pipe. To reduce mechanical limitations, the OD of the pipe and motor on HDD reamers should be the same. There is a recommended bit size (OD) range. Typically, it is 6 to 7 7/8 for a 4 3/4-in mud motor. For the motor to have enough annulus area to operate in, it is better to use 6 1/2 to 6 3/4 PDC bits.

Using oversized HDD bits will make it difficult for the mud motor to make contact with the inner diameter of the drilled hole. This, in turn, reduces the fulcrum effect of the mud motor’s bend, thus making it difficult to steer the mud motor.

For How Long Can You Expect Your Mud Motor to Run?

Mud motors usually offer 100-125 hours of service if used with the right operating conditions. After this period, you should have it inspected and serviced by your supplier as bearings and other components may also need to be replaced.

Any added operational hours can damage the transmission section, which is vital, and this will translate to increased repair costs.

Taking Care of Your Mud Motor

To begin with, try minimizing motor stalls by pumping fresh water through the motor after every job. This is because the mud that remains can damage the motor once it is used again.

The power section of the mud motor is the most expensive to replace. It’s comprised of the rotor and stator. The rotor has one less lobe than the stator, and it is made of chrome-plated steel and a highly engineered rubber within its diameter.

Drilling mud should be free of sand and solids. Otherwise, the stator and rotor will wear, thus reducing the pressure and power the motor will drill at.

It is important to honor the 100-125 hour recommendation for servicing your mud motor. However, you should also try to safeguard it and minimize damage as some components are very costly. When you’re ready to take better care of your drills, rely on Torquato today.

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