Monday, 30 October 2017



Downhole Mud Motors on direction BHA

Major Down Hole Drilling Mud Motor Types

  • The Turbine, which is basically a centrifugal or axial pump.
  • The Positive Displacement Motor (PDM).
Turbines were in wide use some years ago. However, improvements in bit and PDM design have meant that turbines are only used in special applications today `

Drilling Mud Motor Components:

drilling Mud Motors components1.   Dump Valve Assembly 2.   Power Section 3.   Connecting Rod Assembly 4.   Bearing and Drive Shaft Assembly.

Mud Motor Dump Valve Assembly: 

This mud motor component allows the mud to fill or drain from the drill string while tripping. When a minimum flow rate is established, the valve piston on below figure is forced down, closing the ports to the annulus. Thus, all the mud is directed through the motor. When the flow rate becomes less than this minimum value, a spring returns the valve piston to the "open" position, opening the ports to the annulus.
drilling Mud Motors componentsTo avoid the ingress of solids from the annulus when the pumps are off (especially in loose Sand), it's normal to run a float sub as close to the motor as possible.

Mud Motor Power Section: 

This drilling mud motor component consist from mud motor housing, mud motor stator, and mud motor rotator. The positive displacement motor is a reverse application of the Moineau pump. Fluid is pumped into the motor progressive cavities. The force of the fluid movement causes the shaft to rotate within the stator as below figure. Thus, it is a positive- displacement motor (commonly called a PDM). The rotational force is then transmitted through the connecting rod and drive shaft to the bit.
Drilling mud motors are divided into slow-speed, medium-speed and high-speed types. This is done by changing the pitch of the motor stages and by the number of "lobes" and resultant cavities of the stator.

drilling Mud Motors components rotor drilling Mud Motors components rotor

Mud Motor Connecting Rod Assembly: 
drilling Mud Motors components drive shaftThis Drilling Mud Motor Component is attached to the lower end of the rotor. It transmits the torque and rotational speed from the rotor to the drive shaft and bit. Universal joints convert the eccentric motion of the rotor into concentric motion at the drive shaft . On some models of mud motor, reinforced rubber "boots" cover the u-joints. These prevent erosion by the mud.

Mud Motor Bearing and Drive Shaft Assembly:

The drive shaft is one of the mud motors components which is a rigidly-constructed hollow steel component. It is supported within the bearing housing by radial and axial thrust bearings . The bearing assembly transmits drilling thrust and rotational power to the drill bit. Most of the mud flows straight through the center of the drive shaft to the bit.

The bit sub is attached to the drive shaft. When pumping through the motor, the drive shaft will turn the bit sub and the bit.


The drilling 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. In certain applications, compressed air, or other gas, can be used for mud motor input power. Normal rotation of the Drilling Bit  while using a mud motor can be from 60 rpm to over 100 rpm. So there are some factors affecting drilling mud motors selection


To fully understand the drilling mud motors, we have still onlyone step which is the good practice guidelines to how to M/U Mud Motor, RIH, Tag on BTM, Drilling with mud motor, POOH & L/D. Also the limitation of Drilling Mud Motors which is mainly the temperature and the LCM

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