DRILLING MUD MOTORS TYPES & COMPONENTS
Major Down Hole Drilling Mud Motor Types
- The Turbine, which is basically a centrifugal or axial pump.
- The Positive Displacement Motor (PDM).
Drilling Mud Motor Components:1. 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.
To 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.
Mud Motor Connecting Rod Assembly:
This 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.
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.
Mud Motor Bearing and Drive Shaft Assembly:
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.