Mostly, a downhole mud motor is installed in the bottom hole assembly (BHA) directly above the drill bit. The motor supplies the bit in the bottom of the wellbore with drive power. The drive is generated by the drilling fluid that is pumped through the drill string. The power section of the motor (rotor and stator) converts the hydraulic power of the incoming mud fluid into mechanical power resulting in rotation. Compared to the conventional rotary drilling operations, the use of downhole mud motors allows for a significantly lower load and wear of the drill tubes. With an angled bend, downhole motors are essential for directional drilling.
This is a sub that connects a motor with a drill string.
Safety Catch Sub
This appliance provides the ability to remove inner and outer components of the motor from the wellbore if the housing of the motor gets broken during the drilling operations.
Power Section Assembly
This central component of the motor converts hydraulic power of the incoming drilling fluid into mechanical power resulting in drill-bit rotation. The power section consists of two parts, the rotor and the stator. When assembled, these two components form a continuous seal along their contact line. The rotor is a steel bar or tube with a helical (multi-lobed) pattern. It is chrome plated to reduce friction, wear, and corrosion. Other rotor coatings are available, depending on specific application and/or environment in which the motor is to be used. The stator is a length of tubular steel lined with an elastomer compound that is shaped with a helical pattern to mate with the rotor. Various elastomers are available, depending on drilling-fluid type and bottom hole temperature.
Flexible Coupling Assembly
The flexible coupling assembly is attached to the lower end of the rotor and transmits rotational torque and speed to the drive shaft and bit. The coupling assembly converts the eccentric motion of the rotor to the concentric motion of the drive shaft.
Adjustable Bend Housing
The flexible coupling allows for placement of a bend point in its external housing for steerable or single bend motors. Bend-housing angles range from 0 to 3º in most cases and may be either fixed or rig-adjustable.
Bearing Section Assembly
The bearing section assembly supports the motor drive shaft, which in turn transmits drilling thrust and rotational power to the drill bit. The drive shaft is fixed with various thrust and radial bearings that are mud-lubricated or sealed and oil-filled.