How Mud Motors Work
Normal Mud Motor construction consists of
a top sub, which connects the Mud Motor to the Drill String; the Power Section, which consists of the Rotor and Stator; the Transmission Section, where the eccentric power from the rotor is trasmitted as concentric power to the bit; the Bearing Assembly which protects the tool from off bottom and on bottom pressures; and the bottom sub which connects the Mud Motor to the bit.
The use of Mud Motors is greatly dependent on financial efficiency. In straight vertical holes, the mud motor may be used solely for increased Rate of Penetration (ROP), or to minimize erosion and wear on the drill string, since the drill string does not need to be turned as fast.
The majority of Mud Motor use is in the drilling of Directional Holes (see Directional Drilling video) Although other methods may be used to steer the bit to the desired target zone, they are more time consuming which adds to the cost of the well. Mud Motors can be configured to have a bend in them using different settings on the motor itself. Typical Mud Motors can be modified from 0 degrees to 4 degrees with approximately six increments in deviation per degree of bend. The amount of bend is determined by rate of climb needed to reach the target zone. By using a Measurement While Drilling (MWD) Tool, a directional driller can steer the bit to the desired target zone.
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Find more videos like this on Drilling Ahead