A mud motor is commonly known as the drilling motor, is a progressive cavity favorable displacement pump (PCPD) positioned in the drill string to supply additional power to the bit while drilling. The PCPD pump utilizes drilling fluid (commonly referred to as drilling mud, or simply mud) to create eccentric motion in the power area of the motor which is moved as the concentric power to the drill bit (well). The mud motor utilizes different rotor and stator setups to supply optimum efficiency for the preferred drilling operation, typically increasing the variety of lobes and length of power assembly for greater horsepower. In specific applications, compressed air, or other gas, can be utilized for mud motor input power. Typical rotation of the bit while utilizing a mud motor can be from 60 rpm to over 100 rpm.
A mud motor is described in regards to its variety of stages (generally 3), lobe ratio and external diameter. Phases are the number of complete twists that the stator makes from one end to the other, and the lobe ratio is the variety of lobes on the stator, to the number of lobes on the rotor (the stator constantly has one more lobe than the rotor). A greater number of phases or the variety of lobes indicates a more powerful motor, efficient in producing more torque. A smaller number of lobes indicates a reduction in the torque produced but a faster bit rotation speed.
Using mud motors is considerably dependent on financial performance. In straight vertical holes, the mud motor might be utilized entirely for increased rate of penetration (ROP), or to decrease disintegration and wear on the drill string, given that the drill string does not need to be turned as quick.
Most of the mud motor use remains in the drilling of directional holes. Although other techniques may be utilized to guide the bit to the preferred target spot, they consume more time which adds to the expense of the well. Mud motors can be set up to have a bend in them using various settings on the motor itself. Common mud motors can be modified from 0 degrees to 4 degrees with around six increments in deviation per degree of bend. The quantity of bend is determined by a rate of climb needed to reach the target zone. By utilizing a measurement while drilling (MWD) tool, a directional driller can guide the bit to the wanted target zone.
Steerable motors are used to drill the start point. When drilling the beginning point make sure to prevent drilling a soft development right away below a tough one. In difficult, abrasive formations the high side forces at the start can cause severe bit shank wear. Ideally, the beginning point should be chosen in a non-abrasive homogenous development.
Main benefits of Mud Motors
1. Extremely solid rock formations can be drilled with motors using diamond or PDC bits.
2. High penetration rates can be accomplished because of the high count speed rotation.