TonaTec management has 40 years of combined experience in directional drilling in the mining industry. This technology can be utilized in a wide variety of applications including; multiple target intercepts from a single trunk hole, drilling around stuck pipe, tight tolerance vertical pilot holes and acquiring targets that would otherwise be inaccessible due to poor surface access.
The directional drilling motor is a hydraulically driven, positive displacement motor (PDM), utilizing the Moineau principle of driving a drill bit without rotating the drill string.
PDM's are comprised of five basic assemblies and a drill bit:
1. Top Sub
Connects the stator power section to orientation sub, non-magnetic rods, and/or drill rods.
2. Power Section Assembly
Comprised of two elements, the rotor and stator, these elements are driven by hydraulic inflow of drilling fluid to operate the drive shaft bit.
3. U-Joint Assembly & U-Joint Housing
Two joints change eccentric rotation of rotor and stator to a concentric rotation at the drive shaft, a straight or slightly bent (¼° through 2½°) housing. Directional control of the motor is achieved with the bent u-joint housing.
4. Drive Sub Bearing Assembly
A drive shaft (sub) that is housed by upper and lower bearing housings, which contain radial and thrust bearings. This assembly transfers the rotation and torque form the power section through the u-joint assembly to the bit.
5. Drill Bit
The bit and the lower end of the drive sub bearing assembly are the only externally rotating components of the motor including the drill pipe. The “side-tracker” bit is adaptable to all diamond sets and types or polycrystalline or thermal insert configurations and has proved extremely adaptable for directional deflection and control.
The motor is powered by pressurized drilling fluid using a power generation section consisting of a rotor and stator (“power section”). Together, they act as a system of gears, with a rotor inside the stator. Since the metal rotor always has one less gear (lobe) than the elastomer lined stator, the configuration creates a cavity. Under pressure, the fluid within this cavity acts as a wedge and applies a rotational force on the rotor. Torque produced by the motor is proportional to the pressure differential (the pressure difference between the top and bottom of the power section) of the drilling fluid pumped through the PDM. Rotation speed is proportional to the volume of drilling fluid pumped through the motor. Rotation and torque are then transferred from the rotor to the bit through a u-joint assembly and a drive sub bearing assembly.
The u-joint assembly runs inside a slightly bent outer housing and serves three functions:
Transfer rotation speed and torque to the drive sub and bit.
Overcome the eccentric rotation of the rotor.
Facilitate the slight bend in the u-joint housing.
The PDM is commonly used for accurate directional drilling control for applications in mining, oil field, coal mining, civil construction and other areas as an alternative to conventional directional deflection utilizing wedges.
Direction and angle are determined with a down-hole survey instrument which is lowered into the bore-hole to determine the inclination and azimuth of the bit. After surveying, the drill string is rotated to place the bit in the desired direction and water is pumped into the motor to initiate drill bit rotation. Down pressure is applied to the drill string to cause penetration of the bit into the formation. The PDM takes mechanical power generated from the fluid flow and applies that power with R.P.M. and torque to the bit. The motor housing does not rotate but applies an opposing force to the drill hole wall to provide directional change of the borehole.