About Screw Drill

Screw drilling tools, also known as downhole power motors, are used to provide power to the drill bit at the bottom of the well during drilling or workover operations. The name of the screw drill comes from its key part, the rotor, which is shaped as a helical slender rod. A screw drilling tool is essentially a positive displacement pump.

In the past two decades, the emergence of directional wells, horizontal wells, and lateral wells has prompted a qualitative leap in the development of screw drilling tools, and their working life has also been greatly improved.

At the same time, screw drilling tools with special functions for special working conditions have also appeared, such as: high temperature resistant screw drilling tools, high salt resistance screw drilling tools, screw drilling tools for air drilling, etc.

Ⅰ. Structural composition of screw drilling tools

The screw drilling tools china are mainly composed of five parts: bypass valve assembly, anti-drop assembly, motor assembly, universal shaft assembly and drive shaft assembly.

The core part is the motor assembly, which is composed of two parts: the rotor and the stator. Some screw drilling tools have a special anti-drop mechanism on the drive shaft assembly.

Ⅱ. The structure and working principle of screw drilling tools

1. Function of bypass valve assembly

It is mainly composed of valve body, valve core, valve sleeve, spring, sieve plate, seal, and retaining ring for hole.

It has two positions, bypass and off. During the tripping operation, the spring pushes up the valve core, and the screw drilling tool bypass valve is in the bypass position, so that the mud in the drill string can enter the annular space between the wellbore and the drill string, so that the mud does not overflow during tripping. on the drill floor.

When the mud flow and pressure reach a certain value (that is, when the pump is turned on), the valve core moves down, and the bypass hole of the bypass valve is closed. At this time, the mud flows through the motor to do work.

2. The function of preventing the assembly from falling off

When the casing of the screw drilling tool of china mud valve below the anti-dropping assembly is broken or tripped due to abnormal reasons, the anti-dropping lock nut can be seated on the inner step of the anti-dropping joint, and the lower part of the rotor can be taken out to avoid falling objects in the well.

3. The function of the motor assembly

It consists of a stator and a rotor. The stator is formed by injecting rubber bushings on the inner wall of the steel pipe. The rubber inner hole is a helical surface with certain geometric parameters. The rotor is usually a plated multi-head screw.

The rotor and the stator are meshed with each other, which is a spiral sealing line formed by the lead difference between the two, and a sealing cavity is formed at the same time. After the drilling fluid enters the motor, it pushes the rotor to rotate in the stator.

As the rotor rotates in the stator, the sealing cavity of the screw drill moves along the axial direction, generating and disappearing continuously to complete its energy conversion.

That is: convert the pressure energy of the liquid into mechanical energy. The input of the screw motor is a liquid with a certain pressure, the screw motor consumes the pressure of the liquid (pressure energy), and the output is torque and rotational speed (mechanical energy).

4. Function of universal joint shaft assembly

The universal joint shaft assembly consists of two components: the casing and the universal joint shaft. The function of the universal joint shaft is to convert the planetary motion of the motor into the fixed shaft rotation of the transmission shaft, and transmit the torque and speed generated by the motor to the transmission shaft until Drill bit. The structure of the universal shaft mainly includes three types: petal type, spherical hinge type and flexible shaft (flexible shaft) type.

5. Function of drive shaft assembly

The function of the drive shaft is to transmit the rotational power of the motor to the drill bit, while bearing the axial and radial loads generated by the WOB.