The down-hole motor is a kind of downhole drilling tool powered by mud. The mud from the mud pump enters the motor by way of the bypass valve, and a pressure drop between the motor inlet and outlet is created, such pressure drop will drive the motor rotator to rotate, and transmit the torque and rotary speed bit by the universal shaft and transmission shaft. The downhole motor property mainly depends upon its property parameters. This product uses the high and new technology of coating to avoid coating off of rotors resulting from the traditional technology. Its strength and life are greatly improved. It is applicable to directional drilling horizontal drilling, composite drilling, cluster wells, sidetrack wells and well workovers, etc.

1. 1. Working principle of mud motor:

The mud motor is a volumetric power drilling tool that uses drilling fluid as power to convert hydraulic energy into mechanical energy.

When the pressure mud pumped by the mud pump flows into the motor, a certain pressure difference will be formed at the inlet and outlet of the motor, which will push the rotor to revolve and rotate around the axis of the stator, and transmit the speed and torque to the three teeth through the cardan shaft and the transmission shaft. Wheel or PDC drill bit, so as to realize the pilot hole operation.

2. Composition of the mud motor:

The mud motor is mainly composed of four major assemblies: anti-drop assembly, hydraulic motor, cardan shaft and transmission shaft.

3. Hydraulic motor assembly:

It consists of a rotor and a stator. The rotor is a mechanically processed X-head screw with anti-corrosion and wear-resistant chrome plating on the surface. The stator shell is composed of an inner spiral rubber bushing of the X+1 head that is firmly injected into the inner wall of the alloy steel cavity.

The shape and size of the rotor and the stator should ensure the meshing relationship. These meshing points form the sealed cavity of the motor along the axial course, and the rotor rotates helically in the stator.

When the drilling fluid with a certain energy passes through, the cavity moves down along the axial direction, the upper inlet is continuously generated, and the lower outlet gradually disappears, completing its energy conversion, thereby pushing the rotor to perform eccentric revolution and rotation along the inner wall of the stator spiral, and complete the motor. effect. This is the basic working principle of the screw motor.

The helix of the motor rotor can be divided into single-head and multi-head (the number of stator helix is one more than that of the rotor). The fewer the number of heads of the rotor, the higher the speed and the smaller the torque; the more the number of heads, the lower the speed and the greater the torque.

4. The pressure difference of mud motor

Under the existing conditions, if the motor is to work normally and effectively, it is advisable that the pressure drop that each stage of the motor can withstand should not exceed 0.8Mpa. (A lead of the motor is one level, and the lead refers to the length of a complete helix)

The maximum pressure drop is 1.3 times the rated working pressure. If the pressure drop value exceeds this value, the motor will leak, the speed will increase, the wear will be serious, and even the motor will be swelled to death, causing damage to the motor. Users should pay special attention that the mud flow rate used on site should be within the recommended range of use, otherwise it will increase the wear of the stator and affect the efficiency and life of the motor.

The theoretical output torque of the motor is proportional to the pressure drop of the motor, and the output revolution is proportional to the input mud flow. As the load increases, the revolution of the drilling tool decreases, so as long as the reading of the pressure gauge on the ground and the flow of the pump are controlled, it will be able to control the torque and speed of downhole drilling tools.