Application of MKE variable frequency drive in oil drilling rig

2022-12-28

1.Introduction:

With the rapid development of modern power electronics technology and microelectronics technology, as a product of modern industrial revolution, the frequency converter has been increasingly applied to various fields of industrial production. From low voltage to high voltage, from ordinary to special, the frequency converter plays an irreplaceable role in speed regulation and energy saving, and is gradually expanding in depth. At the request of Changqing Oilfield Petroleum Management Bureau's Downhole Operation Branch Company, we have carried out frequency conversion transformation on its drilling equipment - petroleum drilling rig, and received good results.

2.Brief introduction of petroleum drilling rig system

1.Drilling purpose

To drive the drilling tools to break the rocks, drill underground, and obtain oil or natural gas.

2.Core action of rotary drilling rig

Rotating drilling - breaking rocks

Mud circulation - taking away the broken rocks

3.Core system

Lifting system, rotating system, mud circulation system

4.Core components required for core action

Derrick, base, turntable, winch, gantry crane, traveling crane, big hook, water faucet, and mud pump

5.The on-site power system is provided by two 1000KW motors, whose main parameters are shown in the following table:

额定功率	1000kW	额定电压	600V	额定电流	1205A
额定频率	60.5Hz	额定转速	1200r/min	恒功最高转速	1500r/min
最高转速	1500r/min	额定转矩	7958N.m	额定效率	94%
功率因数	0.85	绝缘等级	200级	极数	6
工作制	（S1）	冷却方式	IC06	防护等级	IP44/IP54
备注	编码器（ZFL-H25-102.4BM-G8-26FD-5M-J(4条线增量式，OC）

With the continuous improvement of production efficiency, the requirements for the drilling system are also increasing. During the drilling process, the drilling rods need to be frequently lifted and lowered. Due to the weight of the drilling tools, stable lifting and accurate positioning are required, which is the overall requirement for the drilling rig control system.

3.Configuration of frequency converter

According to the special on-site conditions, we have chosen the KE300A-1200G-T6 (1200KW/660V) frequency converter independently developed and produced by our company. Its basic parameters are:

Input: three-phase, 660V, 50HZ

Output: three-phase, 0-660V, 0-60HZ

Frequency range: 0-60HZ

Maximum frequency: 33.5-300HZ can be set arbitrarily

Basic frequency: 0-60HZ can be set arbitrarily

Startup frequency: 0-5HZ

Torque lift: adjusted to the best according to the load torque

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4.Application effect

After two months of trial operation, the system has shown significant effects:

Before using the variable frequency drive, the lifting and lowering of the derrick was directly coupled with the load through the gearbox at the power frequency of 50Hz. The speed was uncontrolled and the derrick, which weighs around 40 tons, was unstable and difficult to control, especially for heavy drilling rigs. The shock was high, making it difficult to control. After using the variable frequency drive, the lifting and lowering of the derrick can start at a low frequency of 2-5Hz, with slow speed and easy operation to control the lifting and lowering position. Moreover, the low-frequency lifting weight is large, safe, and reliable.
There were originally four gears for drilling, without other speed choices. At the power frequency of 50Hz, the clutch of the rotary table is engaged, which causes great mechanical shock to the drill pipe, motor, and gearbox. Especially when drilling into rock formations, the geological conditions underground are complex and variable, and the load is sometimes light and sometimes heavy. This causes the generator to drop frequency and pressure, and the speed of the turntable fluctuates between fast and slow. This can result in deviation from the designed inclination angle when drilling directional wells. After using the variable frequency drive, the speed of the turntable is continuously adjustable within the set range, reducing the need for frequent gear changes. Depending on the terrain, the speed can be flexibly controlled, and the torque on the turntable is greatly reduced when the turntable drives the drill pipe. The variable frequency drive also uses larger energy storage components to ensure load changes in complex and variable geological conditions.
With the increasing depth of oil drilling, the situation arises where the rotary table needs to be lifted and lowered every 9 meters, and the weight of the load becomes increasingly heavy. Originally, frequent gear changes were required to adapt to the increasingly heavy drilling tools. As the lifting speed was uncontrollable, there was a great impact on the drill pipe when the wellbore jammed, which could cause the drill pipe to break and accidents to occur. The variable frequency drive can lift at low speed, with a large lifting capacity, which results in less impact on the drilling tools, and it is easy to control the lifting and lowering position and speed, making it suitable for frequent lifting and lowering of drilling tools.
After using the variable frequency drive, the mechanical wear and tear of the entire system is reduced. The gearbox and brake system, which used to be frequently damaged, can be repaired less frequently, resulting in significant cost savings. During drilling, the motor can be in a stopped state, while in the past, the motor was directly started at the power frequency, and the starting current was large, which easily damaged the generator. After the motor started running, it remained in a running state, consuming a large amount of energy. The variable frequency drive can achieve continuous soft start, with a small starting current and no impact on the generator set. Previously, more than 3 tons of oil were used per day, but now it is around 2 tons, resulting in significant energy savings. We also have a set of power transformers available, which can be connected directly to the high-voltage grid when conditions permit.

5. Conclusion

The application of variable frequency control in oil drilling rigs is another successful application of emerging high-tech technology in oil fields. Through this practice, it has been proved that the application of variable frequency drives is very extensive. We should seize this opportunity, strive to improve the process and performance of such products, make them more adaptable to field requirements, and make greater efforts to expand the field of variable frequency drives.