1. Overview

The steamed bread machine is the main equipment in the current oil production, and its number is more than 100,000. The total installed capacity of the motor is 35 million kW, and the annual power consumption is over 10 billion kWh. The power consumption of the steamed bread machine accounts for about 40% of the total electricity consumption of the oil field. The operating efficiency is very low, the average operating efficiency is only 25%, the power factor is low, and the power is wasted. Therefore, the energy saving potential of the steamed bread machine is very huge, and the petroleum industry is also a key industry to promote the “energy saving of the motor system”. This paper introduces the use of variable frequency speed control technology to adapt the movement law of the boring machine to the changing conditions of the oil well, to improve the system efficiency and achieve the goal of energy saving and production increase.

2. Several advantages of pumping unit frequency conversion

2.1, greatly improve the power factor, (0.25 ~ 0.5 increased to above 0.9). The supply current is reduced, thereby reducing the load on the grid and the transformer.

2.2. Dynamically adjust the extraction speed to save energy and increase crude oil production.

2.3. Realize the “soft start” of the motor gearbox pumping unit to avoid excessive mechanical impact and prolong the service life of the equipment.

3. Shantou machine load analysis

3.1. The most widely used in China is the beam-type vertical shaft boring machine, which has three parts:

(1) Ground part: It consists of a motor, a reducer and four links.

(2) Downhole section: The oil pump (suction valve, pump cylinder, plunger and drain valve) is suspended at the lower end of the casing.

(3) Sucker rod column: Connect the middle part of the ground pumping unit and the downhole pumping unit.

3.2. The motor load of the boring machine changes according to the cycle. When starting the starting, the load is very large, and the starting torque is required to be large. The load rate is very low during normal operation, generally around 20%, and the high load rate is only 30%. The load curve of the motor has two peaks, which are the 'dead points' of the upper and lower strokes of the boring machine.

Under the condition that the balance is not balanced, the load of the upper and lower strokes is extremely unbalanced. In the upper stroke, the sucker rod column and the liquid column need to be lifted, and the motor needs a lot of energy. During the downstroke, the sucker rod column works on the motor to put the motor in a generating state. Usually, a balance block is added to the crank of the boring machine to eliminate the load imbalance of the up and down stroke. The balance block is well adjusted, and the time and power generated by the power generation state is small. Since the pumping load is changing every moment, the balance weight cannot be completely changed with the pumping load. Most of the boring machine The counterweight is seriously unbalanced, resulting in excessive inrush current. The inrush current can be up to 5 times the operating current, even up to 3 times the rated current. Adjusting the balance weight can reduce the inrush current to 1.5 times the normal operating current.

Load characteristics: It is a constant speed operation. Due to the counterweight, it is a variable torque. The variable power load has two power generation states in one cycle, and the starting torque is large and the inertia is large. The common problem of the steamed bread machine used in domestic oil fields: long running time, “large horse-drawn car”, low efficiency, high energy consumption, inconvenient adjustment of stroke and stroke, and empty pumping.

4. Difficulties in the transformation of traditional steamed bread machine inverter

Shantou machine frequency conversion energy-saving transformation has done a lot of attempts, but they are not very successful, the main problems are:

(1) The steaming machine has two power generation states in one working cycle, especially when the counterweight is unbalanced, the “pumping voltage” generated is very high, and the DC side electrolytic capacitor and the braking resistor are increased. The value does not completely solve the problem, and as the oil layer changes, the 'pumping voltage' also changes.

(2) The starting torque of the steamed bread machine requires a large starting torque. If the inverter parameters are not properly set, it may cause overcurrent or start.

(3) In the past, the design scheme of frequency conversion energy-saving renovation rarely considered the oil level and oil concentration of the oil well. In terms of increasing production, the effect is not good.

5. Solution

The problem of the transformation of the steamed bread machine is as follows: Our company proposes the following solutions:

(1) Adopt variable frequency speed control technology to match the motor speed with the load of the steamer. In the early stage, due to the fresh mining, the oil volume is large, the inverter runs to 65.00 Hz, the motor speed is increased by 30%, the oil recovery rate is increased by 20% compared with the power frequency, and the work efficiency is increased by 1.2 times. In the middle and late wells, the oil volume is reduced, the speed is reduced, and the stroke is reduced. The general frequency runs between 35.00 and 40.00 Hz, and the motor speed drops by 30%. The power saving rate is up to 25% and the power factor is increased.

(2) Dynamically adjust the stroke frequency of the steamed bread machine. As the oil well is pumped from shallow to deep, the oil quantity is gradually reduced, and the pump fullness is insufficient, and the pump efficiency is reduced. When the oil supply capacity of the oil well is less than the displacement of the oil pump, it causes Pump evacuation and liquid hammering. Reduce the frequency, reduce the motor speed, increase the fullness, not only save energy but also increase crude oil production.

(3) Dynamically adjust the speed of the up and down stroke of the boring machine, appropriately reduce the lower stroke speed, increase the fullness of the pump, and appropriately increase the upper stroke speed, which can reduce the leakage coefficient during lifting, and make the boring machine work in the optimal operating state, effectively Increase crude oil production per unit time.

(4) The starting torque is large, the load during operation is low, and the inrush current is large. To solve the problem fundamentally, increase the pole number of the motor or increase the speed ratio of the gearbox to increase the output torque. The inverter runs normally from 80.00 to 90.00 Hz. This also helps to reduce the energy of the power generation state and reduce the 'pumping voltage'.

(5) Treatment of regenerative energy. Increase the capacity of the DC side filter capacitor of the inverter; reduce the braking resistor value, improve the power consumption of the braking system, or directly use feedback braking to reduce energy loss; when generating electricity, the frequency increases.

(6) Air defense pumping, dynamically adjust the stroke frequency of the steamer and the upper and lower stroke speed. Set the motor output power standard value, detect the motor output power in real time, control the motor speed, greater than the standard value, and accelerate. On the contrary, deceleration, to achieve closed-loop control.

6. Conclusion

Because the type and working conditions of oil wells vary widely, the amount of oil seepage and seepage in the well is changing all the time. The load change of the steamed bread machine is irregular. Therefore, the variable frequency speed control technology is adopted to adapt the movement law of the steamed bread machine to the changing working condition of the oil well, thereby improving the system efficiency and achieving the purpose of energy saving and production increase.