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The application of universal frequency converter in the control of beam pumping unit

the application of universal frequency converter in the control of beam pumping unit

[Abstract many enterprises are optimistic about the downstream demand]: This paper mainly introduces the application of frequency converter in the energy-saving transformation of beam pumping unit, one of the important production equipment in the oil field, and explains the energy conservation and improvement of process level through the analysis of equipment and process, The transformation scheme and the problems that should be paid attention to in application are briefly introduced

[Key words]: AC frequency conversion technology universal frequency converter beam pumping unit stroke

preface

most oil fields in China are low-permeability, low-energy and low-yield oil fields, which do not have strong self injection capacity like the oil fields in the Middle East. Most oil fields rely on water injection to kill oil into the well, and then rely on pumping units to lift oil from the formation. Replacing oil with water and oil with electricity is the reality of China's oil fields, and electricity charges account for a large proportion of China's oil production costs. Therefore, the oil industry attaches great importance to saving electric energy

in China's oil exploitation, mechanical oil extraction wells account for the vast majority, among which rod oil extraction (rod pumping wells) accounts for more than 90% of the total mechanical oil extraction. More than 70% of the national oil production is completed by rod pumping units. Its energy consumption has accounted for one third of the energy consumption of oil fields. China consumes about 4.2 billion yuan of electricity every year. As thousands of new wells are put into production in each oilfield every year, together with the renewal of original equipment, thousands of new pumping units are added every year. Pumping units play an important role in China's oil exploitation

at present, beam pumping units are the most common and the largest number of pumping equipment used in oil fields. In 2003, an oil production plant in Shengli Oilfield adopted a universal frequency converter to transform the pumping unit, and the efficiency of the oil well pump was significantly improved, with an average daily oil increase of 2 tons and a power saving rate of more than 30%. The following is a brief introduction to the principle and operation scheme of energy-saving transformation

working principle of beam pumping unit

its action principle is that the AC motor drives the oil pump at a constant speed and reciprocates along the direction of gravity, so as to pump crude oil from hundreds to thousands of meters underground to the ground. Analysis of its load characteristics shows that its inertia is large, and the viscosity of different oil wells is very different. When the viscosity of oil is large, the efficiency of the pump becomes low, and it is often difficult to start. This load is also a periodic load, and the properties of the load on the rising and falling strokes are also different. When falling, it has the properties of potential load. In order to adapt to these complex working conditions, the configuration and actual working state of the pumping unit can only be a big horse pulling a small car. The motion of the beam pumping unit is to lift up and down repeatedly, once a stroke. Its power comes from the two steel sliders with considerable weight driven by the motor. When the sliders are lifted, they act like levers to send the rod of the oil production machine into the well; When the slide block descends, the oil extraction rod brings oil to the wellhead. Due to the constant speed of the motor, the load is reduced and the energy generated by the motor drag cannot be attracted by the load during the decline of the slide block. It is bound to find a channel for energy consumption, resulting in the motor entering the regenerative power generation state, feeding back the excess energy to the electricity, causing the bus voltage of the main circuit to rise, which is bound to have an impact on the whole electricity and lead to the decline of the power supply quality, Danger of power factor reduction; Frequent high-voltage impact will damage the motor, reduce production efficiency and increase maintenance, which is extremely detrimental to the energy conservation and consumption reduction of pumping equipment and cause great economic losses to the enterprise. Two high-quality steel sliders are introduced into the beam pumping unit, which leads to many problems such as large starting impact of the pumping unit

in addition to the above two aspects, the special geographical environment of oil production in the oil field determines that the oil production equipment has its unique operation characteristics: in the early stage of oil production, the oil storage capacity is large, and the liquid supply is sufficient. In order to improve the efficiency, power frequency operation can be adopted to ensure relatively high oil production; In the middle and late stage, due to the reduction of oil reserves, it is easy to cause insufficient liquid supply. If the motor still operates at power frequency, it is bound to waste electric energy and cause unnecessary losses. At this time, it is necessary to consider the actual working conditions, appropriately reduce the motor speed, reduce the stroke, and effectively improve the filling rate

at present, the technical transformation of AC variable frequency speed regulation of beam pumping units mainly has the following two advantages:

(1) improve the power quality and reduce the impact on the film. This is mainly concentrated in occasions where power supply enterprises have high requirements for power quality. In order to avoid the decline of power quality, frequency conversion control needs to be introduced, and its main purpose is to reduce the impact of pumping unit working process on power

(2) energy saving. On the one hand, in order to overcome the large starting torque of oil field pumping units, the motor used is far greater than the actual power required. When working, the utilization rate of the motor is generally 20% - 30%, and the maximum will not exceed 50%. The motor is often in a light load state, resulting in a waste of resources. On the other hand, the continuous change of the working condition of the pumping unit depends on the underground state. If it is always operating at power frequency, it will also cause a waste of electric energy. In order to save energy and improve the working efficiency of the motor, frequency conversion transformation is needed

implementation plan of energy-saving transformation

(I) simple speed reduction method: directly install a frequency converter and reduce the operating frequency of the motor, reduce the motor speed, increase the time of each stroke, and achieve energy-saving effect. In practical application, it can achieve 15% - 30% power saving effect

(II) changing stroke mode: after measuring the well conditions and oil-water ratio, according to the operating characteristics of the beam pumping unit, set different frequencies for the decline and rise in each stroke, and adjust the speed of the motor at any time. The sucker rod drops slowly and rises rapidly, which not only achieves the effect of power saving, but also can effectively adjust the oil-water ratio and improve production. In practical application, the field measurement of nearly 40 reformed beam pumping units shows that the average power saving is 38% compared with the power frequency operation. If the oil production is recalculated, the comprehensive benefit is very considerable

problems and solutions in practical application

there are many problems in practical application, mainly focusing on the treatment of energy generated in the power generation state of beam pumping units. For the first case mentioned above, it is more convenient to use ordinary frequency conversion according to the deployment of Anhui provincial Party committee and provincial government and energy consumption braking unit, which is at the cost of more power consumption, mainly because the power generation affects some vertical installation and cannot feed back electricity. When the frequency converter is not used and the motor is in electric state, it absorbs electric energy from electricity; When the motor is in the power generation state, it releases energy, and the electric energy is directly fed back to the electricity, which is not consumed on the local equipment. The comprehensive performance is that the power factor of the pumping unit power supply system is low, which has a great impact on the power quality. However, when using ordinary frequency converters, the situation has changed. The input of ordinary frequency converter is diode rectification, and the energy cannot flow in the opposite direction. Up