I. INTRODUCTION In recent years, the development of oilfields in China has achieved rapid development. There is an unprecedented huge opportunity for today's increasingly tense energy sources, but it is also facing enormous challenges in comparison with the world's advanced equipment. The production capacity of production equipment is basically in the middle and low level of industrial automation, mainly due to the limitations of technical conditions. The oil pumping system's screw pumping pumping unit is one of the most common new types of power equipment in oil extraction enterprises. In most oil fields, a large number of equipment and technology are being promoted, and there are many units involved in energy saving transformation. The use of frequency converters for energy-efficient operation of the oil machine installations has a very significant effect on control, so the promotion value is very large. So far, a large number of pumping units have used the screw pump to pump oil and have used inverter control to increase the operating efficiency of the equipment and to control the waste of energy.
AB's PowerFlexTM 400 AC drive is an economical and practical drive for speed control of variable torque load fans and pumps. Its variable torque speed control can control the speed of the screw pump in an extremely excellent way, ensuring that the pumping pump of the screw pump works in an appropriate operating state and achieves the purpose of energy saving. As an important means for enterprises to increase efficiency, reduce operating costs, and improve competitiveness, energy conservation has become particularly significant.
Second, screw pump pumping unit introduction Screw pump was introduced in the 30s of last century, was invented by the French engineers, in the country also called the curved rod pump. Due to the inherent advantages of the single-screw pump, it has been widely applied to various industrial fields of the national economy, and has been more widely used in oil field oil extraction devices.
The screw pump is a rotary displacement pump that works in accordance with the principle of the rotary meshing volumetric principle. It is based on the fact that the screw and the bush are intermeshing to produce a volume change in the suction chamber and the discharge chamber to convey the liquid. It is an internally engaged, hermetic screw pump. The main working components consist of a bushing (stator) with a double-headed spiral cavity and a single-headed screw screw (rotor) meshing with it in the stator cavity. When the input shaft is planetaryly rotated around the center of the stator by the universal joint drive rotor, the stator-rotor meshes continuously to form a sealed chamber for uniform axial movement, and the transmission medium is transported from the suction end through the stator-rotor to the press-out end and sucked The medium in the closed chamber flows through the stator without being agitated and destroyed. The internal flow rate is low and the volume remains unchanged. The pressure is stable so that the product does not vortex and stir. The output pressure of each pump is 0.6Mpa, the head is more than 60m, and the self-priming height is generally more than 3m.
Since the stator is made of a variety of elastomeric materials, this type of pump is capable of delivering high viscosity fluids and transporting hard suspended particulate media or fibrous media. This kind of pump has few parts, compact structure, small size and simple maintenance. The rotor and stator are the vulnerable parts of the pump. The structure is simple and easy to install and remove. It is an advanced production pump applied to the current oil field production system.
For the oil extraction enterprises, the power consumption is the main part of their production costs. In the power consumption part, the power consumption of the screw pump accounts for most of the power consumption of the entire screw pump oil pumping device, so reducing its power consumption is the screw The key to energy savings in pumping units. Our company uses the variable torque speed control of the AB FlexFlexTM 400 AC drive in the oil production system of the Daqing Oilfield Company to control the screw pump speed in an excellent way to ensure that the screw pump operates in a suitable operating state and guarantees continuous operation. Pumping, and reached the goal of energy saving.
Third, the application of PowerFlexTM400 frequency converter in the screw pump oil pumping unit The screw pump oil pumping device in the normal condition runs the screw pump oil pumping device movement inside the process the impact to the machine greatly, affects the oil pumping device the life time is very big And wasting electrical energy. At present, the domestic oil production enterprises, the oil production equipment is designed according to the maximum production capacity, but in the vast majority of production processes often do not use so much power.
In the early oil wells, due to the newly exploited, large oil storage capacity and the increased speed, the frequency converter is operated in a high output state, the frequency is increased, the corresponding motor speed is increased, and its oil production is also increased accordingly. Its comprehensive oil recovery rate is comparable. In the case of higher power frequency, the work efficiency is improved significantly.
In the middle and later wells, due to the reduction of well reserves, if the motor is still running at industrial frequency, it will inevitably waste energy and cause unnecessary losses. Therefore, we adopt a way to reduce the speed, reduce the stroke, and generally run the frequency of the inverter to 30~40Hz. Between these, the motor speed drops by 30%, and the general load of the oil extraction equipment is lighter, the energy saving rate can reach about 25%, and the power factor is increased, which reduces the reactive power loss. Compared with the speed of the pumping motor, which keeps the power frequency running, and the output power is almost constant, the frequency conversion control method can avoid the phenomenon of large horse-drawn cars in the production of oil. Therefore, it can avoid the waste of a lot of electric energy.
Adopting the frequency converter to adjust the speed of the screw pump motor can improve the oil production efficiency, reduce the mechanical failure, prolong the service life of the machine, and run efficiently. At the same time, the number of oil extractors in oil fields is very large, and a large number of variable frequency control screw pump oil pumping devices can save a large amount of electric energy and achieve cost savings.
As shown in the figure, the system control circuit design uses manual and automatic operation modes to facilitate the maintenance of electrical appliances and circuits. In the automatic control circuit part, the relay output 1 of the PowerFlexTM 400 inverter is programmed as “motor runningâ€, and the normally open node of the relay output is placed in the automatic control circuit to control the motor operation. The frequency converter operates according to the external starting source and the analog quantity source to control the starting and stopping and the running state, and to achieve more comprehensive protection for the screw pump.
The screw pump motor is mainly controlled by the frequency converter to control its operation according to the flow rate of the screw pump crude oil pipeline. A flow valve with an analog output is installed on the outlet pipe of the screw pump, and the inverter uses the analog output as a feedback signal to control the output of the inverter. When the flow rate feedback is high, it means that there is sufficient pumpable oil downhole, and the frequency converter increases the speed of the screw pump to increase the pumping capacity. When the flow rate feedback value is low, it means that the downhole oil volume is very low. The frequency converter reduces the screw pump speed until it is reduced to a certain low value. The value ensures uninterrupted continuous pumping. According to the experience of debugging, the optimal minimum output control of the inverter is 30Hz, because the pump efficiency will be reduced when the pumping speed is lower, and the energy saving effect is not obvious.
The oil layer's oil layer content is relatively complex. Long-time pumping may cause partial pumping and damage to the oil pumping device. The delay function of the relay output of the PowerFlexTM 400 inverter fully protects the screw pump oil pumping device. We still turn on the relay output of the inverter and select the output condition of the relay output 2 as the analog input 2 overrun. As shown in Figure 2, the signal of the pumping-out valve is connected to the analog input 2 of the inverter. Set the trip point of relay output 2 to the value of 40% to 60% of the area, so that when the oil layer content is very low, the relay output 2 can be set to a certain length of judgment time (120 seconds) based on the anti-evacuation valve signal on the pipeline. To delay the output, if the pump-out valve signal retention time exceeds this judgment time value, the inverter relay output 2 output signal, stop the screw pump motor to protect the oil pumping device, if it is within this judgment time length of oil When it comes up, the relay is not output, and the pumping unit maintains the normal pumping state to continue pumping.
When the screw pump motor is started, since the content of the fluid in the pump pipe is complex, the soft start/soft stop function of the speed-controlled PowerFlexTM 400 inverter with variable torque load characteristics can reduce the mechanical impact on the sucker rod. Heavy-duty oil, paraffin wax, shaka, etc. can effectively prevent shutdowns due to locked rotor overload, etc. to protect the motor and mechanical equipment, reduce maintenance, prevent broken rods, inverters against overvoltage, undervoltage, overload, Short circuit and motor stall can be reliably protected, which has a good effect on extending the life of the motor and reducing the wear of mechanical equipment.
According to the long-term operating characteristics of the oil extraction device, the control circuit uses only one stop button to control. Moreover, we have fully utilized the relay output and delay function in the inverter, which not only saves low-voltage electrical equipment such as relays and time relays, but also saves space and volume of the control cabinet. This can be used in large-area oilfield systems. Save a lot of basic investment funds and spare parts funds.
The advantages of PowerFlexTM 400 frequency converter in the pumping system of the screw pump are also outstanding: the first operation is simple, and the screw pump pumping unit operates synchronously without special adjustment; the second reliability is high: the screw pump pumping unit is reserved. The original control method and circuit are not changed, so as to prepare for failure without affecting production; the third soft start/soft stop: reduce machine vibration, extend the service life of equipment and mold; effectively reduce noise and improve working environment; Reduced, stable oil temperature; extended service life of sealed components, reduced downtime maintenance rate, saving a lot of maintenance costs, while increasing the installed capacity of the transformer; the fourth highest rate of return: according to specific conditions, all investment about 6 to 12 months Save on electricity bills.
IV. Concluding remarks For most companies, the cost of electricity is the last cost controlled by the company. At present, companies are focusing on the control of electricity expenses, because the electricity consumption of electricity equipment is determined by its electromechanical characteristics. As an aspect of oil field production, we should pay attention to energy conservation, pay attention to the adoption of advanced energy-saving mechanisms, and apply advanced technologies to minimize energy consumption, that is, to protect the environment and create economic benefits for enterprises. Practice has proved that speed control inverter technology and a series of technical measures, especially its programmable multi-functional relay output function, can help oilfield enterprises in oil production by applying high-performance and high-quality POWERFLEXTM400 variable torque load characteristics. Reduce a lot of energy costs in the link.