1、 Overview:
The underground oil storage capacity of oil wells in various oil fields across the country varies. When the oil volume cannot
make the pumping unit equipment operate at full load, variable frequency control must be used to reduce the pumping
frequency and adjust it to a speed that the oil volume can meet, so that each oil well can set the speed according to the amount
of oil. This method not only reduces the current method of injecting water into the wellbore, but also allows each oil well to
continuously pump oil, saving the electricity consumed due to water injection and the excess electricity consumed due to insufficient
load. It can be called a time-saving, labor-saving, energy-saving and efficient method. It is worth promoting a way to greatly reduce
the cost of oil extraction.
2、 Market outlook:
In the oil field pumping unit market, there are tens of thousands of pumping units in Daqing Oilfield, thousands of pumping units in Liaohe Oilfield, more than 10000 pumping units in Shengli Oilfield, as well as Jilin Oilfield, Zhongyuan Oilfield, Jianghan Oilfield, Karamay Oilfield, Tuha Oilfield, Changqing Oilfield, etc. Although many variable frequency controls have been used in various oilfields, they account for only a small amount of the total, about 5% of the total, and a large part of them are not installed with variable frequency controls. Each oil field is installed and transformed by stages and batches every year, but there is a big gap. To achieve the automation of variable frequency pumping, it is necessary to implement it in stages and batches. Most oil wells require variable frequency control, which has huge market potential. Adopting variable frequency control is currently the most ideal choice. At present, the number of pumping units controlled by variable frequency control is increasing in major oil production plants across the country. With the demand of oil production plants, the use of variable frequency drives is also gradually increasing. The most commonly used ones are Daqing Oilfield, Liaohe Oilfield, Shengli Oilfield, etc. Currently, the variable frequency drives used in oil fields include ABB, Ximenzi, Fuji, and Jianeng IPC brands.
3、 Energy saving methods:
When analyzing the energy-saving methods of oil field pumping unit energy-saving control cabinets, the first thing to look at is what are the various forms of energy-saving control for oil field pumping units? Due to the fact that the operating condition of the beam pumping unit is not a constant speed state, its operating state is: during the upstroke, the motor is in an energy consuming state, and during the downstroke, the motor is in a generating state. When using a frequency converter, in order to ensure the continuous operation of the frequency converter, the electrical energy generated by the motor must be released. The first method is to add a braking unit and a braking resistor to consume electrical energy in the resistor; The second method is to use feedback braking to feed back electrical energy to the original power grid. Choosing the second feedback braking method on oilfield pumping units is the way to achieve maximum energy savings.
4 Working principle and control method:
For extraction wells with medium and low viscosity crude oil and high water content, the ideal working mode of the pumping unit should be "slow up and fast down". "Slow up" is beneficial for improving the filling degree of the pumping pump and increasing the discharge volume of each stroke. At the same time, "slow up" can effectively reduce the additional dynamic load on the suspension point, thereby reducing stroke loss, improving the working conditions of the oil extraction equipment, and extending the service life of the equipment. 'Quick descent' is beneficial for timely closure of the fixed valve of the oil pump, improving pump efficiency, saving time, and increasing oil production per unit time.
For high-yield and high water content wells, the frequency can be increased and the flushing frequency can be appropriately increased to achieve a "fast up and fast down" increase in liquid production by about 30%. For low yield wells, it has been found in practical experiments that if the flushing frequency is increased, the fluid discharge rate does not increase but decreases. However, if the flushing frequency is reduced, the fluid discharge rate increases by about 20-30%, while saving electricity and extending the life of the pumping unit, tubing, and rod. The economic benefits are astonishing. In short, for different working conditions, appropriate selection of operating parameters can achieve a balance between the supply and production relationship of oil wells, and achieve the goal of increasing production and saving energy.
After using PMD series frequency conversion control, the absorption circuit and discharge circuit of the pumping unit motor during four quadrant operation (such as power generation state) are introduced in the PMD series frequency converter, and a feedback unit circuit is introduced. During normal operation, the feedback unit circuit does not work. When the motor is in a generating state and the bus voltage rises to a certain level, the feedback unit starts working. Through IGBT three-phase SVPWM inverter, the regenerated electrical energy on the DC bus is fed back to the grid. This design is more suitable for controlling pumping units and has a more significant energy-saving effect.
Functional characteristics of PMD series frequency converter
1. Implemented soft start, soft stop, and speed regulation operation process control
The starting current is small, the speed is stable, the performance is reliable, and the impact on the power grid is small. It can achieve arbitrary adjustment of the up and down speed and closed-loop control operation;
2. The flushing, speed, and liquid production of the pumping unit can be determined based on the liquid level and pressure of the oil well, which can effectively reduce energy consumption. Improve pump efficiency, reduce equipment wear and extend service life;
3. A dedicated application program for pumping units, with simplified design, suitable for direct debugging by ordinary oil recovery workers;
4. Built in input filtering device, full process noise filtering, and interference to the power grid is 1/4 of that of ordinary commercial frequency converters;
5. Full voltage automatic tracking, automatic calculation of braking torque, simplifying the operation of application links;
6. Built in feedback braking unit, which can feed back the regenerated electrical energy to the grid. Built in reactor and filter, can be directly connected to the power grid, with an energy feedback efficiency of up to 97%. 15%~25% more energy-efficient than general frequency converters, with heat loss below 3% of resistance braking, reducing heat sources, and enhancing safety;
7. All round drive, compatible with permanent magnet synchronous motor and asynchronous motor control;
8. It has multiple protection functions such as overcurrent, short circuit, overvoltage, undervoltage, phase loss, overheating, etc., ensuring safer and more reliable system operation;
9. Unmanned and fully automated design in the field, allowing for arbitrary control of pumping speed without the need to replace mechanical equipment. Suitable for oil wells in different regions and structures, suitable for different climates and conditions;
10. Optional wireless communication module for seamless integration with oilfield digital systems.