1. Introduction Electricity is a crucial power source for oilfield production. With the deepening of oil and gas exploration and development, electricity consumption will continue to increase. Reducing energy consumption in production, transmission, distribution, and utilization, and improving energy efficiency, are of great significance for ensuring normal oilfield production and improving its economic benefits. Currently, most oilfields in China have entered the late stage of development, with comprehensive water cuts exceeding 80%, and some exceeding 90%. With the increasing water cut, the total produced fluid volume is constantly increasing, leading to a rapid increase in energy consumption. Since oilfield power grids mostly use trunk or radial wiring, which are characterized by simple structure, low equipment costs, and convenient operation, a problem arises when the lines are long. The voltage at the end of the line is low, causing the pumping unit (asynchronous motor) to not operate at its rated voltage, failing to achieve optimal efficiency. This results in increased motor slip, higher winding temperature, accelerated insulation aging, and reduced motor lifespan. The lower voltage also significantly increases power losses in the power grid. Meanwhile, the main load on the oilfield power grid is the asynchronous motor used as the prime mover of the pumping unit. This inductive load requires reactive power absorption from the system during operation, increasing energy and voltage losses in power supply equipment and lines. According to field surveys, approximately 40% of the electricity is used for mechanical oil extraction. The load variation of a single pumping unit well is large and frequent, with the power factor changing from 0.1 to 0.9 within a single stroke, resulting in significant voltage fluctuations at the load connection point. The field survey also revealed the lack of local reactive power compensation measures in the oilfield. Of course, reactive power compensation for this type of load is extremely difficult. Conventional parallel capacitors cannot meet the load characteristics of the pumping unit, resulting in either undercompensation or overcompensation. While using AC contactors to control capacitor switching can improve the compensation method of fixed electrostatic capacitors, it still cannot well adapt to the alternating load characteristics of the pumping unit, resulting in unsatisfactory compensation effects. The transformers used for oil wells in the oilfield operate in several modes: one transformer powering one well, two pumping wells, or multiple wells. The feeder length from the transformer to the well is generally less than 20 meters. Generally, pumping units are equipped with motors ranging from a minimum of 10 kW to a maximum of 55 kW, with most motors being replaced with energy-saving motors. Water injection stations commonly use frequency converters to power the water injection pumps, and compressors are also powered by frequency converters, with some using soft-start methods to achieve both energy savings and limiting starting current. Based on the above, oilfields have significant potential for energy conservation and consumption reduction in their surface electrical systems. 2. Field Survey of a Typical Oilfield In a certain oilfield, the power grid is stepped down to 6 kV via a 35 kV substation and then supplied to various distribution transformers. There are five 6 kV distribution lines, approximately 33 km long, with 59 transformers and a total installed capacity of approximately 8,780 kVA. The distribution transformers step down the voltage to 400 V, supplying power to nearby oil well pumping units, compressors, water injection pumps, and gathering pumps. The actual total power load capacity is approximately 2,000 kVA, with an annual power consumption of 15 million kWh. Measurements were taken at key measuring points of several typical loads in the oilfield; the measurement data and corresponding analysis are as follows. 2.1 Input Side of Injection Pump Inverter The electrical performance of a water injection pump at a water injection station was tested. The pump motor is powered by an inverter. Voltage, current, power factor, active power, and reactive power were measured at both the input and output sides of the inverter. The line voltage waveform showed a slight flat top and contained a small amount of 5th (3.12%) and 7th (2.31%) harmonics, with a peak factor of 1.4. The current exhibited a saddle-shaped waveform, typical of a 6-pulse rectifier circuit. The harmonic voltage drop across the system input impedance caused by the current harmonics resulted in harmonic components of the same order in the voltage, significantly affecting the operation of other electrical equipment connected to this power supply line. The line current contains 5th (37.6%), 7th (19.2%), 1st (10.1%), 13th, 17th, 19th, 23rd, and 25th harmonics, indicating a very high level of harmonics. The peak factor of the current waveform is 1.8, indicating severe distortion. The total apparent power input to the frequency converter is 51.2 kVA, with active power of 36.1 kW and reactive power of 36.3 kvar. The power factor is 0.71. It is evident that the frequency converter input power factor is low and the harmonic content is high. The simultaneous operation of numerous frequency converters significantly impacts the overall energy consumption of the system, primarily through increased line losses in distribution lines and transformers, as well as its impact on the energy consumption of other equipment. 2.2 Frequency Converter Output Side The output side of the frequency converter is the input side of the water pump motor. Figure 1 shows the line voltage and line current waveforms of the frequency converter output. The fundamental frequency is 40.8Hz, and it also contains extremely rich harmonic components. The output voltage is a square wave pulse modulated by unipolar PWM, with very high rise and fall edges, i.e., extremely high du/dt. If the motor-type load is powered through a cable line, it will not only form a high-amplitude traveling wave reflection at the motor end, leading to aging and damage of the motor insulation, but will also significantly increase the energy consumption of the motor and greatly reduce the efficiency of the motor. The voltage and current spectrum contains a large amount of power in the harmonics that affects the braking and pulsating properties of the motor, seriously affecting the efficiency of the motor and increasing energy consumption. The current harmonic content is very rich, with a peak factor as high as 7.2 and a total harmonic distortion rate of 90%. Such current flowing through the motor windings will inevitably cause a considerable proportion of ineffective active power loss. Another aspect of the problem caused by current harmonics is that it leads to a very low power factor of the motor, only 0.26. [ALIGN=CENTER] Figure 1 Analysis of the inverter output side line voltage and line current waveforms shows that the configured inverter lacks an output filter, resulting in abundant high-frequency harmonic components and significantly increasing the motor's power consumption. 2.3 Pumping Unit Measurement Points The power supply side voltage waveform of the pumping unit is intact, with a very low harmonic content and a total harmonic distortion rate of 0.7%. The current waveform is approximately sinusoidal, with a total harmonic distortion rate of 2.7%, mainly containing less than 5% of the 5th and 7th harmonic components. Figure 2 shows the continuous measured curves of the power supply voltage and current. The waveforms indicate that the reciprocating operation of the pumping unit causes the power factor to fluctuate repeatedly within the range of 0.1 to 0.9, with a very low average power factor of approximately 0.4, indicating significant energy-saving potential. The current ranges from 30.63 to 41.71. Question A shows a fluctuation rate of 30.3%. Improving the stability of the load current (peak shaving and valley smoothing) is an effective solution to consider. Figure 3 shows the continuous monitoring curve of the power supply. The load power fluctuates greatly, ranging from 3.67 to 15.1 kW, with a fluctuation rate of 134%. 2.4 The power supply voltage waveform at the compressor measuring point is relatively good, with a low harmonic content and a total harmonic distortion rate of 2.4%. The current waveform is approximately sinusoidal, with a total harmonic distortion rate of 2.2%, mainly containing less than 3% of the 5th harmonic component. [ALIGN=CENTER] Figure 2 Continuous monitoring curves of power supply voltage and current Figure 3 Continuous monitoring curve of power supply [/ALIGN] The compressor power factor fluctuates within a large range, requiring the configuration of dynamic reactive power compensation equipment to improve the power factor and reduce the transformer capacity. The power supply voltage varies between 388.3 and 400.1 V, with a fluctuation rate of 3.0%, which meets the requirements. The current varies between 255.5 and 311.6 A, with a fluctuation rate of 19.9%. The load power fluctuates significantly, ranging from 88.2 to 123 kW, with a fluctuation rate of 33.1%. Energy-saving potential can also be explored by improving the stability of the load current. 3. Comprehensive Energy-Saving Scheme Based on on-site surveys and measurements in the oilfield, the energy-saving and consumption-reducing principles suitable for the oilfield distribution network and load are: a comprehensive energy-saving technical scheme combining fixed compensation and dynamic adjustment compensation; a combination of decentralized compensation and centralized compensation; a combination of low-voltage compensation and high-voltage compensation; a combination of voltage regulation compensation and loss reduction compensation; and a combination of reactive power compensation and harmonic suppression. Specifically, there are the following seven energy-saving ideas: ① Improve the power factor. ② Rationally select transformer capacity and type. ③ Balance the load and smooth peak and valley loads. ④ Variable frequency speed regulation technology and its transformation. ⑤ Dynamic reactive power compensation and harmonic suppression. ⑥ Voltage adjustment and dynamic voltage support. ⑦ Increase the distribution network voltage level and increase the conductor cross-section. 3.1 Improve the power factor (1) Use asynchronous motors rationally to reduce the reactive power transmitted by the line. The reactive power consumed by asynchronous motors in the oilfield power grid is given by the formula, where is the reactive power required for the motor to run under no-load conditions; and are the active and reactive power respectively when running under rated load; and is the actual load of the motor. Obviously, when the active load decreases, the load factor β decreases, and only a small part of the reactive load decreases, while most of it remains unchanged. This is disproportionate to the decrease in active power demand, and the power factor deteriorates. Therefore, the capacity of the motor should be as close as possible to the load it carries. The method of checking the feeder line with the lowest power factor can be used to find the motor with insufficient load. The appropriate capacity can be determined by clamp current or by measuring the load curve. The small capacity motor can replace the large capacity motor with insufficient load to avoid the problem of a large motor driving a small load. (2) Add reactive power compensation devices. When relying solely on improving the natural power factor is insufficient to meet the power factor requirements for economical operation, reactive power compensation devices are required. Based on the characteristics of the oilfield power grid, electrostatic capacitors are generally selected as compensation devices, and a combination of centralized and individual compensation methods can be used. To adjust the capacitor capacity during operation, they can be connected in several groups and switched on or off according to load changes. The compensation capacity required to improve the power factor can be calculated using the following formula: where is the capacity of the compensation capacitor; is the active load; is the phase angle before the power factor change; and is the phase angle after the power factor change. However, field measurements revealed that the pumping well operates 8-12 times per minute, with the power factor varying widely within the range of 0.1-0.9 throughout the day. The method of switching capacitors according to load changes is difficult to meet the requirements. This manifests as: discontinuous compensation capacity, requiring tiered switching, failing to achieve optimal compensation effect; numerous transient processes causing significant system impact; easy damage to capacitors and other components; failure of the compensation device to operate in harmonic environments; and potential harmonic amplification. Considering that the 6 kV distribution network in the oilfield is stepped down to 400 kV by a distribution transformer... For oil pumping wells powered by a 400V voltage level, and with a line length not exceeding 20m, the most reasonable location for local dynamic power factor compensation when a single transformer powers multiple wells is the high-voltage side of a 6kV/0.4kV step-down transformer. Figure 4 shows the main circuit topology of the low-voltage dynamic reactive power compensation device. This topology connects to the 6kV side of the transformer and a fixed capacitor bank to implement dynamic reactive power compensation (local reactive power compensation). [ALIGN=CENTER] Figure 4 Main Circuit Topology of New Dynamic Reactive Power Compensation [/ALIGN] Figure 4 is the schematic diagram of the new dynamic reactive power supply. Only two modules are shown in the figure; the reactive power supply capacity can be increased by adding modules. The step-up transformer is used for wiring, and the device is connected to different voltage levels (6~35kV) through the transformer. (kV). The low-voltage side has two windings, one star-connected and one delta-connected, with a coil turns ratio of [value missing] and a line voltage of 400V. Each module consists of two sets of delta-connected TCR branches, one connected to the transformer delta winding and the other connected to the Y winding. Each branch can use phase control or switching mode. When the required capacity is large, multiple modules can be connected in parallel, with only one module in phase control mode at any given time. By controlling the thyristor control angle α of each TCR branch to vary between 90° and 180°, the reactor current can be adjusted within the range of 0 to the maximum capacity. Due to the phase control method, high-order harmonics will be generated in the branch. When the positive and negative half-wave trigger pulses are symmetrical, the amplitude of the fundamental and harmonic currents is determined only by the control angle α. Studies have shown that the above structure can achieve a 12-pulse effect, that is, the order of the harmonic current injected into the dynamic reactive power supply system is 12/k±1, where k is a positive integer. In the large-capacity mode, since there is only one set of phase control modules, the harmonic content is even smaller. The dynamic reactive power compensation device does not require any additional filtering devices, and the harmonics injected into the system can meet the national standards. 3.2 Reasonable Selection of Transformer Capacity and Type The existing transformer capacity in the oilfield is excessive, and the phenomenon of "oversized power supply for small loads" is very serious. Many substations operate with two transformers in parallel, resulting in low operating efficiency of the distribution transformers. Therefore, the operating methods of the system itself vary greatly: the losses of distribution transformers of the same capacity are also different; changes in the power factor have a significant impact on transformer losses. Currently, some non-energy-saving transformers, such as the S7, are still operating in the oilfield's power grid. These transformers have high copper and iron losses, severe monthly aging, and increased maintenance workload. To address the impact of transformers on power consumption in the distribution network, measures such as installing low-loss distribution transformers, adding low-voltage capacitors at the connection end to strengthen operation management, and rationally allocating transformer capacity are adopted to adjust the transformers used in the distribution network and ensure they operate at their optimal working condition. For practical situations where a large number of transformers supply power to single wells or extraction wells, the load power is not large, with the maximum power pumping unit only 55 kW. A thyristor-switched capacitor (TSC) compensation method on the low-voltage side can be considered. This can dynamically compensate for the reactive power demand of the pumping unit, significantly reducing the apparent power requirement of the transformers, reducing the total transformer capacity, and achieving energy saving and consumption reduction. When the system is operating under three-phase minor balance, its voltage and current contain a large number of negative sequence components. Due to the presence of negative sequence components, the three-phase minor balance has an adverse effect on electrical equipment. Negative-sequence voltage generates braking torque, reducing the maximum torque and output power of the induction motor and potentially causing motor vibration. Because the negative-sequence reactance of the motor is very small (only 1/5 to 1/7 of the positive-sequence reactance), the negative-sequence current generated by the negative-sequence voltage is large, increasing copper losses in the motor. Increased copper losses not only reduce motor efficiency but also cause overheating, accelerating insulation aging. When a transformer operates under unbalanced load, if one phase current has already reached the transformer's rated current, the currents of the other two phases must be lower than the rated current. In this case, the transformer capacity is not fully utilized. For example, when a three-phase transformer supplies power to a single-phase line voltage load, the transformer utilization rate is approximately 57.7%; if it supplies power to a single-phase phase voltage load, the utilization rate is only 33.3%. If the rated capacity is maintained under unbalanced load, it will cause localized overheating of the transformer, increasing losses. The phase-by-phase control mode of TSC can balance the three-phase load, improve transformer capacity utilization, and achieve energy-saving benefits. 3.3 Load Balancing, Peak Shaving and Valley Leveling Because electrical energy cannot be stored, and the power load on the power grid varies over time, power shortages occur during peak hours and power generation capacity is wasted during off-peak hours. Line losses during operation are related not only to the peak-to-valley difference but also to the duration of those peaks and valleys. Studies show that losses under unbalanced load conditions are greater than those under balanced load conditions. The more balanced the load, the smaller the increment of current change, and thus the smaller the losses. This indicates that line losses are related not only to the magnitude of the current increment but also to the duration of each increment. The difference between the minimum and maximum current absorbed in each stroke of the pumping unit is extremely significant, resulting in large load current fluctuations and a high line loss ratio. It can be envisioned that, from the system perspective, if the pumping unit's operating characteristics meet the following conditions: ① absorption of stable, harmonic-free sinusoidal current; ② three-phase power balance; ③ no inrush current or large starting current; ④ power factor of 1, then the energy-saving problem of the pumping unit will be readily solved. Therefore, the Unified Load Conditioner (Unified Load Conditioner) is crucial. The concept of a Supercapacitor Quality Conditioner (ULQC) emerged, whose main circuit topology is essentially a parallel-type active power filter (APF) with energy storage devices and their chopper control circuits configured on the DC bus. The ULQC operates in parallel with the load, and through active filtering, reactive and negative sequence compensation, and short-term active power support, it ensures that the load, from the system perspective, reaches the ideal pumping unit load conditions, thus improving power quality and achieving energy savings. The ULQC is a compensation device based on a supercapacitor energy storage control system (as shown in Figure 5), providing short-term active power support to reduce load impact disturbances. Supercapacitors are a new type of energy storage element that has emerged in recent years, offering many significant advantages over battery energy storage and showing a trend of replacing batteries in specific applications. ULQC is a three-phase voltage source converter based on IGBTs. Supercapacitors are connected to the ULQC's high-voltage DC bus via a DC-DC converter. The circuit topology is shown in Figure 5. VT1 to VT6 in the figure constitute the ULQC inverter. Besides filtering and dynamic reactive power compensation, it can also provide active power to the load for a short time due to its energy storage system. Of course, it can also quickly absorb the sudden decrease in active power when the load changes abruptly from heavy load to light load or even no load, avoiding drastic changes in system voltage. CS is a supercapacitor. The withstand voltage of a single supercapacitor is very low, generally below 3V. Therefore, in practical applications, a large number of capacitors need to be connected in series to achieve usable voltage. The voltage level is as follows. When ULQC is required for active power compensation, the boost circuit consisting of VI8 raises the voltage at the supercapacitor terminals to the required DC bus voltage and maintains it near the specified voltage value. VT1 to VT6 operate as PWM inverters. When it is necessary to charge CS or absorb some active power, this is accomplished by the buck circuit consisting of VT7, with VT1 to VT6 operating as PWM rectifiers. The neutral point of the ULQC DC capacitor can be removed to form a three-phase four-wire system. In this case, an additional bridge arm is needed to control the neutral potential. [ALIGN=CENTER] Figure 5 Load Quality Regulator [/ALIGN] For fluctuating loads, the system can maintain a basically constant output power, with the fluctuating power portion compensated by the ULQC. When the active power drawn by the load is less than the basic power provided by the system, the power difference is absorbed by the ULQC to charge the supercapacitor energy storage system, and the ULQC converter operates in high-frequency rectification mode; when the active power drawn by the load is greater than the basic power provided by the system, the power difference is provided by the ULQC, the supercapacitor energy storage system discharges, and the ULQC converter operates in high-frequency inverter mode. 3.4 Variable Frequency Speed ​​Regulation Technology and its Retrofit For motors with a wide range of speed regulation requirements, the use of variable frequency speed regulation technology has very significant energy-saving benefits. In all aspects of oilfield production, the widespread adoption of suitable motor variable frequency technology can avoid wasting motor efficiency, improve motor operating efficiency, and reduce motor no-load operating losses. Considering an oilfield of 1200... The kVA water injection pump, using the latest cascaded multi-level H-bridge series technology for variable frequency speed control, can achieve annual electricity savings of up to 600,000 yuan, with a payback period of approximately one year. In the aforementioned field measurement data, motors already equipped with frequency converters can also achieve considerable energy savings through retrofitting. For example, by adding a source filter to the output side of the frequency converter to remove high-order harmonics, an ideal sinusoidal voltage can be obtained to power the motor. This eliminates a large amount of additional losses, braking, and pulsating torque caused by harmonics, significantly improving energy utilization efficiency, protecting motor insulation, and extending service life. 3.5 Dynamic Reactive Power Compensation and Harmonic Suppression Approximately 50% of the reactive power in the oilfield power distribution network is consumed in the transmission, transformation, and distribution stages, while the remaining 50% is consumed by power users. Through optimized reactive power and voltage operation of the power grid, while ensuring qualified voltage at each node, and aiming for optimal network loss, dynamic centralized control of the on-load tap changer positions of transformers and the switching of reactive power compensation equipment (capacitive and inductive) in substations is implemented to achieve hierarchical local balance of reactive power across the entire network, comprehensively improving voltage quality and reducing power loss. When the power grid meets voltage regulation conditions, raising or lowering the operating voltage can achieve the effect of reducing losses and saving energy. To reduce reactive power loss, it is necessary to reduce the flow of reactive power in the power grid. Due to the dispersed locations of oilfield wellheads, power distribution lines are laid radially to the wellhead transformers. kV lines are long, with large voltage drops at the ends, low power factors, and severe reactive power losses. The best solution is to implement reactive power compensation locally to improve the power factor of the load, reduce the reactive power output of generators, and reduce reactive power consumption in transmission, transformation, and distribution equipment, thereby reducing losses. However, oilfield distribution networks contain a significant proportion of frequency converters and rectifiers, which often have high harmonic content, making it difficult for reactive power compensation equipment to operate normally or even causing damage. Sometimes, even when reactive power compensation equipment is in operation, it may amplify existing harmonic components in the system, triggering protection actions and reducing system reliability. Therefore, the comprehensive management of dynamic reactive power compensation and harmonic suppression has a significant impact on improving the load power factor and reducing active power losses, especially for users with low power factors. By implementing parallel reactive power compensation and optimized filter configuration in the distribution network, using 400V voltage-level thyristor switched filters (TSFs) with reasonable configuration, reactive power optimization and harmonic suppression in the distribution network can improve the power factor of the grid and reduce distribution network losses, which is the most effective measure for energy conservation and consumption reduction. TSF (Thyristor Switching Filter) is a reactive power compensation and harmonic suppression device that combines the advantages of traditional dynamic compensation devices and power filters. It can suppress power fluctuations in the power grid caused by load changes. TSF not only filters out harmonic currents in the power system but also quickly and automatically tracks changes in reactive load, performing local reactive power compensation to ensure the user's power factor remains within specified limits. TSF filters out system harmonics, preventing harmonic transmission in the power grid and providing a stable and clean power environment. Because TSF uses thyristor-controlled reactors, it can automatically switch filter banks on and off, eliminating surge impacts and arc reignition, thus ensuring the safe operation of power transformers and improving power quality. A standard TSF (Transient Switching Filter) structure should have the ability to limit changes in device current and reduce switching transients through thyristor switching. Analysis of the switching transient process shows that a minimum switching transient can be achieved if the following two conditions are met: the capacitor is charged before the positive and negative peaks of the voltage; and the thyristor is triggered at the positive and negative peaks of the system voltage. Analysis of the TSF's operating mode shows that because the voltage across the capacitor is already equal to the system line voltage when the TSF filter is connected to the system, no charging and discharging oscillations due to a voltage difference between the capacitor and the line voltage occur after the thyristor is turned on, thus achieving a minimum switching transient. 3.6 Voltage Regulation and Dynamic Voltage Support When the system voltage deviates, it has a significant impact on the operation of electrical equipment connected to the power grid. Electrical equipment is designed and manufactured according to its rated voltage. When the voltage deviates significantly from the rated voltage, the operating performance of the equipment deteriorates, and it may be damaged due to overvoltage or overcurrent. For asynchronous motors, this results in fluctuations in electromagnetic torque, increased losses, reduced efficiency, and shortened lifespan. It also causes problems with grid voltage and frequency stability, insulation issues, core saturation, and resonance faults, increasing losses and reducing economic efficiency. Therefore, voltage regulation is essential for addressing voltage fluctuations in the oilfield power grid that exceed acceptable limits. Although the range and rate of change in load reactive power requirements vary greatly, they all cause changes in the voltage at the power source point. This affects the operating efficiency of electrical equipment connected to that point and leads to mutual interference between loads from different users. To prevent this, voltage variations are generally specified to be within a certain range. In some cases, when large, rapid load changes cause voltage drops that could endanger the safe operation of other equipment or cause sudden changes in system voltage, this limit becomes even smaller. Therefore, voltage regulation is crucial when load reactive power requirements are constantly changing. Voltage regulation measures in oilfield power grids can be divided into two categories: one relies on adjusting the output voltage of generators and transformers to regulate the network voltage; the other relies on changing reactive power distribution and line parameters to achieve voltage regulation. Adjusting generator terminal voltage and transformer tap changes are only effective when the reactive power supply in the power system is sufficient. When reactive power is insufficient, to prevent generators from being severely overloaded due to excessive reactive power output, it is often necessary to lower the overall voltage level of the power system to reduce reactive power consumption. In this case, even methods such as adjusting transformer taps can only locally increase the voltage at certain points in the system. While this approach aims to lower the voltage level, it actually increases reactive power consumption, forcing generators to operate at lower voltages to limit total reactive power consumption in the system. This leads to an even lower overall system voltage level, creating a vicious cycle of low voltage and insufficient reactive power supply, potentially even causing voltage collapse. Therefore, when the power system lacks reactive power, it is essential to install reactive power sources at appropriate locations to compensate for the missing reactive power. Generally speaking, appropriately installing reactive power compensation devices at load points can reduce the reactive power transmitted on the lines, allowing reactive power to be supplied locally. This reduces power and voltage losses on the lines, thereby correspondingly increasing the voltage level at the load points. 3.7 Increase the Voltage Level and Conductor Cross-Section In the process of power transmission, the network loss of the 6kV distribution network accounts for a considerable proportion of the total network loss. Theoretical calculations show that after upgrading the 6kV power grid to a 10kV system, load loss can be reduced by 64%. Moreover, the transmission lines can meet the needs of increasing power load, increase line transmission capacity, and reduce line losses. In the process of power transmission, while keeping the transmission load constant, increasing the conductor cross-section can reduce line resistance, and the effect of reducing losses and saving electricity is also significant. In the specific implementation of the project, an economic comparison should be conducted based on the actual situation to achieve the best economic benefits. 4. Conclusion The transformation and energy conservation of the power supply system in the later stages of oilfield development is a systematic project. It requires targeted solutions to key problems, a comprehensive understanding and study of the characteristics and laws of the technologies in each system link, and the active learning from domestic and foreign experience and technologies while developing equipment and technologies with unique characteristics and suitable for specific requirements. Only in this way can a series of problems faced by China's oilfield development in the later stages be better solved, thereby achieving a comprehensive balance between the economy and efficiency of oilfield development.