Abstract : This paper introduces the practical application of a HARSVERT-A60/220 high-voltage 6KV frequency converter to drive water injection pumps in an oilfield water injection station, focusing on exploring the operational patterns of the water injection process. The energy-saving effects and additional benefits brought about by the modification are analyzed and summarized. This provides a successful example for achieving energy conservation and efficiency improvement in oilfields using variable frequency speed control.
Keywords : high-pressure water injection pump, pipeline network loss, cavitation phenomenon, variable frequency speed control
1 Introduction
Injecting water into the oil reservoir through injection wells is a widely adopted and important development measure to ensure reservoir pressure and improve oil production rate and recovery rate. In oilfield water injection projects, the injection pump is the primary equipment for meeting water injection needs and ensuring formation pressure. To guarantee water injection requirements over a long period, the capacity of the injection pump is generally selected to be large in the design. However, in actual production, the daily water injection volume is always a parameter with significant fluctuations. Especially in high-pressure water injection systems, the phenomenon of "oversized pump for small loads" is common. There is a large pressure difference between the pump pressure and the dry pressure of the injection pipeline. The injection pressure of the water injection network must be maintained by controlling the outlet valve. This results in a significant waste of electrical energy and is also detrimental to the operation of the pump due to the high pump pressure. While ensuring the requirements of oilfield water injection, how to improve the efficiency of the water injection system and minimize its energy consumption has always been a research topic for us. In recent years, domestic high-pressure high-power frequency conversion technology has made new breakthroughs, creating conditions for us to use AC frequency conversion speed control devices in high-pressure water injection systems. It also allows us to automatically adjust the water injection volume by setting parameters according to the pressure required by the water injection network through the frequency conversion device, which saves a lot of electricity and reduces pump losses, which is of great significance for reducing the production and operation costs of oilfields.
2. Overview of Oilfield Water Injection Technology
Shenyang Oilfield currently has 5 water injection stations with a total of 16 high-pressure water injection pumps and a total installed capacity of 23,400 kW. Currently, 4-5 pumps are operating normally, with a capacity of 7,900 kW. To adapt to changes in water injection volume and achieve rational water injection, the operating mode of the pumps needs to be constantly adjusted. Thus, without speed control measures, the flow rate can only be controlled by the number of pumps in operation or by manually adjusting valves, inevitably leading to increased energy consumption in the water injection system. Taking the No. 2 oil production area as an example: The water injection task in the No. 2 oil production area is mainly undertaken by the Shenyang No. 2 and Shenyang No. 4 water injection stations operating in a network, as shown in Figure 1. The main network pipeline is approximately 8 kilometers long, and the total water injection volume varies from 8,200 to 9,700 m³/day, with fluctuations of +15% and -20%. The pipeline network normally operates two 1800kW high-pressure water injection pumps, with water injection capacities of 250 m³ /h (Shen'er Water Injection Station) and 200 m³ /h (Shen'si Water Injection Station), respectively. The average dry pressure of the pipeline network is 16.9 MPa, and the pump pressure is 18.9 MPa, resulting in a pressure difference of MPa. The water injection volume varies significantly between day and night, and the original equipment can only operate at a fixed speed. Therefore, the water injection volume can only be adjusted by regulating the valve opening, which artificially alters the resistance of the pipeline network, increases pipeline losses, and causes a considerable amount of energy to be wasted on the valves. This results in persistently high water injection unit consumption, which not only makes operation uneconomical but also increases the workload of workers. Untimely adjustments can also cause the pipeline pressure to be too high or too low, and the flow rate to be too large or too small, affecting the production process and the safe operation of the equipment. Therefore, if a variable frequency speed control device is installed on the water injection pump unit, the energy loss caused by the pump-pipe pressure difference can be greatly reduced, or even eliminated. Meanwhile, with the participation of the variable frequency speed control device, through optimized simulation, the water injection pump is operated and the flow and pressure of the water injection pipeline are adjusted according to the optimal principle, so as to minimize the throttling losses in the water distribution room and wellhead, thereby enabling the entire water injection system to operate in the high-efficiency zone and achieve the goal of energy saving.
For details, please click: Application and Practice of Domestic High-Voltage High-Power Frequency Converters in Oilfield Water Injection Systems
