Long Distance Motor Control Technology of Electric Submersible Progressive Cavity Pump in Deep Well Lifting, a Case Study

Abstract

The electric submersible progressing cavity pump (ESPCP) lifting technology has the advantages of rod-free pipe offset wear, low energy consumption, high system efficiency and high degree of digitalization. It is suitable for heavy oil wells, sand wells, gas wells, highly deviated wells, horizontal wells, platform wells and other complex condition of producing wells. ESPCP was widely used in recent years, and nearly 1,000 wells were applied in PetroChina. However, deep well lifting has been the bottleneck that electric submersible progressing cavity pump is difficult to break through. The deepest setting depth of pump of ESPCP in China was around 2,500 meters. With the increase of the setting depth of pump, the lifting capacity of the ESPCP gradually decreases, and the failure rate also increases. The fundamental reason is that the current variable-frequency drive cannot meet the needs of long-distance motor control. In this paper, the terminal voltage and output power loss of the motor under the conditions of different cable lengths were analyzed through experiments, and the reasons for the power shortage of the long-distance motor were summarized. A novel long distance motor control technology of ESPCP based on vector control and revised filter was developed in this paper. A new vector control model suitable for long-distance motor control was established. The angle between dq-axis and stationary coordinate was calculated based on three-phase inductance of motor to get the maximum armature current. The compensation model was built according to the load and cable loss. At the same time, the inverter voltage was increased to 1140 V, and the motor structure was optimized. The validity of the model was verified by experiments. Through the long distance drive experiment of ESPCP with new vector control technology, the actual output power of the motor was increased by 40% compared with the formed control method. ESPCP with this new control technology was carried out in Xinjiang oilfield, and the depth of pump setting was over 3,000 meters which was the deepest record of ESPCP application in China. This long distance motor control technology of ESPCP provides an effective method to solve the low output power caused by long cable and overload, and the setting depth and applied range of ESPCP is extended.