INVT GD350-UL for Direct-drive Screw Pump

Abstract: Screw pump oil recovery is a commonly used oil recovery equipment in oil fields, which is directly connected to a flexible shaft to drive the screw pump to rotate and lift crude oil to the ground. This oil extraction system has the characteristics of no wear of tubing and sucker rod, reliable operation, low maintenance workload, and no noise pollution. It is suitable for special mining conditions such as conventional blocks, urban oil fields, and offshore platforms. It is particularly suitable for heavy oil sand wells, high inclination wells, cluster wells, horizontal wells, and coalbed methane drainage gas production wells.

Keywords: GD350-UL, Direct-drive screw pump, BACKSPIN.

1. Background

A domestic customer has been commissioned by Venezuelan Petroleum to seek a control solution for a direct-drive screw pump system. The grid voltage/frequency of Venezuela is using 460V, 60Hz, and has high requirements for current harmonics. According to its requirements, active filters, output filters, lightning protection measures, etc. will be configured for this application.
2. Introduction of Solution

2.1 Principle of Equipment

The electric submersible screw pump oil production system mainly consists of a submersible direct-drive motor, a protector, a coupling, a screw pump, and a ground control cabinet. Multiple sealing chambers are formed between the outer surface of the rotor and the inner surface of the stator rubber liner along the entire length of the screw pump. As the rotor rotates, a sealing chamber is continuously formed between the suction end rotor and the inner surface of the stator rubber liner, which moves towards the discharge end and finally disappears at the discharge end. It is sucked in under the pressure difference at the suction end and pushed from the suction end to the discharge end, with the pressure continuously increasing and the flow rate being very uniform. The process of screw pump operation is essentially the continuous formation, displacement, and disappearance of the sealing chamber.
Process characteristics

a). High efficiency screw pump lifting well fluid, with a large flow area and low friction, the system efficiency is higher than that of rod pumping wells with pumping units. Compared with electric rod wells, the energy-saving rate is over 90%, and compared with ordinary rod pumping wells, the energy-saving rate is over 60%.
b). Adopting a direct-drive motor, the starting torque is high, up to 1.8~2 times the rated torque, which is in line with the starting characteristics of screw pumps.
c). Screw pump continuous lifting, low shear effect, high efficiency of heavy oil pumping.
d). No ground equipment, small footprint, suitable for well cluster development.
e). Rodless oil extraction, no noise, no loss of pipes and rods, and no leakage points at the wellhead.

 2.2 Introduction to INVT's solution

According to actual needs, this system is designed and developed by the customer, and the VFD adopts the INVT GD350-UL series drive. Configure PLC card and HMI to achieve data recording and intuitive display. And PID automatic control can be achieved through feedback of wellhead pressure.
Configure active filters to reduce current harmonics, configure DC reactor to provide power factor, by configuring an sine wave output filter, effective control of a 500m motor can be achieved.

Direct-drive screw pump torque release non-standard function(Backspin), achieving effective stop and avoiding the phenomenon of stop and high-speed (without control), configure a braking unit to effectively release energy while stop.

2.2.1 Characteristics of the solution

a). Low voltage 460V, 60Hz power supply, long distance between VFD and motor.
b). Direct-drive screw pump non-standard function, stop torque release, equipped with braking unit.
c). One drive two variable frequency control scheme, HMI local control, and remote local switching.
d). Setting frequency and wellhead pressure to achieve manual and automatic operation switching.

2.2.2 Scheme System Diagram

Scheme diagram

2.2.3 Scheme Configuration Table

3. Product/solution advantages

a). The integrated solution of VFD, PLC card, and HMI can record waveforms such as current, and the operating data is intuitive.
b). The GD350-UL series VFD is a high-performance VFD that can drive synchronous motor and asynchronous motor. It integrates torque control, speed control, and position control, making it a driver with excellent control performance.
c). External fault data is intuitive and can quickly locate fault points.
d). Using an active filter, the current harmonic THDi is ≤ 5%.
e). By using an output filter, the motor can be controlled remotely with low du/dt and no impact on the motor.

4. Parameters setting of VFD

VFD is using V/f control

5. On site application photo

6. Conclusion

The submersible direct-drive motor of the direct drive screw pump has the characteristics of low output speed, large torque, high efficiency, and low energy consumption. The coupling with high wear resistance and corrosion resistance can buffer, reduce vibration, and improve the dynamic performance of the shaft. Its oil extraction method has a large displacement, no pulsation in flow rate, and can be directly connected to the original mechanism. It is suitable for extracting high viscosity crude oil such as sand wells. By cooperating with a variable frequency system with stepless speed regulation, its pumping advantages can be amplified, providing more energy-saving and efficient electric control oil recovery solutions for the oilfield.