The Four Components Of A Screw Pump

Jan 28, 2025

The surface driven downhole single screw pump oil production system (referred to as the screw pump oil production system) consists of four parts. Electrical control part: including electrical control box and cables; Ground drive part: including gearbox and drive motor, wellhead dynamic seal, support frame, square card, etc; Underground pump section: including stator and rotor of screw pump; Supporting tools: including dedicated wellhead, special light rod, sucker rod stabilizer, tubing stabilizer, sucker rod anti reverse device, tubing anti detachment device, wax remover, anti evacuation device, screen tube, etc.
1) Electric control part
The electrical control box is the control part of the screw pump well, which controls the start and stop of the motor. This device can automatically display and record the current and cumulative operating time of the screw pump well during normal production, and has overload and underload automatic protection functions to ensure normal production of the production well.
2) Ground drive part
(1) Working principle of ground drive device
The ground drive device is the main surface equipment of the single screw pump oil production system, which transmits power to the downhole pump rotor, enabling the rotor to achieve planetary motion and realize the mechanical device for pumping crude oil. In terms of transmission forms, there are hydraulic transmission and mechanical transmission; There are two types of speed changes: continuously variable speed and graded speed.
(2) Types and advantages and disadvantages of ground driving devices
The types of single screw pump drive devices are generally divided into two categories: mechanical drive devices and hydraulic drive devices.
The transmission part of the mechanical drive device is composed of an electric motor and a reducer, which have the advantages of simple equipment, low price, easy management, and energy saving. It can achieve graded speed regulation and is relatively convenient. Its disadvantage is that it cannot achieve stepless speed regulation.
The hydraulic drive device is composed of a prime mover, a hydraulic motor, and a hydraulic transmission part. Its advantage is that it can achieve low-speed start-up and is used for the extraction of high viscosity and high sand content crude oil; The speed can be adjusted arbitrarily; Due to the installation of a hydraulic anti reverse device, the reverse speed of the pumping rod has been slowed down. Its disadvantage is that it is difficult to insulate hydraulic components and pipelines on the ground during cold seasons, and the price is relatively high, making it difficult to manage.
① The main function of a gearbox is to transmit power and achieve first level deceleration. It transmits the power of the motor from the input shaft to the output shaft through gears, and the output shaft is connected to a light rod. The light rod then transmits the power to the rotor of the downhole screw pump through a pumping rod. In addition to transmitting power, the gearbox also transfers the axial load of the sucker rod to the Christmas tree.
② The motor is the power source of the single screw pump well, which converts electrical energy into mechanical energy. Generally, three-phase asynchronous motors are used.
③ The function of dynamic sealing at the wellhead is to prevent well fluid from flowing out and to seal the wellhead.
④ The function of the square card is to connect the output shaft of the gearbox with the light rod.
3) Underground pump section
A single screw pump consists of a stator and a rotor. The stator is formed by casting nitrile rubber inside a steel casing. The inner surface of the liner is a double helix curved surface (or multiple helix curved surface), and the stator is matched with the rotor of the screw pump. The rotor rotates inside the stator to achieve suction function. The rotor is made of alloy steel that has been quenched and tempered, then milled, polished, and chrome plated. Each cross-section is a circular single screw.
4) Supporting tools section
① Specialized wellhead: simplifies the use, maintenance, and upkeep of the Christmas tree, while enhancing the strength of the wellhead and reducing the vibration of the ground driving device, playing a role in protecting the light rod and sealing the wellhead when changing the disc root.
② Special light rod: high strength, anti fracture, high smoothness, conducive to wellhead sealing.
③ Sucker rod stabilizer: to avoid or slow down the wear of the rod and tubing, to center the sucker rod in the tubing, and to reduce the fatigue of the sucker rod.
④ Tubing stabilizer: reduces the vibration of the tubing string.
⑤ Anti reverse device for sucker rod: prevents the sucker rod from retracting.
⑥ Oil pipe anti detachment device: Anchor the pump and oil pipe to prevent oil pipe detachment.
⑦ Wax inhibitor: Delaying the sedimentation rate of gum in crude oil on the inner wall of the tubing.
⑧ Anti evacuation device: Insufficient formation fluid supply can cause damage to single screw pumps. Installing wellhead flow or pressure evacuation protection devices can effectively prevent this phenomenon from occurring.
⑨ Screen tube: filters oil reservoir fluids.