How to prevent partial wear of downhole pump plunger?

In many oil reservoirs worldwide, the downhole pressure does not have the ability to lift the produced fluids to the surface. In order to produce these fluids, pumps are used to artificially lift the fluids; this method is referred to as artificial lift. More than seventy percent of all currently producing oil wells are being produced by artificial lift methods. One of the most applied artificial lift methods is sucker rod pump.

Sucker rod pumps are considered a well-established technology in the oil and gas industry and thus are easy to apply, very common worldwide, and low in capital and operational costs. Many advancements in technology have been applied to improve sucker rod pumps performance, applicability range, and diagnostics. With these advancements, it is important to be able to constantly provide an updated review and guide to the utilization of the sucker rod pumps.

The oil well pump is downhole equipment for pumping oil. The liquid that is sucked contains sand, wax, water, gas and corrosive substances. It works downhole from hundreds of meters to thousands of meters, and the internal pressure of the pump may be as high as 10 MPa or more. Therefore, its working environment is complicated and the conditions are harsh, and the pumping performance directly affects the oil well production. Therefore, the oil well pump should generally meet the following requirements:

(1) Simple structure, high strength, good quality, and reliable sealing of the connecting part;

(2) The manufacturing material has good wear resistance and corrosion resistance, and has a long service life;

(3) The specifications and types can meet the needs of oil well drainage, and have strong adaptability;

(4) Easy to get up and down;

(5) Sand and gas control should be considered in the structure, and necessary auxiliary equipment should be

The downhole pump plunger fall velocities against multiphase flow conditions and the plunger upstroke velocity profiles are insignificant compared to sleeve fall velocity during a shut-in. High fall velocities occurred during the fall in the shut-in stage primarily due to high sleeve height (up to 18-in) and low tubing wellhead pressures. The fall velocity of the sleeves was found to be significantly high in mild and severe deformation wells compared to no deformation wells. Consequently, the wells with deformation are exposed to the plungers reaching excessive kinetic energy more frequently. The high plunger fall velocity was concluded to be the root cause of the tubing deformation of PAGL wells and advised to be avoided considering the correlation between repetitive high plunger fall velocity and the wells with tubing deformation.

New impact-abrasion tests allowing one to evaluate performance of hardmetals operating in conditions of intensive abrasion, severe fatigue and high impact loads can be of great importance for many industrial applications. The plunger is the key component of the pump. Reciprocate up and down in the pump barrel to achieve oil pumping. Existing plunger rotation is achieved by downhole hydraulics. Due to the complex downhole conditions, the plunger rotation is irregular, and the rotation angle of the plunger is unpredictable, which can easily cause uneven wear of the plunger. Thereby reducing the service life of the pump, increasing the number of muscle operations, affecting the normal production of the oil well.

In order to solve the problem of plunger partial wear, Sanjack Group has developed a forced way to rotate the plunger during the pumping process, thereby effectively preventing the plunger from wearing. The schematic diagram of the design structure is as follows:

1Sucker Rod
2Sleeve
3Track Shaft
4Steel Ball
5Screw plug
6Connection Joint

 

This design has a track shaft between the joint and the sleeve. A spiral groove is formed on the track shaft, and two steel balls matched with the spiral groove of the track shaft are provided in the sleeve. The track shaft can move up and down along the steel ball in the sleeve and rotate under the guidance of the steel ball.

The track shaft is connected with the joint, thereby driving the joint to rotate. When working, the sleeve is connected with the sucker rod, and the joint is connected with the plunger of the sucker pump. When the sucker rod travels upward, the sucker rod pulls the sleeve upward, and the steel ball in the sleeve moves along the spiral groove.

Thus, the track shaft is forced to rotate the plunger by 90°. When the track shaft moves a certain distance, the track shaft drives the plunger and the sucker rod to move up. When the sucker rod travels downward, the sucker rod pushes the sleeve down, and the steel ball in the sleeve moves along the spiral groove, thereby forcing the track shaft to rotate the plunger by 90°.

When the track shaft moves a certain distance, the track shaft pushes the plunger and the sucker rod down, and the moving distance of the track shaft up and down is limited by the steps and screw plugs in the sleeve. After completing a stroke, the plunger rotates 180°. Therefore, the plunger is prevented from being abraded, the plunger is evenly worn, and the service life of the pump is improved.

This new design has a simple structure and is easy to manufacture, which can effectively prevent the eccentric wear of the plunger, extend the service life of the pump, reduce the operating costs, and save costs.