Electric submersible screw pump

submersible screw pump

The electric submersible screw pump is a new type of oil production equipment that combines the advantages of an electric submersible pump and a screw pump. The ground drive of the screw pump is directly driven by a motor through a reducer, eliminating the sucker rod and solving the problem of oil pumping. Problems such as tripping, broken rods and eccentric wear caused by rod threads and couplings. Compared with other oil production equipment, electric submersible screw pumps have the advantages of adapting to a wide range of fluids in a well, no rod wear, simple management, high efficiency and energy saving, etc., and are suitable for conventional oil pumping equipment such as rod pumps, electric submersible pumps, etc. that are difficult to operate. Heavy oil wells, sand-bearing wells, and gas-bearing wells. Especially in oil production operations in horizontal wells and directional wells where rod pumps are difficult to adapt to.

 

Compared with rod pumps, electric submersible screw pumps have the following advantages:

1. Energy saving. The greater the viscosity of crude oil, the more significant the energy saving and consumption reduction.
2. No airlock will occur and it also has demulsifying effect.
3. The pumping is continuous and smooth without disturbing the oil layer.
4. There is no sucker rod, which eliminates losses caused by rod wear or tripping, and small-sized oil pipes can be used
5. Can be used in inclined wells, directional wells and horizontal wells
6. Small space occupied on the ground, no leakage at the wellhead, no noise, and simple daily management
7. Increase pump depth and displacement
8. The heat generated by the unit under the pump plays a role in heating under the pump.

 

Compared with electric submersible pumps, electric submersible screw pumps have the following advantages:

1. For the same lift and displacement, much less electricity is used
2. The speed of the electric submersible pump is 2900rpm, while the speed of the electric submersible screw pump is 150~360rpm.
3. Protectors, motor oil, small flat cables and power cables are the same
4. The system efficiency is high, especially for heavy oil wells
5. Very little emulsification effect on well fluid
6. The wax in the oil is not easy to scale in the pump barrel
7. No need to consider gas separation when the free gas content is less than 40%

 

Main system components

The electric submersible screw pump oil production system is divided into three parts: underground, surface and power transmission. The underground part mainly includes screw pumps, flexible shafts, protectors, reducers and submersible motors. The ground part mainly includes control cabinets and wellheads. The power transmission part has cables and cable clips.

 

1) Cable protection device

When the unit passes through the curved well section during tripping, the cable protection block on the unit enables the unit to roll through the deflection point in the wellbore, keeping the cable away from the extrusion surface between the unit and the casing wall, and away from the tubing coupling. Together with the steel cable protection device, the cable will not be damaged.

 

2) Anchor and centralise device

A series of centralizers and anchors designed according to the working conditions of the screw pump can effectively ensure the reliability of the electric submersible screw pump unit in underground operation and extend the service life of the system.

 

3) Submersible motor structure

  • High-quality silicon steel sheet
  • PTFE high-temperature resistant tank insulation -215℃ (420°F)
  • High-temperature resistant thrust bearing
  • High temperature resistant O-ring seal -180℃ (420°F)
  • High-temperature motor oil
  • For good temperature of 180℃
  • Class C insulating paint 215℃ (420°F)
  • Anti-rotation rotor bearing
  • High-quality silicon steel sheet
  • FPA high-temperature resistant tank insulation -215℃ (420°F)
  • Dip four times in insulating paint
  • AFLAS capsule seal 210°C (420°F)
  • High-temperature resistant thrust bearing
  • High-temperature motor oil

 

4) Protector structure

(1) Subsidence protector

  • Suitable for vertical wells
  • High load bearing thrust bearing
  • Tungsten carbide mechanical seal
  • Monel K-500 high-strength shaft
  • Simple structure

(2) Capsule protector

  • Suitable for inclined wells/vertical wells
  • High load bearing thrust bearing
  • Carbide mechanical seal
  • Monel K-500 high-strength shaft
  • Effectively isolate the inner cavity of the motor from the fluid in the well

 

(3) Combined protector

  • Suitable for inclined wells/vertical wells
  • High load bearing thrust bearing
  • Carbide mechanical seal
  • Monel K-500 high-strength shaft

 

5) Frequency conversion speed regulating device

The frequency conversion speed control device designed for electric submersible screw pump products effectively realizes the free adjustment of the motor frequency within 2-60HZ, thereby effectively meeting the requirements of downhole motors operating at different speeds under different oil well conditions. It can effectively realize the soft start of the motor, reduce frequent starts, stop damage to the motor, cables, and downhole screw pumps, and effectively reduce operating energy consumption and equipment maintenance costs.

 

On-site application and effects

 

1. Application in 3-5-120 well

The well belongs to layer 42, with production well section 1410~1416 module and viscosity 2417mpa, s. The original well uses a 12-type beam machine (3.6-meter stroke, 4.5 times/min, 55-kilowatt motor), a 44-inch thickening pump, a depth of 802 meters, and a daily liquid production of 20.4-23.5 cubic meters. Due to thick oil and severe sand production, the well’s operations have been affected many times and normal and continuous production has been impossible.

After normal start-up using ESPCP, the daily fluid production is 25.5~26.2m³, the pump efficiency is 76.2~83.8%, the daily average oil increase is 2.1m³, and the dynamic fluid level is 643 meters. It can be seen that for heavy oil wells and sandy wells, using ESPCP has obvious advantages. Not only does the oil well production increase, the energy-saving effect is obvious, but the system efficiency is much higher than that of tubular pumps and electric pumps.

 

2. Application in Well 821-X7

The well belongs to the 4² layer, with a production section of 1441-1446 meters. The viscosity is 3736mPa.s and the density is 0.9838 g/cm³. Chloride ion 4333 mg/L, sulfate 25 mg/L, total salinity 7570 mg/L, water content 30.2%, sand content 0.2%, deflection point 650 meters, maximum well inclination 28.02°, daily liquid production 18 m³/ d.

It can be seen from the use of this well that for heavy oil wells and inclined wells, the use of ESPCP can achieve more than 75% of the pump efficiency while meeting the oil well production, which has obvious advantages. Using ESPCP, low-power motors can meet the requirements, and the energy-saving effect is obvious.

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