In recent years, with the exploitation of high viscosity crude oil and the development of tertiary oil recovery, screw pump has been widely used, the workload of screw pump wells has been increasing, and the operation technology has been developing.
I. Composition of Screw Pump Oil Production System
Screw pump can be divided into single cylinder and series type according to the basic structure, and can be divided into ground drive and underground drive according to the driving mode. The ground-driven screw pump mainly has two forms: belt drive and direct drive. Downhole drive screw pump can be divided into two forms: electric drive and hydraulic drive. At present, the surface-driven underground elastic screw pump oil production system has been widely used in oil fields.
The ground-driven downhole single screw pump is mainly composed of four parts: the electric control part, the ground-driven part, the downhole screw pump and supporting tools, as shown in figure 1- 1.
Fig. 1- 1 Schematic diagram of underground single screw pump oil production driven by surface.
1- electric cabinet; 2- motor; 3 belts; 4 square clips; 5- Balance block; 6- pressure gauge; 7- sucker rod; 8- tubing; 9- centralizer; 10- dynamic liquid level; 1 1- screw pump; 12- casing; 13- anti-rotation anchor; 14- sieve tube; 15- plug; 16- Reservoir
(1) electronic control part
The electric control box is the control part of the screw pump well, which controls the start and stop of the motor; Record the current and cumulative running time of screw pump well during normal production; With automatic protection function of overload and underload.
(2) Ground driving part
The ground driving device is the main ground equipment of the screw pump oil production system, and it is a mechanical device that transmits power to the rotor of the downhole pump and realizes the pumping of crude oil. The driving device of mechanical transmission is mainly composed of reducer, motor, sealing box and square pliers.
(3) downhole screw pump
1, structure of ground-driven single screw pump
It is mainly composed of stator, rotor and limit joint. The stator is made of high-quality steel shell filled with rubber, and the rubber sleeve is a double-line or multi-line helicoid; The rotor is a single-headed or multi-headed helicoid made of high-strength steel, which engages with the inner surface of stator rubber after hard plating to form a sealed cavity. The stator is lowered with the tubing and anchored, and the rotor is connected with the sucker rod.
2. The working principle of ground-driven downhole single screw pump.
The motor and the driving device make the sucker rod rotate clockwise, and the sucker rod drives the rotor of the downhole screw pump to do planetary motion in the stator sleeve; When the rotor moves, the oil absorption sealing cavity moves up from the oil absorption end axially, and a new sealing cavity is formed at the same time. With the upward movement of the sealed cavity, the sucked liquid moves from the suction end to the discharge end. The continuous formation, upward movement and disappearance of the sealed cavity play the role of a pump, lifting oil, sand, water and gas to the ground together.
(4) Support tools
(1) Special wellhead: it can protect the polished rod and seal the wellhead.
(2) polished rod: used for wellhead sealing.
(3) sucker rod centralizer: avoid or slow down the wear of sucker rod and oil well.
(4) tubing centralizer: it can reduce the vibration and wear of tubing string.
(5) Anti-reverse device of sucker rod: to prevent the sucker rod from reversing and back-screwing.
(6) Anti-dropping device for tubing: fix the pump and tubing to prevent tubing from falling off.
(7) Paraffin inhibitor: delay the deposition rate of paraffin and colloid in crude oil on the inner wall of tubing.
(8) Anti-evacuation device: insufficient liquid supply in the formation will cause damage to the screw pump, and the installation of wellhead flow or pressure anti-evacuation device can effectively avoid this phenomenon.
(9) Screen tube: filtering reservoir fluid.
Second, the model and basic parameters of single screw pump
(A) single screw pump model representation method
Label example:
GLB 120- 14 is a single-barrel single-screw pump with a nominal displacement of 120mL/r and a total stage of 14, and the sucker rod rotates.
(2) Basic parameters of single screw pump
See table 2- 1 for the basic parameters of single screw pump.
Table 2- 1 Basic parameters of single screw pump
Third, the characteristics of screw pump oil production system
Screw pump is a positive displacement pump with few moving parts, no valve parts and complicated flow channels, small oil flow disturbance and even displacement. Because the cylindrical rotor moves on the inner surface of the stator rubber bushing, it has rolling and sliding characteristics, and sand particles in oil are not easy to deposit. At the same time, the uniform volume change between the rotor and the stator produces swabbing and pushing effect, which makes the oil-gas mixed transportation effect better. Compared with other oil recovery methods, it has unique characteristics in exploiting crude oil with high viscosity, high sand content and high gas content.
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