How to achieve long stroke with short pump barrel?
An artificial-lift pumping system using a surface power source to drive a downhole pump assembly. A beam and crank assembly creates reciprocating motion in a sucker-rod string that connects to the downhole pump assembly. The pump contains a plunger and valve assembly to convert the reciprocating motion to vertical fluid movement.
Long stroke Sucker rod pump generally refers to the plunger pump driven by the reciprocating motion of the sucker rod up and down. Sucker rod pump is the most widely used mechanical oil recovery method because of its simple structure, strong adaptability, convenient maintenance and management, and long service life. Sucker rod pump is the most commonly used single cylinder and single acting pump, and its displacement depends on pump diameter, stroke and the number of punching. The efficiency of pump is about 50% in medium deep well, which is suitable for medium and low production well.
The existing mechanical oil recovery pump is a single plunger pump. With the development of oilfield production, the stroke length of the sucker rod pump is getting longer and longer. In order to increase the stroke length of the sucker rod pump, all the manufacturers use longer pump barrel to increase the stroke length. However, as the length of the pump barrel increases, the difficulty of processing the inner wall of the pump barrel and the treatment of the surface of the inner wall will increase exponentially.
Also the processing cost will increase significantly. And the longer pump barrel is more easily deformed, which brings great difficulties to assembly, transportation and operations.
In order to solve this problem, San Jack has developed a long stroke pump with short barrel.
The long stroke sucker rod pump adopts double plunger structure. There is a connection rod between upper plunger and lower plunger. There are traveling valves in top of upper plunger and bottom of lower plunger. A barrel extension is connected at the lower end of the barrel of the sucker rod pump.
The standing valve is installed at the bottom of the barrel extension. When the sucker rod pump is working, the upper and lower plungers work alternately in the pump barrel to achieve long stroke. The structure diagram is as follows:
| 1 | Standing Valve | 2 | Barrel extension | 3 | Traveling valve | 4 | Lower Plunger | 5 | Connection Rod |
| 6 | Barrel | 7 | Upper Plunger | 8 | Traveling valve | 9 | Tubing | 10 | Sucker Rod |
During the upstroke, the sucker rod drives the upper and lower plungers to move upward. Traveling valve closed and standing valve open. When the upper plunger exposes the upper end of the pump barrel, the lower plunger enters the pump barrel and the plunger continues to rise. When the upper end of the lower plunger reaches the upper end of the pump barrel, the pump barrel and extension are filled with crude oil.The pump reaches the maximum stroke length and the upstroke is completed.
During the downstroke, the sucker rod drives the upper and lower plungers downward. At this time, the traveling valve opens and the standing valve closes. The crude oil enters the tubing through the traveling valve, lower plunger, plunger connecting pipe and upper plunger. When the bottom of the lower plunger exposes the bottom of the pump barrel, the upper plunger enters the pump barrel, the plunger continues to descend to the designated position, and the down stroke is completed.
The new sucker rod pump has a simple structure and is easy to manufacture. It can achieve long stroke a short with short pump barrel which greatly reduces the manufacturing difficulty and manufacturing cost. It can be produced without updating the equipment and it brings convenience to the transportation and use of pumps.
Sanjack is the only manufacturer in China which can product all the parts of sucker rod pump. Meanwhile, the precision rolling pipe plant of SJ is the main supplier of barrel tube for other sucker rod pump manufacturers in China.
Multi-inspection, including self-inspection, teammate-inspection and inspector-inspection, shall be done during the machining process of pump parts. Some key points, like the outer diameter of the plunger and thread accuracy, shall be 100% multi-inspected. All the produced parts shall be marked with track number by the laser engraving machines.
To improve the anti-corrosion property and hardness, Surface treatment isrequired on all the parts of sucker rod pump according to the requirement of client, spray welding on plunger, chrome-plating on barrel and phosphating on all accessories.
We can finish spray welding process on various kinds of plungers of which the length is within 8 meters, and can complete chrome-plating on barrel with ID ranging from 1 1/16’’(26.99mm) to 5 3/4’’ (146.05 mm) and length within 34 ft (10363 mm).
