Development and Application of Self - synchronous Linear Vibrating Screen

Authors: Mao Guozhong, Zhao Baozhong (Yellow River Drilling General Company of Shengli Petroleum Administration Bureau)

At present, most of the vibrating screens used in China are single - axis inertial vibrating screens, whose motion trajectories are circular or quasi - circular. This type of screen has a simple structure, but its screening efficiency is low, the service life of the screen mesh is short, and the loss of drilling fluid is large. Since the early 1970s, the experiment and research on self - synchronous linear vibrating screens have been carried out. However, due to the unreasonable overall layout of the vibrating screen, the fixing method of the screen mesh, the performance of the elastomer and the motor, etc., the screen is bulky, its performance is unstable, and the service life of the screen mesh is short. So far, an economical and practical self - synchronous linear vibrating screen has not been introduced. Abroad, a lot of work has been done on self - synchronous linear vibrating screens. Several companies have successively introduced self - synchronous linear vibrating screens, such as the Derrick Company in the UK and the KEM - TRON Company in the US. When bidding for foreign drilling projects, self - synchronous linear vibrating screens have become essential equipment. At present, most of the linear screens used in China are imported, which are mainly applied to offshore drilling platforms and onshore deep - well teams. Judging from the application effect, the purification effect and treatment capacity of the drilling fluid can basically meet the design requirements, but the screen mesh needs to be replaced frequently, and the imported screen mesh is expensive. Therefore, it is urgent to develop a high - performance and long - life self - synchronous linear vibrating screen suitable for the current domestic drilling situation. The Yellow River Drilling Company has adopted composite elastic elements to improve the screening effect, and carried out structural modifications on the vibrating screen in many aspects to improve the working performance of the self - synchronous linear vibrating screen.
Working Principle
The double - motor self - synchronous vibration exciter device is shown in Figure 1.

Two eccentric rotors with masses  and  are driven by two motors respectively, and rotate in opposite directions around points  and  on the box  with a radius  and a speed . Their centrifugal forces are , and the reaction forces of the support springs are  and . For the screen box to make linear vibration, first, , , , that is, the centrifugal forces .
As can be seen from Figure 1, at any position, the horizontal components of the centrifugal forces of the eccentric rotors cancel each other out. Therefore, every time the rotor rotates one circle, a reciprocating exciting force is generated in the vertical direction, making the screen box move in a reciprocating straight - line motion. If the characteristics of the two motors in the system are the same, the stiffness and damping of each support point are equal, and there is no phase difference at startup, then the two eccentric blocks will operate synchronously under ideal conditions. In actual work, synchronous operation cannot be achieved at all times. Because the two vibration exciters are installed on a base at a certain angle, due to the action of gravity, their initial phase angles are not equal. There will be a phase difference after startup. At this time, although the centrifugal forces generated by  and  are equal, due to the different angles with the vertical direction, the components in the horizontal and vertical directions are different, and an unbalanced force will be generated, causing the screen box to move and swing on the support springs. It is precisely this movement and swing that make  and  follow each other. Due to the existence of inertial force, the phase difference gradually decreases, and finally the phase difference becomes zero, reaching a stable state and achieving an ideal synchronous state.
Structural Features and Performance Parameters
2.1 Structure
The structure of the self - synchronous linear vibrating screen is shown in Figure 2.

In Figure 2, the flow - equalizing and regulating structure is composed of guide vanes and a flow - equalizing plate. The middle of the screen box is a frame structure with a crossbeam. The vibration exciter is seated in the middle of the crossbeam at a certain angle. Angle - adjusting mechanisms are installed on the left and right sides of the front end of the screen box to meet the requirements of different screening particles and displacement. A single - layer prestressed hooked - edge screen mesh is used, which is fixed bidirectionally by six transverse pressure plates and a longitudinal compression frame. The pressure plates are connected to the screen box with special anti - detachment bolts. The bolts and the pressure plates are designed to be inserted and then rotated by 90°, which is convenient for replacing the screen mesh. The motion trajectory of this equipment is linear, and it has a double - screen parallel structure (stand - by), with the advantages of high screening efficiency, large processing capacity, the ability to use ultra - fine screen meshes, and a long service life of the screen mesh.
2.2 Features
(1) The motion trajectory of the screen box is linear, so the drill cuttings move regularly on the screen surface, and the chip removal is smooth. The angle of the screen box is adjustable, which is suitable for different screening particles and has a good screening effect.
(2) The adoption of the drilling fluid regulating and flow - equalizing structure reduces the scouring of the screen mesh.
(3) The use of prestressed screen mesh and a two - way screen - fixing mechanism makes it convenient and fast to replace the screen mesh. At the same time, it extends the service life of the screen mesh. Ultra - fine screen meshes above 200 meshes can be used without clogging the screen holes and without leakage of drilling fluid.
(4) The use of special springs makes it safe, durable, and has a low noise level.
2.3 Performance Parameters
Screen mesh size: (2 pieces) ;
Amplitude: ;
Excitation frequency: ;
Processing capacity: ;
Weight: ;
Exciting force: .
Field Test Situation
3.1 Well Ying45 - X9
After the successful trial - production of the prototype, it was first tested in Well Ying45 - X9. This well is a directional well with a depth of 2500m. The vibrating screen was started to be used when the well depth was 780m. The formation lithology is mainly mudstone, and the maximum viscosity of the drilling fluid is 50s. From the start of using the vibrating screen to the completion of the well, it ran for a total of 210h. Five pieces of screen meshes were replaced in the lower layer, two of 60 meshes and three of 40 meshes. The average service time was 42h. The screen meshes replaced were mainly from the No. 2 screen body, and the screen meshes of the No. 1 and No. 3 screen bodies were in good condition. Two pieces of 175 - mesh screen meshes were used in the upper layer and were not damaged. The vibrating screen operated stably, and the angle - adjusting and flow - equalizing regulating mechanisms operated normally. This proves that the basic structure of the vibrating screen is feasible and can use fine screen meshes. The existing problem is that the service life of the screen mesh is short. Through analysis, it is mainly because the overall rigidity of the screen box is insufficient, and the vibration of the screen mesh and the screen box cannot be completely synchronous.
3.2 Well Wang24 - X30
The second test of the vibrating screen was carried out in the directional well Wang24 - X30. The completed well depth is 2325m. The vibrating screen was started to be used when the well depth was 750m. It ran for a total of 192h. Three pieces of 40 - mesh screen meshes were replaced. The density of the drilling fluid was , and the maximum viscosity was 55s. The average service time of the screen mesh was 64h, and other components operated normally, proving that the improvement of the vibrating screen has achieved results. The reason for the damage of two pieces of screen meshes this time was due to human factors, that is, the fixing screws of the screen mesh were loose and not discovered in time, resulting in the accumulation of sand and premature damage of the screen mesh. Through the tests of the two wells, it was found that the vibrating screen still needs to be improved in details such as the installation of the drilling fluid inlet device, the fixing of the screen mesh, and the rigidity of the screen box. Therefore, a double - screen parallel structure was newly added, a single - layer screen mesh was used, a two - way screen - fixing mechanism and a combined buffer box were used.
3.3 Well Jiao5 - X281
After the improvement, the vibrating screen was tested in the directional well Jiao5 - X281. The completed well depth is 2560m. The small - cycle started from 750m, and the upper formation is mainly mudstone. The maximum viscosity of the drilling fluid is 60s. The vibrating screen ran for 130h. 60 - mesh hooked - edge screen meshes were used without replacement, without leakage of drilling fluid and without clogging of the screen holes. Due to the poor oil - gas show, the well was filled and redrilled. The vibrating screen was used for another 120h. The screen mesh was used for a cumulative of 250h without damage. After that, the vibrating screen was used in Well Guangbei9 - 16 for 168h. The No. 1 screen mesh was used for a cumulative of 418h, and the No. 2 screen mesh was used for 380h. In Well Guang3 - X28, the screen was used for 102h and worked normally. As of October 2002, more than 80 self - synchronous linear vibrating screens have been applied in Shengli, Huabei, Daqing, Liaohe and other oilfields, among which 64 were in Shengli Oilfield. They have been applied to more than 1000 wells, including 38 horizontal wells, 6 scientific test wells, and 62 directional wells. They were also applied in the Xuegu - 1 and Xuegu - 2 wells in cooperation with Chevron in Shengli Oilfield and were highly praised. Compared with the old - type vibrating screen, the average drilling cost per well is saved by about 14,000 yuan.
Conclusions
(1) The motion trajectory of the self - synchronous linear vibrating screen is easy to achieve, and it has the advantages of simple structure, reliable operation, high efficiency, and long life.
(2) The overall layout of the self - synchronous linear vibrating screen is reasonable, with a small volume, compact structure, and is easy to transport and install.
(3) The self - synchronous linear vibrating screen can use ultra - fine screen meshes above 200 meshes, has a high purification effect on drilling fluid, creates conditions for providing high - quality low - solid - phase drilling fluid for drilling, and can reduce down - hole accidents at the same time.
(4) This vibrating screen uses special springs with a low noise level, which is beneficial to the health of engineering personnel.
References
[1] Gong Weian. Drilling Fluid Solids Control Technology and Equipment. Beijing: Petroleum Industry Press, 1995 - 04
[2] Shen Hong. Mechanical Engineering Handbook. Beijing: Machinery Industry Press, 1983 - 11

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