Research and Practice of Raising the Elliptic Drilling Fluid Vibrating Screen

At present, the drilling fluid vibrating screen commonly used by most drilling companies in China is a uniaxial oval drilling fluid vibrating screen. Due to its simple structure, large processing capacity, easy screen replacement, adjustable excitation force amplitude, rapid and stable startup and shutdown The advantages of convenient use and maintenance are called mainstream products. When the shaker rotation center on the drilling fluid vibrating screen is located directly above the center of mass of the screen frame, solid particles on the vibrating screen surface will accumulate in the middle or at the exit end, and even the particles will exit the drilling fluid vibrating screen. Back to the middle part. This is because the long axis of the elliptic curve of the vibration trajectory, speed, and acceleration of the shaker screen box is tilted in the middle of the shaker. Therefore, the screen at the outlet must have a large downward tilt angle so that the cuttings can be smoothly discharged from the screen. Otherwise, due to the long-term vibration of some rock cuttings on the screen, the life of the screen is greatly shortened, but increasing the inclination of the screen will cause a lot of mud loss.

In addition, this structure is not suitable for long-term use of the excitation motor. The above disadvantages have been proven by a lot of practice. Although the newly developed ordinary elliptical drilling fluid vibrating screen moves the motor from the screen box to the base so that it does not participate in vibration, in order to prolong the service life of the vibration motor, remove the counterweight, and make the screen length of the drilling fluid vibrating screen. Improvements such as shortening have not yet solved the fundamental problem of short screen life, making it impossible to promote the application in a large area. To this end, we have conducted multiple aspects of research and practice on drilling fluid shakers.

1. Change the shape of drilling fluid shaker

The vibration shape of a common drilling fluid shaker is formed because the rotation center of the shaker is directly above the center of mass of the drilling fluid shaker screen frame. When designing a drilling fluid vibrating screen, in order to minimize or avoid solid particles from gathering at the outlet end or flowing back to the middle, it is required that the acute angle between the elliptical long axis at the outlet end and the horizontal plane is not less than 45 degrees. That is, the easier it is for the solid phase particles to be thrown forward, the less it is likely to agglomerate at the outlet end or flow back to the middle. For the inlet end, due to the forward thrust of the drilling fluid, the discharge speed of the solid particles is basically not affected by the angle between the major axis of the ellipse and the horizontal. Therefore, as long as the conditions for discharging solid phase particles at the outlet end are improved, the problem of short life of the drilling fluid vibrating screen can be solved. It is confirmed through research and analysis that moving the center of rotation of the exciter toward the outlet end will increase the acute angle between the long axis of the outlet end and the horizontal plane. According to this principle, we have made a large number of optimization calculations and experiments on the position of the vibration center of the shaker of the drilling fluid shaker. The theoretical basis of the optimization calculation can be based on the dynamic calculation analysis of the drilling fluid shaker in the basis of drilling mechanics. "To get the direction of the vibration trajectory at any point. It can be known that when the mass of the shaker screen box member is unchanged, and the spring stiffness and the position of the spring relative to the center of mass of the screen box are not changed, only the position of the shaker rotation center can be changed to change the vibration characteristics of the drilling fluid shaker. Changing the rigidity and position of the spring can also change the characteristics, but it has been proved in practice that its effect is not obvious.

How much the moving distance is, after many repeated experiments, it is concluded that when the acute angle between the ellipse's long axis and the horizontal plane is not less than 75 degrees, the speed of solid phase particle discharge reaches the optimal state.

2. How to add drilling fluid to the screen area

According to actual and experimental results, when the drilling fluid covers 75% of the entire screen area (the remaining 25% is the outlet screen, if the drilling fluid covers the entire screen, the mud will be lost), the life of the screen can be reached Or close to this working state. The drilling fluid shaker model can be changed at any time according to the drilling fluid processing capacity. However, this is difficult to achieve in the field. In order to meet the requirements of this change as much as possible, a drilling fluid extension groove is designed at the inlet end of the drilling fluid. Its bottom plate consists of several fixed plates and movable plates. The movable plate can rotate around the rotation axis of the chain segment. It is convenient on site to change the rotation angle of each movable plate. When the amount of liquid treatment is small, the movable plate can be closed completely so that the liquid flows to the outlet screen. Practice has proved that this measure can effectively reduce the beating time of particles on the screen and is beneficial to the extension of the screen life.

3. Drilling fluid vibrating screen adopts laminated bonding screen

In order to increase the life of the screen of the drilling fluid vibrating screen, especially the life of the fine mesh screen, a layer of coarse screen is usually used as the lining screen, and the surface screen and the lining screen are tensioned separately, resulting in the vibrating screen. The complicated structure of the box increases the difficulty of manufacturing and installation, especially it is difficult to keep the tension of the surface screen and the lining screen consistent. Therefore, the friction between the two layers of screens is caused during the use of this process, and some particles are easily sandwiched between the two layers of screens, which accelerates the damage of the screens. After repeated experiments and studies, a laminated bonding screen was used instead of the original double-layer screen structure. This screen is a 50 mm strip of rubber uniformly arranged between the face screen and the lined screen. The width of the rubber strip is 5 mm. The face screen and the lining screen are bonded together, and then the tensioned hook edge is uniformly pressed to make it a whole. The adoption of such a screen structure simplifies the complicated structure in which the two layers of screens are tensioned separately, reduces the difficulty of manufacturing and replacing the screens, and more importantly increases the life of the vibrating screens.

4 Conclusion

1. By taking the above measures, the statistics of the use of 30 drilling fluid vibrating screens on the site show that the average life of the screen is 300 hours from the ordinary oval drilling fluid vibrating screen, and even the screen life is only tens of hours. , Increased to more than 600 hours of the new oval drilling fluid shaker. The improved elliptical drilling fluid vibrating screen that has been improved and developed has been widely used in various major places in the country.

2. The improved new-type elliptical drilling fluid vibrating screen has a good screening effect, and the available components contained in the solid phase particles discharged from the outlet end are reduced to the lowest point, which is conducive to the full recovery of the drilling fluid and reduces the drilling cost.

3. As the new oval drilling fluid vibrating screen overcomes the shortcomings of ordinary oval drilling fluid vibrating screens and circular vibrating screens on the shaker rotation center, which makes it difficult to guarantee the design requirements for processing and manufacturing, the idiot has vibrated the ordinary oval drilling fluid The sieve has a large amount of drilling fluid processing capacity, can be started or stopped quickly and smoothly, and is easy to maintain and maintain.

4. It is easier to manufacture, install and lower than biaxial elliptical drilling fluid vibrating screen.

Double-layer drilling fluid shaker