The core objective of solid phase control in drilling fluid is to remove harmful solid particles from the drilling fluid and retain useful solid phases, so as to ensure that the density, viscosity, water loss and other properties of the drilling fluid meet the requirements of the drilling process. Reasonable solid-phase control can:

1. Prevent the blockage and damage of oil and gas channels;

2. Reduce drilling torque and friction;

3. Reduce the pressure fluctuations caused by annular suction;

4. Increase the mechanical drilling rate (ROP);

5. Extend the service life of the drill bit;

6. Reduce the wear of the circulation system and mechanical components.

The solid phase control system of drilling fluid is the general term for all solid control equipment (such as vibrating screens, vacuum degasser, desander, desilter, centrifuge, etc.)
 among which the vibrating screen, as the primary solid control equipment, is the "first line of defense" of the entire system.

The drilling fluid vibrating screen mainly works by the motor driving the vibrator to rotate, generating periodic inertial forces that cause the screen box to vibrate in a specific direction. After the solid particles such as drill cuttings carried by the drilling fluid are sent to the screen surface, they undergo a throwing motion under the action of vibration and gravity. The liquid and fine particles smaller than the screen holes pass through the screen, while the large particles are separated and discharged.

The main factors affecting the performance of vibrating screens include: separated particle size and processing capacity. Both depend on parameters such as the mesh count of the screen, vibration mode, amplitude, inclination Angle and the nature of the material.

Vibrating screens can be classified into the following types based on the movement trajectory of the screen frame:

1. Circular vibrating screen: The motion trajectory is circular. The material moves at a relatively fast speed on the screen surface, making it suitable for the separation of coarse particles.

2. Elliptical vibrating screen: The excitation device is fixed directly above the center of mass of the screen box. The screen box needs to be tilted at a certain Angle to accelerate the forward movement of materials by gravity and prevent particles from being thrown backward. The mobility of the sand grains has been improved, but the processing capacity has relatively decreased.

3. Linear vibrating screen: It generates linear excitation by two main shafts with eccentric blocks rotating synchronously in opposite directions. The movement direction is constant and the screening accuracy is high.

4. Double-track vibrating screen: Different areas of the screen box present different motion trajectories (such as elliptical at the feeding end and linear at the discharging end). It takes into account both the rapid conveying of materials and the efficiency of fine particle separation.

The mesh count of a screen refers to the number of holes per inch of length. The larger the mesh count, the smaller the pore size, and the finer the particle size that can be screened out. Common mesh sizes (unit: mesh) : 20, 40, 45, 60, 80, 100, 110, 120, 140, 160, 165, 200, etc.

Large mesh size → small separated particle size → high screening accuracy;

Small mesh size → large processing capacity, but poor separation effect on fine particles.

Common types of screen mesh structures

1. Plate and frame type: Sturdy structure, easy to replace;

2. Wavy type: Increase the effective screening area and enhance the processing capacity;

3. Hook-edge type: Stable installation with good tension;

4. Flat plate type: Suitable for linear motion screens, with uniform material distribution.

The factors affecting the performance of vibrating screens include

Screen inclination Angle: Appropriately increasing the inclination Angle can enhance the material conveying speed, but if it is too large, it may reduce the separation accuracy.

2. Amplitude and frequency: A large amplitude helps prevent the screen holes from clogging, and a high frequency is conducive to the separation of fine particles.

3. Material properties: The density, viscosity and sand content of the slurry will all affect the screening efficiency.

4. Maintenance conditions: The tension of the screen mesh, the lubrication of the exciter, the fatigue degree of the spring, etc. will all affect the performance.

In conclusion, the drilling fluid vibrating screen is a key device in the solid control system, and its performance directly affects the quality of the drilling fluid and the drilling efficiency. The correct selection of vibration mode, screen mesh size and operating parameters, and flexible adjustment in combination with the construction stage, can significantly improve the solid-phase control effect, reduce drilling costs and extend the service life of equipment.