In oilfield drilling solids control system, drilling fluid decanter centrifuge is used for separation of suspension containing solid particles ( diameter ≥2μm) and drilling mud. how does drilling fluid decanter centrifuge work?
Decanter Centrifuge Working Principle
The separation of solid and liquid phases in mud is accomplished in a centrifuge drum. The separation working principle of centrifuge is to use the high speed rotation of the drum to drive the high speed rotation of mud, the mud is thrown to the wall of the drum to form a “liquid ring”. The solid particles in the “liquid ring” are subjected to centrifugal force many times greater than their own gravity. Solid particles overcome the resistance of mud viscosity and quickly settle onto the inner wall of the drum to form a solid phase layer. The liquid forms a liquid layer. The ratio of centrifugal force to its own gravity is called the separation factor of a centrifuge. Centrifuges with larger separation factors can separate finer particles from the mud.
Three Types Decanter Centrifuge
Three Types Decanter Centrifuge according to the size of the separation factor: Low speed decanter centrifuge, Medium speed decanter centrifuge, High speed decanter centrifuge.
1. Low speed decanter centrifuge: also known as barite recovery centrifuge. Its separation factor is 500~700μm, for low density solid phase, its separation point is 6~10μm, for high density solid phase, the separation point is 4~7μm, This type decanter centrifuge is used to recover barite.
2. Medium speed decanter centrifuge: its separation factor is about 800μm, and can separate 5-7μm solid phase from drilling mud, This is the most used centrifuge in the drilling solids control.
3. High speed decanter centrifuge: its separation factor is about 1200~2100μm, High speed decanter centrifuge and low speed decanter centrifuge can be connected as decanter centrifuge system. In this centrifuge system, the low-speed centrifuge as the first stage can separate and recover barite in the mud tank. The liquid from the low-speed centrifuge is discharged into a buffer tank first. Then the liquid in the buffer tank can be transfer to high-speed decanter centrifuge by centrifugal pump. Solids separated by high-speed decanter centrifuges are removed from the mud tank and the liquid is returned to the mud circulation system. The use of “centrifuge system” can remove harmful solids effectively and save a large of barite. Drilling projects at home and abroad are already using the centrifuge systems.
