The purpose of a shale shaker is to induce drilling fluid to flow through a screen, transport solids across a screen surface, and discharge solids off the end of the screen. While, how a shale shaker screens fluids?
Drilling fluid is a rheologically complex system. At the bottom of the hole, faster drilling is possible if the fluid has a low viscosity. Drilling fluid flows downward, onto, and through shaker screens. the upward stroke moves the drilling fluids through the screen. large solids do not follow the screen on the downward stroke, so they can be propelled from the screen surface. when the screen moves on the downward stroke, the large solids are suspended above the screen and come in contact with the screen at a farther point toward the discharge end of the shaker. this is the reason that the elliptical, circular, and linear motion screens transport solids.
Screens are moved upward through the fluid with the elliptical, circular, and linear motion shale shakers. The linear motion shaker has an advantage because solids can be transported out of a pool of liquid and discharged from the system. The pool of liquid creates two advantages:
Not only does it provide an additional head to the fluid, but it also provides inertia or resistance to the fluid as the screen moves upward. This significantly increases the flow capacity of the shaker. The movement of the shaker screen through the drilling fluid causes the screen to shear the fluid. This decreases the viscosity and is an effective component to allow the shaker to process drilling fluid.
The upward movement of the shaker screen through the fluid is similar to pumping the drilling fluid through the screen openings. If the fluid gels on the screen wires, the effective opening size is decreased. This would be the same as pumping drilling fluid through a smaller-diameter pipe. With the same head applied, less fluid flows through a smaller pipe in a given period of time than a larger pipe. If a shaker screen becomes water wet while processing NAF, the water ring around the screen opening effectively decreases the opening size available to pass the fluid. This, too, greatly reduces the flow capacity of the shaker.