Determination of shaker screen:
Drilling fluid shale shaker can eliminate the solid particles size depend on the mesh size and shape. Field data shows that use the shaker screen with 12 mesh number most can eliminate only 10% of the solid phase. Therefore, we should use 80~120 mesh fine screen to eliminate more drilling cuttings.
However, it will occur the following new problems: The mesh area of fine screen is less than the conventional screen, thus will reduce the treating capacity; The thin wire strength is low, the service life is shorter than the conventional screen; When high viscosity drilling fluid through the fine screen, the mesh will be blocked easily.
For increasing the service life and anti-clogging ability of shaker screen, we often use the laminated screen which has two or three layers screen, the lower coarse screen plays the support role. In addition, we can also use the double or multiple screen which has a certain space distance between layer and layer. Generally the upper is coarse screen, and the lower is fine screen. The upper coarse screen can eliminate bigger solid particles, can reduce the burden of the fine screen to remove fine solid phase more effectively.
Number of shakers applied:
The number of shakers applied in a rig is mainly determined by the ratio of the maximum mud circulating output of the rig and the treating capacity of a single shaker, usually 2 or 3 units on a rig. As a rule of thumb 75 %~ 80 % of the total length of the screen should be covered by flowing mud and this may permit using the entire capacity of the shaker including consideration of dealing with mud surge.
Arrangement of shakers
Serial arrangement: In this kind of arrangement, the coarse mesh shaker processes the fluid initially and the fine mesh shakers process the underflow of the precedent coarse one.
Parallel arrangement: The shakers are arranged in a parallel mode and mud flows onto all the shakers through a distributor.