Solids control refers to a well drilling technique used to provide drilling fluid to deep well drilling rigs and to clean this fluid for further use. The technique is often called mud drilling because it uses a flow of water and mud to bring solids out of bore holes and cool the drilling rig equipment. This drilling fluid also facilitates the necessary hydrostatic pressure to prevent the influx of natural formation fluids into the bore hole. This technique has increased the safety of the well drilling process while making explorative drilling a cost-effective option.

The well drilling processes and methods of solids control have seen a variety of evolutions over time. From simple gravity controlled solids removal pits to complex mechanical solids control systems, the various techniques and equipment used to remove solids from drilling fluid have made mud drilling possible. With the creation of solids control measures, bore drilling has become far more economical as the drilling solution is reused.
 

One of the earliest known uses of solids control in a well drilling process that occurred in the late 19th century. A series of processing pits were used to capture the drilling fluid from well drilling rigs. As the fluid passed from one pit to the next, it was allowed to settle. The force of gravity caused the solids to settle out of the liquid. The drilling fluid could then be channeled to a pumping station where it was sent on to the drilling equipment for re-use.

Usually, we use some kinds of solids control equipment to remove the harmful particles in the drilling fluids, including mud tank, shale shaker, vacuum degasser, desander, desilter, drilling mud decanter centrifuge and other assistant equipment. They are combined to five stages as a complete drilling fluid system. Drilling mud shale shaker is used to separate the big solids with diameter above 75μm, and 45~74μm for desander, and 15~44μm for desilter. Sometimes desander & desilter are combined as high efficient mud cleaner. When air enters into the drilling fluids, vacuum degasser is used to separate the air. If no air in the mud, the degasser would work as a big agitator. All these equipments are mounted on the top of the mud tank. After separating the solids, the clean mud would be pumped into the borehole again.